01716nas a2200169 4500008004100000022001400041245015100055210006900206260007100275300001400346490000700360520099000367100003001357700001901387700001501406856012501421 2013 eng d a1525-779700aCharacterization of conformation and interaction of gene delivery vector polyethylenimine with phospholipid bilayer at different protonation state0 aCharacterization of conformation and interaction of gene deliver a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT a3759-37680 v143 a

Polyethylenimine (PEI) is a pH sensitive polymer possessing stretched and coiled conformation at low and high pH, respectively. It is an efficient gene delivery agent. Thus, the interaction of PEI with the biomembrane is very crucial to understand the gene delivery mechanism. In this report, we have investigated the structural properties of PEI and bilayer due to the interaction of PEI with lipid molecules. PEI has coil structure at high pH while at low pH it is elongated. The neutral PEI chain predominately settles itself at the bilayer water interface. We do not find any disruption or pore formation on the bilayer due to interaction of neutral PEI chain. PEI at low pH gets elongated due to electrostatic interaction between charges of the protonated sites. This protonated PEI chain interacts with bilayer membrane, which leads to formation of water/ion channel through the membrane. We have analyzed the structure of the channel and water dynamics along the channel.

1 aChoudhury, Chandan, Kumar1 aKumar, Abhinaw1 aRoy, Sudip uhttps://library.ncl.res.in/content/characterization-conformation-and-interaction-gene-delivery-vector-polyethylenimine-001870nas a2200229 4500008004100000022001400041245012800055210006900183260005700252300001200309490000700321520101000328653002601338653001801364653002301382653003401405100001601439700002001455700001501475700002301490856012701513 2013 eng d a1610-294000aCharacterization of the structures and dynamics of phosphoric acid doped benzimidazole mixtures: a molecular dynamics study0 aCharacterization of the structures and dynamics of phosphoric ac a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcJAN a109-1180 v193 a

Benzimidazole-based polymer membranes like poly(2,5-benzimidazole) (ABPBI) doped with phosphoric acid (PA) are electrolytes that exhibit high proton conductivity in fuel cells at elevated temperatures. The benzimidazole (BI) moiety is an important constituent of these membranes, so the present work was performed in order to achieve a molecular understanding of the BI-PA interactions in the presence of varying levels of the PA dopant, using classical molecular dynamics (MD) simulations. The various hydrogen-bonding interactions, as characterized based on structural properties and hydrogen-bond lifetime calculations, show that both BI and PA molecules exhibit dual proton-acceptor/donor functionality. An examination of diffusion coefficients showed that the diffusion of BI decreases with increasing PA uptake, whereas the diffusion of PA slightly increases. The hydrogen-bond lifetime calculations pointed to the existence of competitive hydrogen bonding between various sites in BI and PA.

10aDiffusion coefficient10aHydrogen bond10amolecular dynamics10aRadial distribution functions1 aMore, Minal1 aPahari, Swagata1 aRoy, Sudip1 aVenkatnathan, Arun uhttps://library.ncl.res.in/content/characterization-structures-and-dynamics-phosphoric-acid-doped-benzimidazole-mixtures-002476nas a2200205 4500008004100000022001400041245009900055210006900154260011000223300001400333490000700347520165000354100001702004700002402021700003002045700001502075700002602090700002702116856012702143 2015 eng d a1744-683X00aCompact polar moieties induce lipid-water systems to form discontinuous reverse micellar phase0 aCompact polar moieties induce lipidwater systems to form discont aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAY a5417-54240 v113 a

The role of molecular interactions in governing lipid mesophase organization is of fundamental interest and has technological implications. Herein, we describe an unusual pathway for monoolein/water reorganization from a bicontinuous mesophase to a discontinuous reverse micellar assembly, directed by the inclusion of polar macromolecules. This pathway is very different from those reported earlier, wherein the Fd3m phase formed only upon addition of apolar oils. Experiments and molecular dynamics simulations indicate that hydrophilic ternary additives capable of inducing discontinuous phase formation must (i) interact strongly with the monoolein head group and (ii) have a compact molecular architecture. We present a detailed investigation that contrasts a monoolein-water system containing polyamidoamine (PAMAM) dendrons with one containing their linear analogs. The Fd3m phase forms only on the addition of PAMAM dendrons but not their linear analogs. Thus, the dendritic architecture of PAMAM plays an important role in determining lipid mesophase behavior. Both dendrons and their linear analogs interact strongly with monoolein through their amine groups. However, while linear polymers adsorb and spread on monoolein, dendrons form aggregates that interact with the lipid. Dendrons induce formation of an intermediate reverse hexagonal phase, which subsequently restructures into the Fd3m phase. Finally, we demonstrate that other additives with compact structures that are known to interact with monoolein, such as branched polyethylenimine and polyhedral silsesquioxane cages, also induce the formation of the Fd3m phase.

1 aKumar, Manoj1 aPatil, Naganath, G.1 aChoudhury, Chandan, Kumar1 aRoy, Sudip1 aAmbade, Ashootosh, V.1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/compact-polar-moieties-induce-lipid-water-systems-form-discontinuous-reverse-micellar-001803nas a2200229 4500008004100000022001400041245012700055210006900182260000900251300000900260490000800269520100900277653001801286653001701304653002501321653001701346100002201363700002301385700001501408700001901423856013101442 2019 eng d a0301-010400aComparison of different water models for melting point calculation of methane hydrate using molecular dynamics simulations0 aComparison of different water models for melting point calculati cJAN  a6-140 v5163 a

Molecular dynamics simulation is a powerful tool to understand the gas hydrate nucleation, growth, and dissociation at molecular level. Prerequisite of super-cooling during gas hydrate formation and a certain degree of super-healing during melting shows significant hysteresis in the transition between solid and liquid state due to large nucleation barrier. Different water models quantitatively differ in their prediction of thermodynamic and kinetic properties of bulk water, including phase behaviour. The present work carries out a systematic investigation of the effect of the chosen water model on the phase behaviour, in particular, the decomposition of methane hydrate. Void-induced melting has been used to predict the melting point of methane hydrate using TIP4P/Ice, TIP4P/2005, TIP4P, and SPC/E water models. This method avoids the need for a predetermined interface for melting point calculations and thus may have its importance in identifying dissociation kinetics of bulk hydrate.

10adecomposition10aGas hydrates10aVoid-induced melting10aWater models1 aChoudhary, Nilesh1 aChakrabarty, Suman1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/comparison-different-water-models-melting-point-calculation-methane-hydrate-using-molecular