Copper-thioarylazoimidazole complexes: Structures, photochromism and redox interconversion between Cu(II) ↔ Cu(I) and correlation with DFT calculation

Reaction of Cu(ClO₄)₂·6H₂O, SRaaiNR′ (1-alkyl-2-[(o-thioalkyl)phenylazo]imidazole) and NH₄SCN (1:1:2 mol ratio) affords distorted square pyramidal, [Cu^II(SRaaiNR′)(SCN)₂] (3) compound while identical reaction with [Cu(MeCN)₄](ClO₄) yields -SCN- bridged coordination polymer, [Cu^I(SRaaiNR′)(SCN)]_n (4). These two redox states [Cu^II and Cu^I] are interconvertible; reduction of [Cu^II(SRaaiNR′)(SCN)₂] by ascorbic acid yields [Cu^I(SRaaiNR′)(SCN)]_n while the oxidation of [Cu^I(SRaaiNR′)(SCN)]_n by H₂O₂ in presence of excess NH₄SCN affords [Cu^II(SRaaiNR′)(SCN)₂]. They are structurally confirmed by single crystal X-ray diffraction study. Cyclic voltammogram of the complexes show Cu(II)/Cu(I) redox couple at ∼0.4 V and azo reductions at negative to SCE. UV light irradiation in MeCN solution of [Cu^I(SRaaiNR′)(SCN)]_n (4) show trans-to-cis isomerisation of coordinated azoimidazole. The reverse transformation, cis-to-trans, is very slow with visible light irradiation while the process is thermally accessible. Quantum yields (?_t→c) of trans-to-cis isomerisation are calculated and free ligands show higher ? than their Cu(I) complexes. The activation energy (E_a) of cis-to-trans isomerisation is calculated by controlled temperature experiment. Copper(II) complexes, 3, do not show photochromism. DFT and TDDFT calculation of representative complexes have been used to determine the composition and energy of molecular levels and results have been used to explain the solution spectra, photochromism and redox properties of the complexes.     

The affinity concept in bioseparation: evolving paradigms and expanding range of applications

The meaning of the word affinity in the context of protein separation has undergone evolutionary changes over the years. The exploitation of molecular recognition phenomenon is no longer limited to affinity chromatography modes. Affinity based separations today include precipitation, membrane based purification and two-phase/three-phase extractions. Apart from the affinity ligands, which have biological relationship (in vivo) with the target protein, a variety of other ligands are now used in the affinity based separations. These include dyes, chelated metal ions, peptides obtained by phage display technology, combinatorial synthesis, ribosome display methods and by systematic evolution of ligands by exponential enrichment (SELEX). Molecular modeling techniques have also facilitated the designing of biomimetic ligands. Fusion proteins obtained by recombinatorial methods have emerged as a powerful approach in bioseparation. Overexpression in E. coli often result in inactive and insoluble inclusion bodies. A number of interesting approaches are used for simultaneous refolding and purification in such cases. Proteomics also needs affinity chromatography to reduce the complexity of the system before analysis by electrophoresis and mass spectrometry are made. At industrial level, validation, biosafety and process hygiene are also important aspects. This overview looks at these evolving paradigms and various strategies which utilize affinity phenomenon for protein separations.     

In silico modeling and hydrogen peroxide binding study of rice catalase

Homology modeling of the catalase, CatC cloned and sequenced from rice (Oryza sativa L., cv Ratna an Indica cultivar) has been performed based on the crystal structure of the catalase CatF (PDB code 1m7s) by using the software MODELLER. With the aid of molecular mechanics and molecular dynamics methods, the final model is obtained and is further assessed by PROCHECK and VERIFY - 3D graph, which show that the final refined model is reliable. With this model, a flexible docking study with the hydrogen peroxide, the substrate for catalase, is performed and the results indicate that Arg310, Asp343 and Arg346 in catalase are three important determinant residues in binding as they have strong hydrogen bonding contacts with the substrate. These hydrogen-bonding interactions play an important role for the stability of the complex. Our results may be helpful for further experimental investigations.     

A bioconjugate of Pseudomonas cepacia lipase with alginate with enhanced catalytic efficiency

A bioconjugate of Pseudomonas cepacia lipase with alginate was prepared by simple adsorption. Atomic force microscope (AFM) images showed that this bioconjugate resulted from adsorption rather than entrapment of the enzyme as enzyme molecules were visible on the gel surface. The soluble bioconjugate exhibited increased enzyme activity in terms of high effectiveness factor (effectiveness factor was 3 for the immobilized preparation) and greater Vmax/Km value (Vmax/Km increased 25 times upon immobilization). This constitutes one of the less frequently observed instances of lipase activation by lid opening as a result of binding to a predominantly hydrophilic molecule. The bioconjugate was also more stable at 55 degrees C as compared to the free enzyme and could be reused for oil hydrolysis up to 4 cycles without any loss in activity. Fluorescence emission spectroscopy showed that the immobilized enzyme had undergone definite conformational changes.     

Effects of murine endotoxemia on lymphocyte subsets and clearance of staphylococcal pulmonary infection

In a model of staphylococcal pneumonia initiated during systemic endotoxemia in BALB/c mice, a significant reduction of the number of circulating CD4+ and CD8+ T-lymphocytes, B-lymphocytes, and NK cells, as well as lung-resident total T- and CD4+ T-lymphocytes was demonstrated. Staphylococcus aureus exposure only induced a similar decrease of lymphocyte subsets in the blood. However, the number of lung-resident total T- and CD4+ T-lymphocytes was increased. More viable bacteria were recovered from the lungs of S. aureus-infected mice than from those animals previously treated with lipopolysaccharide (LPS) followed by a staphylococcal challenge. These results indicate that LPS-induced reduction in the number of circulating lymphocyte subsets and lung-resident total T- and CD4+ T-lymphocytes do not increase susceptibility to staphylococcal respiratory infection. Moreover, LPS challenge prior to S. aureus exposure significantly improves clearance of the bacteria in the lung.     

MiRANN: a reliable approach for improved classification of precursor microRNA using Artificial Neural Network model

MicroRNA (miRNA) is a special class of short noncoding RNA that serves pivotal function of regulating gene expression. The computational prediction of new miRNA candidates involves various methods such as learning methods and methods using expression data. This article has proposed a reliable model - miRANN which is a supervised machine learning approach. MiRANN used known pre-miRNAs as positive set and a novel negative set from human CDS regions. The number of known miRNAs is now huge and diversified that could cover almost all characteristics of unknown miRNAs which increases the quality of the result (99.9% accuracy, 99.8% sensitivity, 100% specificity) and provides a more reliable prediction. MiRANN performs better than other state-of-the-art approaches and declares to be the most potential tool to predict novel miRNAs. We have also tested our result using a previous negative set. MiRANN, opens new ground using ANN for predicting pre-miRNAs with a promise of better performance.     

Lipoxin A4 inhibits immune cell binding to salivary epithelium and vascular endothelium

Lipoxins are formed by leukocytes during cell-cell interactions with epithelial or endothelial cells. Native lipoxin A(4) (LXA(4)) binds to the G protein-coupled lipoxin receptors formyl peptide receptor 2 (FPR2)/ALX and CysLT1. Furthermore, LXA(4) inhibits recruitment of neutrophils, by attenuating chemotaxis, adhesion, and transmigration across vascular endothelial cells. LXA(4) thus appears to serve as an endogenous "stop signal" for immune cell-mediated tissue injury (Serhan CN; Annu Rev Immunol 25: 101-137, 2007). The role of LXA(4) has not been addressed in salivary epithelium, and little is known about its effects on vascular endothelium. Here, we determined that interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) receptor activation in vascular endothelium and salivary epithelium upregulated the expression of adhesion molecules that facilitates the binding of immune cells. We hypothesize that the activation of the ALX/FPR2 and/or CysLT1 receptors by LXA(4) decreases this cytokine-mediated upregulation of cell adhesion molecules that enhance lymphocyte binding to both the vascular endothelium and salivary epithelium. In agreement with this hypothesis, we observed that nanomolar concentrations of LXA(4) blocked IL-1β- and TNF-α-mediated upregulation of E-selectin and intercellular cell adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells (HUVECs). Binding of Jurkat cells to stimulated HUVECs was abrogated by LXA(4). Furthermore, LXA(4) preincubation with human submandibular gland cell line (HSG) also blocked TNF-α-mediated upregulation of vascular cell adhesion molecule-1 (VCAM-1) in these cells, and it reduced lymphocyte adhesion. These findings suggest that ALX/FPR2 and/or CysLT1 receptor activation in endothelial and epithelial cells blocks cytokine-induced adhesion molecule expression and consequent binding of lymphocytes, a critical event in the pathogenesis of Sj?gren's syndrome (SS).     

Haptoglobin polymorphism among fourteen populations of India

Haptoglobin (HP) is a serum protein that has the capability of binding the extracorpuscular haemoglobin released during haemolysis. It plays an important role in protection of haemolytic disease by reducing the oxidative and peroxidative potential at free haemoglobin. The present study was aimed to determine the prevalence of HP polymorphism among different Indian populations, anthropologically belonging to diverse ethnicity. The polymorphism was screened among 642 unrelated individuals belonging to 14 population groups of India including both tribal and non-tribal caste groups from different geographical regions of India with distinct linguistic affiliations. An attempt is also made to understand the distribution of HP polymorphism among the studied populations. The result reveals the HP gene to be polymorphic in all the studied populations. Except the two tribal populations (Thotis of Andhra Pradesh and Patelias of Rajasthan) and one caste population (Rajput of Himachal Pradesh), all the studied populations are found to obey the Hardy-Weinberg equilibrium. The significance of the present study is elucidated with the prevalence of high mutant HP*2 allele frequency in India. Selection could be one of the most plausible explanations for this high HP frequency because of its uniformly high occurrence among all the studied populations.     

Molecular identification of GHS-R and GPR38 in Suncus murinus

We previously identified ghrelin and motilin genes in Suncus murinus (suncus), and also revealed that motilin induces phase III-like strong contractions in the suncus stomach in vivo, as observed in humans and dogs. Moreover, repeated migrating motor complexes were found in the gastrointestinal tract of suncus at regular 120-min intervals. We therefore proposed suncus as a small laboratory animal model for the study of gastrointestinal motility. In the present study, we identified growth hormone secretagogue receptor (GHS-R) and motilin receptor (GPR38) genes in the suncus. We also examined their tissue distribution throughout the body. The amino acids of suncus GHS-R and GPR38 showed high homology with those of other mammals and shared 42% amino acid identity. RT-PCR showed that both the receptors were expressed in the hypothalamus, medulla oblongata, pituitary gland and the nodose ganglion in the central nervous system. In addition, GHS-R mRNA expressions were detected throughout the stomach and intestine, whereas GPR38 was expressed in the gastric muscle layer, lower intestine, lungs, heart, and pituitary gland. These results suggest that ghrelin and motilin affect gut motility and energy metabolism via specific receptors expressed in the gastrointestinal tract and/or in the central nervous system of suncus.     

Gender discrimination in undernutrition with mediating factors among Bengalee school children from Eastern India

This study was undertaken to determine age and sex variations in the prevalence of underweight and stunting, and to assess the impact of some socio-economic variables on undernutrition among 6–16 year old school children of Bengalee ethnicity in Chapra, West Bengal, India. The subjects were selected randomly from various schools and madrassas of the Chapra Block. A total of 725 children (342 boys and 383 girls) aged 6–16 years were measured and data on their socio-economic status were collected. Age and sex combined rates of underweight and stunting were 44.40% and 37.20%, respectively. Weight-for-age Z-score (WAZ) showed significant association with per-capita income (PCI) among boys (F = 5.45) and girls (F = 8.14). Height-for-age Z-score (HAZ) has also shown the association with per-capita income among boys (F = 4.43) and girls (F = 9.69). The WAZ was significantly associated with fathers’ educational status (FOS) (t = ?2.95) and the number of living rooms (NLR) (t = ?2.91) among girls. The HAZ showed significant association with number of siblings (NS) among girls (F = 4.25). Linear regression analyses revealed that NLR (t = 2.04) and NS (t = 1.95) had a significant impact on HAZ among boys. Among girls, PCI (t = 3.38), FOS (t = 2.87) and NLR (t = 2.81) had a significant impact on WAZ and also PCI (t = 3.28) and FOS (t = 2.90) had a significant impact on HAZ. NLR had significant associations with underweight (χ² = 3.59) and stunting (χ² = 4.20) among boys. Among girls, PCI had significant associations with underweight (χ² = 11.15) and stunting (χ² = 11.64). FOS also showed significant associations with underweight (χ² = 8.10) as well as stunting (χ² = 8.28) among girls. NLR showed a significant association with underweight (χ² = 7.75). Logistics regression analyses revealed that FOS (Wald = 8.00) and NLR (Wald = 4.09) were significant predictors of stunting among boys. Among girls, PCI was a significant predictor of underweight (Wald = 10.95) as well as stunting (Wald = 10.45). FOS, NLR and NS were also significant predictors of stunting (Wald = 8.16), underweight (Wald = 7.68) and stunting (Wald = 6.97) respectively. The present study revealed that the nutritional status of the children was unsatisfactory and it is of paramount importance not only to increase the amount of food supplementation given but also to promote gender equality.