Modeling the weak hydrogen bonding of pyrrole and dichloromethane through Raman and DFT study

Raman spectra of neat pyrrole (C(4)H(5)N) and its binary mixtures with dichloromethane (CH(2)Cl(2), DCM) with varying mole fractions of C(4)H(5)N from 0.1 to 0.9 were recorded in order to monitor the influence of molecular interaction on spectral features of selected vibrational bands of pyrrole in the region 600-1600 cm(-1). Only 1369 cm(-1) vibrational band of pyrrole shows a significant change in its peak position in going from neat pyrrole to the complexes. The 1369 cm(-1) band shows (～6 cm(-1)) blue shift upon dilution and the corresponding linewidth shows the maximum shift at C?=?0.5 mole fraction of pyrrole upon dilution which clearly indicates that the concentration fluctuation model plays major role. Quantum chemical calculation using density functional theory (DFT) and ab-initio (MP2 and HF) methods were performed employing high level basis set, 6-311++G(d,p) to obtain the ground state geometry of neat pyrrole and its complexes with DCM in gas phase. Basis set superimpose error (BSSE) correction was also introduced by using the counterpoise method. In order to account for the solvent effect on vibrational features and changes in optimized structural parameters of pyrrole, polarizable continuum model (PCM) (bulk solvations) and PCM (specific plus bulk solvations) calculations were performed. Two possible configurations of pyrrole + DCM complex have been predicted by B3LYP and HF methods, whereas the MP2 method gave only single configuration in which H atom of DCM is bonded to π ring of the pyrrole molecule. This affects significantly the ring vibrations of pyrrole molecule, which was also observed in our experimental results.     

Response of Rhizobium leguminosarum to nickel stress

Rhizobium leguminosarum strain P-5 biovar viciae was sensitive to Ni²⁺ (MIC, 75 M) and showed concentration-dependent Ni²⁺ uptake in a wide concentration range (50–500 M). Ni²⁺ uptake up to a certain threshold limit also increased thiol content (66 nmol mg^–1 protein), proline content (10.85 nmol mg^–1 protein) and urease specific activity (500 nmol min^–1 mg^–1 protein) maximum corresponding to 100 M Ni²⁺ as the external concentration or 151 nmol Ni²⁺ mg^–1 protein as the intracellular buildup. Proline synthesis was stimulated most even at much lower Ni²⁺ concentration (25 M). Higher intracellular Ni²⁺ load neither favoured thiol nor proline biosynthesis nor urease activity. Ni²⁺ requirement of urease was ascertained by using EDTA-grown cells and the addition of bicarbonate (NaHCO₃, 100 mM) to the crude extract. The induction of thiol or proline by Ni²⁺, therefore, reflects the possible strategies adopted by bacterial cells to overcome the environmental stress.     

Gene Expression in the Cyanobacterium <Emphasis Type="Italic">Anabaena</Emphasis> sp. PCC7120 under Desiccation

The N₂-fixing cyanobacterium Anabaena sp. PCC7120 showed an inherent capacity for desiccation tolerance. A DNA microarray covering almost the entire genome of Anabaena was used to determine the genome-wide gene expression under desiccation. RNA was extracted from cells at intervals starting from early to late desiccation. The pattern of gene expression in DNA fragments was categorized into seven types, which include four types of up-regulated and three types of down-regulated fragments. Validation of the data was carried out by RT-PCR on selected up-regulated DNA fragments and was consistent with the changes in mRNA levels. Our conclusions regarding desiccation tolerance for Anabaena sp. PCC7120 are as follows: (i) Genes for osmoprotectant metabolisms and the K⁺ transporting system are up-regulated from early to mid-desiccation; (ii) genes induced by osmotic, salt, and low-temperature stress are up-regulated under desiccation; (iii) genes for heat shock proteins are up-regulated after mid-desiccation; (iv) genes for photosynthesis and the nitrogen-transporting system are down-regulated during early desiccation; and (v) genes for RNA polymerase and ribosomal protein are down-regulated between the early and the middle phase of desiccation. Profiles of gene expression are discussed in relation to desiccation acclimation.     

Copper uptake and its compartmentalization in Pseudomonas aeruginosa strains: Chemical nature of cellular metal

Copper-sensitive (Cu^s) and copper-resistant (Cu^r) strains of Pseudomonas aeruginosa were characterized in terms of Cu²⁺ sensitivity, uptake and its compartmentalization in the possible cell sectors. Minimum inhibitory concentrations (MICs) of Cu²⁺ for the Cu^r strain (3.2 mM and 0.12 mM in enriched- and in minimal-medium, respectively) were almost 5-fold higher over that of its sensitive counterpart. While Cu^s strain accumulated Cu²⁺ to a maximum of 1.8 mol mg^–1 protein, Cu^r strain increased it to 2.37 mol mg^–1 protein. Both the strains also demonstrated energy- and pH-dependent Cu²⁺ uptake through the broad-substrate range divalent cation (Zn²⁺, Mg²⁺, Co²⁺) uptake system as well as through the system specific for Cu²⁺. Cell-fractionation study revealed that in Cu^r strain, periplasm and membrane are the main Cu²⁺ binding sites, whereas, in case of Cu^s strain, it is the cytoplasm. The overall observations indicate that the Cu^r strain restricted Cu²⁺ sequestration exterior to the cytoplasm as the possible strategy for Cu-resistance. The chemical nature of Cu²⁺ deposition in the respective strains was also ascertained by X-ray powder diffraction analysis.     

Two new species of Cololejeunea (Spruce) Schiffn. from Western Ghats,India

Introduction. During a recent floristic survey of liverworts from Western Ghats, India, two interesting liverworts of genus Cololejeunea were collected from forests in Mahabaleshwar in the state of Maharashtra.

Methods. After critical investigation, they have been described as new to science and both species, C. ghatensis G.Asthana & A.Srivastava sp. nov. and C. mehrana G.Asthana & A.Srivastava sp. nov. are illustrated and described here.

Key results. Cololejeunea ghatensis is an epiphyllous species growing on angiosperm leaves and has been collected near Chinaman Waterfall, Robbers Cave, Connaught Peak and Polo Ground area. Cololejeunea mehrana has been collected near Monkey point and the latter has an interesting habitat as it was found growing on moss leaves. Cololejeunea ghatensis is monoicous and C. mehrana is dioicous.     

Identification of maltooligosyltrehalose synthase and maltooligosyltrehalose trehalohydrolase enzymes catalysing trehalose biosynthesis in Anabaena 7120 exposed to NaCl stress

Anabaena 7120 cells were exposed to NaCl (25-175 mM) stress. Maximum growth was recorded in media containing 150mM NaCl. Short-term exposure (48h) of the cyanobacterial biomass to 150mM NaCl, induced highest trehalose level (37mM). Control cells lacking NaCl did not show any trace of trehalose as ascertained by NMR and HPLC analysis. Trehalose biosynthesis observed with NaCl plus high temperature (40 degrees C) indicated that its production was specifically triggered by NaCl, not temperature. The increase in trehalose level during NaCl stress was the result of overexpression of the trehalose-forming enzymes maltooligosyltrehalose synthase (MTSase), EC 5.4.99.15 (114kDa) and maltooligosyltrehalose trehalohydrolase (MTHase), EC 3.2.1.141 (68 kDa) as evidenced by SDS-PAGE analysis. To our knowledge this is the first report of induced trehalose biosynthesis in Anabaena 7120 during salt-stress, accompanied by identification of MTSase and MTHase enzymes on gel. It is suggested that Anabaena 7120 cells synthesize the osmolyte trehalose to withstand osmotic fluctuations.     

Bioengineering of the digestive tract: approaching the clinic

The field of regenerative medicine is developing technologies that, in the near future, will offer alternative approaches to either cure diseases affecting the gastrointestinal tract or slow their progression by leveraging the intrinsic ability of our tissues and organs to repair after damage. This article will succinctly illustrate the three technologies that are closer to clinical translation—namely, human intestinal organoids, sphincter bioengineering and decellularization, whereby the cellular compartment of a given segment of the digestive tract is removed to obtain a scaffold consisting of the extracellular matrix. The latter will be used as a template for the regeneration of a functional organ, whereby the newly generated cellular compartment will be obtained from the patient's own cells. Although clinical application of this technology is approaching, product development challenges are being tackled to warrant safety and efficacy.     

Structural Aspects and Chaperone Activity of Human HspB3: Role of the “C-Terminal Extension”

HspB3, an as yet uncharacterized sHsp, is present in muscle, brain, heart, and in fetal tissues. A point mutation correlates with the development of axonal motor neuropathy. We purified recombinant human HspB3. Circular dichroism studies indicate that it exhibits β-sheet structure. Gel filtration and sedimentation velocity experiments show that HspB3 exhibits polydisperse populations with predominantly trimeric species. HspB3 exhibits molecular chaperone-like activity in preventing the heat-induced aggregation of alcohol dehydrogenase (ADH). It exhibits moderate chaperone-like activity towards heat-induced aggregation of citrate synthase. However, it does not prevent the DTT-induced aggregation of insulin, indicating that it exhibits target protein-dependent molecular chaperone-like activity. Unlike other sHsps, it has a very short C-terminal extension. Fusion of the C-terminal extension of αB-crystallin results in altered tertiary and quaternary structure, and increase in polydispersity of the chimeric protein, HspB3αB-CT. The chimeric protein shows comparable chaperone-like activity towards heat-induced aggregation of ADH and citrate synthase. However, it shows enhanced activity towards DTT-induced aggregation of insulin. Our study, for the first time, provides the structural and chaperone functional characterization of HspB3 and also sheds light on the role of the C-terminal extension of sHsps.