02688nas a2200181   4500008004100000022001400041245012000055210006900175260011000244300001400354490000700368520191700375100001902292700002702311700001702338700002502355856012602380       2016                        eng d  a1463-907600aUnraveling origins of the heterogeneous curvature dependence of polypeptide interactions with carbon nanostructures0 aUnraveling origins of the heterogeneous curvature dependence of   aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a5910-59240 v183 a<p>Emerging nanotechnology has rapidly broadened interfacial prospects of biological molecules with carbon nanomaterials (CNs). A prerequisite for effectively harnessing such hybrid materials is a multifaceted understanding of their complex interfacial interactions as functions of the physico-chemical characteristics and the surface topography of the individual components. In this article, we address the origins of the curvature dependence of polypeptide adsorption on CN surfaces (CNSs), a phenomenon bearing an acute influence upon the behavior and activity of CN-protein conjugates. Our benchmark molecular dynamics (MD) simulations with the amphiphilic full-length amyloid beta (A beta) peptide demonstrate that protein adsorption is strongest on the concave (inner) CN-surface, weakest on the convex (outer) surface, and intermediary on the planar surface, in agreement with recent experimental reports. The curvature effects, however, are found to manifest non-uniformly between the amino acid subtypes. To understand the underlying interplay of the chemical nature of the amino acids and surface topography of the CNs, we performed high-level quantum chemical (QM) calculations with amino acid analogs (MA) representing their five prominent classes, and convex, concave and planar CN fragments. Molecular electrostatic potential maps reveal pronounced curvature dependence in the mixing of electron densities, and a resulting variance in the stabilization of the non-covalentty bound molecular complexes. Interestingly, our study revealed that the interaction trends of the high-level QM calculations were captured well by the empirical force field. The findings in this study have important bearing upon the design of carbon based bio-nanomaterials, and additionally, provide valuable insights into the accuracy of various computational techniques for probing non-bonded interfacial interactions.</p>1 aJana, Asis, K.1 aTiwari, Mrityunjay, K.1 aVanka, Kumar1 aSengupta, Neelanjana  uhttp://library.ncl.res.in/content/unraveling-origins-heterogeneous-curvature-dependence-polypeptide-interactions-carbon-001697nas a2200145   4500008004100000245009400041210006900135260000800204300001600212490000700228520117100235100001801406700001701424856011001441       2017                        eng d00aUnusual role of the aromatic solvent in single site Al(I) chemistry: insights from theory0 aUnusual role of the aromatic solvent in single site AlI chemistr  cJUL  a13957-139630 v233 aThe single site activation of strong σ bonds (such as that of H-H, P-H and N-H) remains a significant challenge in main group chemistry, with only a few cases reported to date. In this regard, recent exciting experiments done with Al(I) complexes hold significance, because they, too, have been seen to activate a variety of strong σ bonds. Such chemistry is generally seen to occur in aromatic solvents. The current computational studies with density functional theory (DFT) reveal the interesting reason for this: it is seen that an explicit aromatic solvent molecule acts as a catalyst by converting the Al(I) complex to Al(III) during the process. Different cases of σ bond activation by Al(I) complexes have been investigated and the efficiency for the H-X (X=H, NHtBu, PPh2) bond activation in the presence of an explicit benzene solvent molecule has been seen to be orders of magnitude higher than in its absence. The current work therefore reveals the chemistry of Al(I) complexes to be richer and more complex than realized to date, and shows it to be dependent on metal-solvent cooperativity, the first known example of its kind in main group chemistry.1 aJain, Shailja1 aVanka, Kumar  uhttp://library.ncl.res.in/content/unusual-role-aromatic-solvent-single-site-ali-chemistry-insights-theory01640nas a2200169   4500008004100000245014000041210006900181260000800250300001100258490000800269520097000277100002501247700002501272700001701297700002901314856012701343       2018                        eng d00aUnderstanding interactions between lignin and ionic liquids with experimental and theoretical studies during catalytic depolymerisation0 aUnderstanding interactions between lignin and ionic liquids with  cJUL  a98-1080 v3093 aCompared to H2SO4, Bronsted acidic ionic liquid (BAIL, [C3SO3HMIM][HSO4]) catalyzed depolymerization of lignin yielded higher concentration of low molecular weight products under mild conditions (120 degrees C) as proven by GC and GC-MS. To comprehend this disparity in catalytic activity among H2SO4 and BAIL (at similar H+ concentration), experimental techniques [1D(H-1) NMR, 2D(N-15/H-1 HMBC) NMR and RAMAN] have been employed. Based on these studies, it has been proven that the transfer of electron density from substrate to the electron deficient imidazolium ring via formation of hydrogen bond between -OH/OCH3 (substrate) and -N1C2H2N3-(cation) is possible, while the anion plays an important role. Further, density functional theory (DFT) calculations also corroborated this fact by showing a change in the bond angle and decrease in bond length (C-2-H-2 in imidazole), due to the presence of weak and strong hydrogen bonding between the substrate and IL.1 aSingh, Sandip, Kumar1 aBanerjee, Subhrashis1 aVanka, Kumar1 aDhepe, Paresh, Laxmikant  uhttp://library.ncl.res.in/content/understanding-interactions-between-lignin-and-ionic-liquids-experimental-and-theoretical01751nas a2200181   4500008004100000022001400041245008300055210006900138260000900207300001400216490000800230520115100238100002101389700002101410700002701431700001701458856009401475       2020                        eng d  a1089-563900aUnraveling the hidden role of the counteranion in ``cation in a cage'' systems0 aUnraveling the hidden role of the counteranion in cation in a ca  cOCT   a8040-80490 v1243 a<p>The current work showcases general principles at play in systems consisting of cations present inside molecular cages. Such systems, relevant to chemistry and biology, have been carefully investigated by computational methods. The important Ge(II)-encapsulating cage systems have been studied first. The very fact that such compounds exist appears highly unlikely, given the highly reactive nature of the Ge(II) dication. Our studies reveal what really occurs in solution when such complexes are formed: the Ge(II) dications are actually present as [Ge-X](+) (where X is the ``non-coordinating'' counterion employed in such systems) during entry and subsequent existence at the center of the cage. Hence, what is actually present is a ``pseudomonocation''. Interestingly, such pseudomonocation-encapsulated cages are seen to be equally relevant in systems of biological importance, such as for dicationic s block-based ionophores. In explaining such cases, the concept of ``isoionicity'' is introduced, demonstrating that the counterion-coordinated dications are isoionic with a monocation, such as Li(I), isolated in the same ionophore.</p>
1 aMukherjee, Anagh1 aGhule, Siddharth1 aTiwari, Mrityunjay, K.1 aVanka, Kumar  uhttp://library.ncl.res.in/content/unraveling-hidden-role-counteranion-cation-cage-systems01310nas a2200241   4500008004100000022001400041245004000055210003500095260000900130300001600139490000700155520067300162653002000835653000800855653001300863653002300876100002400899700001500923700001700938700002400955700001900979856007000998       2021                        eng d  a1433-785100aUnsymmetrical sp(2)-sp(3) disilenes0 aUnsymmetrical sp2sp3 disilenes  cSEP   a20706-207100 v603 aDisilenes with differently coordinated silicon atoms are not known. Here, we have shown the high yield synthesis of a range of disilenes (2-4 and 6) upon reaction of a hypersilyl silylene PhC(NtBu)(2)SiSi(SiMe3)(3) (1) with aliphatic chlorophosphines. The most striking characteristic of these disilenes is the presence of two differently coordinated Si atoms (one is three-coordinated, the other four-coordinated). The analogous reaction with Ph2PCl did not afford the desired disilene, but, surprisingly, led to the first tetraphosphinosilane (8). DFT calculations were performed to understand the bonding in disilenes and differences in reactivity of the complexes.10achlorophosphine10aDFT10adisilene10ahypersilylsilylene1 aBisai, Milan, Kumar1 aDas, Tamal1 aVanka, Kumar1 aGonnade, Rajesh, G.1 aSen, Sakya, S.  uhttp://library.ncl.res.in/content/unsymmetrical-sp2-sp3-disilenes