The Relationship of Visiting Insect Diversity and Density of Valeriana jatamansi with Increasing Altitude in Western Himalaya

Proceedings of the National Academy of Sciences, India Section B: Biological Sciences - In light of the recent evidences that pollinators have a significant implication for maintenance of...     

Interaction and thermal studies on graphene oxide in NC/DEGDN/GO nanocomposites

Before considering the uses of graphene oxide (GO) in nitrate ester-based materials for performance and safety improvement, its interaction, compatibility and dispersion with the host matrices need to be well understood. This work addresses the interaction and dispersity of GO with nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN)-based nanocomposites. The GO and DEGDN were successfully synthesised and characterised. The NC/DEGDN proved to be a good hosting matrix for the dispersion of GO nanosheets. Analysis of atomic force microscopy (AFM) showed that the thicknesses of dispersed GO were in the range of 1–4 nm suggesting that the GO in the nanocomposite consists of 1–2 layers for a 0.5% w/w GO containing nanocomposite and 2–4 layers for a 0.75% w/w nanocomposite. ATR-FTIR spectroscopy analysis established red-shifting of 744 to 752 cm⁻¹ for the O–NO₂ bond stretching vibrations, indicating bond stabilization by donor electron from the GO. The Raman spectra analysis showed GO peaks blue-shifting and broadening which is attributed to hydrogen bonding interaction between GO sheets and –NO₂ groups. The activation energy of nitrate ester decomposition of NC/DEGDN/GO nanocomposites increases as a function of GO content from 167 kJ mol⁻¹ and reaches a maximum of 214 kJ mol⁻¹ for a 0.5% w/w GO loading. This suggests an improvement of the nitrate ester bond stability. These findings open a new direction to the application of GO in nitrate ester-based materials for increased stability, safety and shelf life.

Before considering the use of graphene oxide (GO) in nitrate ester-based materials for improved safety and performance its interaction, compatibility, and dispersion with the host matrices needs to be well understood.     

Effect of processor temperature on film dosimetry

Optical density (OD) of a radiographic film plays an important role in radiation dosimetry, which depends on various parameters, including beam energy, depth, field size, film batch, dose, dose rate, air film interface, postexposure processing time, and temperature of the processor. Most of these parameters have been studied for Kodak XV and extended dose range (EDR) films used in radiation oncology. There is very limited information on processor temperature, which is investigated in this study. Multiple XV and EDR films were exposed in the reference condition (d_max., 10 × 10 cm², 100 cm) to a given dose. An automatic film processor (X-Omat 5000) was used for processing films. The temperature of the processor was adjusted manually with increasing temperature. At each temperature, a set of films was processed to evaluate OD at a given dose. For both films, OD is a linear function of processor temperature in the range of 29.4–40.6°C (85–105°F) for various dose ranges. The changes in processor temperature are directly related to the dose by a quadratic function. A simple linear equation is provided for the changes in OD vs. processor temperature, which could be used for correcting dose in radiation dosimetry when film is used.     

Sorting of cadherin–catenin-associated proteins into individual clusters

The cytoplasmic tails of classical cadherins form a multiprotein cadherin–catenin complex (CCC) that constitutes the major structural unit of adherens junctions (AJs). The CCC in AJs forms junctional clusters, “E clusters,” driven by cis and trans interactions in the cadherin ectodomain and stabilized by α-catenin–actin interactions. Additional proteins are known to bind to the cytoplasmic region of the CCC. Here, we analyze how these CCC-associated proteins (CAPs) integrate into cadherin clusters and how they affect the clustering process. Using a cross-linking approach coupled with mass spectrometry, we found that the majority of CAPs, including the force-sensing protein vinculin, interact with CCCs outside of AJs. Accordingly, structural modeling shows that there is not enough space for CAPs the size of vinculin to integrate into E clusters. Using two CAPs, scribble and erbin, as examples, we provide evidence that these proteins form separate clusters, which we term “C clusters.” As proof of principle, we show, by using cadherin ectodomain monoclonal antibodies (mAbs), that mAb-bound E-cadherin forms separate clusters that undergo trans interactions. Taken together, our data suggest that, in addition to its role in cell–cell adhesion, CAP-driven CCC clustering serves to organize cytoplasmic proteins into distinct domains that may synchronize signaling networks of neighboring cells within tissues.

The core structural unit of adherens junctions (AJs), the cadherin–catenin complex (CCC), consists of four proteins—a classical cadherin (E-cadherin in epithelia), β-catenin, α-catenin, and p120-catenin (1–4). In the process of cell–cell adhesion, the CCC forms clusters driven by both extracellular and intracellular binding events (5–8). The clustering of cadherin molecules is essential to reinforce weak individual trans adhesive bonds (9–12). In addition, the continuous and fast reassembly of CCC clusters within AJs renders them both highly adhesive and yet flexible (7, 13). While the importance of CCC clustering in cell–cell adhesion was demonstrated more than two decades ago (14), many of the molecular events associated with clustering are still poorly understood. One critical question, which is the focus of this work, is the role of proteins that associate with the CCC, CCC-associated proteins (CAPs), and, in particular, how these proteins change the properties of CCC clusters.While several mechanisms for CCC clustering have been proposed (12), the best-characterized involves the formation of cis interaction between E-cadherin ectodomains. Cooperative cis and trans interactions arrange cadherin trans dimers into a paracrystalline lattice with a lateral intercadherin (center-to-center) spacing of ∼7 nm (15). The stability of these extracellular clusters is further enhanced by the binding of α-catenin to actin filaments (16–18). Accumulating data suggest that AJs consist of numerous such paracrystalline nanoclusters interspersed with less dense CCC regions (7, 15, 19–21). However, under certain conditions, cadherin clusters can be formed that do not seem to require the formation of ordered ectodomain lattices. For example, clusters are observed in cells expressing a cis interaction–incompetent cadherin mutant although they are less stable than wild-type paracrystalline clusters (20, 22). The underlying clustering mechanism in these cases is unclear.Here we identified CAPs using a cross-linking agent that only detects proteins up to about 1.5 nm from a target. We provide evidence that most of these CAPs interact with the CCCs outside of cadherin clusters. Our results indicate that CCC clusters that integrate CAPs (C clusters) have fundamentally different structures from the “canonical structures” constrained by cadherin cis interactions. We term the latter “E clusters” to indicate that they are driven by extracellular interactions. We found that two CAPs, scribble and erbin, produced a set of CCC clusters that are spatially distinct from E clusters and from one another. It then appears that C clusters have distinct properties that depend on those of the CAPs themselves. To establish proof of principle, we show that anti-cadherin monoclonal antibodies (mAbs), which, similar to CAPs, are too large to be compatible with an E-cluster lattice, generate distinct adhesive clusters. Taken together, our data show that CAPs are both able to spatially separate C from E clusters and form CAP-dependent C clusters that are separate from one another. In addition to their role in cell–cell adhesion, our results thus suggest that CCC clustering serves as a mechanism for organizing cellular proteins into distinct domains within cell–cell contacts.