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Luis E. Aguirre Alexandre de Oliveira David Se? Simon ?opar Pedro L. Almeida Miha Ravnik Maria Helena Godinho Slobodan ?umer 《Proceedings of the National Academy of Sciences of the United States of America》2016,113(5):1174-1179
Probing the surface morphology of microthin fibers such as naturally occurring biofibers is essential for understanding their structural properties, biological function, and mechanical performance. The state-of-the-art methods for studying the surfaces of biofibers are atomic force microscopy imaging and scanning electron microscopy, which well characterize surface geometry of the fibers but provide little information on the local interaction potential of the fibers with the surrounding material. In contrast, complex nematic fluids respond very well to external fields and change their optical properties upon such stimuli. Here we demonstrate that liquid crystal droplets deposited on microthin biofibers—including spider silk and cellulosic fibers—reveal characteristics of the fibers’ surface, performing as simple but sensitive surface sensors. By combining experiments and numerical modeling, different types of fibers are identified through the fiber-to-nematic droplet interactions, including perpendicular and axial or helicoidal planar molecular alignment. Spider silks align nematic molecules parallel to fibers or perpendicular to them, whereas cellulose aligns the molecules unidirectionally or helicoidally along the fibers, indicating notably different surface interactions. The nematic droplets as sensors thus directly reveal chirality of cellulosic fibers. Different fiber entanglements can be identified by depositing droplets exactly at the fiber crossings. More generally, the presented method can be used as a simple but powerful approach for probing the surface properties of small-size bioobjects, opening a route to their precise characterization.Natural microfilaments produced by plants, insects, or spiders are fascinating materials not just because of their specific properties such as wear resistance, elasticity, tensile strength, and toughness (1–5) but also because of their microorganization (6–9). Their macroscopic properties can match properties of materials like kevlar but are at the same time biocompatible and biodegradable (10). These fascinating macroscopic properties actually originate from bulk and surface properties of the fibers (1). The chemical composition of the threads combined with their morphology determines the final properties of the material (11–13). The mechanical properties of the spider fibers are determined by the existence of a lyotropic liquid crystalline phase, from which the threads are drawn (14). Such silks are known to include nanoscale networks of defects and cavities that yield surface structures notably dependent on the spider species (3). These differences do not affect much the mechanical performance of the fibers (1, 3, 5). From a technological perspective, many attempts have been made to reproduce these natural bionetworks (15–17). In fact cellulose-based fibers with few micrometers of diameter, produced by electrospinning, can also acquire different morphologies depending upon the processing conditions, giving diverse features of the final threads and mats (18). Therefore, probing the surface structure of the microfibers is crucial for a complete understanding of their individual and interthreaded properties.From another perspective, nematic complex fluids are materials which are inherently responsive to diverse external stimuli, notably including diverse surface interactions which in the literature are known as the surface anchoring (19). Being effectively elastic materials, the orientational order of nematics responds on long, typically micrometer scales (20–22), which results in a spatially varying birefringence that can be optically detected (23). Recently, it was demonstrated that glass fibers induce numerous defects in a well-aligned nematic liquid crystal cell and thus provide a simple illustration of topological phenomena (24). It is also known that liquid crystal droplets can considerably change their structure by the action of otherwise imperceptibly small external stimuli (21). Pierced nematic and chiral nematic droplets develop defects that can be controlled by the liquid crystal elasticity, chirality, and surface boundary conditions (25, 26) indicating exceptional sensitivity. Therefore, to generalize, putting nematics into contact with diverse surfaces (18, 27) can be used as a simple but very powerful technique to detect the surface properties of microobjects such as biological fibers.In this paper we demonstrate the surface morphology sensing of biorelevant fibers, including spider silk and cellulosic microfibers, by nematic droplets that are sprayed onto the fibers. Specifically, we explore the chiral and achiral nature of the fiber’s surface and the in-plane or perpendicular alignment fields the fibers impose on the nematic. Droplets with degenerate in-plane and perpendicular alignment of the nematic at their free surfaces are explored, combining experiments and numerical modeling, to allow for tuning of the sensing precision. Further, the entanglement sites of the fiber webs are explored, with the droplets deposited at the sites clearly revealing contact, noncontact, and entangled morphologies. 相似文献
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Vernica Frana Diniz Rocha Thiago Pereira Cavalcanti Jailton Azevedo Helena Ferreira Leal Giulyana Evelyn Oliveira Silva Allan Roberto Xavier Malheiros Ledilce Almeida Ataide Jos Admiro Lima Filho Antonio Raimundo Pinto Almeida Nadia de Andrade Khouri Mitermayer Galvo Reis Joice Neves Reis 《The American journal of tropical medicine and hygiene》2021,104(3):848
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Amgalan Anar Maher Alexander S. Ghosh Satyaki Chui Helena C. Bogdan Paul Irimia Andrei 《Age (Dordrecht, Netherlands)》2022,44(5):2509-2525
GeroScience - Adults aged 60 and over are most vulnerable to mild traumatic brain injury (mTBI). Nevertheless, the extent to which chronological age (CA) at injury affects TBI-related brain aging... 相似文献
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Sanna Matilainen Pirjo Isohanni Liliya Euro Tuula L?nnqvist Helena Pihko Tero Kivel? Sakari Knuutila Anu Suomalainen 《European journal of human genetics : EJHG》2015,23(3):325-330
Mutations in SUCLA2, encoding the ß-subunit of succinyl-CoA synthetase of Krebs cycle, are one cause of mitochondrial DNA depletion syndrome. Patients have been reported to have severe progressive childhood-onset encephalomyopathy, and methylmalonic aciduria, often leading to death in childhood. We studied two families, with children manifesting with slowly progressive mitochondrial encephalomyopathy, hearing impairment and transient methylmalonic aciduria, without mtDNA depletion. The other family also showed dominant inheritance of bilateral retinoblastoma, which coexisted with mitochondrial encephalomyopathy in one patient. We found a variant in SUCLA2 leading to Asp333Gly change, homozygous in one patient and compound heterozygous in one. The latter patient also carried a deletion of 13q14 of the other allele, discovered with molecular karyotyping. The deletion spanned both SUCLA2 and RB1 gene regions, leading to manifestation of both mitochondrial disease and retinoblastoma. We made a homology model for human succinyl-CoA synthetase and used it for structure–function analysis of all reported pathogenic mutations in SUCLA2. On the basis of our model, all previously described mutations were predicted to result in decreased amounts of incorrectly assembled protein or disruption of ADP phosphorylation, explaining the severe early lethal manifestations. However, the Asp333Gly change was predicted to reduce the activity of the otherwise functional enzyme. On the basis of our findings, SUCLA2 mutations should be analyzed in patients with slowly progressive encephalomyopathy, even in the absence of methylmalonic aciduria or mitochondrial DNA depletion. In addition, an encephalomyopathy in a patient with retinoblastoma suggests mutations affecting SUCLA2.Mitochondrial diseases are caused by genetic defects in nuclear or mitochondrial DNA (mtDNA) that disrupt function of the respiratory chain, compromising the synthesis of ATP. Most childhood-onset phenotypes are caused by autosomal recessive mutations in nuclear-encoded mitochondrial proteins. Mitochondrial diseases can manifest at any age, with almost any symptom, in almost any tissue, although the tissues with the largest dependence on oxidative energy supply, such as the central nervous system, sensory organs and skeletal muscle,1 are most commonly affected. The wide clinical and genetic heterogeneity with overlapping phenotypes makes the diagnostics of mitochondrial diseases challenging.2mtDNA depletion syndrome is associated with many clinical phenotypes and has a variable genetic background. It can be caused by several nuclear genes, which typically impair mtDNA replication, repair or nucleotide synthesis.3 One of these genes is SUCLA2, encoding the β-subunit of the Krebs cycle enzyme ADP-forming succinyl-CoA synthetase (SCS-A). SCS catalyzes the reversible conversion of succinyl-CoA to succinate, accompanied by substrate-level phosphorylation of ADP or GDP.4 The enzyme is a heterodimer composed of a catalytic α-subunit, encoded by SUCLG1 and a β-subunit that determines the enzymes'' substrate specificity for either ADP (SUCLA2) or GDP (SUCLG2). SCS is widely expressed in mammalian tissues, with predominance of either the ADP- or GDP-forming form in each tissue. SUCLG1 is ubiquitously expressed, whereas expression of SUCLA2 dominates in catabolic tissues, in which the main source of energy is ATP, such as the brain, and is induced in heart and skeletal muscle.4, 5 Patients with SUCLA2 mutations typically have progressive childhood-onset Leigh-like encephalomyopathy associated with dystonia, hypotonia, sensorineural hearing deficit, lesions of the basal ganglia, depletion of mtDNA and methylmalonic aciduria.3, 6 Over 20 patients and five different mutations in SUCLA2 have been described.6, 7, 8, 9, 10We report here molecular basis of mitochondrial encephalomyopathy, also combined with bilateral retinoblastoma, in patients with clinical symptoms or signs previously described in association with SUCLA2 mutations: encephalomyopathy with hearing deficit and methylmalonic aciduria. 相似文献
110.
Yuanyuan Feng Hannah McGowan Azin Semsar Hamid R. Zahiri Ivan M. George Timothy Turner Adrian Park Andrea Kleinsmith Helena M. Mentis 《International journal of computer assisted radiology and surgery》2018,13(9):1463-1472