@article {43796, title = {Partially bio-based poly(amide imide)s by polycondensation of aromatic diacylhydrazides based on lignin-derived phenolic acids and aromatic dianhydrides: synthesis, characterization, and computational studies}, journal = {Journal of Polymer Science Part A-Polymer Chemistry}, volume = {55}, year = {2017}, month = {NOV}, pages = {3636-3645}, type = {Article}, abstract = {

Two new bio-based diacylhydrazide monomers, namely, 4,4-(propane-1,3-diylbis(oxy))bis(3-methoxybenzohydrazide) and 4,4-(propane-1,3-diylbis(oxy))bis(3,5-dimethoxybenzohydrazide) were synthesized starting from lignin-derived phenolic acids, namely, vanillic acid and syringic acid. A series of poly(amide imide)s was synthesized by polycondensation of these diacylhydrazide monomers with commercially available aromatic dianhydrides. Poly(amide imide)s showed inherent viscosity in the range 0.44-0.56 dLg(-1) and exhibited good solubility in organic solvents. Poly(amide imide)s could be cast into transparent, flexible, and tough films from their N,N-dimethylacetamide solutions. Poly(amide imide)s showed 10\% weight loss in the temperature range 340-364 degrees C indicating their good thermal stability. Glass transition temperature (T-g) of poly(amide imides)s were measured by DSC and DMA which were in the range 201-223 degrees C and 214-248 degrees C, respectively. The T-g values of poly(amide imide)s were dependent on the number methoxy substituents on aromatic rings of diacylhydrazide monomers. Molecular dynamics simulation studies revealed that chain rigidity is the dominant factor for observed trends in T-g. (c) 2017 Wiley Periodicals, Inc.

}, keywords = {Biobased Polymers, Computational studies, Glass-transaction temperature, lignin, Monomers, Plant oils, Polyimide, Reneable resources, Renewable resources, Step-growth polymers, structure-property relations, Sustanaible Polymers, Thermal night, Thermosetting resins, Vanillin}, issn = {0887-624X}, doi = {10.1002/pola.28748}, author = {Kuhire, Sachin S. and Sharma, Pragati and Chakrabarty, Suman and Wadgaonkar, Prakash P.} } @article {46651, title = {Protonation-induced dynamic allostery in PDZ domain: evidence of perturbation-independent universal response network}, journal = {Journal of Physical Chemistry Letters}, volume = {11}, year = {2020}, month = {NOV }, pages = {9026-9031}, type = {Article}, abstract = {

Dynamic allostery is a relatively new paradigm where certain external perturbations may lead to modulation of conformational dynamics at a distant part of a protein without significant changes in the overall structure. While most well-characterized examples of dynamic allostery involve binding with other entities like small molecules, peptides, or nucleic acids, in this work we demonstrate that chemical modifications like protonation may lead to significant dynamical allosteric response in a PDZ domain protein. Tuning the protonation states of two histidine residues (H317 and H372), we identify the allosteric pathways responsible for the dynamic response. Interestingly, the same set of residues that constitute the allosteric response network upon ligand binding seem to be responsible for protonation-induced dynamic allostery. Thus, we propose the existence of an inherent universal response network in signaling proteins, where the same set of residues can respond to varying types of external perturbations in terms of rearrangement of hydrogen-bonded network and redistribution of electrostatic interaction energies.

}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.0c02885}, author = {Kumawat, Amit and Chakrabarty, Suman} }