Stereoselective Synthesis of Phosphorus Analogs of (R)-Carnitine and (R)-Gabob

Bioreduction of 3-substituted-2-oxoalkanephosphonates by baker's yeast afforded corresponding 2-hydroxy-alkanephosphonates in good yields and ee value. These compounds ( 2a,b ) could serve as useful chirons for the stereoselective synthesis of phosphorus analogs of (R)-Carnitine and (R)-GABOB.     

Asymmetric bioreduction of substituted acenaphthenequinones using plant enzymatic systems： A novel strategy for the preparation of （＋）- and （-）-mono hydroxyacenaphthenones

Regio- and enantioselective reduction of substituted acenaphthenequinones were conducted under mild reaction conditions using plant enzymatic systems. A screening of 15 plants allowed the selection of two suitable plants fulfilling enantiocomple- mentarity. The （＋）- and （-）-mono hydroxyacenaphthenones were achieved with high conversion and good enantiomeric purity using peach （Prunus persica （L.） Batsch., conversion 98%, 71% ee） and carrot （Daucus carota L., conversion 95%, 81% ee）, respectively.     

乳酸杆菌A09吸附还原Ag（Ⅰ）的谱学表征

Pooley[1]发现氧化亚铁硫杆菌(Thiobacillusferroxidans)和氧化硫硫杆菌(Thiobacillusthiooxidans)能在其细胞表面累积银,形成Ag2S,每克干重细胞吸附250mgAg2S.文献[2]也报导了类似的研究结果.一些霉菌也具有吸收金、银等重金属的能力[3].Brierley等[4]研究了用微生物制备回收贵金属的去除剂(MRA),用它能从摄影废液中回收银,每克MRA累积94mgAg;同时指出,贵金属生物吸附也包含金属离子被还原为金属的过程.在微生物吸附还原贵金属前期研究[5－9]的基础上,我们从金、银矿土等不同来源的细菌菌株中,筛选获得一株吸附、还原Ag＋…     

Ag+生物吸附的谱学研究

我们曾经研究了地衣芽孢杆菌R08和啤酒酵母废菌体吸附Pd2+以及巨大芽孢杆菌D01吸附Au3+过程的作用机理。有关乳酸杆菌A09吸附Ag+1的作用特点已有报道。本文在此基础上，进一步用谱学技术研究A09菌体吸附还原Ag+的作用机理。     

Bragg-regime engineering by columnar thinning of chiral sculptured thin films

Using a microscopic-to-continuum model of sculptured thin films (STFs) as two-phase composite materials, we have examined the optical consequences of post-deposition, uniform, columnar thinning of chiral STFs. Our results indicate that thinning processes such as etching and bioreduction can be useful in engineering the Bragg regimes of STFs after deposition. Uniform columnar thinning blue-shifts the Bragg regime and can improve the Bragg features of a chiral STF.     

A convenient approach to (S)-2-ethylhexan-1-ol mediated by baker’s yeast

The baker’s yeast (Saccharomyces cerevisiae) mediated asymmetric bioreduction of 2-ethylhex-2-enal (1) went smoothly under a mild condition and afforded a high yield of (S)-2-ethylhexan-1-ol (2a) with excellent enantioselectivity in biphasic system.     

Microbial reduction of sulfur-containing ketones by Geotrichum sp.

Bioreduction of some β-carbonyl phenyl sulfides, sulfoxides and sulfones (1, 3, 5, 8, 11 and 13) by Geotrichum sp. was studied. Reduction of β-carbonyI phenyl sulfoxides (5 and 8) gave anti-Prelog sulfoxide alcohols. (S, Ss)-3-Chloro-1-phenylsulfinylpropan-2-ol (9) was obtained in high yield with 95% e. e. after recrystallization from methylene chloride-petroleum ether.     

Bioreduction of hexavalent chromium: Effect of compost-derived humic acids and hematite

Composting can enhance the nutrient elements cycling and reduce carbon dioxide production. However, little information is available regarding the application of compost for the remediation of the contaminated soil. In this study, we assess the response of the redox capacities (electron accepting capacities (EAC) and electron donating capacities (EDC)) of compost-derived humic acids (HAs) to the bioreduction of hexavalent chromium (Cr(VI)), especially in presence of hematite. The result showed that the compost-derived HAs played an important role in the bioreduction of Cr(VI) in presence and absence of hematite under the anoxic, neutral (pH 7) and motionless conditions. Based on the pseudo-first order kinetic model, the rate constants of Cr(VI) reduction increased by 1.36–2.0 times when compost-derived HAs was added. The redox capacity originating from the polysaccharide structure of compost-derived HAs made them effective in the direct Cr(VI) reduction (without MR-1) at pH 7. Meanwhile, the reduction rates were inversely proportional to the composting treatment time. When iron mineral (Fe₂O₃) and compost-derived HAs were both present, the rate constants of Cr(VI) reduction increased by 2.35–5.09, which were higher than the rate of Cr(VI) reduction in HA-only systems, indicating that the hematite played a crucial role in the bioreduction process of Cr(VI). EAC and quinonoid structures played a major role in enhancing the bioreduction of Cr(VI) when iron mineral and compost-derived HAs coexisted in the system. The results can extend the application fields of compost and will provide a new insight for the remediation of Cr(VI)-contaminated soil.     

Phyllanthin-assisted biosynthesis of silver and gold nanoparticles: a novel biological approach

Abstract  The anisotropic gold and spherical–quasi-spherical silver nanoparticles (NPs) were synthesized by reducing aqueous chloroauric acid (HAuCl₄) and silver nitrate (AgNO₃) solution with the extract of phyllanthin at room temperature. The rate of reduction of HAuCl₄ is greater than the AgNO₃ at constant amount of phyllanthin extract. The size and shape of the NPs can be controlled by varying the concentration of phyllanthin extract and thereby to tune their optical properties in the near-infrared region of the electromagnetic spectrum. The case of low concentration of extract with HAuCl₄ offers slow reduction rate along with the aid of electron-donating group containing extract leads to formation of hexagonal- or triangular-shaped gold NPs. Transmission electron microscopy (TEM) analysis revealed that the shape changes on the gold NPs from hexagonal to spherical particles with increasing initial concentration of phyllanthin extract. The Fourier transform infrared spectroscopy and thermogravimetric analyses reveal that the interaction between NPs and phyllanthin extract. The cyclic voltammograms of silver and gold NPs confirms the conversion of higher oxidation state to zero oxidation state. Graphical abstract  Anisotropic gold and silver nanoparticles were synthesized by a simple procedure using phyllanthin extract as reducing agent. The rate of bioreduction of AgNO₃ is lower than the HAuCl₄ at constant concentration of phyllanthin extract. The required size of the nanoparticles can be prepared by varying the concentration of phyllanthin with AgNO₃ and HAuCl₄.