Cloning,Expression, and Characterization of a Novel (<Emphasis Type="Italic">S</Emphasis>)-Specific Alcohol Dehydrogenase from <Emphasis Type="Italic">Lactobacillus kefir</Emphasis>

A gene encoding a novel (S)-specific NADH-dependent alcohol dehydrogenase (LK-ADH) was isolated from the genomic DNA of Lactobacillus kefir DSM 20587 by thermal asymmetric interlaced-polymerase chain reaction. The nucleotide sequence of (S)-LK-ADH gene (adhS) was determined, which consists of an open reading frame of 1,044 bp, coding for 347 amino acids with a molecular mass of 37.065 kDa. After a BLAST similarity search in GenBank database, the amino acid sequence of (S)-LK-ADH showed some homologies to several zinc containing medium-chain alcohol dehydrogenases. This novel gene was deposited into GenBank with the accession number of EU877965. adhS gene was subcloned into plasmid pET-28a(+), and recombinant (S)-LK-ADH was successfully expressed in E. coli BL21(DE3) by isopropyl-β-d-1-thiogalactopyranoside induction. Purified enzyme showed a high enantioselectivity in the reduction of acetophenone to (S)-phenylethanol with an ee value of 99.4%. The substrate specificity and cofactor preference of recombinant (S)-LK-ADH were also tested.     

Crystalline O,O′-di-sec-butyl and O,O′-diethyl dithiophosphate platinum(II) complexes: Synthesis, C and P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour

Crystalline bis(O,O′-di-sec-butyldithiophosphato)platinum(II) was prepared and studied by means of ¹³C, ³¹P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S₂P(O-sec-C₄H₉)₂}₂], in which the dithiophosphate groups display structural equivalence in both ³¹P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S,S′-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS₂P], in this molecule. The planar configuration of the [PtS₄] chromophore in structure 1 is governed by the dsp²-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from ethanol and the other one precipitated from an aqueous solution) are all characterised by almost rhombic ³¹P chemical shift tensors. The observed essential dispersion of the ³¹P NMR chemical shift is caused by a coexistence of six optical isomers of molecule 1. The thermal behaviour of this compound was studied by means of simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour shows that the mass of 1 is lost in three steps, involving successive thermal decompositions of the organic and inorganic parts of this compound with platinum(II) dithio-meta-phosphate and reduced metallic platinum as the intermediate and the final products, respectively.     

Cloning, Expression and Characterization of NADP-Dependent Isocitrate Dehydrogenase from Staphylococcus aureus

The Krebs cycle dictates oxidative and reductive conditions in Staphylococcus aureus and is mainly regulated by isocitrate dehydrogenase (IDH) which plays pivotal role in the growth and pathogenesis of the bacteria. In the present study, IDH gene from S. aureus ATCC12600 was cloned in the Sma I site of pQE 30 vector; the resultant clone was named as UVIDH1. The insert in the clone was sequenced (accession number HM067707), and the sequence showed complete homology with IDH sequence of other S. aureus strains reported in the database indicating presence of single enzyme in S. aureus, and considerable sequence homology with other bacteria was observed; however, only 24 % homology was found with NADP-dependent human IDH. Phylogenetically, the S. aureus IDH showed close identity with Bacillus subtilis and high degree of variability with other bacteria and human IDH. The expression of IDH in the clone UVIDH1 was induced with 1 mM IPTG, and the recombinant IDH was purified by passing through nickel metal chelate column; the purified recombinant IDH showed a single band in SDS–PAGE with a molecular weight of 40 kDa; K _m and V _max for isocitrate are 8.2?±?0.28 and 525?±?25 μM NADPH/mg/min, respectively, and for cofactor NADP 67.5?±?2.82?μM and V _max 50.5?±?2.12 μM NADPH/mg/min.     

An efficient method for the resolution of rac-VANOL by molecular complexation with (1S,2S)-(+)-diaminocyclohexane

An efficient and convenient process has been developed for the resolution of VANOL using commercially available (1S,2S)-(+)-diaminocyclohexane as the resolving reagent, with (R)- and (S)-VANOL being isolated in 86% and 74% yields, respectively. The resolving reagent was recovered in 91% yield and could be reused without any decrease in its efficiency. The X-ray structural analysis of a molecular crystal consisting of (R)-VANOL and (1S,2S)-(+)-diaminocyclohexane revealed that hydrogen bonding interactions between the functional groups of the host and guest molecules dominated the stereochemistry of the guest in the molecular complex.     

Enantiopure vic-amino alcohols and vic-diamines from (1R,2S)-1,2-dihydroxy-1,2-dihydronaphthalene

(1S,2S)-2-Hydroxy-1-amino-1,2,3,4-tetrahydronaphthalene, (1R,2R)-1-hydroxy-2-amino-1,2,3,4-tetrahydronaphthalene, (1S,2R)-1,2-diamino-1,2,3,4-tetrahydronaphthalene, (2R,3S)-2-hydroxy-3-amino-1,2,3,4-tetrahydronaphthalene and (2S,3S)-2,3-diammino-1,2,3,4-tetrahydronaphthalene have been synthesized from (1R,2S)-1,2-dihydroxy-1,2-dihydronaphthalene. The latter was obtained, using a protocol reported in a previous paper, from naphthalene using an Escherichia coli recombinant strain containing the naphthalene dioxygenase gene cloned from Pseudomonas fluorescens N3.     

Hydrothermal synthesis of TiO2 anatase nanocrystals using hexaprismatic-shaped oxo-carboxylate complexes

The molecular structural chemistry of titanium oxo-carboxylate complexes is critically reviewed with particular emphasis on the understanding of the various characterised molecular shapes. Among the four crucial parameters thought to have a structural influence on these shapes (nature of the OR alkoxy group, molar ratio C = O/Ti, stoichiometric ratio S = XCOOH/Ti and chemical nature of the carboxylic X moiety), it was concluded that the nature of R group, the C ratio and the steric hindrance of X were of minor importance. From the available data, it was also concluded that a high S ratio seems to favour corner-sharing versus edge-sharing of TiO₆ octahedra and that it was not possible to establish a clear correlation between the pK_a value of the carboxylic acid and the observed molecular shape. During this study, a new titanium oxo-carboxylate complex was obtained by reacting titanium isopropoxide with phenylacetic acid (PAAH, X = PhCH₂ at S = 3/2). This hexaprismatic Ti₆O₆(OPrⁱ)₆(PAA)₆ complex was characterised by single-crystal X-ray diffraction and used as a molecular precursor of TiO₂ anatase nanocrystals after hydrolysis by NMe₄OH and autoclaving at T = 200 °C. The size and size distribution of these nanocrystals were found to decrease as the R = Ti/NMe₄ ratio was increased. Nucleation and growth of anatase nanocrystals was found to be deeply modified by the presence of phenylacetate ions in the solution, but there was no evidence of an influence of the molecular anisotropy of the molecular precursor on the final shape of the nanocrystals. To cite this article: A. Rammal et al., C. R. Chimie 5 (2002) 59–66     

Molecular cloning, expression and sequence analysis of DNA polymerase I from an Iranian thermophilic bacterium, Bacillus sp. G (2006)

Thermostable DNA polymerases are widely used in DNA amplification reactions such as the Polymerase Chain Reaction (PCR), requiring the activity of the enzymes at high temperatures. The aim of the present study was to assess the potential biotechnological capabilities of Iranian thermostable DNA polymerases. To this end, we cloned the gene encoding a DNA polymerase from a novel thermophilic eubacterium, Bacillus sp. G (2006). Phylogentic analysis of this gene revealed that the new isolate belongs to the genera Bacillus. Sequence analysis of the fragment produced by degenerate primers also showed that it consists of 2,631 bp encoding an 876 amino acid protein, and subsequent amino acid sequence analysis of this DNA polymerase showed that it belongs to family A-type DNA polymerases. The expression vector pET28a (+) was chosen for expression of the gene fragment in the mesophilic host bacterium E. coli BL21. This expression vector has some advantages such as attachment of a Poly-His tag to the N-terminus of the protein for the ease of purification and a powerful promoter of lac-Z induced by IPTG. The band corresponding to the protein product was observed in the molecular weight range of about 100KDa on the SDS-PAGE gel after heat and Ni⁺²-NTA column chromatography. Using the dot blot technique, the polymerase activity of the enzyme was qualitatively confirmed at 70 °C. Therefore, it is suggested that optimizations of this activity could make this enzyme appropriate for PCR processes in future.     

A tandem enzyme reaction to produce optically active halohydrins,epoxides and diols

The recombinant halohydrin dehalogenase from Agrobacterium radiobacter AD1 was used to obtain enantiomerically pure halohydrins and epoxides by kinetic resolution. By adding an excess of the recombinant epoxide hydrolase from the same organism the reversible conversion was drawn to completion. Halohydrins such as (S)-2,3-dichloro-1-propanol (E>100) and (S)-2-chloro-1-phenylethanol (E=73) were obtained with an enantiomeric excess of higher than 99%. This is a novel biocatalytic route for obtaining enantiomerically pure aromatic halohydrins and epoxides.     

Cloning, Sequencing, and Expression of Nitrile Hydratase Gene of Mutant 4D Strain of Rhodococcus rhodochrous PA 34 in E. coli

The NHase encoding gene of mutant 4D was isolated by PCR amplification. The NHase gene of mutant 4D was successfully cloned and expressed in Escherichia coli by using Ek/LIC Duet cloning kits (Novagen). For the active expression of the NHase gene, the co-expression of small cobalt transporter gene (P-protein gene) has also been co-expressed with NHase gene E. coli. The nucleotide sequence of this NHase gene revealed high homology with the H-NHase of Rhodococcus rhodochrous J1. The recombinant E. coli cells showed higher NHase activity (5.9?U/mg?dcw) as compared to the wild (4.1?U/mg?dcw) whereas it is less than the mutant strain (8.4?U/mg?dcw). Addition of cobalt ion in Luria?CBertani medium is needed up to a very small concentration (0.4?mM) for NHase activity. The recombinant E. coli exhibited maximum NHase activity at 6?h of incubation and was purified with a yield of 56?% with specific activity of 37.1?U/mg protein.     

3-(((1S,3S)-3-((R)-Hydroxy(4-(trifluoromethyl)phenyl)methyl)-4-oxocyclohexyl)methyl)pentane-2,4-dione: Design and Synthesis of New Stereopure Multi-Target Antidiabetic Agent

The chiral drug candidates have more effective binding affinities for their specific protein or receptor site for the onset of pharmacological action. Achieving all carbon stereopure compounds is not trivial in chemical synthesis. However, with the development of asymmetric organocatalysis, the synthesis of certain vital chiral drug candidates is now possible. In this research, we have synthesized 3-(((1S,3S)-3-((R)-hydroxy(4-(trifluoromethyl)phenyl)methyl)-4-oxocyclohexyl)methyl)pentane-2,4-dione (S,S,R-5) and have evaluated it potential as multi-target antidiabetic agent. The stereopure compound S,S,R-5 was synthesized with a 99:1 enantiomeric ratio. The synthesized compound gave encouraging results against all in vitro antidiabetic targets, exhibiting IC₅₀ values of 6.28, 4.58, 0.91, and 2.36 in α-glucosidase, α-amylase, PTP1B, and DPPH targets, respectively. The molecular docking shows the binding of the compound in homology models of the respective enzymes. In conclusion, we have synthesized a new chiral molecule (S,S,R-5). The compound proved to be a potential inhibitor of the tested antidiabetic targets. With the observed results and molecular docking, it is evident that S,S,R-5 is a potential multitarget antidiabetic agent. Our study laid the baseline for the animal-based studies of this compound in antidiabetic confirmation.     

Thermal behavior of poly(thiocarbonylthio-1,3-phenylene)

The thermal behavior of poly(thiocarbonylthio-1,2-phenylene) (PTCTP) was investigated from the points of view of both thermal transitions and the reactions which occur on heating at high temperature. In order better to understand the latter, S,S-diphenyldithiocarbonate (DPDTC) was synthesized and its degradation studied.For the thermal transitions it was found that, compared with the analogous poly(1,3-phenylenecarbonate) (PPC), T_g did not change, whereas there was a decrease in T_m.The degradation proceeds through different reaction pathways: the first step seems to be the breaking of the S-carbonyl bond followed by the evolution of CO mainly and, to a lesser extent, of COS. The other reaction products are mainly disulfide and sulfide moieties.     

First total synthesis of glabramycin B and revision of its relative configuration

Structural revision of glabramycin B, which is an antibacterial 10-membered lactone isolated from a fermentation broth of Neosartorya glabra, was achieved by enantioselective synthesis of our proposed structure. The correct structure of glabramycin B was presumed on comparison with related compounds, and synthesis of it was succeeded via dianion alkylation, Shiina's lactonization and Stille cross-coupling. By this synthesis, we were able to correct the reported structural misassignment, and to confirm the relative configuration of glabramycin B to be 10S*,11S*,15R*,20S*.     

Hydroxynitrile lyase catalysed synthesis of heterocyclic (R)- and (S)-cyanohydrins

Heterocyclic saturated five- and six-membered ring ketones sometimes bearing a methyl substituent were reacted with HCN under enzyme catalysis using recombinant hydroxynitrile lyase from Hevea brasiliensis, as a rule (S)-selective, and Prunus amygdalus, (R)-selective. The resulting cyanohydrins were stereochemically characterised. The steric outcome of these transformations was interpreted by molecular modelling.     

Stereochemical analysis of d-glucopyranosyl-sulfoxides via a combined NMR,molecular modeling and X-ray crystallographic approach

(S)-α-Methoxyphenylacetic acid (MPAA) was used as an NMR shift reagent in combination with molecular modeling to predict the absolute configuration of a representative epimeric pair of glucopyranosyl sulfoxides. The correctness of this assignment was confirmed by X-ray crystallographic examination of one of the epimers, 3a1. The crystal structure of ethyl 2,3-di-O-acetyl-4,6-O-benzylidene-1-thio-β-d-glucopyranoside S-oxide monohydrate 3a1 was solved by direct methods and was shown to bear the (R)-configuration at the sulfinyl center in accordance with our prediction. Furthermore, the conformation of 3a1 in the solid state was found to be remarkably similar to that predicted by molecular mechanics calculations.     

Rheo-optical Raman study of microscopic deformation in high-density polyethylene under hot drawing

In situ observation of the microscopic structural changes in high-density polyethylene during hot drawing was performed by incorporating a temperature-controlled tensile machine into a Raman spectroscopy apparatus. It was found that the load sharing and molecular orientation during elongation drastically changed at 50°C. The microscopic stress of the crystalline chains decreased with increasing temperature and diminished around 50°C. Moreover, the orientation of the crystalline chains was greatly promoted above 50°C. These microscopic structural changes were caused by the thermal activation of the molecular motion within lamellar crystalline chains owing to the onset of relaxation of the crystalline phase.     

First way of enantioselective synthesis of moxifloxacin intermediate

A new method of enantioselective synthesis of(S,S)-2,8-diazobicyclo [4.3.0] nonane was found by using(R)-2-amino-2phenyl-ethanol as chiral induction reagent.The entire synthetic process included 8 steps which were easy to operate with high yield.The purification method was only simple recrystallization or even used directly in the next step without further purification.The total yield was 29%.     

Gene Cloning, Expression, and Characterization of a Cyclic Nucleotide Phosphodiesterase from Arthrobacter sp. CGMCC 3584

Based on thermal asymmetric interlaced polymerase chain reaction, the arpde gene encoding a cyclic nucleotide-specific phosphodiesterase was cloned from Arthrobacter sp. CGMCC 3584 for the first time. The 930-bp region encoded a 309-amino-acid protein with a molecular weight of 33.6 kDa. The recombinant ArPDE was able to hydrolyze 3′,5′-cAMP, 3′,5′-cGMP, and 2′,3′-cAMP. The K _m values of ArPDE for 3′,5′-cAMP and 3′,5′-cGMP were 6.82 and 12.82 mM, respectively. ArPDE was thermostable and displayed optimal activity at 45 °C and pH 7.5. The enzyme did not require any metal cofactors, although its activity was stimulated by 2 mM Co²⁺ and inhibited by Zn²⁺. Nucleotides, reducing agents, and sulfhydryl reagents had different inhibitory effects on the activity of ArPDE. NaF, the actual compound used to improve the industrial yield of cAMP, exhibited 62 % inhibitions at concentrations of 10 mM.     

Purification, Characterization, and Heterologous Expression of a Thermostable β-1,3-1,4-Glucanase from Bacillus altitudinis YC-9

Purification, characterization, gene cloning, and heterologous expression in Escherichia coli of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9 have been investigated in this paper. The donor strain B. altitudinis YC-9 was isolated from spring silt. The native enzyme was purified by ammonium sulfate precipitation, diethylaminoethyl-cellulose anion exchange chromatography, and Sephadex G-100 gel filtration. The purified β-1,3-1,4-glucanase was observed to be stable at 60 °C and retain more than 90 % activity when incubated for 2 h at 60 °C and remain about 75 % and 44 % activity after incubating at 70 °C and 80 °C for 10 min, respectively. Acidity and temperature optimal for this enzyme was pH 6 and 65 °C. The open reading frame of the enzyme gene was measured to be 732 bp encoding 243 amino acids, with a predicted molecular weight of 27.47 kDa. The gene sequence of β-1,3-1,4-glucanase showed a homology of 98 % with that of Bacillus licheniformis. After being expressed in E. coli BL21, active recombinant enzyme was detected both in the supernatants of the culture and the cell lysate, with the activity of 102.7 and 216.7 U/mL, respectively. The supernatants of the culture were used to purify the recombinant enzyme. The purified recombinant enzyme was characterized to show almost the same properties to the wild enzyme, except that the specific activity of the recombinant enzyme reached 5392.7 U/mg, which was higher than those ever reported β-1,3-1,4-glucanase from Bacillus strains. The thermal stability and high activity make this enzyme broad prospect for industry application. This is the first report on β-1,3-1,4-glucanase produced by B. altitudinis.     

A Novel Dextran Dextrinase from Gluconobacter oxydans DSM-2003: Purification and Properties

Dextran has already been widely applied in food, pharmaceutical, and chemical industries. In this study, a novel intracellular dextran dextrinase (DDase, EC 2.4.1.2) from Gluconobacter oxydans DSM-2003 exhibiting catalytic activity to synthesize dextran from maltodextrin was purified to homogeneity by ultrasonic cell disruption, ion exchange chromatography, and gel filtration. This procedure showed 187.5-fold purification from the cell-free extract with 41.9 % yield. And the apparent molecular weight was estimated to be 62 kDa by SDS-PAGE. It was different from the reported literatures, which found that the molecular weight of intracellular and extracellular DDase of G. oxydans ATCC-11894 was 300 and 152 kDa, respectively. Otherwise, it showed different physicochemical characteristics (optimal temperature and pH, thermal, pH stability, effect of metal ions) from the DDase of G. oxydans ATCC-11894. This indicated that DDase of G. oxydans DSM-2003 was a novel one compared to the reported literatures.