Affine Hall-Littlewood Functions for A(1)((1)) And Some Constant Term Identities of Cherednik-Macdonald-Mehta Type

We study t-analogs of string functions for integrable highest weight representations of the affine Kac-Moody algebra A(1)((1)). We obtain closed form formulas for certain t-string functions of levels 2 and 4. As corollaries, we obtain explicit identities for the corresponding affine Hall-Littlewood functions, as well as higher level generalizations of Cherednik's Macdonald and Macdonald-Mehta constant term identities.

Crystal structure of a daturalactone - a withanolide

The crystal structure of a daturalactone derivative has been determined by X-ray structural analysis. The compound crystallizes in orthorhomic space group P2(1)2(1)2(1) with cell parameters a = 15.141(1) angstrom, b = 18.425(1) angstrom, c = 19.251(2) angstrom. The structure was solved by direct methods and refined to R = 0.082. The asymmetric unit contains two non-equivalent molecules. Extensive hydrogen bonding is present. The conformations of the rings are A: a distorted half-chair, B: a perfect half-chair, C: a chair, D: an envelope-half chair and E: a twist boat. Ring junctions A/B, B/C, C/D are all trans fused. Methyl carbons C(18), C(19), C(27) and the lactone moiety is beta-oriented whereas the methyl carbons C(21) and C(28) are alpha-oriented.

Dynamic structure of charge carrier in polyaniline by near-infrared excited resonance Raman spectroscopy

New vibrational Raman features characteristic to the conductive form of polyaniline have been observed with the near-infrared excitation at 1047 nm. Based on an analogy with the resonance Raman spectrum of Michler's ketone in the lowest excited triplet (T-1) state, we consider these features as due to a dynamic structure of a diimino-1,4-phenylene unit in the polyaniline chain exchanging a positive charge very rapidly. This consideration directly leads to a conducting mechanism in which a positive charge migrates from one nitrogen to the other through the conjugated chain of polyaniline.

Effect of strain rate on the high-temperature low-cycle fatigue properties of a nimonic PE-16 superalloy

Strain-rate effects on the low-cycle fatigue (LCF) behavior of a NIMONIC PE-16 superalloy have been evaluated in the temperature range of 523 to 923 K. Total-strain-controlled fatigue tests were per-formed at a strain amplitude of +/-0.6 pct on samples possessing two different prior microstructures: microstructure A, in the solution-annealed condition (free of gamma' and carbides); and microstructure B, in a double-aged condition with gamma' of 18-nm diameter and M23C6 carbides. The cyclic stress response behavior of the alloy was found to depend on the prior microstructure, testing temperature, and strain rate. A softening regime was found to be associated with shearing of ordered gamma' that were either formed during testing or present in the prior microstructure. Various manifestations of dynamic strain aging (DSA) included negative strain rate-stress response, serrations on the stress-strain hysteresis loops, and increased work-hardening rate. The calculated activation energy matched well with that for self-diffusion of Al and Ti in the matrix. Fatigue life increased with an increase in strain rate from 3 x 10(-5) to 3 x 10(-3) s-1, but decreased with further increases in strain rate. At 723 and 823 K and low strain rates, DSA influenced the deformation and fracture behavior of the alloy. Dynamic strain aging increased the strain localization in planar slip bands, and impingement of these bands caused internal grain-boundary cracks and reduced fatigue life. However, at 923 K and low strain rates, fatigue crack initiation and propagation were accelerated by high-temperature oxidation, and the reduced fatigue life was attributed to oxidation-fatigue interaction. Fatigue life was maximum at the intermediate strain rates, where strain localization was lower. Strain localization as a function of strain rate and temperature was quantified by optical and scanning electron microscopy and correlated with fatigue life.

Effects of halogen substitution in nucleic acid components. Structure of sodium 5-bromocytidine 5'-phosphate hydrate

The conformation of 5-bromocytidine 5'-monophosphate in the title compound, Na+.C9H11BrN3O8P-.1.25H2O, is anti, C(3')-endo and gauche-gauche, similar to that in analogous non-halogenated nucleosides/nucleotides. The Na ion coordinates directly with phosphate O atoms and base atoms. Br is not involved in any stacking interaction.

First total synthesis of (±)-myltayl-4(12)-ene and single-crystal X-ray structure of exo-12-normyltaylan-4-yl 4-nitrobenzoate

The total synthesis of the unusual sesquiterpene (+/-)-myltayl-4(12)-ene 3 starting from the readily available cyclogeraniol 5 and the single-crystal X-ray structure of the 4-nitrobenzoate 12 of the noralcohol 11 are described.

Potassamide induced in situ benzylation of 5,6-dihydroisoquinolines: Structure of novel products

Potassamide induced in situ benzylation of 1-alkyl-4-cyano-3-methoxy-5,6-dihydroisoquinolines (1a-b) with benzyl iodide gave the 5-benzyl-, 5,9-dibenzyl- and 4,4-dibenzyl-5,6-dihydroisoquinolines (9a-b, 8a-b and 10a-b), isoquinoline derivatives (4a-b) and diastereomeric mixture of 4-benzyl-1,2,3,4-tetrahydroisoquinolin-3(2H)-ones (11a-b & 11'a-b). Structures were assigned on the basis of spectral data [Mass, H-1 & C-13 NMR, 2D NOESY]. A few reactions carried out to transform the diastereomeric mixture of compounds 11a and 11's to the spirobenzylisoquinoline system 7a isomeric with naturally occurring ochotensane system ga are discussed.

Primary structure of sesbania mosaic virus coat protein: its implications to the assembly and architecture of the virus

Sesbania mosaic virus (SMV) is a plant virus that infects Sesbania grandiflora plants in Andhra Pradesh, India. The amino acid sequence of the coat protein of SMV was determined using purified peptides generated by cleavage with trypsin, chymotrypsin, V8 protease and clostripain. The 230 residues so far determined were compared to the corresponding residues of southern bean mosaic virus (SBMV), the type member of sobemoviruses. The overall identity between the sequences is 61.7%. The amino terminal 64 residues, which constitute an independent domain (R-domain) known to interact with RNA, are conserved to a lower extent (52.5%). Comparison of the positively charged residues in this domain suggests that the RNA-protein interactions are considerably weaker in SMV. The residues that constitute the major domain of the coat protein, the surface domain (S-domain, residues 65-260), are better conserved (66.5%). The positively charged residues of this domain that face the nucleic acid are well conserved. The longest conserved stretch of residues (131-142) corresponds to the loop involved in intersubunit interactions between subunits related by the quasi 3-fold symmetry. A unique cation binding site located on the quasi 3-fold axis contributes to the stability of SMV. These differences are reflected in the increased stability of the SMV coat protein and its ability to be reconstituted with RNA at pH 7.5. A major epitope was identified using monoclonal antibodies to SMV in the segment 201-223 which contains an exposed helix in the capsid structure. This region is highly conserved between SMV and SBMV (70%) suggesting that it could represent the site of an important function such as vector recognition.

Crystal structure of Salmonella typhimurium 2-methylcitrate synthase: Insights on domain movement and substrate specificity

2-Methylcitric acid (2-MCA) cycle is one of the well studied pathways for the utilization of propionate as a source of carbon and energy in bacteria such as Salmonella typhimurium and Escherichia coli. 2-Methylcitrate synthase (2-MCS) catalyzes the conversion of oxaloacetate and propionyl-CoA to 2-methylcitrate and CoA in the second step of 2-MCA cycle. Here, we report the X-ray crystal structure of S. typhimurium 2-MCS (StPrpC) at 2.4 A resolution and its functional characterization. StPrpC was found to utilize propionyl-CoA more efficiently than acetyl-CoA or butyryl-CoA. The polypeptide fold and the catalytic residues of StPrpC are conserved in citrate synthases (CSs) suggesting similarities in their functional mechanisms. In the triclinic P1 cell, StPrpC molecules were organized as decamers composed of five identical dimer units. In solution, StPrpC was in a dimeric form at low concentrations and was converted to larger oligomers at higher concentrations. CSs are usually dimeric proteins. In Gram-negative bacteria, a hexameric form, believed to be important for regulation of activity by NADH, is also observed. Structural comparisons with hexameric E. coil CS suggested that the key residues involved in NADH binding are not conserved in StPrpC. Structural comparison with the ligand free and bound states of CSs showed that StPrpC is in a nearly closed conformation despite the absence of bound ligands. It was found that the Tyr197 and Leu324 of StPrpC are structurally equivalent to the ligand binding residues His and Val, respectively, of CSs. These substitutions might determine the specificities for acyl-CoAs of these enzymes. (C) 2010 Elsevier Inc. All rights reserved.

Reaction of normal and pseudo 2-formylbenzenesulfonyl chlorides with amines:experimental and theoretical studies on the structure of 2-formyl benzenesulfonamides in solid, solution and gas phases

The reaction of 2-formylbenzenesulfonyl chloride 1 and its pseudo isomer 2 with primary amines give either the corresponding sulfonamido Schiff bases or the corresponding 2-formylbenzenesulfonamide depending on the concentration of the amine used. The derivatives exist as an equilibrium mixture of the corresponding sulfonamide and 2-alkyl-3-hydroxy(or 3-aminoalkyl)-benzisothiazole-1,1-dioxide. Spectroscopic studies suggest that 2-formylbenzenesulfonamides exist as benzisothiazole-1,1-dioxides in the solid state, as a mixture of 2-formylbenzenesulfonamide and the corresponding benzisothiazole-1,1-dioxide in solution and as 2-formyl-benzenesulfonamides in the gas phase.

Synthesis and x-ray crystal structure of a CuII-theophylline complex: [Cu(theo)2 (H2O)3]·2H2O

The complex [Cu-II (theo)(2)(H2O)(3)].2H(2)O (theo = theophylline) was obtained from aqueous solution. The crystals belong to the monoclinic system, space group P2(1)/n, and are reflection twins about the (001) face. The structure was solved using data from a twinned crystal and refined to final R and R(W) values of 0.069 and 0.064, respectively. Copper has a square-pyramidal coordination with two thee molecules coordinating through N(7) at equatorial positions. The remaining sites are occupied by water molecules. O(6) of one of the thee molecules is at the other axial site at a longer distance of 3.18 Angstrom. This could lead to an alternate (4+1+1) octahedral coordination geometry for Cu-II. The packing is stabilized by stacking interactions between the theophylline moieties at an average separation of 3.46 Angstrom.

The complete primary structure of a unique mannose/glucose-specific lectin from field bean (Dolichos lab lab)

The complete amino acid sequence of two non identical subunits of the glucose/mannose-specific lectin from Dolichos lab lab (field bean) has been determined by sequential Edman analyses of the intact subunits and peptides derived by enzymatic and chemical cleavage. Peptides were purified by reverse phase high performance liquid chromatography and ion pair chromatography. The D. lab lab lectin is a glycoprotein having two polypeptide chains of 132 and 105 amino acid residues. The amino acid sequence of the D. Lab lab lectin is compared with the various lectins of the family Leguminosae. The D. lab lab lectin is the only species of the tribe Phaseoleae that contains two nonidentical subunits of almost equal size and that shows a specificity to glucose/ mannose. The lectin shows a greater homology to the glucose/mannose specific lectins, especially concanavalin A. The unique subunit architecture of the D. lab lab lectin indicates the presence of new post translational cleavage sites.

The primary structure of sheep liver cytosolic serine hydroxymethyltransferase and an analysis of the evolutionary relationships among serine hydroxymethyltransferases

The complete amino-acid sequence of sheep liver cytosolic serine hydroxymethyltransferase was determined from an analysis of tryptic, chymotryptic, CNBr and hydroxylamine peptides. Each subunit of sheep liver serine hydroxymethyltransferase consisted of 483 amino-acid residues. A comparison of this sequence with 8 other serine hydroxymethyltransferases revealed that a possible gene duplication event could have occurred after the divergence of animals and fungi. This analysis also showed independent duplication of SHMT genes in Neurospora crassa. At the secondary structural level, all the serine hydroxymethyltransferases belong to the alpha/beta category of proteins. The predicted secondary structure of sheep liver serine hydroxymethyltransferase was similar to that of the observed structure of tryptophan synthase, another pyridoxal 5'-phosphate containing enzyme, suggesting that sheep liver serine hydroxymethyltransferase might have a similar pyridoxal 5'-phosphate binding domain. In addition, a conserved glycine rich region, G L Q G G P, was identified in all the serine hydroxymethyltransferases and could be important in pyridoxal 5'-phosphate binding. A comparison of the cytosolic serine hydroxymethyltransferases from rabbit and sheep liver with other proteins sequenced from both these sources showed that serine hydroxymethyltransferase was a highly conserved protein. It was slightly less conserved than cytochrome c but better conserved than myoglobin, both of which are well known evolutionary markers. C67 and C203 were specifically protected by pyridoxal 5'-phosphate against modification with [C-14]iodoacetic acid, while C247 and C261 were buried in the native serine hydroxymethyltransferase. However, the cysteines are not conserved among the various serine hydroxymethyltransferases. The exact role of the cysteines in the reaction catalyzed by serine hydroxymethyltransferase remains to be elucidated.

The Reaction of a Nitro-Capped Cobalt(III) Cage Complex With Base: the Crystal Structure of a Contracted Cage Complex, and the Mechanism of Its Formation

The synthesis, properties and crystal structure of the cage complex (1-hydroxy-8-methyl-3,6,10,13,15,18-hexaazabicyclo[6.6.5]nonadecane)cobalt(III) chloride hydrate ([Co(Me,OH-absar)] C13.H2O) are reported. The mechanism of the formation of this contracted cavity cage from a nitro-capped hexaazabicycloicosane type cage has been investigated. Treatment of (1-methyl-8-nitro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane)cobalt(III) chloride ([Co(Me,NO2-sar)] 3+) with excess base in aqueous solution leads initially to rapid (t1/2 < 1 ms) and reversible deprotonation of one coordinated secondary amine. This species undergoes a retro-Mannich type reaction and imine hydrolysis (t1/2 almost-equal-to 90 s). Quenching the reaction with acid gives rise to a pair of isomeric intermediate species which have been isolated and characterized. They have a pendant arm macrocyclic structure, resulting from the loss of a methylene unit from one of the arms of the cap. Heating either isomer in aqueous solution gives the new cage compound with the contracted cap. It is postulated that this occurs through a Nef reaction, resulting in the formation of a ketone which then condenses with the coordinated primary amine. A comparison with the corresponding bicycloicosane analogue indicates a reduced chromophoric cavity size for the contracted cage. The reduction potential of the cobalt(III)/cobalt(II) couple is 170 mV more negative for the smaller cage, and, in the electronic spectrum of the cobalt(III) complex, the d-d transitions are both shifted to higher energy, corresponding to a stronger ligand field.

The structure of amorphous platinum disulfide as studied by anomalous x-ray-scattering

Anomalous X-ray scattering (AXS) has been applied to study the structure of amorphous platinum disulfide, Pt1-xS2, prepared by the precipitation process. The local atomic arrangement in amorphous Pt1-xS2 was determined by the least-squares variational method so as to reproduce the experimental differential interference function at the Pt L(III) absorption edge by the AXS method as well as the ordinary interference function by MoK alpha. The structural unit in amorphous Pt1-xS2 is found to be a PtS6 octahedron, similar to that in crystalline PtS2. These octahedra share both their corners and edges, while only edge-sharing linkages occur in crystalline PtS2.