The structure of (2S*, 4S*)-4-methoxy-4-phenyl-4-(trimethylsilyl)-2-butyl 3,5-dinitrobenzoate, C21H26N2O7Si, is presented and discussed. The compound was synthesized by a stereoselective [1-4] retro-Brook reaction, followed by acylation using 3,5-dinitrobenzoyl chloride. The Si-O-carboxy chain adopts a sterically hindered conformation resembling a five-membered ring.

The relative and absolute stereochemistry of five compounds, (1R,2S,4R,5S)-exo-2-acetoxy-3,3-dimethylbicyclo[3.1.0]hexan-exo-4-yl camphanoate, C20H28O6, (I), (1R,2S,4R,5S,6R)-exa-2-acetoxy-3,3,exo-6-trimethylbicyclo[3.1.0]hexan-exo-4-yl camphanoate, C21H30O6, (II), (1R,2S,4R,5S, 6R)-exo-2-acetoxy-3,3,exo-6-trimethylbicyclo[3.1.0]hexan-exo-4-yl camphanoate, C21H30O6, (III), (1S,2S,4R,5R,6S)-exo-2-acetoxy-endo-6-(3-butenyl)-3,3,exo-6-trimethylbicyclo[3.1.0]hexan-exo-4-yl camphanoate, C25H36O6, (IV), and (1S,2S,4R,5R,6S)endo-2-acetoxy-3,3,exo-6-trimethylbicyclo [3.1.0]hexan-endo-4-yl camphanoate, C21H30O6, (V), (camphanoate is 4,7,7-trimethyl-3-oxo-2-oxabicyclo[2.2.1]heptane-1-carboxylate) have been determined and the conformation of the five-membered ring of each one is discussed. These compounds were synthesized by an enantioselective esterase-catalysed hydrolysis followed by acylation with camphanoyl chloride.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

MOTIVATION: The prediction reliability of seven multiple alignment servers currently available on the Internet (ClustalW, MAP, PIMA, Block Maker, MSA, MEME and Match-Box) has been evaluated in terms of power (sensitivity) and confidence (selectivity). Therefore, the alignments obtained have been respectively compared to refined structural alignments for 20 families of related proteins with low levels of identity. RESULTS: Results clearly show that any powerful method remains reliable when the rate of identity falls. For some methods, power and confidence decrease linearly with the rate of identity, while other methods emphasize reliability at the cost of a lower power. Increasing the number of related sequences included in the alignment may either improve or decrease the quality of the predictions substantially. For some methods, the gain in power or in confidence is quite systematic; for others, the effect of the addition of homologous sequences is highly unpredictable. Extracting the consensus between two different methods may increase the overall confidence of the predictions tremendously. Our conclusions induce users of sequence alignment methods on the Internet to select the most suitable technique according to their requirements in terms of selectivity and sensitivity. AVAILABILITY: The aligned sequences of the 20 alignments of structure can be obtained automatically by sending the message 'send: cabios_tests.txt' by e-mail to 'matchbox@biq.fundp.ac.be'. CONTACT: eric.depiereux@fundp.ac.be

A survey of the major known structural aspects of monoamine oxidase (MAO) is given and a first partial model of human MAO A is presented. This 3D model has been established using secondary structure predictions and fold recognition methods. It shows two alpha/beta domains (the FAD-binding N-terminal and central domains) and an alpha+beta domain. The C-terminal region is predicted to be responsible for anchoring the protein into the mitochondrial membrane and was not modeled. The covalent binding of the flavin cofactor to a cysteine residue is well predicted. The model is validated with experimental data from the literature and should be useful in designing new experimental studies (site-directed mutagenesis, chemical modification, specific antibodies). This first step towards the 3D structure of monoamine oxidase should contribute to a better understanding of the mechanisms of action and inhibition of this drug target in the treatment of clinical depression.

The structures of three compounds, namely, dimethyl 2-{(1S)-1-[(4S)-2,2-dimethyl-1,3-dioxolan-4-yl]-2-methyl-2-nitropropyl}malonate [C14H23NO8, (I)], dimethyl 2-{(1S)-1-[(4S)-2,2-dimethyl-1,3-dioxolan-4-yl]-2-methyl-2-(phenylsulfonyl)propyl}malonate [C20H28O8S, (II)], and dimethyl (3S)-2,2-dimethyl-3-[(4S)-2,2-dimethyl-1,3-dioxolan-4-yl]cyclopropane-1,1-dicarboxylate [C14H22O6, (III)], which are intermediates in the synthesis of chrysanthemic acid, are presented and discussed.

The structure of (2S)-1-[(1S,2R)-2-methyl-1-phenyl­cyclopentyl]-2-propyl 3,5-dinitrobenzoate, C22H24N2O6, (I), has been determined and the observed conformation is discussed. The observed proximity of the phenyl and dinitrobenzoate moieties can be explained by intramolecular electrostatic forces. Compound (I) was synthesized by carbocyclization followed by acylation with 3,5-dinitrobenzoyl chloride.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

In the crystal of the title compound, C12H16Se2, the packing involves quadrupolar interactions, and the 1,3-diselenane cycle adopts a chair conformation. This compound was synthesized using diselenocyanate and benzaldehyde.

MOTIVATION:The Match-Box software comprises protein sequence alignment tools based on strict statistical thresholds of similarity between protein segments. The method circumvents the gap penalty requirement: gaps being the result of the alignment and not a governing parameter of the procedure. The reliable conserved regions outlined by Match-Box are particularly relevant for homology modelling of protein structures, prediction of essential residues for site-directed mutagenesis and oligonucleotide design for cloning homologous genes by polymerase chain reaction (PCR).RESULTS:The method produces reliable results, as assessed by tests performed on protein families of known structures and of low sequence similarity. A reliability score is computed in relation to a threshold of similarity progressively raised to extend the aligned regions to their maximal length, up to the significance limit of matching segments. The score obtained at each position is printed below the sequences and allows a discriminant reading of each aligned region.AVAILABILITY:Sequences may be submitted to a Web server at http://www.fundp.ac.be/sciences/biologie/bms/+ ++matchbox_submit.html or sent by e-mail to matchbox/biq.fundp.ac.be (help available by just mailing help).

A Cl-terminated poly(methylphenyl)silane is synthesized and analyzed by 29Si-NMR spectroscopy. Assignments are proposed for the different peaks observed. A modification of the chemical shifts of the peaks relative to the main chain atoms is observed upon heating. From these experimental results and computational calculations on model compounds, the assignments of the three main peaks to configurationally different Si atoms are confirmed. © 1996 John Wiley & Sons, Inc.

d-glucose deprivation for a 45 min period reduces the ATP and creatine phosphate concentrations of astrocytes. Recovery experiments were initiated by reincubating the cells with d-glucose and glucose replacement metabolites. No recovery of ATP concentration could be obtained even after 1 h of reincubation with the replacement metabolites. After a 45 min incubation period without d-glucose, 14CO2 production fell to 36% and 21% of controls when the cells were reincubated respectively with d-[U-14C]-glucose and l-[2-14C]-pyruvate as substrate marker. When reincubated for 1 h in the presence of l-malate (1 mM) +l-pyruvate (10 mM) with l-[2-14C]-pyruvate as marker, a total recovery of 14CO2 production was ascertained. Reincubation of the glucose deprived cells in the presence of d-glucose (10 mM) did not increase the 14CO2 production indicating that the cells were unable to use d-glucose for oxidative purposes. As pyruvate concentration was dramatically decreased in glucose deprived cells, astrocytes were treated with α-ketovalerate (25 mM) which led to an 8-fold increase in pyruvate concentration. In these conditions 14CO2 production did not increase when the cells were incubated in the presence of l-malate (1 mM). O2 consumption of State 4 in astrocytes, submitted to glucose deprivation, decreased. These cells treated with FCCP could not be uncoupled and when reincubated in the presence of replacement metabolites only a 20% increase of oxygen consumption took place.

A search of the Cambridge Structural Database (CSD, version 5.05, 1993) was performed in order to compare the geometrical features of the hydrogen bonds involving on the one hand amino groups and on the other hand carboxylates, sulfonates or monohydrogen phosponates. Phosphonates were not considered because only four entries containing amino and phosphonate moieities were located in the CSD. The hydroxylic group of monohydrogen phosphonates primarily acts as a hydrogen-bond donor. The three moieties under study show NH...O hydrogen bonds with similar geometrical features. This statistical analysis has focused on the hydrogen-bond distances and angles and on the distributions of the H atoms around the acceptor O atoms of carboxylates, sulfonates or monohydrogen phosphonates.

Substituting a phosphinic, phosphonic, or sulfonic group for the carboxylic function of GABA led to GABAB agonists or antagonists. In order to determine the electronic properties which are important for agonism or antagonism at GABAB receptors, the atomic charges and the molecular electrostatic potentials (MEP) of GABA, its phosphinic, phosphonic, and sulfonic analogues have been compared. The atomic charges and the MEP have been obtained by ab initio molecular orbital (MO) calculations.

Epidemiological studies suggest that alcohol consumption is an independent risk factor for the development of non—insulin-dependent diabetes mellitus (NIDDM). Alcoholism is known to be associated with increased plasma levels of two novel diols, 2,3-butanediol and 1,2-propanediol, metabolites known to impair insulin action in isolated adipocytes. This study examines whether 2,3-butanediol and 1,2-propanediol have the capacity to impair insulin action acutely in vivo in the rat. Using the euglycemic-hyperinsulinemic clamp, it is shown that the two diols reduce whole-body glucose utilization (by ∼30%), with the onset of insulin resistance in vivo occurring at plasma concentrations of 2,3-butanediol (33 μmol/L) at least one order of magnitude (P < .001) lower than 1,2-propanediol (432 μmol/L). Tracer methodologies using [U-14C]glucose and 2-deoxy[1-3H]glucose indicate that the reduction in whole-body glucose utilization is accompanied by a reduction in glucose uptake and glycogen synthesis in the skeletal muscle and heart. The association between elevated plasma diol levels and insulin resistance demonstrated in this report raises the question of whether there is a link between he high plasma diol levels in alcohol abusers and their increased susceptibility to NIDDM.

Kemit is a molecular modeling package based on the PHIGS standard and its extension PHIGS+. This contribution will address important concepts of PHIGS, hierarchy and interactivity, with particular emphasis on their utility in molecular modeling programs for particular options as real-time generation of new conformations and flexible superimpositions of molecular structures. A few words are also added on display realism.