Ugi three-component reaction of alcohols,amines and isocyanides: A new approach to the synthesis of cyclic amidines

We have developed a novel, simple, efficient and one pot synthetic protocol for the synthesis of cyclic amidines via Ugi three-component reaction of alcohols, amines, and isocyanides.     

Thin-Layer Chromatographic Determination of Alpha-Amyrin in the Bark of Mallotus philippensis Lamk

JPC – Journal of Planar Chromatography – Modern TLC - A simple, precise, and accurate high-performance thin-layer chro-matographic method has been established for determination of...     

Sampling free energy surfaces as slices by combining umbrella sampling and metadynamics

Metadynamics (MTD) is a very powerful technique to sample high‐dimensional free energy landscapes, and due to its self‐guiding property, the method has been successful in studying complex reactions and conformational changes. MTD sampling is based on filling the free energy basins by biasing potentials and thus for cases with flat, broad, and unbound free energy wells, the computational time to sample them becomes very large. To alleviate this problem, we combine the standard Umbrella Sampling (US) technique with MTD to sample orthogonal collective variables (CVs) in a simultaneous way. Within this scheme, we construct the equilibrium distribution of CVs from biased distributions obtained from independent MTD simulations with umbrella potentials. Reweighting is carried out by a procedure that combines US reweighting and Tiwary–Parrinello MTD reweighting within the Weighted Histogram Analysis Method (WHAM). The approach is ideal for a controlled sampling of a CV in a MTD simulation, making it computationally efficient in sampling flat, broad, and unbound free energy surfaces. This technique also allows for a distributed sampling of a high‐dimensional free energy surface, further increasing the computational efficiency in sampling. We demonstrate the application of this technique in sampling high‐dimensional surface for various chemical reactions using ab initio and QM/MM hybrid molecular dynamics simulations. Further, to carry out MTD bias reweighting for computing forward reaction barriers in ab initio or QM/MM simulations, we propose a computationally affordable approach that does not require recrossing trajectories. © 2016 Wiley Periodicals, Inc.     

A Study on Deletion in Polymer Region of Amelogenin (Amel Y) Gene: Significant Importance in Sex Determination and Identification of Sexual Assault Perpetrator

Accurate gender determination is crucial in many scientific disciplines, especially in prenatal diagnosis of X-linked diseases and forensic investigations. Today, molecular techniques, especially typing for a length variation in the X–Y homologous amelogenin gene (AMEL X and AMEL Y), are used for gender assignation. This amelogenin is an integral part of most PCR multiplex kits for gender determination marker, but in 1998 there was a report of two normal males being typed as female with this marker. Subsequently, a small number of males with amelogenin deleted genes have been reported in various populations but little data are available characterizing these deletions. This review aims to explore possible relationships among the AMEL Y deleted samples and Y-chromosome microsatellite haplotypes. Also, attempts are made to determine the frequency of males with AMEL Y deleted gene in various countries across the globe. Although some studies have shown that males with AMEL Y deleted gene are extremely rare in most populations, typing an additional gender-determining locus should be considered in forensic investigations where the reference sample is of unknown gender.     

Nanoporous morphology of alumina films prepared by sol–gel dip coating method on alumina substrate

Nanoporous crack free alumina thin films were fabricated in two phases gamma (??) and alpha (??) by sol?Cgel dip coating method. The thickness of the mesoporous films was increased with binder by varying its concentration, and with increasing the number of coating. The porosity, pore size, surface area and phase were controlled by sintering temperature. Interconnected pore structure of 8?C15?nm diameter were successfully prepared by repeating the deposition several times. FESEM, BET, AFM and XRD techniques were employed for the microstructural characterization.     

Mistake in Hirsch's proof of the Brouwer Fixed Point Theorem

A mistake in Hirsch's proof of the Brouwer Fixed Point Theorem, based on the Simplicial Approximation Theorem, is pointed out along with some elaboration of its nature and possible ways to salvage Hirsch's proof.