Evidence for synchronous cleavage of N-H and C-C bonds: bis(2,2￠-bipyridyl)copper(II) permanganate oxidation of cobalt(III) bound and unbound α-amino acids

Summary Oxidation of pentaamminecobalt(III) complexes of α-aminoacids by bis(2,2¢-bipyridyl) copper(II) permanganate in 50% HOAc-50% H₂O (v/v) aqueous acetic acid medium. This oxidation as a diagnostic tool to find out the fraction proceeding by synchronous cleavages of N-H and C-C bonds.     

Molecular Diffusion Measurement in Lipid Bilayers over Wide Concentration Ranges: A Comparative Study

Molecular diffusion in biological membranes is a determining factor in cell signaling and cell function. In the past few decades, three main fluorescence spectroscopy techniques have emerged that are capable of measuring molecular diffusion in artificial and biological membranes at very different concentration ranges and spatial resolutions. The widely used methods of fluorescence recovery after photobleaching (FRAP) and single‐particle tracking (SPT) can determine absolute diffusion coefficients at high (>100 μm^?2) and very low surface concentrations (single‐molecule level), respectively. Fluorescence correlation spectroscopy (FCS), on the other hand, is well‐suited for the intermediate concentration range of about 0.1–100 μm^?2. However, FCS in general requires calibration with a standard dye of known diffusion coefficient, and yields only relative measurements with respect to the calibration. A variant of FCS, z‐scan FCS, is calibration‐free for membrane measurements, but requires several experiments at different well‐controlled focusing positions. A recently established FCS method, electron‐multiplying charge‐coupled‐device‐based total internal reflection FCS (TIR‐FCS), referred to here as imaging TIR‐FCS (ITIR–FCS), is also independent of calibration standards, but to our knowledge no direct comparison between these different methods has been made. Herein, we seek to establish a comparison between FRAP, SPT, FCS, and ITIR–FCS by measuring the lateral diffusion coefficients in two model systems, namely, supported lipid bilayers and giant unilamellar vesicles.     

Atmospheric-Pressure Plasma Reduction of Metal Cation-Containing Polymer Films to Produce Electrically Conductive Nanocomposites by an Electrodiffusion Mechanism

We describe an atmospheric-pressure plasma process for the reduction of metal cation-containing polymer films to form electrically conductive patterns. Thin films of poly(acrylic) acid (PAA) containing silver ions (Ag⁺) were prepared by mixing the polymer with silver nitrate (AgNO₃) in solution to produce a cross-linked precipitate, homogenizing, and depositing onto a substrate by doctor’s blade. Exposing the Ag–PAA films to a scanning microplasma resulted in reduction of the bulk dispersed Ag⁺ in a desired pattern at the film surface. The processed films were characterized by scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and current–voltage measurements. The resistances of the patterned features were found to depend on the thickness of the films, the microplasma scan rate, residual solvent in the film, and electric field created between the microplasma and the substrate. Together these results show that the formation of conductive features occurs via an electrodiffusion process where Ag⁺ diffuses from the film bulk to the surface to be reduced by the microplasma.     

Mass Spectrometry Based Mechanistic Insights into Formation of Tris Conjugates: Implications on Protein Biopharmaceutics

We present here extensive mass spectrometric studies on the formation of a Tris conjugate with a therapeutic monoclonal antibody. The results not only demonstrate the reactive nature of the Tris molecule but also the sequence and reaction conditions that trigger this reactivity. The results corroborate the fact that proteins are, in general, prone to conjugation and/or adduct formation reactions and any modification due to this essentially leads to formation of impurities in a protein sample. Further, the results demonstrate that the conjugation reaction happens via a succinimide intermediate and has sequence specificity. Additionally, the data presented in this study also shows that the Tris formation is produced in-solution and is not an in-source phenomenon. We believe that the facts given here will open further avenues on exploration of Tris as a conjugating agent as well as ensure that the use of Tris or any ionic buffer in the process of producing a biopharmaceutical drug is monitored closely for the presence of such conjugate formation.

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Spinodal decomposition in a model colloid-polymer mixture in microgravity

We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.     

Thermal degradation of pentaerythritol phosphate alcohol

Intumescent material, 2,6,7-trioxa-1-phosphabicyclo-[2,2,2]-octane-4-methanol phosphate (PEPA), is synthesized and characterized using FTIR, ¹HNMR and ¹³CNMR. The degradation properties of PEPA are studied by employing TG and TG?CMS technique. The activation energies for the degradation process of PEPA are calculated by using TG curves obtained from multiple heating rates (Friedman, Kissinger?CAkahira?CSunose and Flynn?CWall?COzawa methods). The degradation that is occurring in the temperature region 307?C366?°C has the highest activation energy. Eventhough the calculated activation energies for the degradation differ depending on the approximation method employed, the trend in variation of activation energy for degradation is similar. Single ion monitoring technique proved the evolution of H₂O, CO/C₂H₄, HCHO, C₂H₅OH/HCOOH and trace amounts of C₂H₇O₃P and C₄H₉O₄P from the degrading PEPA. The thermal conductivity and stability of the char formed during the TG analysis are also discussed.     

A modified evidential methodology of identifying influential nodes in weighted networks

How to identify influential nodes in complex networks is still an open hot issue. In the existing evidential centrality (EVC), node degree distribution in complex networks is not taken into consideration. In addition, the global structure information has also been neglected. In this paper, a new Evidential Semi-local Centrality (ESC) is proposed by modifying EVC in two aspects. Firstly, the Basic Probability Assignment (BPA) of degree generated by EVC is modified according to the actual degree distribution, rather than just following uniform distribution. BPA is the generation of probability in order to model uncertainty. Secondly, semi-local centrality combined with modified EVC is extended to be applied in weighted networks. Numerical examples are used to illustrate the efficiency of the proposed method.     

On Growth Types of Quotients of Coxeter Groups by Parabolic Subgroups

The principal objects studied in this note are infinite, non-affine Coxeter groups W. A well-known result of de la Harpe asserts that such groups have exponential growth. We study the growth type of quotients of W by parabolic subgroups and by a certain class of reflection subgroups. Our main result is that these quotients have exponential growth as well.