Targeted expression of L-myo- inositol 1-phosphate synthase from Porteresia coarctata (Roxb.) Tateoka confers multiple stress tolerance in transgenic crop plants

Improving crop tolerance to osmotic stresses is a longstanding goal of agricultural biotechnology. In the present work the PcINO1 gene coding for a salt-tolerant L-myo-inositol-1-phosphate synthase (MIPS) from Porteresia coarctata (Roxb.) Tateoka, a halophytic wild rice was introgressed into cultivated mustard, Brassica juncea var B85. The transgenic plants demonstrate increased tolerance to salinity and oxidative stress with elevated level of inositol in both roots and shoots. The yield and crop quality of transgenic Brassica plants remain uncompromised and the plants were able to stably grow, set seeds and germinate in saline environments. When targeted to seeds of Nicotiana, PcINO1 was able to improve the seed survival rate under salinity and dehydration. Inositol and its derivatives regulate stress responses in various ways, serving as compatible solutes or signaling molecules. It is implicated that engineering inositol metabolism may affect the plant metabolic network leading to a stress tolerant phenotype as enumerated here in transgenic crop plants. How inositol itself or its derivatives affect the overall metabolic pathways leading to a stress-tolerant phenotype remains an intriguing question for future investigations.     

SBION: A Program for Analyses of Salt-Bridges from Multiple Structure Files

Salt-bridge and network salt-bridge are specific electrostatic interactions that contribute to the overall stability of proteins. In hierarchical protein folding model, these interactions play crucial role in nucleation process. The advent and growth of protein structure database and its availability in public domain made an urgent need for context dependent rapid analysis of salt-bridges. While these analyses on single protein is cumbersome and time-consuming, batch analyses need efficient software for rapid topological scan of a large number of protein for extracting details on (i) fraction of salt-bridge residues (acidic and basic). (ii) Chain specific intra-molecular salt-bridges, (iii) inter-molecular salt-bridges (protein-protein interactions) in all possible binary combinations (iv) network salt-bridges and (v) secondary structure distribution of salt-bridge residues. To the best of our knowledge, such efficient software is not available in public domain. At this juncture, we have developed a program i.e. SBION which can perform all the above mentioned computations for any number of protein with any number of chain at any given distance of ion-pair. It is highly efficient, fast, error-free and user friendly. Finally we would say that our SBION indeed possesses potential for applications in the field of structural and comparative bioinformatics studies.

Availability

SBION is freely available for non-commercial/academic institutions on formal request to the corresponding author (ni.ca.vinurub.hcetoib@eejrenabka).     

Optimum Calcium Concentration: A Crucial Factor in Regulating Sperm Motility In Vitro

Sperm motility can be maintained in vitro by incubation in a defined medium under specific conditions. In most studies, the exact role of various constituents of epididymal fluid, including calcium, has remained obscure. Most of the culture media have included millimolar concentrations of calcium, but previous reports have indicated that millimolar calcium inhibits sperm motility. In this present study, we sought the optimum concentration of extracellular calcium required for optimum sperm motility. This study showed that extracellular calcium has a concentration-dependent biphasic role in motility regulation. It promoted motility and velocity at lower (10 µM) concentration whereas notably inhibited it at higher concentrations. When external membrane-bound calcium was removed by ethylene glycol tetraacetic acid, motility decreased considerably. To confirm the motility-inhibiting role of calcium above 10 µM, a sperm motility-stimulating protein (MSP) recently reported from our laboratory was used which at 0.9 μM induces motility in 60–70 % cells. Calcium at 10 µM had no appreciable effect on the motility-promoting activity of the MSP but depressed the activity above 10 µM. Thus, our present results emphasize the biphasic role of extracellular calcium and the importance of its optimum concentration in different buffers and media used for sperm motility initiation.     

Curcumin Alters the Salt Bridge-containing Turn Region in Amyloid β(1–42) Aggregates

Amyloid β (Aβ) fibrillar deposits in the brain are a hallmark of Alzheimer disease (AD). Curcumin, a common ingredient of Asian spices, is known to disrupt Aβ fibril formation and to reduce AD pathology in mouse models. Understanding the structural changes induced by curcumin can potentially lead to AD pharmaceutical agents with inherent bio-compatibility. Here, we use solid-state NMR spectroscopy to investigate the structural modifications of amyloid β(1–42) (Aβ₄₂) aggregates induced by curcumin. We find that curcumin induces major structural changes in the Asp-23–Lys-28 salt bridge region and near the C terminus. Electron microscopy shows that the Aβ₄₂ fibrils are disrupted by curcumin. Surprisingly, some of these alterations are similar to those reported for Zn²⁺ ions, another agent known to disrupt the fibrils and alter Aβ₄₂ toxicity. Our results suggest the existence of a structurally related family of quasi-fibrillar conformers of Aβ₄₂, which is stabilized both by curcumin and by Zn^2+.     

Cubane-like water clusters in a 3D supramolecular network of zinc with pyridine-2,6-dicarboxylic acid and 5-aminotetrazole

The reaction of zinc ions with pyridine-2,6-dicarboxylic acid (H₂PDA) and 5-aminotetrazole (HATZ) in hydrothermal condition gives rise to a 2D interdigitated network of composition [Zn₂(PDA)(ATZ)₂]·4H₂O (1). The two independent zinc(II) ions, both located on a crystallographic twofold axis, show a different coordination environment, namely a highly distorted trigonal bipyramidal and a tetrahedral geometry. An octameric cluster of lattice water molecules in the lattice voids produces a 3D supramolecular architecture through hydrogen bonding. Thermogravimetry, infrared spectra, and elemental analysis have also been applied to characterize 1. Fluorescence study indicates the intraligand π-π^∗ transition perturbed by the metal ion.     

Combination of covalent and hydrogen bonding in the formation of 3D uranyl-carboxylate networks

Four compounds containing uranyl cation [UO₂]²⁺ have been synthesized hydrothermally by reacting uranyl acetate and uranyl nitrate with various N/O donor ligands. The structure of all compounds was elucidated by single crystal X-ray diffraction study. Compound [(UO₂)(6-methylnicotinato)₃](H₃O)·4H₂O (1) is a discrete complex (0D), that gives rise in the crystal to hydrophilic channels, while [(UO₂)(OH)(μ₂-3-pyridylpropionato)]_n (2) and [(UO₂)(H₂O)(μ₃-4,4′-oxybis(benzoato)]_n (3) show the formation of 1D coordination polymers. Moreover, oxalate anions, formed in situ by using 5-methylisophthalic or 2,3-pyrazinedicarboxylic acid as reactant ligands, gave rise to a 2D coordinating network [(UO₂)₂(μ₂-oxalate)(μ₂-OH)₂(H₂O)₂]_n·nH₂O (4). All the complexes expanded their dimensionality to 3D through hydrogen bonds.     

N,N′-Olefin Functionalized Bis-Imidazolium Gold(I) Salt Is an Efficient Candidate to Control Keratitis-Associated Eye Infection

Keratitis treatment has become more complicated due to the emergence of bacterial or fungal pathogens with enhanced antibiotic resistance. The pharmaceutical applications of N-heterocyclic carbene complexes have received remarkable attention due to their antimicrobial properties. In this paper, the new precursor, 3,3′-(p-phenylenedimethylene) bis{1-(2- methyl-allyl)imidazolium} bromide (1a) and its analogous PF₆ salt (1b) were synthesized. Furthermore, silver(I) and gold(I) -N-heterocyclic carbene (NHC) complexes [Ag₂LBr₂/Au₂LBr₂; 2a/3a], [(Ag₂L₂)(PF₆)₂/(Au₂L₂)(PF₆)₂; 2b/3b] were developed from their corresponding ligands. All compounds were screened for their antimicrobial activities against multiple keratitis-associated human eye pathogens, including bacteria and fungi. Complexes 2a and 3a showed highest activity, and the effectiveness of 3a was also studied, focusing eradication of pathogen biofilm. Furthermore, the structures of 1a, 2a and 3b were determined using single crystal X-ray analysis, 2b and 3a were optimized theoretically. The mechanism of action of 3a was evaluated by scanning electron microscopy and docking experiments, suggesting that its target is the cell membrane. In summary, 3a may be helpful in developing antimicrobial therapies in patients suffering from keratitis-associated eye infections caused by multidrug-resistant pathogens.