Rational design of carbonitrile-carboxaldehyde cation receptor models: probing the nature of the heteroatom–metal interaction

Amino acids are constituents of proteins and enzymes which take part almost in all metabolic reactions. Glutamic acid, with an ability to form a negatively charged side chain, plays a major role in intra and intermolecular interactions of proteins, peptides, and enzymes. An exhaustive conformational analysis has been performed for all eight possible forms at B3LYP/cc-pVTZ level. All possible neutral, zwitterionic, protonated, and deprotonated forms of glutamic acid structures have been investigated in solution by using polarizable continuum model mimicking water as the solvent. Nine families based on the dihedral angles have been classified for eight glutamic acid forms. The electrostatic effects included in the solvent model usually stabilize the charged forms more. However, the stability of the zwitterionic form has been underestimated due to the lack of hydrogen bonding between the solute and solvent; therefore, it is observed that compact neutral glutamic acid structures are more stable in solution than they are in vacuum. Our calculations have shown that among all eight possible forms, some are not stable in solution and are immediately converted to other more stable forms. Comparison of isoelectronic glutamic acid forms indicated that one of the structures among possible zwitterionic and anionic forms may dominate over the other possible forms. Additional investigations using explicit solvent models are necessary to determine the stability of charged forms of glutamic acid in solution as our results clearly indicate that hydrogen bonding and its type have a major role in the structure and energy of conformers.     

Symbiotic interaction of endophytic bacteria with arbuscular mycorrhizal fungi and its antagonistic effect on Ganoderma boninense

Endophytic bacteria (Pseudomonas aeruginosa UPMP3 and Burkholderia cepacia UMPB3), isolated from within roots of oil palm (Elaeis guineensis Jacq.) were tested for their presymbiotic effects on two arbuscular mcorrhizal fungi, Glomus intraradices UT126 and Glomus clarum BR152B). These endophytic bacteria were also tested for antagonistic effects on Ganoderma boninense PER 71, a white wood rot fungal pathogen that causes a serious disease in oil palm. Spore germination and hyphal length of each arbuscular mycorrhizal fungal (AMF) pairing with endophytic bacteria was found to be significantly higher than spores plated in the absence of bacteria. Scanning electron microscopy (SEM) showed that the endophytic bacteria were scattered, resting or embedded on the surface hyaline layer or on the degraded walls of AMF spores, possibly feeding on the outer hyaline spore wall. The antagonistic effect of the endophytic bacteria was expressed as severe morphological abnormalities in the hyphal structures of G. boninense PER 71. The effects of the endophytic bacteria on G. boninense PER 71 hyphal structures were observed clearly under SEM. Severe inter-twisting, distortion, lysis and shriveling of the hyphal structures were observed. This study found that the effect of endophytic bacteria on G. intraradices UT126 and G. clarum BR152B resembled that of a mycorrhiza helper bacteria (MHB) association because the association significantly promoted AMF spore germination and hyphal length. However, the endophytic bacteria were extremely damaging to G. boninense PER 71.     

Kinetic behaviour of free lipase and mica-based immobilized lipase catalyzing the synthesis of sugar esters

The utilization of natural mica as a biocatalyst support in kinetic investigations is first described in this study. The formation of lactose caprate from lactose sugar and capric acid, using free lipase (free-CRL) and lipase immobilized on nanoporous mica (NER-CRL) as a biocatalyst, was evaluated through a kinetic study. The apparent kinetic parameters, K(m) and V(max), were determined by means of the Michaelis-Menten kinetic model. The Ping-Pong Bi-Bi mechanism with single substrate inhibition was adopted as it best explains the experimental findings. The kinetic results show lower K(m) values with NER-CRL than with free-CRL, indicating the higher affinity of NER-CRL towards both substrates at the maximum reaction velocity (V(max,app)>V(max)). The kinetic parameters deduced from this model were used to simulate reaction rate data which were in close agreement with the experimental values.     

Clinical Signs of Radiologic Pneumonia in Under-Five Hypokalemic Diarrheal Children Admitted to an Urban Hospital in Bangladesh

Background

Clinical signs of pneumonia are often veiled in under-five diarrheal children presenting with hypokalemia, making clinical diagnosis of pneumonia very difficult in such population. However, there is no published report that describes the influences of hypokalemia on the clinical signs of pneumonia in diarrheal children. Our objective was to assess the influences of hypokalemia, and their outcome in such children.

Methods

We prospectively enrolled all under-five diarrheal children (n = 180) admitted to the Special Care Ward of the Dhaka Hospital of icddr,b from September-December 2007 with radiological pneumonia who also had their serum potassium estimated. We compared the clinical features and outcome of the diarrheal children having pneumonia with (cases = 55) and without hypokalemia (controls = 125).

Results

The case-fatality among the cases was 2 times higher compared to the controls, but the difference was not statistically significant (p = 0.202). In logistic regression analysis, after adjusting for potential confounders such as age of the patient, clinical dehydration, severe wasting, abnormally sleepy, lower chest wall in-drawing, nasal flaring and inability to drink on admission, under-five diarrheal children with pneumonia who presented with nutritional edema had 3 times more risk to have hypokalemia compared to those without nutritional edema (OR = 2.76, 95% CI = 1.01–7.51) and these hypokalemic children were 64% less likely to present with fast breathing (OR = 0.36, 95% CI = 0.17–0.74).

Conclusion and significance

The results of our analysis are simple but may have great public health implications and underscore the importance of diligent assessment for pneumonia in under-five diarrheal children having risk of hypokalemia as in children with nutritional edema even in absence of fast breathing, a useful sign of pneumonia. This may help for early initiation of first dose of parental antibiotics along with potassium supplementation before referral to tertiary hospitals by health workers to combat probability of deaths in such population especially in resource limited settings.     

Effects of some neurokinin A analogues on tachykinin-induced contraction of guinea pig trachea.

A series of analogues of neurokinin A (NKA) has been synthesized and characterized by testing for their abilities, in vitro, to contract guinea pig tracheal smooth muscle or to antagonize NKA-, NKB- and SP-induced contraction of this tissue. Substitution of NKA residues Gly8 or Leu9 by conformationally restricting amino acids produced peptides that were antagonists of NKA action, but the type and specificity of the antagonism depended on the size of the peptide. Thus, while [Ala5, Aib8, Leu10]NKA(2-10) showed no agonism and was a specific, competitive antagonist of NKA, [Ala5, Aib8, Leu10]NKA(4-10) was a noncompetitive antagonist of NKA and substance P (SP) and was itself a weak agonist at concentrations above 10(-7) M.     

Secretory expression of thermostable T1 lipase through bacteriocin release protein

The extracellular production of T1 lipase was performed by co-expression of pJL3 vector encoding bacteriocin release protein in prokaryotic system. Secretory expression was optimized by considering several parameters, including host strains, inducer (IPTG) concentration, media, induction at A(600 nm), temperature, and time of induction. Among the host strains tested, Origami B excreted out 18,100 U/ml of lipase activity into culture medium when induced with 50 microM IPTG for 12 h. The Origami B harboring recombinant plasmid pGEX/T1S and pJL3 vector was chosen for further study. IPTG at 0.05 mM, YT medium, induction at A(600 nm) of 1.25, 30 degrees C, and 32 h of induction time were best condition for T1 lipase secretion with Origami B as a host.     

Preparation of human Melanocortin-4 receptor agonist libraries: linear peptides X-Y-DPhe7-Arg8-Trp(or 2-Nal)9-Z-NH2

Two libraries of hMC4R agonists, X-Y-DPhe⁷-Arg⁸-2-Nal⁹-Z-NH₂ and X-Y-DPhe⁷-Arg⁸-Trp⁹-Z-NH₂, totaling 185 peptides were prepared using Irori radiofrequency tagging technology and Argonaut Quest 210 Synthesizer, where X stands for N-caps, Y for His⁶ surrogates and Z for Gly¹⁰ surrogates. As a result of this study, His-modified pentapeptides with Trp were found to be more hMC4R potent than the corresponding 2-Nal analogs, novel N-caps and Gly surrogates were identified and 19 new peptides which are potent hMC4R agonists (EC₅₀ 1–15 nM) and selective against hMC1R were discovered.     

Synthesis and properties of new substituted 1,2,4-triazoles: potential antitumor agents

Cycloaddition of the reactive intermediates 4 with 1-(cyanomethyl)benzotriazole (5) and its N-2 isomer 9 furnished, after spontaneous rearrangements, the 1,2,4-triazole derivatives 8 and 10. Analogously, reaction of 4 with ethyl cyanoacetate lead to the 1,3,5-trisubstituted 1,2,4-triazoles 12, which gave on treatment with hydrazine the corresponding hydrazides 13. Treatment of 13d with galactose or phenyl isothiocayanate gave the 1-D-galactose-acylhydrazone 14 and the 1,2,4-triazole derivative 15, respectively. Compounds 8c; 10b,c; 13a,c and 14 were selected for the antitumor screening, whereby 8c, 13a, and 13c showed remarkable activity against leukemia, ovarian, renal and lung cancers (8c with Gl(50) of 0.70 microM, 0.07 microM against leukemia (CCRF-CEM and RPMI-8226), 0.02 microM against ovarian (OVCAR-3) and 0.60 microM against renal (CARKI-1) and lung cancers, respectively).     

Calcineurin-independent regulation of plasma membrane Ca2+ ATPase-4 in the vascular smooth muscle cell cycle

Calcineurin mediates repression of plasma membrane Ca²⁺-ATPase-4 (PMCA4) expression in neurons, whereas c-Myb is known to repress PMCA1 expression in vascular smooth muscle cells (VSMC). Here, we describe a novel mouse VSMC line (MOVAS) in which ⁴⁵Ca efflux rates decreased 50%, fura 2-AM-based intracellular Ca²⁺ concentrations ([Ca²⁺]_i) increased twofold, and real-time RT-PCR and Western blot revealed a 40% decrease in PMCA4 expression levels from G₀ to G₁/S in the cell cycle, where PMCA4 constituted 20% of total PMCA protein. Although calcineurin activity increased fivefold as MOVAS progressed from G₀ to G₁/S, inhibition of this increase with either BAPTA or retroviral transduction with peptide inhibitors of calcineurin (CAIN), or its downstream target nuclear factor of activated T cells (NFAT) (VIVIT), had no effect on the repression of PMCA4 mRNA expression at G₁/S. By contrast, Ca²⁺-independent activity of the calmodulin-dependent protein kinase-II (CaMK-II) increased eightfold as MOVAS progressed from G₀ to G₁/S, and treatment with an inhibitor of CaMK-II (KN-93) or transduction of a c-Myb-neutralizing antibody significantly alleviated the G₁/S-associated repression of PMCA4. These data show that G₁/S-specific PMCA4 repression in proliferating VSMC is brought about by c-Myb and CaMK-II and that calcineurin may regulate cell cycle-associated [Ca²⁺]_i through alternate targets. calcineurin; c-Myb; plasma membrane Ca²⁺-ATPase-4; cell cycle     

Thiosugar nucleosides. Synthesis and biological activity of 1,3,4-thiadiazole, thiazoline and thiourea derivatives of 5-thio-D-glucose

New acylated 5-thio-beta-D-glucopyranosylimino-disusbstituted 1,3,4-thiadiazols 8, and 11 were prepared, via spontaneous rearrangements, by cycloaddition of the glycosyl isothiocyanate 2 with the reactive intermediates 1-aza-2-azoniaallene hexachloroantimonates 4 and 6, respectively. Reaction of 2 with aminoacetone or chloroethylamine afforded the acylated 5-thio-beta-D-glucopyranosyl-4-imidazoline-2-thione nucleoside 16 and glucopyranosylamino-2-thiazoline derivative 18, respectively. Deblocking of 8, 11, 17 and 19 furnished the free nucleoside analogues 9, 12, 18 and 20, respectively. Analogously, treatment of 2 with chloroethylamine in the 1:2 ratio afforded the thioureylendisaccharide 21. No in vitro antiviral activity against HIV-1, HIV-2, human cytomegallovirus (HMCV), has been found for the new synthesized compounds.