Specific inhibitors of methane oxidation in Methylosinus trichosporium

Methane oxidation by washed cell suspensions of Methylosinus trichosporium OB3B was selectively inhibited by 25 compounds, including metal binding components such as carbon monoxide (85% O₂: 15% CO), KCN (10^-6 M), αα′-dipyridyl (10^-4 M), 8-quinolinol (10^-4 M), thiosemicarbazide (10^-5 M), thiourea (10^-5 M), hydroxylamine (10^-4 M), histidine (10^-2 M), British Anti-Lewisite (5x10^-3 M), and miscellaneous known inhibitors of other oxygenases. A role for copper in the methane oxygenase system was suggested by the pattern of inhibition and relief of inhibition by added metal ions.     

The genetics of complex diseases

Genetic factors influence virtually every human disorder, determining disease susceptibility or resistance and interactions with environmental factors. Our recent successes in the genetic mapping and identification of the molecular basis of mendelian traits have been remarkable. Now, attention is rapidly shifting to more-complex, and more-prevalent, genetic disorders and traits that involve multiple genes and environmental effects, such as cardiovascular disease, diabetes, rheumatoid arthritis and schizophrenia. Rather than being due to specific and relatively rare mutations, complex diseases and traits result principally from genetic variation that is relatively common in the general population. Unfortunately, despite extensive efforts by many groups, only a few genetic regions and genes involved in complex diseases have been identified. Completion of the human genome sequence will be a seminal accomplishment, but it will not provide an immediate solution to the genetics of complex traits.     

The "prismane" protein resolved: X-ray structure at 1.7 Å and multiple spectroscopy of two novel 4Fe clusters

The three-dimensional structure of the native "putative prismane" protein from Desulfovibrio vulgaris (Hildenborough) has been solved by X-ray crystallography to a resolution of 1.72?Å. The molecule does not contain a [6Fe-6S] prismane cluster, but rather two 4Fe clusters some 12?Å apart and situated close to the interfaces formed by the three domains of the protein. Cluster 1 is a conventional [4Fe-4S] cubane bound, however, near the N-terminus by an unusual, sequential arrangement of four cysteine residues (Cys 3, 6, 15, 21). Cluster 2 is a novel 4Fe structure with two μ₂-sulfido bridges, two μ₂-oxo bridges, and a partially occupied, unidentified μ₂ bridge X. The protein ligands of cluster 2 are widely scattered through the second half of the sequence and include three cysteine residues (Cys 312, 434, 459), one persulfido-cysteine (Cys 406), two glutamates (Glu 268, 494), and one histidine (His 244). With this unusual mixture of bridging and external type of ligands, cluster 2 is named the "hybrid" cluster, and its asymmetric, open structure suggests that it could be the site of a catalytic activity. X-ray absorption spectroscopy at the Fe K-edge is readily interpretable in terms of the crystallographic model when allowance is made for volume contraction at 10?K; no Fe··Fe distances beyond 3.1?Å could be identified. EPR, Mössbauer and MCD spectroscopy have been used to define the oxidation states and the magnetism of the clusters in relation to the crystallographic structure. Reduced cluster 1 is a [4Fe-4S]¹⁺ cubane with S?=?3/2; it is the first biological example of a "spin-admixed" iron-sulfur cluster. The hybrid cluster 2 has four oxidation states from (formally) all Fe^III to three Fe^II plus one Fe^III. The four iron ions are exchange coupled resulting in the system spins S?=?0, 9/2, 0 (and 4), 1/2, respectively, for the four redox states. Resonance Raman spectroscopy suggests that the bridging ligand X which could not be identified unambiguously in the crystal structure is a solvent-exchangeable oxygen.     

Distribution of zooplankton associated with the Endeavour Ridge Hydrothermal Plume

Enhanced zooplankton biomass was found in shallow (<900 m)and deep (>900 m) net samples collected over the EndeavourRidge hydrothermal plume in 1991 and 1992. This enhanced biomasswas manifest in considerably higher abundance values for mostspecies in proximity to the vent field compared with abundancevalues from net samples collected 10–50 km off-axis. Thespecies most enriched in abundance by the hydrothermal plumewere those normally found in the mid-depth scattering layerat 400–900 m depth. These mid-depth animals were alsothe dominant fauna in the deep scattering layers that overliethe hydrothermal plume at depths of 1200–1900 m near themain vent field. The abundance and biomass dominants were specieswith pronounced ontogenetic migration patterns, and their associatedpredators. The abundance of many typically deep species wasalso enhanced over the main vent field. Faimal compositionsof net samples were compared using a similarity measure andaverage linkage rule. Deep fauna in proximity to the vent fieldbut not associated with scattering layers (Group 1), were similarto deep fauna 10–50 km off axis. The fauna of the deepscattering layer over the vent field (Group 2) was most similarto surface and mid- depth scattering layer fauna found withina 50km radius of the vent field. Statistical tests of linkagesobtained using a bootstrap method indicate that the abundanceand taxonomic composition of the two faunal groups were significantlydistinct in 1992, but not in 1991. We conclude that there wasconsiderable infiltration of shallow fauna into the deep scatteringlayers within 2–3 km of the main vent field, less extensiveinfiltration 10–15 km to the noilh and south of the ventfield in 1991, and insignificant infiltration at stations 50kmto the west of the vent field in 1992. A bootstrap analysiscomparing the faunal composition of nets towed above 900 m depthshowed that shallow fauna were not significantly distinct betweenthe two sampling years or up to 50 km away from the vent field.     

Hydrocarbon production in Anacystis montana and Botryococcus braunii

The production of labelled aliphatic hydrocarbons in Anacystis montana and Botryococcus braunii has been studied using Na₂CO₃ [¹⁴C] as a carbon source. The major hydrocarbon produced by A. montana is pentadecane (ca 93%) accompanied by a pentadecene (ca 4%) and other hydrocarbons in the range C₁₃-C₁₇. Long chain (C₂₁-C ₃₃) hydrocarbons could not be detected in this organism. The variety of unsaturated hydrocarbons (C₂₅-C₃₁) previously reported in Botryococcus braunii is confirmed and contrasts with the synthesis of unsaturated C₁₇ hydrocarbons only, in axenic cultures prepared from single cell isolates of this colonial alga.     

Intestinal microsomes: polyunsaturated fatty acid metabolism and regulation of enterocyte transport properties

Recent evidence has suggested that transport of nutrients from the lumen to the interior of the gastrointestinal epithelium and exit of nutrients from the enterocyte to the circulation is governed by physicochemical properties of brush border and basolateral membranes, respectively. The main determinants of membrane properties are phospholipid, cholesterol, and fatty acyl chain composition (chain length and degree of unsaturation). Lipid synthesis occurs in enterocyte microsomes and the fine tuning of lipid composition is done at other subcellular sites by deacylation-reacylation or by changing the polar head group (e.g., by phosphatidylethanolamine methyltransferase). The present paper will focus on the mechanisms by which enterocyte membranes adapt functional properties in response to external stimuli. It is proposed that under the influence of internal or external stress, the enzymes of lipid metabolism in microsomes are modulated. These changes in lipid synthesis are reflected in other subcellular membranes, changing their physicochemical status and thus transport phenomena. One of the initial events appears to be alteration in desaturase enzyme activity. Our results suggest that desaturase activity and the fatty acyl profiles of the intestinal mucosal phospholipid rapidly respond to physiological conditions such as fasting and dietary fat treatment.     

Inhibitors of hepatitis C virus NS3.4A protease 1. Non-charged tetrapeptide variants

Tetrapeptide-based peptidomimetic compounds have been shown to effectively inhibit the hepatitis C virus NS3.4A protease without the need of a charged functionality. An aldehyde is used as a prototype reversible electrophilic warhead. The SAR of the P1 and P2 inhibitor positions is discussed.     

Signatures of demographic history and natural selection in the human major histocompatibility complex Loci

Many lines of evidence show that several HLA loci have experienced balancing selection. However, distinguishing among demographic and selective explanations for patterns of variation observed with HLA genes remains a challenge. In this study we address this issue using data from a diverse set of human populations at six classical HLA loci and, employing a comparative genomics approach, contrast results for HLA loci to those for non-HLA markers. Using a variety of analytic methods, we confirm and extend evidence for selection acting on several HLA loci. We find that allele frequency distributions for four of the six HLA loci deviate from neutral expectations and show that this is unlikely to be explained solely by demographic factors. Other features of HLA variation are explained in part by demographic history, including decreased heterozygosity and increased LD for populations at greater distances from Africa and a similar apportionment of genetic variation for HLA loci compared to putatively neutral non-HLA loci. On the basis of contrasts among different HLA loci and between HLA and non-HLA loci, we conclude that HLA loci bear detectable signatures of both natural selection and demographic history.     

Substituted N-{3-[(1,1-dioxido-1,2-benzothiazol-3-yl)(phenyl)amino]propyl}benzamide analogs as potent Kv1.3 ion channel blockers. Part 2

We report the synthesis and in vitro activity of a series of novel substituted N-{3-[(1,1-dioxido-1,2-benzothiazol-3-yl)(phenyl)amino]propyl}benzamide analogs. These analogs showed potent inhibitory activity against Kv1.3. Several demonstrated similar potency to the known Kv1.3 inhibitor PAP-1 when tested under the IonWorks patch clamp assay conditions. Two compounds 13i and 13rr were advanced further as potential tool compounds for in vivo validation studies.     

Plasmid-associated transfer of tetracycline resistance in Bacteroides ruminicola

Tetracycline resistance was transferred at frequencies between 10(-7) and 10(-6) per recipient cell in anaerobic matings between two strains of the strictly anaerobic rumen bacterium Bacteroides ruminicola. The donor strain, 223/M2/7, was a multiple-plasmid-bearing tetracycline-resistant strain from the ovine rumen, and the recipient, F101, was a rifampin-resistant mutant of B14, a bovine strain belonging to B. ruminicola subsp. brevis. Resistance transfer could occur in the presence of DNase, but not in dummy mating mixtures in which filtrate from a donor culture replaced donor cells. Acquisition of tetracycline resistance by the recipient was accompanied by the appearance of a 19.5-kilobase pair plasmid (designated pRRI4) which was homologous with a plasmid of similar size and restriction pattern present in the donor strain. A transconjugant (F115) carrying pRRI4 was also able to act as a donor of tetracycline resistance and plasmid DNA in matings with another recipient. Derivatives of F115 that had spontaneously lost tetracycline resistance lacked detectable plasmid DNA. It is concluded that pRRI4 mediated the transfer of tetracycline resistance. Transfer of resistance was not detectably enhanced by pregrowth of the donor in medium containing tetracycline. Transfer of tetracycline resistance was not detected from 223/M2/7 to a strain, 23 belonging to B. ruminicola subsp. ruminicola.