Self-assembly of alkynylplatinum(II) terpyridine amphiphiles into nanostructures via steric control and metal–metal interactions

A series of mono- and dinuclear alkynylplatinum(II) terpyridine complexes containing the hydrophilic oligo(para-phenylene ethynylene) with two 3,6,9-trioxadec-1-yloxy chains was designed and synthesized. The mononuclear alkynylplatinum(II) terpyridine complex was found to display a very strong tendency toward the formation of supramolecular structures. Interestingly, additional end-capping with another platinum(II) terpyridine moiety of various steric bulk at the terminal alkyne would lead to the formation of nanotubes or helical ribbons. These desirable nanostructures were found to be governed by the steric bulk on the platinum(II) terpyridine moieties, which modulates the directional metal−metal interactions and controls the formation of nanotubes or helical ribbons. Detailed analysis of temperature-dependent UV-visible absorption spectra of the nanostructured tubular aggregates also provided insights into the assembly mechanism and showed the role of metal−metal interactions in the cooperative supramolecular polymerization of the amphiphilic platinum(II) complexes.Square-planar d⁸ platinum(II) polypyridine complexes have long been known to exhibit intriguing spectroscopic and luminescence properties (1–54) as well as interesting solid-state polymorphism associated with metal−metal and π−π stacking interactions (1–14, 25). Earlier work by our group showed the first example, to our knowledge, of an alkynylplatinum(II) terpyridine system [Pt(tpy)(C ≡ CR)]⁺ that incorporates σ-donating and solubilizing alkynyl ligands together with the formation of Pt···Pt interactions to exhibit notable color changes and luminescence enhancements on solvent composition change (25) and polyelectrolyte addition (26). This approach has provided access to the alkynylplatinum(II) terpyridine and other related cyclometalated platinum(II) complexes, with functionalities that can self-assemble into metallogels (27–31), liquid crystals (32, 33), and other different molecular architectures, such as hairpin conformation (34), helices (35–38), nanostructures (39–45), and molecular tweezers (46, 47), as well as having a wide range of applications in molecular recognition (48–52), biomolecular labeling (48–52), and materials science (53, 54). Recently, metal-containing amphiphiles have also emerged as a building block for supramolecular architectures (42–44, 55–59). Their self-assembly has always been found to yield different molecular architectures with unprecedented complexity through the multiple noncovalent interactions on the introduction of external stimuli (42–44, 55–59).Helical architecture is one of the most exciting self-assembled morphologies because of the uniqueness for the functional and topological properties (60–69). Helical ribbons composed of amphiphiles, such as diacetylenic lipids, glutamates, and peptide-based amphiphiles, are often precursors for the growth of tubular structures on an increase in the width or the merging of the edges of ribbons (64, 65). Recently, the optimization of nanotube formation vs. helical nanostructures has aroused considerable interests and can be achieved through a fine interplay of the influence on the amphiphilic property of molecules (66), choice of counteranions (67, 68), or pH values of the media (69), which would govern the self-assembly of molecules into desirable aggregates of helical ribbons or nanotube scaffolds. However, a precise control of supramolecular morphology between helical ribbons and nanotubes remains challenging, particularly for the polycyclic aromatics in the field of molecular assembly (64–69). Oligo(para-phenylene ethynylene)s (OPEs) with solely π−π stacking interactions are well-recognized to self-assemble into supramolecular system of various nanostructures but rarely result in the formation of tubular scaffolds (70–73). In view of the rich photophysical properties of square-planar d⁸ platinum(II) systems and their propensity toward formation of directional Pt···Pt interactions in distinctive morphologies (27–31, 39–45), it is anticipated that such directional and noncovalent metal−metal interactions might be capable of directing or dictating molecular ordering and alignment to give desirable nanostructures of helical ribbons or nanotubes in a precise and controllable manner.Herein, we report the design and synthesis of mono- and dinuclear alkynylplatinum(II) terpyridine complexes containing hydrophilic OPEs with two 3,6,9-trioxadec-1-yloxy chains. The mononuclear alkynylplatinum(II) terpyridine complex with amphiphilic property is found to show a strong tendency toward the formation of supramolecular structures on diffusion of diethyl ether in dichloromethane or dimethyl sulfoxide (DMSO) solution. Interestingly, additional end-capping with another platinum(II) terpyridine moiety of various steric bulk at the terminal alkyne would result in nanotubes or helical ribbons in the self-assembly process. To the best of our knowledge, this finding represents the first example of the utilization of the steric bulk of the moieties, which modulates the formation of directional metal−metal interactions to precisely control the formation of nanotubes or helical ribbons in the self-assembly process. Application of the nucleation–elongation model into this assembly process by UV-visible (UV-vis) absorption spectroscopic studies has elucidated the nature of the molecular self-assembly, and more importantly, it has revealed the role of metal−metal interactions in the formation of these two types of nanostructures.     

Soil biodiversity and soil community composition determine ecosystem multifunctionality

Biodiversity loss has become a global concern as evidence accumulates that it will negatively affect ecosystem services on which society depends. So far, most studies have focused on the ecological consequences of above-ground biodiversity loss; yet a large part of Earth’s biodiversity is literally hidden below ground. Whether reductions of biodiversity in soil communities below ground have consequences for the overall performance of an ecosystem remains unresolved. It is important to investigate this in view of recent observations that soil biodiversity is declining and that soil communities are changing upon land use intensification. We established soil communities differing in composition and diversity and tested their impact on eight ecosystem functions in model grassland communities. We show that soil biodiversity loss and simplification of soil community composition impair multiple ecosystem functions, including plant diversity, decomposition, nutrient retention, and nutrient cycling. The average response of all measured ecosystem functions (ecosystem multifunctionality) exhibited a strong positive linear relationship to indicators of soil biodiversity, suggesting that soil community composition is a key factor in regulating ecosystem functioning. Our results indicate that changes in soil communities and the loss of soil biodiversity threaten ecosystem multifunctionality and sustainability.It has long been recognized that biodiversity can be the mechanism behind the performance of an ecosystem, particularly in communities of above-ground organisms (1–5). In soils below ground, however, the functioning of biodiversity is not well understood (6). Soils are highly diverse. It has been estimated that 1 g of soil contains up to 1 billion bacteria cells consisting of tens of thousands of taxa, up to 200 m fungal hyphae, and a wide range of mites, nematodes, earthworms, and arthropods (7, 8). This vast and hidden diversity contributes to the total terrestrial biomass and is intimately linked to above-ground biodiversity (9, 10).In recent years several studies have shown that anthropogenic activities, such as agricultural intensification and land use change, reduce microbial and faunal abundance and the overall diversity of soil organisms (11–13). This has triggered increasing concern that reduced biodiversity in soils may impair numerous ecosystem functions, such as nutrient acquisition by plants and the cycling of resources between above- and below-ground communities (6, 11, 13, 14). However, to date research has largely focused on the effects of specific groups of organisms, such as soil microbes (15, 16), mycorrhizal fungi (17, 18), and soil fauna (19, 20), or on large-scale correlative analysis in the field (13). However, soil organisms interact within complex food webs, and therefore changes in diversity within one trophic group or functional guild may alter the abundance, diversity, and functioning of another (21, 22). Hence, it is important to know how changes in soil biodiversity and the simplification of the soil community composition influences ecosystem functioning. However, whether reductions of biodiversity in soil communities have consequences for the overall performance of an ecosystem remains unresolved. Moreover, recent studies show that above-ground plant diversity influences multiple ecosystem functions, defined as ecosystem multifunctionality (23). However, it is still unclear whether ecosystem multifunctionality is likewise influenced by soil biodiversity.Here we manipulated soil biodiversity and soil community composition in model grassland microcosms simulating European grassland. We tested whether changes in soil biodiversity and soil community composition influenced multiple ecosystem functions. To manipulate soil biodiversity and soil community composition, we inoculated the grassland microcosms with different soil communities. The soil inoculum was prepared by fractionating soil communities according to size, using filters of decreasing mesh size (19). This method reduces the abundance of different groups of soil organisms at different mesh sizes, thus altering the community composition and the overall diversity of soil organisms simultaneously (19). To maintain the different soil community treatments and to prevent microbial contamination, we maintained the communities in self-contained microcosms in which we could restrict external contamination (24). Additionally, the experiment was repeated and performed for a longer period to confirm initial results and include additional measures on ecosystem characteristics. We hypothesized that soil biodiversity loss reduces ecosystem functioning and multifunctionality. Specifically, we hypothesized that plant diversity, decomposition, and the recycling of nutrients is impaired when the diversity and abundance of various groups of soil biota (e.g., fungi, mycorrhizal fungi, bacteria, and nematodes) are reduced.     

Insect capa neuropeptides impact desiccation and cold tolerance

The success of insects is linked to their impressive tolerance to environmental stress, but little is known about how such responses are mediated by the neuroendocrine system. Here we show that the capability (capa) neuropeptide gene is a desiccation- and cold stress-responsive gene in diverse dipteran species. Using targeted in vivo gene silencing, physiological manipulations, stress-tolerance assays, and rationally designed neuropeptide analogs, we demonstrate that the Drosophila melanogaster capa neuropeptide gene and its encoded peptides alter desiccation and cold tolerance. Knockdown of the capa gene increases desiccation tolerance but lengthens chill coma recovery time, and injection of capa peptide analogs can reverse both phenotypes. Immunohistochemical staining suggests that capa accumulates in the capa-expressing Va neurons during desiccation and nonlethal cold stress but is not released until recovery from each stress. Our results also suggest that regulation of cellular ion and water homeostasis mediated by capa peptide signaling in the insect Malpighian (renal) tubules is a key physiological mechanism during recovery from desiccation and cold stress. This work augments our understanding of how stress tolerance is mediated by neuroendocrine signaling and illustrates the use of rationally designed peptide analogs as agents for disrupting protective stress tolerance.All organisms live in variable environments, and the ability to adapt to change, via either evolution or phenotypic plasticity, is critical for survival. Insects are ectotherms with high surface area to volume ratios; maintaining water balance and tolerating temperature fluctuations thus are essential adaptations. In desiccating environments, a key mechanism used by insects to maintain water balance is to reduce the rate of water loss (1, 2). In low-temperature environments insects face both chilling and low availability of water, thus requiring that they be both cold and desiccation tolerant (3). Both cold and desiccation stress result in decreased hemolymph volume and increased hemolymph osmolarity (4), so it is reasonable to expect mechanistic overlap between these stresses. Indeed, similar molecular mechanisms, including calcium signaling pathways, appear to modulate cold and desiccation responses (5, 6). Several studies have shown that freeze-tolerant insects can improve their cold tolerance in response to a mild desiccation stress (7–9), and artificial selection for desiccation tolerance in Drosophila melanogaster impacts the ability to recover from chill coma (10).Recent work has demonstrated that disrupted ion and water gradients between the insect gut and hemocoel contribute to low-temperature injury and that osmotic balance must be restored following exposure to cold (11–13). Ion and water balance in insects is regulated by the balance between excretion by the Malpighian tubules and absorption by the midgut and hindgut/rectum (14). Insect renal (Malpighian) tubules move fluid at the highest rates observed in biology and play key roles in transport and excretion of ions and water via transporters and water channels (15). Given the role of Malpighian tubules in osmoregulation, it is possible that tubule epithelia play additional, still undefined, roles in cold tolerance, in addition to those described for gut (16).In arid environments, cuticular and respiratory water losses are the main routes of water loss in Drosophila species (17). Desiccation in drosophilids also is accompanied by changes in the expression of genes associated with environmental sensing and cuticular structure (18), and one study has shown that selection for desiccation-tolerance is linked to polymorphisms in Malpighian tubule ion transport genes (19). The latter observation thus implicates tubule function in abiotic stress tolerance, providing a physiological link between desiccation and cold tolerance via ion- and water-transport mechanisms.Furthermore, although a potential role for the CNS in cold tolerance has been suggested (20), little is known about the control mechanisms that govern physiological responses to cold tolerance in insects. Such control mechanisms could occur via neuroendocrine signaling, in which Malpighian tubule function may act as an integrating physiological process for desiccation and cold tolerance, especially because insect osmoregulation is subject to highly sophisticated endocrine control, and several families of neuropeptides regulate diuresis (21). Among these are the capa peptides encoded by the capability (capa) neuropeptide gene (22). Capa peptides are distributed throughout the Insecta (23), including crop pests and disease vectors. In dipteran insects, capa is diuretic, acting on the Malpighian tubules to modulate cell-signaling and ion-transport pathways (24). CapaR, the G protein-coupled receptor for the capa peptides, is localized exclusively in tubule principal cells, and we have shown previously that targeted knockdown of capaR increases whole-fly survival under desiccation stress caused by reduced capa-stimulated diuresis (25). Capa/capaR signaling is functionally conserved in the tubules of dipteran disease vector species including mosquitoes and tsetse flies (24) and is of increasing interest as a target for insect control through the design of peptide mimetic analogs (26). Such agents overcome the inherent limitations of peptide physicochemical characteristics and increase their therapeutic potential, because blocking or overstimulating insect neuropeptide receptors may lead to reduction of pest fitness and/or death (27).Here, using a combination of molecular genetics, physiology, and synthetic peptide mimetic analogs, we show that tolerance to desiccation and cold in D. melanogaster are dramatically impacted by capa peptide signaling. Furthermore, we provide data suggesting a key novel physiological role for Malpighian tubules in cold stress survival.     

Potentiation of cytotoxic chemotherapy by growth hormone-releasing hormone agonists

The dismal prognosis of malignant brain tumors drives the development of new treatment modalities. In view of the multiple activities of growth hormone-releasing hormone (GHRH), we hypothesized that pretreatment with a GHRH agonist, JI-34, might increase the susceptibility of U-87 MG glioblastoma multiforme (GBM) cells to subsequent treatment with the cytotoxic drug, doxorubicin (DOX). This concept was corroborated by our findings, in vivo, showing that the combination of the GHRH agonist, JI-34, and DOX inhibited the growth of GBM tumors, transplanted into nude mice, more than DOX alone. In vitro, the pretreatment of GBM cells with JI-34 potentiated inhibitory effects of DOX on cell proliferation, diminished cell size and viability, and promoted apoptotic processes, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide proliferation assay, ApoLive-Glo multiplex assay, and cell volumetric assay. Proteomic studies further revealed that the pretreatment with GHRH agonist evoked differentiation decreasing the expression of the neuroectodermal stem cell antigen, nestin, and up-regulating the glial maturation marker, GFAP. The GHRH agonist also reduced the release of humoral regulators of glial growth, such as FGF basic and TGFβ. Proteomic and gene-expression (RT-PCR) studies confirmed the strong proapoptotic activity (increase in p53, decrease in v-myc and Bcl-2) and anti-invasive potential (decrease in integrin α3) of the combination of GHRH agonist and DOX. These findings indicate that the GHRH agonists can potentiate the anticancer activity of the traditional chemotherapeutic drug, DOX, by multiple mechanisms including the induction of differentiation of cancer cells.Glioblastoma multiforme (GBM) is one of the most aggressive human cancers, and the afflicted patients inevitably succumb. The dismal outcome of this malignancy demands great efforts to find improved methods of treatment (1). Many compounds have been synthesized in our laboratory in the past few years that have proven to be effective against diverse malignant tumors (2–14). These are peptide analogs of hypothalamic hormones: luteinizing hormone-releasing hormone (LHRH), growth hormone-releasing hormone (GHRH), somatostatin, and analogs of other neuropeptides such as bombesin and gastrin-releasing peptide. The receptors for these peptides have been found to be widely distributed in the human body, including in many types of cancers (2–14). The regulatory functions of these hypothalamic hormones and other neuropeptides are not confined to the hypothalamo–hypophyseal system or, even more broadly, to the central nervous system (CNS). In particular, GHRH can induce the differentiation of ovarian granulosa cells and other cells in the reproductive system and function as a growth factor in various normal tissues, benign tumors, and malignancies (2–4, 6, 11, 14–18). Previously, we also reported that antagonistic cytototoxic derivatives of some of these neuropeptides are able to inhibit the growth of several malignant cell lines (2–14).Our earlier studies showed that treatment with antagonists of LHRH or GHRH rarely effects complete regression of glioblastoma-derived tumors (5, 7, 10, 11). Previous studies also suggested that growth factors such as EGF or agonistic analogs of LHRH serving as carriers for cytotoxic analogs and functioning as growth factors may sensitize cancer cells to cytotoxic treatments (10, 19) through the activation of maturation processes. We therefore hypothesized that pretreatment with one of our GHRH agonists, such as JI-34 (20), which has shown effects on growth and differentiation in other cell lines (17, 18, 21, 22), might decrease the pluripotency and the adaptability of GBM cells and thereby increase their susceptibility to cytotoxic treatment.In vivo, tumor cells were implanted into athymic nude mice, tumor growth was recorded weekly, and final tumor mass was measured upon autopsy. In vitro, proliferation assays were used for the determination of neoplastic proliferation and cell growth. Changes in stem (nestin) and maturation (GFAP) antigen expression was evaluated with Western blot studies in vivo and with immunocytochemistry in vitro. The production of glial growth factors (FGF basic, TGFβ) was verified by ELISA. Further, using the Human Cancer Pathway Finder real-time quantitative PCR, numerous genes that play a role in the development of cancer were evaluated. We placed particular emphasis on the measurement of apoptosis, using the ApoLive-Glo Multiplex Assay kit and by detection of the expression of the proapoptotic p53 protein. This overall approach permitted the evaluation of the effect of GHRH agonist, JI-34, on the response to chemotherapy with doxorubicin.     

The evolution of self-control

Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.Since Darwin, understanding the evolution of cognition has been widely regarded as one of the greatest challenges for evolutionary research (1). Although researchers have identified surprising cognitive flexibility in a range of species (2–40) and potentially derived features of human psychology (41–61), we know much less about the major forces shaping cognitive evolution (62–71). With the notable exception of Bitterman’s landmark studies conducted several decades ago (63, 72–74), most research comparing cognition across species has been limited to small taxonomic samples (70, 75). With limited comparable experimental data on how cognition varies across species, previous research has largely relied on proxies for cognition (e.g., brain size) or metaanalyses when testing hypotheses about cognitive evolution (76–92). The lack of cognitive data collected with similar methods across large samples of species precludes meaningful species comparisons that can reveal the major forces shaping cognitive evolution across species, including humans (48, 70, 89, 93–98).To address these challenges we measured cognitive skills for self-control in 36 species of mammals and birds (Fig. 1 and Tables S1–S4) tested using the same experimental procedures, and evaluated the leading hypotheses for the neuroanatomical underpinnings and ecological drivers of variance in animal cognition. At the proximate level, both absolute (77, 99–107) and relative brain size (108–112) have been proposed as mechanisms supporting cognitive evolution. Evolutionary increases in brain size (both absolute and relative) and cortical reorganization are hallmarks of the human lineage and are believed to index commensurate changes in cognitive abilities (52, 105, 113–115). Further, given the high metabolic costs of brain tissue (116–121) and remarkable variance in brain size across species (108, 122), it is expected that the energetic costs of large brains are offset by the advantages of improved cognition. The cortical reorganization hypothesis suggests that selection for absolutely larger brains—and concomitant cortical reorganization—was the predominant mechanism supporting cognitive evolution (77, 91, 100–106, 120). In contrast, the encephalization hypothesis argues that an increase in brain volume relative to body size was of primary importance (108, 110, 111, 123). Both of these hypotheses have received support through analyses aggregating data from published studies of primate cognition and reports of “intelligent” behavior in nature—both of which correlate with measures of brain size (76, 77, 84, 92, 110, 124).Open in a separate windowFig. 1.A phylogeny of the species included in this study. Branch lengths are proportional to time except where long branches have been truncated by parallel diagonal lines (split between mammals and birds ∼292 Mya).With respect to selective pressures, both social and dietary complexities have been proposed as ultimate causes of cognitive evolution. The social intelligence hypothesis proposes that increased social complexity (frequently indexed by social group size) was the major selective pressure in primate cognitive evolution (6, 44, 48, 50, 87, 115, 120, 125–141). This hypothesis is supported by studies showing a positive correlation between a species’ typical group size and the neocortex ratio (80, 81, 85–87, 129, 142–145), cognitive differences between closely related species with different group sizes (130, 137, 146, 147), and evidence for cognitive convergence between highly social species (26, 31, 148–150). The foraging hypothesis posits that dietary complexity, indexed by field reports of dietary breadth and reliance on fruit (a spatiotemporally distributed resource), was the primary driver of primate cognitive evolution (151–154). This hypothesis is supported by studies linking diet quality and brain size in primates (79, 81, 86, 142, 155), and experimental studies documenting species differences in cognition that relate to feeding ecology (94, 156–166).Although each of these hypotheses has received empirical support, a comparison of the relative contributions of the different proximate and ultimate explanations requires (i) a cognitive dataset covering a large number of species tested using comparable experimental procedures; (ii) cognitive tasks that allow valid measurement across a range of species with differing morphology, perception, and temperament; (iii) a representative sample within each species to obtain accurate estimates of species-typical cognition; (iv) phylogenetic comparative methods appropriate for testing evolutionary hypotheses; and (v) unprecedented collaboration to collect these data from populations of animals around the world (70).Here, we present, to our knowledge, the first large-scale collaborative dataset and comparative analysis of this kind, focusing on the evolution of self-control. We chose to measure self-control—the ability to inhibit a prepotent but ultimately counterproductive behavior—because it is a crucial and well-studied component of executive function and is involved in diverse decision-making processes (167–169). For example, animals require self-control when avoiding feeding or mating in view of a higher-ranking individual, sharing food with kin, or searching for food in a new area rather than a previously rewarding foraging site. In humans, self-control has been linked to health, economic, social, and academic achievement, and is known to be heritable (170–172). In song sparrows, a study using one of the tasks reported here found a correlation between self-control and song repertoire size, a predictor of fitness in this species (173). In primates, performance on a series of nonsocial self-control control tasks was related to variability in social systems (174), illustrating the potential link between these skills and socioecology. Thus, tasks that quantify self-control are ideal for comparison across taxa given its robust behavioral correlates, heritable basis, and potential impact on reproductive success.In this study we tested subjects on two previously implemented self-control tasks. In the A-not-B task (27 species, n = 344), subjects were first familiarized with finding food in one location (container A) for three consecutive trials. In the test trial, subjects initially saw the food hidden in the same location (container A), but then moved to a new location (container B) before they were allowed to search (Movie S1). In the cylinder task (32 species, n = 439), subjects were first familiarized with finding a piece of food hidden inside an opaque cylinder. In the following 10 test trials, a transparent cylinder was substituted for the opaque cylinder. To successfully retrieve the food, subjects needed to inhibit the impulse to reach for the food directly (bumping into the cylinder) in favor of the detour response they had used during the familiarization phase (Movie S2).Thus, the test trials in both tasks required subjects to inhibit a prepotent motor response (searching in the previously rewarded location or reaching directly for the visible food), but the nature of the correct response varied between tasks. Specifically, in the A-not-B task subjects were required to inhibit the response that was previously successful (searching in location A) whereas in the cylinder task subjects were required to perform the same response as in familiarization trials (detour response), but in the context of novel task demands (visible food directly in front of the subject).     

Air-stable droplet interface bilayers on oil-infused surfaces

Droplet interface bilayers are versatile model membranes useful for synthetic biology and biosensing; however, to date they have always been confined to fluid reservoirs. Here, we demonstrate that when two or more water droplets collide on an oil-infused substrate, they exhibit noncoalescence due to the formation of a thin oil film that gets squeezed between the droplets from the bottom up. We show that when phospholipids are included in the water droplets, a stable droplet interface bilayer forms between the noncoalescing water droplets. As with traditional oil-submerged droplet interface bilayers, we were able to characterize ion channel transport by incorporating peptides into each droplet. Our findings reveal that droplet interface bilayers can function in ambient environments, which could potentially enable biosensing of airborne matter.Inspired by the pitcher plant (1), it was recently found that nano/microstructured hydrophobic substrates can be impregnated with lubricating fluids to create slippery surfaces for droplets (2–5). In contrast to dry, superomniphobic surfaces (6), lubricant-infused surfaces demonstrate stable liquid repellency at extreme pressures and temperatures (5, 7), are self-healing to mechanical damage (5), and their wettability and optical properties can be tuned (7, 8). A wide variety of applications are being explored for lubricant-infused surfaces, such as enhancing condensation heat transfer (9, 10), self-cleaning (11), fog harvesting (12), and omniphobic textiles (13), or minimizing ice nucleation (14, 15), ice adhesion (16, 17), and biofouling (18). Though previous studies have characterized the dynamics and possible wetting states of isolated droplets on lubricant-infused surfaces (5, 19–22), the interactive behavior of multiple droplets has not been reported.For the more traditional scenario of water droplets completely submerged in a reservoir of immiscible fluid, the physics of droplet–droplet interactions are well known. Water droplets submerged in crude oil can exhibit stable noncoalescence; this is because the crude oil contains surface-active components, such as resins and asphaltenes, which congregate at the droplet interfaces (23). When amphiphilic phospholipids are introduced into an oil reservoir containing water droplets, droplet interface bilayers (DIBs) can form between adjacent water droplets (24, 25). Recently, DIBs have emerged as an ideal model membrane system due to attractive features such as durability (26, 27), tunable size and curvature (28–30), deformability (31), facile electrical characterization of ion channels (32–35), the option to introduce asymmetry into the system (36), and droplet interchangeability (26, 32). In the absence of any stabilizing agents, water droplets colliding in an immiscible fluid will exhibit coalescence when their interaction time exceeds the time required to drain the film of fluid trapped between the droplets (37, 38). Droplet collision is typically controlled by applying a constant force (i.e., gravity) (39, 40), constant approach velocity (41, 42), or constant flow rate (43, 44). For experimental studies in pure oil baths, the time required for colliding water droplets to exhibit film rupture and coalesce typically ranges from 10⁻³ to 10² s, depending on parameters such as oil viscosity, droplet size, and the flow field (40, 42–44).Here, we show that water droplets in an ambient environment exhibit noncoalescence when colliding on an oil-infused surface, even in the absence of any surfactants. This phenomenon is due to the oil meniscus that surrounds each water droplet; when the oil menisci of neighboring droplets overlap, the menisci spontaneously merge together to minimize their surface energies and an oil film is squeezed upward to form a barrier between the colliding droplets. Though droplet coalescence will eventually occur due to film drainage, the time required for film rupture is several hours for moderate-viscosity [∼100 centistokes (cSt)] oils and is 1–3 orders of magnitude longer compared with droplets submerged in an oil bath (40, 42–44). These findings should refine the understanding of using oil-infused substrates for processes involving droplet–droplet interactions, such as condensation (9, 10) and fog harvesting (12).When incorporating amphiphilic phospholipids into the water droplets, we demonstrate that the thinning oil membrane between noncoalescing droplets gets replaced by a stable lipid bilayer, somewhat analogous to the formation of a black lipid membrane in an aperture painted with oil (45). To our knowledge, this is the first report of producing droplet interface bilayers in an ambient environment. We show that air-stable DIBs still allow for the robust electrical characterization of ion channels inserted in the lipid bilayer. Previously, it has been demonstrated that black lipid membranes or DIBs can be used for biosensing (46–50), light sensing (26), microscale biobatteries (26), electrical circuits (51, 52), and engineering tissue-like material (53). However, these suspended lipid bilayers have always been confined to fluid reservoirs (25, 45). We suggest that our air-stable DIBs will allow for an unprecedented degree of control regarding the fabrication, manipulation, transportation, and utilization of functional droplet networks.     

Structural interactions of a voltage sensor toxin with lipid membranes

Protein toxins from tarantula venom alter the activity of diverse ion channel proteins, including voltage, stretch, and ligand-activated cation channels. Although tarantula toxins have been shown to partition into membranes, and the membrane is thought to play an important role in their activity, the structural interactions between these toxins and lipid membranes are poorly understood. Here, we use solid-state NMR and neutron diffraction to investigate the interactions between a voltage sensor toxin (VSTx1) and lipid membranes, with the goal of localizing the toxin in the membrane and determining its influence on membrane structure. Our results demonstrate that VSTx1 localizes to the headgroup region of lipid membranes and produces a thinning of the bilayer. The toxin orients such that many basic residues are in the aqueous phase, all three Trp residues adopt interfacial positions, and several hydrophobic residues are within the membrane interior. One remarkable feature of this preferred orientation is that the surface of the toxin that mediates binding to voltage sensors is ideally positioned within the lipid bilayer to favor complex formation between the toxin and the voltage sensor.Protein toxins from venomous organisms have been invaluable tools for studying the ion channel proteins they target. For example, in the case of voltage-activated potassium (Kv) channels, pore-blocking scorpion toxins were used to identify the pore-forming region of the channel (1, 2), and gating modifier tarantula toxins that bind to S1–S4 voltage-sensing domains have helped to identify structural motifs that move at the protein–lipid interface (3–5). In many instances, these toxin–channel interactions are highly specific, allowing them to be used in target validation and drug development (6–8).Tarantula toxins are a particularly interesting class of protein toxins that have been found to target all three families of voltage-activated cation channels (3, 9–12), stretch-activated cation channels (13–15), as well as ligand-gated ion channels as diverse as acid-sensing ion channels (ASIC) (16–21) and transient receptor potential (TRP) channels (22, 23). The tarantula toxins targeting these ion channels belong to the inhibitor cystine knot (ICK) family of venom toxins that are stabilized by three disulfide bonds at the core of the molecule (16, 17, 24–31). Although conventional tarantula toxins vary in length from 30 to 40 aa and contain one ICK motif, the recently discovered double-knot toxin (DkTx) that specifically targets TRPV1 channels contains two separable lobes, each containing its own ICK motif (22, 23).One unifying feature of all tarantula toxins studied thus far is that they act on ion channels by modifying the gating properties of the channel. The best studied of these are the tarantula toxins targeting voltage-activated cation channels, where the toxins bind to the S3b–S4 voltage sensor paddle motif (5, 32–36), a helix-turn-helix motif within S1–S4 voltage-sensing domains that moves in response to changes in membrane voltage (37–41). Toxins binding to S3b–S4 motifs can influence voltage sensor activation, opening and closing of the pore, or the process of inactivation (4, 5, 36, 42–46). The tarantula toxin PcTx1 can promote opening of ASIC channels at neutral pH (16, 18), and DkTx opens TRPV1 in the absence of other stimuli (22, 23), suggesting that these toxin stabilize open states of their target channels.For many of these tarantula toxins, the lipid membrane plays a key role in the mechanism of inhibition. Strong membrane partitioning has been demonstrated for a range of toxins targeting S1–S4 domains in voltage-activated channels (27, 44, 47–50), and for GsMTx4 (14, 50), a tarantula toxin that inhibits opening of stretch-activated cation channels in astrocytes, as well as the cloned stretch-activated Piezo1 channel (13, 15). In experiments on stretch-activated channels, both the d- and l-enantiomers of GsMTx4 are active (14, 50), implying that the toxin may not bind directly to the channel. In addition, both forms of the toxin alter the conductance and lifetimes of gramicidin channels (14), suggesting that the toxin inhibits stretch-activated channels by perturbing the interface between the membrane and the channel. In the case of Kv channels, the S1–S4 domains are embedded in the lipid bilayer and interact intimately with lipids (48, 51, 52) and modification in the lipid composition can dramatically alter gating of the channel (48, 53–56). In one study on the gating of the Kv2.1/Kv1.2 paddle chimera (53), the tarantula toxin VSTx1 was proposed to inhibit Kv channels by modifying the forces acting between the channel and the membrane. Although these studies implicate a key role for the membrane in the activity of Kv and stretch-activated channels, and for the action of tarantula toxins, the influence of the toxin on membrane structure and dynamics have not been directly examined. The goal of the present study was to localize a tarantula toxin in membranes using structural approaches and to investigate the influence of the toxin on the structure of the lipid bilayer.     

Luminescence color switching of supramolecular assemblies of discrete molecular decanuclear gold(I) sulfido complexes

A series of discrete decanuclear gold(I) μ₃-sulfido complexes with alkyl chains of various lengths on the aminodiphosphine ligands, [Au₁₀{Ph₂PN(C_nH_2n+1)PPh₂}₄(μ₃-S)₄](ClO₄)₂, has been synthesized and characterized. These complexes have been shown to form supramolecular nanoaggregate assemblies upon solvent modulation. The photoluminescence (PL) colors of the nanoaggregates can be switched from green to yellow to red by varying the solvent systems from which they are formed. The PL color variation was investigated and correlated with the nanostructured morphological transformation from the spherical shape to the cube as observed by transmission electron microscopy and scanning electron microscopy. Such variations in PL colors have not been observed in their analogous complexes with short alkyl chains, suggesting that the long alkyl chains would play a key role in governing the supramolecular nanoaggregate assembly and the emission properties of the decanuclear gold(I) sulfido complexes. The long hydrophobic alkyl chains are believed to induce the formation of supramolecular nanoaggregate assemblies with different morphologies and packing densities under different solvent systems, leading to a change in the extent of Au(I)–Au(I) interactions, rigidity, and emission properties.Gold(I) complexes are one of the fascinating classes of complexes that reveal photophysical properties that are highly sensitive to the nuclearity of the metal centers and the metal–metal distances (1–59). In a certain sense, they bear an analogy or resemblance to the interesting classes of metal nanoparticles (NPs) (60–69) and quantum dots (QDs) (70–76) in that the properties of the nanostructured materials also show a strong dependence on their sizes and shapes. Interestingly, while the optical and spectroscopic properties of metal NPs and QDs show a strong dependence on the interparticle distances, those of polynuclear gold(I) complexes are known to mainly depend on the nuclearity and the internuclear separations of gold(I) centers within the individual molecular complexes or clusters, with influence of the intermolecular interactions between discrete polynuclear molecular complexes relatively less explored (34–38), and those of polynuclear gold(I) clusters not reported. Moreover, while studies on polynuclear gold(I) complexes or clusters are known (34–54), less is explored of their hierarchical assembly and nanostructures as well as the influence of intercluster aggregation on the optical properties (34–38). Among the gold(I) complexes, polynuclear gold(I) chalcogenido complexes represent an important and interesting class (44–51). While directed supramolecular assembly of discrete Au₁₂ (52), Au₁₆ (53), Au₁₈ (51), and Au₃₆ (54) metallomacrocycles as well as trinuclear gold(I) columnar stacks (34–38) have been reported, there have been no corresponding studies on the supramolecular hierarchical assembly of polynuclear gold(I) chalcogenido clusters.Based on our interests and experience in the study of gold(I) chalcogenido clusters (44–46, 51), it is believed that nanoaggegrates with interesting luminescence properties and morphology could be prepared by the judicious design of the gold(I) chalcogenido clusters. As demonstrated by our previous studies on the aggregation behavior of square-planar platinum(II) complexes (77–80) where an enhancement of the solubility of the metal complexes via introduction of solubilizing groups on the ligands and the fine control between solvophobicity and solvophilicity of the complexes would have a crucial influence on the factors governing supramolecular assembly and the formation of aggregates (80), introduction of long alkyl chains as solubilizing groups in the gold(I) sulfido clusters may serve as an effective way to enhance the solubility of the gold(I) clusters for the construction of supramolecular assemblies of novel luminescent nanoaggegrates.Herein, we report the preparation and tunable spectroscopic properties of a series of decanuclear gold(I) μ₃-sulfido complexes with alkyl chains of different lengths on the aminophosphine ligands, [Au₁₀{Ph₂PN(C_nH_2n+1)PPh₂}₄(μ₃-S)₄](ClO₄)₂ [n = 8 (1), 12 (2), 14 (3), 18 (4)] and their supramolecular assembly to form nanoaggregates. The emission colors of the nanoaggregates of 2−4 can be switched from green to yellow to red by varying the solvent systems from which they are formed. These results have been compared with their short alkyl chain-containing counterparts, 1 and a related [Au₁₀{Ph₂PN(C₃H₇)PPh₂}₄(μ₃-S)₄](ClO₄)₂ (45). The present work demonstrates that polynuclear gold(I) chalcogenides, with the introduction of appropriate functional groups, can serve as building blocks for the construction of novel hierarchical nanostructured materials with environment-responsive properties, and it represents a rare example in which nanoaggregates have been assembled with the use of discrete molecular metal clusters as building blocks.     

Self-assembly of amphiphilic Janus dendrimers into uniform onion-like dendrimersomes with predictable size and number of bilayers

A constitutional isomeric library synthesized by a modular approach has been used to discover six amphiphilic Janus dendrimer primary structures, which self-assemble into uniform onion-like vesicles with predictable dimensions and number of internal bilayers. These vesicles, denoted onion-like dendrimersomes, are assembled by simple injection of a solution of Janus dendrimer in a water-miscible solvent into water or buffer. These dendrimersomes provide mimics of double-bilayer and multibilayer biological membranes with dimensions and number of bilayers predicted by the Janus compound concentration in water. The simple injection method of preparation is accessible without any special equipment, generating uniform vesicles, and thus provides a promising tool for fundamental studies as well as technological applications in nanomedicine and other fields.Most living organisms contain single-bilayer membranes composed of lipids, glycolipids, cholesterol, transmembrane proteins, and glycoproteins (1). Gram-negative bacteria (2, 3) and the cell nucleus (4), however, exhibit a strikingly special envelope that consists of a concentric double-bilayer membrane. More complex membranes are also encountered in cells and their various organelles, such as multivesicular structures of eukaryotic cells (5) and endosomes (6), and multibilayer structures of endoplasmic reticulum (7, 8), myelin (9, 10), and multilamellar bodies (11, 12). This diversity of biological membranes inspired corresponding biological mimics. Liposomes (Fig. 1) self-assembled from phospholipids are the first mimics of single-bilayer biological membranes (13–16), but they are polydisperse, unstable, and permeable (14). Stealth liposomes coassembled from phospholipids, cholesterol, and phospholipids conjugated with poly(ethylene glycol) exhibit improved stability, permeability, and mechanical properties (17–20). Polymersomes (21–24) assembled from amphiphilic block copolymers exhibit better mechanical properties and permeability, but are not always biocompatible and are polydisperse. Dendrimersomes (25–28) self-assembled from amphiphilic Janus dendrimers and minidendrimers (26–28) have also been elaborated to mimic single-bilayer biological membranes. Amphiphilic Janus dendrimers take advantage of multivalency both in their hydrophobic and hydrophilic parts (23, 29–32). Dendrimersomes are assembled by simple injection (33) of a solution of an amphiphilic Janus dendrimer (26) in a water-soluble solvent into water or buffer and produce uniform (34), impermeable, and stable vesicles with excellent mechanical properties. In addition, their size and properties can be predicted by their primary structure (27). Amphiphilic Janus glycodendrimers self-assemble into glycodendrimersomes that mimic the glycan ligands of biological membranes (35). They have been demonstrated to be bioactive toward biomedically relevant bacterial, plant, and human lectins, and could have numerous applications in nanomedicine (20).Open in a separate windowFig. 1.Strategies for the preparation of single-bilayer vesicles and multibilayer onion-like vesicles.More complex and functional cell mimics such as multivesicular vesicles (36, 37) and multibilayer onion-like vesicles (38–40) have also been discovered. Multivesicular vesicles compartmentalize a larger vesicle (37) whereas multibilayer onion-like vesicles consist of concentric alternating bilayers (40). Currently multibilayer vesicles are obtained by very complex and time-consuming methods that do not control their size (39) and size distribution (40) in a precise way. Here we report the discovery of “single–single” (28) amphiphilic Janus dendrimer primary structures that self-assemble into uniform multibilayer onion-like dendrimersomes (Fig. 1) with predictable size and number of bilayers by simple injection of their solution into water or buffer.     

From the Cover: Why the proportion of transmission during early-stage HIV infection does not predict the long-term impact of treatment on HIV incidence

Antiretroviral therapy (ART) reduces the infectiousness of HIV-infected persons, but only after testing, linkage to care, and successful viral suppression. Thus, a large proportion of HIV transmission during a period of high infectiousness in the first few months after infection (“early transmission”) is perceived as a threat to the impact of HIV “treatment-as-prevention” strategies. We created a mathematical model of a heterosexual HIV epidemic to investigate how the proportion of early transmission affects the impact of ART on reducing HIV incidence. The model includes stages of HIV infection, flexible sexual mixing, and changes in risk behavior over the epidemic. The model was calibrated to HIV prevalence data from South Africa using a Bayesian framework. Immediately after ART was introduced, more early transmission was associated with a smaller reduction in HIV incidence rate—consistent with the concern that a large amount of early transmission reduces the impact of treatment on incidence. However, the proportion of early transmission was not strongly related to the long-term reduction in incidence. This was because more early transmission resulted in a shorter generation time, in which case lower values for the basic reproductive number (R₀) are consistent with observed epidemic growth, and R₀ was negatively correlated with long-term intervention impact. The fraction of early transmission depends on biological factors, behavioral patterns, and epidemic stage and alone does not predict long-term intervention impacts. However, early transmission may be an important determinant in the outcome of short-term trials and evaluation of programs.Recent studies have confirmed that effective antiretroviral therapy (ART) reduces the transmission of HIV among stable heterosexual couples (1–3). This finding has generated interest in understanding the population-level impact of HIV treatment on reducing the rate of new HIV infections in generalized epidemic settings (4). Research, including mathematical modeling (5–10), implementation research (11), and major randomized controlled trials (12–14), are focused on how ART provision might be expanded strategically to maximize its public health benefits (15, 16).One concern is that if a large fraction of HIV transmission occurs shortly after a person becomes infected, before the person can be diagnosed and initiated on ART, this will limit the potential impact of HIV treatment on reducing HIV incidence (9, 17, 18). Data suggest that persons are more infectious during a short period of “early infection” after becoming infected with HIV (19–22), although there is debate about the extent, duration, and determinants of elevated infectiousness (18, 23). The amount of transmission that occurs also will depend on patterns of sexual behavior and sexual networks (17, 24–27). There have been estimates for the contribution of early infection to transmission from mathematical models (7, 17, 21, 24–26) and phylogenetic analyses (28–31), but these vary widely, from 5% to above 50% (23).In this study, we use a mathematical model to quantify how the proportion of transmission that comes from persons who have been infected recently affects the impact of treatment scale-up on HIV incidence. The model is calibrated to longitudinal HIV prevalence data from South Africa using a Bayesian framework. Thus, the model accounts for not only the early epidemic growth rate highlighted in previous research (5, 9, 18), but also the heterogeneity and sexual behavior change to explain the peak and decline in HIV incidence observed in sub-Saharan African HIV epidemics (32, 33).The model calibration allows uncertainty about factors that determine the amount of early transmission, including the relative infectiousness during early infection, heterogeneity in propensity for sexual risk behavior, assortativity in sexual partner selection, reduction in risk propensity over the life course, and population-wide reductions in risk behavior in response to the epidemic (32, 33). This results in multiple combinations of parameter values that are consistent with the observed epidemic and variation in the amount of early transmission. We simulated the impact of a treatment intervention and report how the proportion of early transmission correlates with the reduction in HIV incidence from the intervention over the short- and long-term.     

Epileptic baboons have lower numbers of neurons in specific areas of cortex

Epilepsy is characterized by recurrent seizure activity that can induce pathological reorganization and alter normal function in neocortical networks. In the present study, we determined the numbers of cells and neurons across the complete extent of the cortex for two epileptic baboons with naturally occurring seizures and two baboons without epilepsy. Overall, the two epileptic baboons had a 37% average reduction in the number of cortical neurons compared with the two nonepileptic baboons. The loss of neurons was variable across cortical areas, with the most pronounced loss in the primary motor cortex, especially in lateral primary motor cortex, representing the hand and face. Less-pronounced reductions of neurons were found in other parts of the frontal cortex and in somatosensory cortex, but no reduction was apparent in the primary visual cortex and little in other visual areas. The results provide clear evidence that epilepsy in the baboon is associated with considerable reduction in the numbers of cortical neurons, especially in frontal areas of the cortex related to motor functions. Whether or not the reduction of neurons is a cause or an effect of seizures needs further investigation.Epilepsy is associated with structural changes in the cerebral cortex (e.g., refs. 1–6), and partial epilepsies (i.e., seizures originating from a brain region) may lead to loss of neurons (7) and altered connectivity (8). The cerebral cortex is a heterogeneous structure comprised of multiple sensory and motor information-processing systems (e.g., refs. 9 and 10) that vary according to their processing demands, connectivity (e.g., refs. 11 and 12), and intrinsic numbers of cells and neurons (13–16). Chronic seizures have been associated with progressive changes in the region of the epileptic focus and in remote but functionally connected cortical or subcortical structures (3, 17). Because areas of the cortex are functionally and structurally different, they may also differ in susceptibility to pathological changes resulting from epilepsy.The relationship between seizure activity and neuron damage can be difficult to study in humans. Seizure-induced neuronal damage can be convincingly demonstrated in animals using electrically or chemically induced status epilepticus (one continuous seizure episode longer than 5 min) to reveal morphometric (e.g., refs. 18 and 19) or histological changes (e.g., refs. 20 and 21). Subcortical brain regions are often studied for vulnerability to seizure-induced injury (21–27); however, a recent study by Karbowski et al. (28) observed reduction of neurons in cortical layers 5 and 6 in the frontal lobes of rats with seizures. Seizure-induced neuronal damage in the cortex has also been previously demonstrated in baboons with convulsive status epilepticus (29).The goal of the present study was to determine if there is a specific pattern of cell or neuron reduction across the functionally divided areas of the neocortex in baboons with epilepsy. Selected strains of baboons have been studied as a natural primate model of generalized epilepsy (30–36) that is analogous to juvenile myoclonic epilepsy in humans. The baboons demonstrate generalized myoclonic and tonic-clonic seizures, and they have generalized interictal and ictal epileptic discharges on scalp EEG. Because of their phylogenetic proximity to humans, baboons and other Old World monkeys share many cortical areas and other features of cortical organization with humans (e.g., refs. 9 and 10). Cortical cell and neuron numbers were determined using the flow fractionator method (37, 38) in epileptic baboon tissue obtained from the Texas Biomedical Research Institute, where a number of individuals develop generalized epilepsy within a pedigreed baboon colony (31–36). Our results reveal a regionally specific neuron reduction in the cortex of baboons with naturally occurring, generalized seizures.     

Application of desorption electrospray ionization mass spectrometry imaging in breast cancer margin analysis

Distinguishing tumor from normal glandular breast tissue is an important step in breast-conserving surgery. Because this distinction can be challenging in the operative setting, up to 40% of patients require an additional operation when traditional approaches are used. Here, we present a proof-of-concept study to determine the feasibility of using desorption electrospray ionization mass spectrometry imaging (DESI-MSI) for identifying and differentiating tumor from normal breast tissue. We show that tumor margins can be identified using the spatial distributions and varying intensities of different lipids. Several fatty acids, including oleic acid, were more abundant in the cancerous tissue than in normal tissues. The cancer margins delineated by the molecular images from DESI-MSI were consistent with those margins obtained from histological staining. Our findings prove the feasibility of classifying cancerous and normal breast tissues using ambient ionization MSI. The results suggest that an MS-based method could be developed for the rapid intraoperative detection of residual cancer tissue during breast-conserving surgery.Breast cancer is the most commonly diagnosed carcinoma in women in the United States and Western countries. Breast conservation surgery (BCS) has become the preferred treatment option for many women with early-stage breast cancer (1). BCS entails resection of the tumor, with a clean margin of normal tissue around it. Surgery is usually followed by radiation therapy. Results from seven large randomized prospective studies, with the largest two having over 20 y of follow-up, have shown equal survival when comparing BCS coupled with whole-breast radiation and mastectomy (2, 3).Normally, breast surgeons aim to remove a patient’s tumor, along with a rim of normal tissue that is free of cancer. Preoperative mammography, ultrasonography, or MRI may be used by the surgeon to guide adequate resection (4–6). Despite numerous improvements in imaging and surgical technique, the need for reexcision to achieve complete tumor resection in the United States typically ranges from 20–40% (7–15), and has been reported as being as high as 60% (16). The importance of reexcision is underscored by numerous studies, which have shown that incomplete resection of tumor and positive margins are associated with increased locoregional recurrence compared with negative margins (12, 17–20). Furthermore, the landmark meta-analysis performed by the Early Breast Cancer Trialists’ Collaborative Group (18, 21) directly linked local recurrence to survival, placing great emphasis on the surgeon’s role in minimizing local recurrence by obtaining adequate margins.Breast tumor reexcisions are accompanied by a number of undesirable problems: The completion of therapy is delayed, infection rates are increased, cost is increased, there can be a negative psychological impact on the patient, and there can be diminished aesthetic outcomes (22–24). The development of an intraoperative technique that allows the fast and accurate identification of residual tumor at surgical resection margins could decrease the reexcision rate, and therefore improve the care delivered to patients with cancer who are receiving BCS.To this end, multiple intraoperative methods have been explored, with various benefits as well as limitations. These methods include touch frozen section analysis (25), touch preparation cytology (26), specimen radiography (27, 28), rf spectroscopy (29, 30), Raman spectroscopy (31), radioguided occult lesion localization (32), near-IR fluorescence (33, 34), and high-frequency ultrasound (35–37). The intraoperative application of MRI, which has been successfully applied in brain surgery (38–42), is limited in its application in BCS. These limitations include MRI interpretation in the presence of acute surgical changes; lack of real-time imaging, requiring the interruption of surgery; and accurate localization of tumor based on images requiring development of fiducials (43–46).Mass spectrometry imaging (MSI) has been applied to investigate the molecular distribution of proteins, lipids, and metabolites without the use of labels (47, 48). In particular, the newly developed ambient ionization technique of desorption electrospray ionization (DESI) allows direct tissue analysis with little to no sample preparation (49, 50). Therefore, with the advantage of easy use, DESI-MSI has great potential in the application of intraoperative tumor assessment. The development of DESI-MSI enables the correlation of lipid distribution in two or three dimensions with tissue morphology (47, 51) and the distinction of cancerous from noncancerous tissues based on lipidomic information (52–54). Distinctive lipid profiles associated with different human cancers have been investigated by DESI-MSI (55–58). Moreover, the grades and subtypes of human brain tumors have been discriminated using this technique. Additionally, tumor margins have been delineated using DESI-MSI, and the results have been correlated with histopathological examination (59, 60).It has been reported that breast cancer demonstrates metabolic profiles that are distinct from those metabolic profiles found in normal breast tissue. This finding suggests a potential for using metabolite information for breast cancer diagnosis and tumor margin identification (61, 62). Here, we demonstrate an MS-based methodology for using lipidomic information to distinguish cancerous from noncancerous tissue and to delineate tumor boundaries.     

Predictive Value of Brain Natriuretic Peptides in Patients on Peritoneal Dialysis: Results from the ADEMEX Trial

Background and objectives: Natriuretic peptides have been suggested to be of value in risk stratification in dialysis patients. Data in patients on peritoneal dialysis remain limited.Design, setting, participants, & measurements: Patients of the ADEMEX trial (ADEquacy of peritoneal dialysis in MEXico) were randomized to a control group [standard 4 × 2L continuous ambulatory peritoneal dialysis (CAPD); n = 484] and an intervention group (CAPD with a target creatinine clearance ≥60L/wk/1.73 m²; n = 481). Natriuretic peptides were measured at baseline and correlated with other parameters as well as evaluated for effects on patient outcomes.Results: Control group and intervention group were comparable at baseline with respect to all measured parameters. Baseline values of natriuretic peptides were elevated and correlated significantly with levels of residual renal function but not with body size or diabetes. Baseline values of N-terminal fragment of B-type natriuretic peptide (NT-proBNP) but not proANP(1–30), proANP(31–67), or proANP(1–98) were independently highly predictive of overall survival and cardiovascular mortality. Volume removal was also significantly correlated with patient survival.Conclusions. NT-proBNP have a significant predictive value for survival of CAPD patients and may be of value in guiding risk stratification and potentially targeted therapeutic interventions.Plasma levels of cardiac natriuretic peptides are elevated in patients with chronic kidney disease, owing to impairment of renal function, hypertension, hypervolemia, and/or concomitant heart disease (1–7). Atrial natriuretic peptide (ANP) and particularly brain natriuretic peptide (BNP) levels are linked independently to left ventricular mass (3–5,8–16) and function (3,6–17) and predict total and cardiovascular mortality (1,3,8,10,12,18) as well as cardiac events (12,19). ANP and BNP decrease significantly during hemodialysis treatment but increase again during the interdialytic interval (1,2,4,6,7,14,17,20–23). Levels in patients on peritoneal dialysis (PD) have been found to be lower than in patients on hemodialysis (11,24–26), but the correlations with left ventricular function and structure are maintained in both types of dialysis modalities (11,15,27,28).The high mortality of patients on peritoneal dialysis and the failure of dialytic interventions to alter this mortality (29,30) necessitate renewed attention into novel methods of stratification and identification of patients at highest risk to be targeted for specific interventions. Cardiac natriuretic peptides are increasingly considered to fulfill this role in nonrenal patients. Evaluations of cardiac natriuretic peptides in patients on PD have been limited by small numbers (3,9,11,12,15,24–26) and only one study examined correlations between natriuretic peptide levels and outcomes (12). The PD population enrolled in the ADEMEX trial offered us the opportunity to evaluate cardiac natriuretic peptides and their value in predicting outcomes in the largest clinical trial ever performed on PD (29,30). It is hoped that such an evaluation would identify patients at risk even in the absence of overt clinical disease and hence facilitate or encourage interventions with salutary outcomes.