Studies on molecular structure and tautomerism of a vitamin B<Subscript>6</Subscript> analog with density functional theory

This work presents a computational study on the molecular structure and tautomeric equilibria of a novel Schiff base L derived from pyridoxal (PL) and o-phenylenediamine by using the density functional method B3LYP with basis sets 6-31 G(d,p), 6-31++G(d,p), 6-311 G(d,p) and 6-311++G(d,p). The optimized geometrical parameters obtained by B3LYP/6-31 G(d,p) method showed the best agreement with the experimental values. Tautomeric stability study of L inferred that the enolimine form is more stable than its ketoenamine form in both gas phase and solution. However, protonation of the pyridoxal nitrogen atom (LH) have accelerated the formation of ketoenamine form, and therefore, both ketoenamine and enolimine forms could be present in acidic media.     

Stressor-induced changes to the protoscoleces of Echinococcus granulosus of Indian buffalo origin

In the present study viable protoscoleces of Echinococcus granulosus were exposed to in vitro anthelmintic treatment to observe efficacy against Indian buffalo isolates. Evaluation criteria included morphological changes, viability scores and expression of peptides as a product of prestressed protoscoleces. Protoscolex changes included presence of bladder-like structure and morphological distortion. Two peptides of relative molecular weight (Mr) 40 and 70 kDa were visualized when proteins were separated by discontinuous gel electrophoresis. These two peptides seemed to be products of prestressed protoscoleces.     

Soral crypsis: protective mimicry of a coccid on an Indian fern

Herbivory with crypsis is not well documented in ferns. The present record of cryptic coloration of coccid Saissetia filicum Boisduval (Homoptera: Coccidae) to the sori of a fern species Asplenium nidus L. (Aspleniaceae) is unique. Predatory beetles (Jauravia sp., Coleoptera: Coccinellidae) that feed on the coccids, are suggested to be selective pressure for the development of the present homopteran soral crypsis. A higher rate of effective predation is noticed in the vegetative leaves than the fertile leaves. Aggressive ants were found harvesting honeydew secretions from the coccids and defending the trophobionts as well as the host fern from their natural enemies. In addition, a possible three-way mutualistic relationship among the coccids, its host fern and the tending ant is suggested. Differential numbers of coccids on vegetative and fertile leaves is correlated with their phenol content and degree of predation by beetles. Such coloration mimicry by the coccids may enable them to obtain the necessary blend of sorus of the host fern needed to evade beetle detection and attack.     

Fertility of the Tibetans migrated to Northen India

This paper aims to study the fertility rate of the migrant Tibetans residing in Northern India and finding out the factors which are affecting the fertility level among them. Data are reported on age at menarche, age at marriage, first childbirth, use of contraception, widowhood, migration and on various fertility measures in the Tibetan of Northern India living at low and moderate altitude (600–2000 m), who have migrated from high altitude (4000 m above sea level) in Tibet. The migrant Tibetans reported a relatively lower fertility as compared to the high and moderate altitude populations. This lower fertility is mostly attributable to the use of contraception, the later mean age at marriage and first childbirth, and relatively high proportion of widows in the migrant Tibetans. However, the social as well as biological changes in population during migration should not be overlooked, which have a sufficient impact on fertility.     

Insight to structural subsite recognition in plant thiol protease-inhibitor complexes : Understanding the basis of differential inhibition and the role of water

Background  

This work represents an extensive MD simulation / water-dynamics studies on a series of complexes of inhibitors (leupeptin, E-64, E-64-C, ZPACK) and plant cysteine proteases (actinidin, caricain, chymopapain, calotropin DI) of papain family to understand the various interactions, water binding mode, factors influencing it and the structural basis of differential inhibition.     

Taxonomic assessment of opal phytoliths from grasses of deltaic West Bengal,India

In the present study, taxonomic potential of opal phytoliths was examined in grasses from lower Gangetic delta, West Bengal, India. The study revealed that finer classification of phytoliths can increase the efficacy of opal silica as taxonomic proxy by minimizing the influences of multiplicity and redundancy. We isolated 187 phytolith sub‐morphotypes, categorized under 10 major groups, from 110 grass species belonging to 45 genera, 21 sub‐tribes, 13 tribes and 7 subfamilies. Cluster and correspondence analyses showed that all the significantly represented subfamilies can be clearly distinguished on the basis of either principal morphotypes or sub‐morphotypes. However, genus/species level discrimination may only be possible by deploying phytolith based identification key developed by utilizing detailed grass phytolith micro‐morphometry and frequency attributes. We conclude that grass phytolith characteristics provide useful and significant information for distinguishing grass taxa of deltaic West Bengal.     

Amino acid substitution in alpha-helix 7 of Cry1Ac delta-endotoxin of Bacillus thuringiensis leads to enhanced toxicity to Helicoverpa armigera Hubner.

Insecticidal proteins or delta-endotoxins of Bacillus thuringiensis are highly toxic to a wide range of agronomically important pests. The toxins are formed of three structural domains. The N-terminal domain is a bundle of eight alpha-helices and is implicated in pore formation in insect midgut epithelial membranes. All the delta-endotoxins share a common hydrophobic motif of eight amino acids in alpha-helix 7. A similar motif is also present in fragment B of diphtheria toxin (DT). Site-directed mutagenesis of Cry1Ac delta-endotoxin of B. thuringiensis was carried out to substitute its hydrophobic motif with that of DT fragment B. The mutant toxin was shown to be more toxic to the larvae of Helicoverpa armigera (cotton bollworm) than the wild-type toxin. Voltage clamp analysis with planar lipid bilayers revealed that the mutant toxin opens larger ion channels and induces higher levels of conductance than the wild-type toxin.     

Evidence for nonlinear capacitance in biomembrane channel system.

The electrophysiological properties of voltage-dependent anion channels from mitochondrial membrane have been studied in a bilayer membrane system. It was observed that the probability of opening of the membrane channel depends on externally applied voltage and the plot is a bell-shaped curve symmetric around probability axis. A scheme of conformational energy levels under varying externally applied voltage was formulated. Assuming that the probability follows Boltzmann distribution, we arrive at an expression of change in energy containing a separate term identical to the energy of a capacitor. This fact indicates the possibility of existence of an added capacitance due to the channel protein. Further it was shown that the aforesaid channel capacitor could be a function of voltage leading to nonlinearity. We have offered a general method of calculating nonlinear capacitance from the experimental data on opening probability of a membrane channel. In case of voltage-dependent anion channel the voltage dependence of the capacitor has a power 0.786. The results have been interpreted in view of the structural organization of the channel protein in the membrane. Our hypothesis is that the phenomenon of capacitor behaviour is a general one for membrane channels.     

Iron(III) induced 2-phenyl imidazolidine ring hydrolysis of a new binucleating Schiff base ligand: X-ray structure of the mononuclear Fe(NNO)2 end product

The reaction of triethylenetetramine, salicylaldehyde and benzaldehyde in 1:2:1 mole ratio in methanol at room temperature affords a novel μ-bis(tridentate) ligand H₂L′ through the formation of an imidazolidine ring within the parent hexadentate precursor in a two step reaction. The ligand H₂L′ reacts with Fe(ClO₄)₂ · 6H₂O in aqueous methanol in the presence of triethylamine to form the mononuclear [Fe^IIIL](ClO₄) complex, (where L²⁻ is the anion of the parent hexadentate H₂saltrien ligand) after the cleavage of the imidazolidine ring. The mononuclear complex has a structure with an N₄O₂ donor atom set of the hexadentate ligand forming a distorted octahedral coordination geometry around the metal atom as established from a crystal structure determination. The Fe-N(imine) distances are 1.934(10) and 1.948(9) Å, Fe-N(amine) distances are 2.062(8) and 2.076(9) Å and Fe-O(phenol) distances are 1.864(8) and 1.872(7) Å. The terminal oxygen donor atoms occupy cis positions and the remaining four nitrogen atoms (two cis amine and two trans imine) complete the coordination sphere. The mononuclear complex has a magnetic moment 1.89 μ_B corresponding to the low-spin 3d⁵ configuration. The UV-Vis spectrum of the end product, after the imidazolidine ring hydrolysis, is different from the spectrum of the initial reaction mixture containing the μ-bis(tridentate) ligand H₂L′.