Evidence for positive Darwinian selection on the hepcidin gene of Perciform and Pleuronectiform fishes

Hepcidin is a small cysteine-rich peptide that plays an important role in antimicrobial activity and in maintaining iron homeostasis in vertebrates. Here we report on the underlying mechanism that maintains high sequence diversities among the hepcidin-like variants of perciform and pleuronectiform fishes. In contrast to mammals, maximum likelihood-based codon substitution analyses revealed that positive Darwinian selection (nonsynonymous to synonymous substitution, ω > 1) is the likely cause of accelerated rate of amino acid substitutions in the hepcidin mature peptide region of these fishes. Comparison of models incorporating positive selection (ω > 1) at certain sites with models not incorporating positive selection (ω < 1) failed to reject (p = 0) the evidence of positive selection among the codon sites of percifom and pleuronectiform hepcidin. The adaptive evolution of this peptide in perciform and pleuronectiform fishes might be directed by pathogens when the host is exposed to new habitats/environments.     

Synthesis,structure, thermal studies on Zn(II), Cd(II) complexes of N-(2-pyridylmethyl)pyridine-2-carbaldimine and N-(2-pyridylmethyl)pyridine-2-methylketimine

The bivalent zinc and cadmium complexes of two Schiff bases N-(2-pyridylmethyl)pyridine-2-carbaldimine (L1), N-(2-pyridylmethyl)pyridine-2-methylketimine (L2), tridentate ligands with an N₃ chromophore and coordinating with two five-membered chelate rings, were synthesized. Complexes [Zn(L1)(NO₃)₂] (1), [Zn(L2)(NO₃)₂] (2), [Cd(L1)(NO₃)₂(H₂O)] (3) and [Cd(L2)(NO₃)₂(CH₃OH)] (4) were characterized by X-ray crystallography. In 1 and 2, Zn(II) has a distorted square-pyramidal geometry where as in 3 and 4, Cd(II) possesses a pseudo-pentagonal-bipyramidal geometry. The following trends in the bond lengths are observed: M–N_im < M–N_py; Zn–N > Zn–O; Cd–N < Cd–O. The final residues from the thermogravimetric analysis are ZnO and CdO, the SEM studies revealed, respectively, their porous and spherical natures. The average activation energy (E) for the loss of pyridine rings obtained from the Friedman fitting of the DSC data, for 1, 2, 3, and 4 are 193.8(2), 114.5(3), 127.1(4), and 63.7(3) kJ mol⁻¹ and their logarithmic pre-exponential factor (A) are 11.22, 5.31, 6.88, and 2.09, respectively.     

Prediction of the structures of helical membrane proteins based on a minimum unfavorable contacts approach

An understanding of structure–function relationships of membrane proteins continues to be a challenging problem, owing to the difficulty in obtaining their structures experimentally. This study suggests a method for modeling membrane protein structures that can be used to generate a reliable initial conformation prior to the use of other approaches for sampling conformations. It involves optimizing the orientation of hydrophilic residues so as to minimize unfavorable contacts with the hydrophobic tails of the lipid bilayer. Starting with the optimized initial conformation for three different proteins modeled based on this method, two independent approaches have been used for sampling the conformational space of the proteins. Both approaches are able to predict structures reasonably close to experimental structures, indicating that the initial structure enables the sampling of conformations that are close to the native structure. Possible improvements in the method for making it broadly applicable to helical membrane proteins are discussed. © 2015 Wiley Periodicals, Inc.     

Amine grafted Fe3O4 immobilized graphene oxide as a recyclable and effectual nanocomposite for the regioselective ring opening reaction

Research on Chemical Intermediates - This work describes the synthesis of magnetic graphene oxide (MGO), where iron oxide (Fe3O4) nanoparticles were uniformly deposited over the sheets of the...     

Data acquisition for experiments with multi-detector arrays

Experiments with multi-detector arrays have special requirements and place higher demands on computer data acquisition systems. In this contribution we discuss data acquisition systems with special emphasis on multi-detector arrays and in particular we describe a new data acquisition system, AMPS which we have developed recently which is in regular use in experiments at the Pelletron Laboratory, Mumbai. This includes the in-house development of a dedicated crate controller, PC interface card and software.     

C3H4: Theoretical study of structures and stabilities of isomers

The various isomers including stable structures, carbenes, and diradicals on the C₃H₄ surface have been investigated. The two carbenes propenylidene and cyclopropylidene have been found to have singlet ground states. Vinylmethylene is predicted to have a triplet ground state with a planar diradical type of structure. The syn and anti forms of this state are degenerate. This is in agreement with the observation of two triplet states in the electron spin resonance (ESR ) spectra. The π electrons are found to be delocalized over the three carbons. The singlet diradical structures are found to be more stable than the carbene structures, which retain the CH₂ (DOUBLE BOND) CH allylic structures. The orbital compositions of the frontier orbitals of all systems have been determined to examine the nature of these orbitals. © 1996 John Wiley & Sons, Inc.     

Sintered and 3D-Printed Bulks of MgB2-Based Materials with Antimicrobial Properties

Pristine high-density bulk disks of MgB₂ with added hexagonal BN (10 wt.%) were prepared using spark plasma sintering. The BN-added samples are machinable by chipping them into desired geometries. Complex shapes of different sizes can also be obtained by the 3D printing of polylactic acid filaments embedded with MgB₂ powder particles (10 wt.%). Our present work aims to assess antimicrobial activity quantified as viable cells (CFU/mL) vs. time of sintered and 3D-printed materials. In vitro antimicrobial tests were performed against the bacterial strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Enterococcus faecium DSM 13590, and Enterococcus faecalis ATCC 29212; and the yeast strain Candida parapsilosis ATCC 22019. The antimicrobial effects were found to depend on the tested samples and microbes, with E. faecium being the most resistant and E. coli the most susceptible.     

Synthesis, structure and magnetic behavior of a new three-dimensional Manganese phosphite-oxalate: [C2N2H10][Mn2(OH2)2(HPO3)2(C2O4)]

A novel manganese phosphite-oxalate, [C₂N₂H₁₀][Mn₂^II(OH₂)₂(HPO₃)₂(C₂O₄)] has been hydothermally synthesized and its structure determined by single-crystal X-ray diffraction. The structure consists of neutral manganese phosphite layers, [Mn(HPO₃)]_∞, formed by MnO₆ octahedra and HPO₃ units, cross-linked by the oxalate moieties. The organic cations occupy the middle of the 8-membered one-dimensional channels. Magnetic studies indicate weak antiferromagnetic interactions between the Mn²⁺ ions.     

A simple and efficient route to 2-arylimidazo[1,2-a]pyridines and zolimidine using automated grindstone chemistry

A green and efficient mechanochemical method for the synthesis of a series of 2-arylimidazo[1,2-a]pyridines was developed using an electrical grinder. I₂ catalyzed mechanochemical grinding facilitates the cyclocondensation reaction between various aryl methyl ketones and 2-aminopyridines to afford 2-arylimidazo[1,2-a]pyridines in good yields at ambient temperature. The method was successfully used for the gram-scale synthesis of a marketed drug, zolimidine. The noticeable advantages of this environmentally sustainable protocol include mild conditions, simple instrumentation, inexpensive catalyst, atom economy, short reaction time etc.     

Selective synthesis of ureas and tetrazoles from amides controlled by experimental conditions using conventional and microwave irradiation

An efficient synthetic procedure has been achieved for selective synthesis of 1,5-disubstituted tetrazoles and diaryl ureas from secondary amides in situ in the presence of NaN₃ and POCl₃ as solvent, both by conventional and microwave methods. The reaction conditions were optimized to yield selectively either tetrazoles or urea derivatives from reasonable to excellent yields. These conversions have been tested and verified with various secondary amide precursors. The synthesized compounds were characterized by ¹H NMR, ¹³C NMR and ESI-MS spectroscopic techniques.