The origin of size-selective gas transport through polymers of intrinsic microporosity

An analysis of the diffusivity of light gases through Polymers of Intrinsic Microporosity (PIMs) shows that smaller H2 and He gas molecules have a transport mechanism that is similar to that of porous materials, whereas larger gas molecules, CH4, N2, O2 and CO2, show activated transport similar to that of conventional dense polymers. A typical and defining feature of PIMs, which differentiate their properties from other high free volume polymers, glassy polymers and rubbers, is the change in slope of the plot of the diffusion coefficient as a function of the gas diameter, with a stronger size-selective trend for the larger gas molecules than for He and H2. Deviation from this trend is observed for a polymer-gas combination with strong mutual affinity (i.e. an amine modified PIM with CO2). Molecular modelling shows that size selectivity in PIMs originates from the presence of bottlenecks between the individual free volume elements. For the latest generation of highly rigid PIMs, ageing studies show that diffusivity is differentially reduced for larger gas molecules, thus further enhancing their size-selectivity

Polymers of Intrinsic Microporosity Containing Troger Base for CO2 Capture

Properties of four polymers of intrinsic microporosity containing Tröger’s base units were assessed for CO2 capture experimentally and computationally. Structural properties included average pore size, pore size distribution, surface area, and accessible pore volume, whereas thermodynamic properties focused on density, CO2 sorption isotherms, and enthalpies of adsorption. It was found that the shape of the contortion site plays a more important role than the polymer density when assessing the capacity of the material, and that the presence of a Tröger base unit only slightly affects the amount adsorbed at low pressures, but it does not have any significant influence on the enthalpy of adsorption fingerprint. A comparison of the materials studied with those reported in the literature allowed us to propose a set of guidelines for the design of polymers for CO2 capture applications

3D-QSAR studies and shape based virtual screening for identification of novel hits to inhibit MbtA in Mycobacterium tuberculosis

Mycobacterium tuberculosis, the pathogen responsible for tuberculosis, uses various strategies to survive in a variety of host lesions. The re-emergence of multi-drug-resistant strains of M. tuberculosis underlines the necessity to discover new molecules. Inhibitors of aryl acid adenylating enzyme, MbtA, involved in siderophore biosynthesis in M. tuberculosis, are being explored as potential anti tubercular agents. In this study, we have used 3D-QSAR models and shape based virtual screening to identify novel MbtA inhibitors. 3D-QSAR studies were carried out on nucleoside bisubstrate derivatives. Both Comparative Molecular Field Analysis (r2 = .944 and r2 pred = .938) and Comparative Molecular Similarity Indices Analysis (r2 = .892 and r2 pred = .842) models, developed using Gasteiger charges with all fields, predicted efficiently. A total of 13 hits were identified as novel prospective inhibitors for MbtA by utilizing an insilico workflow. Out of 13 hits, five top ranked hits were used for further molecular dynamics studies to gain more insights about the stability of the complexes