The Experts below are selected from a list of 348 Experts worldwide ranked by ideXlab platform

Howard E Smith - One of the best experts on this subject based on the ideXlab platform.

Shangtian Yang - One of the best experts on this subject based on the ideXlab platform.

  • lecithin enhanced biotransformation of cholesterol to Androsta 1 4 diene 3 17 dione and Androsta 4 ene 3 17 dione
    Journal of Chemical Technology & Biotechnology, 2002
    Co-Authors: Zhi Feng Wang, Yu Liang Huang, James F Rathman, Shangtian Yang
    Abstract:

    A biotransformation process using Mycobacterium sp was studied for Androsta-1, 4-diene-3,17-dione (ADD) and Androsta-4-ene-3,17-dione (AD) production from cholesterol. Cholesterol has a poor solubility in water (∼1.8 mg dm−3 at 25 °C), which makes it difficult to use as the substrate for biotransformation. Lecithin is a mixture of phospholipids of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), which behave like surfactants and can form planar bi-layer structures in an aqueous medium. Therefore, a small amount of lecithin (<1 g dm−3) can be used to form stable colloids with cholesterol at a relatively high concentration (20 g dm−3) in water. In this work, an energy density of 1000 J cm−3 from sonication was provided to overcome the self-association of cholesterol and to generate a stable lecithin–cholesterol suspension that could be used for enhanced biotransformation. The lecithin–cholesterol suspension was stable and could withstand typical autoclaving conditions (121 °C, 15 psig, 20 min). In contrast to conventional surfactants, such as Tween 80, that are commonly used to help solubilize cholesterol, lecithin did not change the surface tension of the aqueous solution nor cause any significant foaming problem. Lecithin was also biocompatible and showed no adverse effect on cell growth. Compared with the medium with Tween 80 as the cholesterol-solubilizing agent, lecithin greatly improved the biotransformation process in regard to its final product yield (∼59% w/w), productivity (0.127–0.346 g dm−3 day−1), ADD/AD ratio (6.7–8), as well as the long-term process stability. Cells can be reused in repeated batch fermentations for up to seven consecutive batches, but then lose their bioactivity due to aging problems, possibly caused by product inhibition and nutrient depletion. © 2002 Society of Chemical Industry

Zhi Feng Wang - One of the best experts on this subject based on the ideXlab platform.

  • lecithin enhanced biotransformation of cholesterol to Androsta 1 4 diene 3 17 dione and Androsta 4 ene 3 17 dione
    Journal of Chemical Technology & Biotechnology, 2002
    Co-Authors: Zhi Feng Wang, Yu Liang Huang, James F Rathman, Shangtian Yang
    Abstract:

    A biotransformation process using Mycobacterium sp was studied for Androsta-1, 4-diene-3,17-dione (ADD) and Androsta-4-ene-3,17-dione (AD) production from cholesterol. Cholesterol has a poor solubility in water (∼1.8 mg dm−3 at 25 °C), which makes it difficult to use as the substrate for biotransformation. Lecithin is a mixture of phospholipids of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), which behave like surfactants and can form planar bi-layer structures in an aqueous medium. Therefore, a small amount of lecithin (<1 g dm−3) can be used to form stable colloids with cholesterol at a relatively high concentration (20 g dm−3) in water. In this work, an energy density of 1000 J cm−3 from sonication was provided to overcome the self-association of cholesterol and to generate a stable lecithin–cholesterol suspension that could be used for enhanced biotransformation. The lecithin–cholesterol suspension was stable and could withstand typical autoclaving conditions (121 °C, 15 psig, 20 min). In contrast to conventional surfactants, such as Tween 80, that are commonly used to help solubilize cholesterol, lecithin did not change the surface tension of the aqueous solution nor cause any significant foaming problem. Lecithin was also biocompatible and showed no adverse effect on cell growth. Compared with the medium with Tween 80 as the cholesterol-solubilizing agent, lecithin greatly improved the biotransformation process in regard to its final product yield (∼59% w/w), productivity (0.127–0.346 g dm−3 day−1), ADD/AD ratio (6.7–8), as well as the long-term process stability. Cells can be reused in repeated batch fermentations for up to seven consecutive batches, but then lose their bioactivity due to aging problems, possibly caused by product inhibition and nutrient depletion. © 2002 Society of Chemical Industry

Pablo Diaz J Cruz - One of the best experts on this subject based on the ideXlab platform.

  • preparation of 17α iodoethynylAndrosta and 17α 2 iodoethenyl Androsta 4 6 dien 17β ol 3 ones as active site directed photoaffinity ligands for androgen binding proteins
    Steroids, 1992
    Co-Authors: Pablo Diaz J Cruz, Scott N Mason, Benjamin J Danzo, Howard E Smith
    Abstract:

    Abstract Unsaturated analogues of androst-4-en-17β-ol-3-one, each with a 17α-iodoethynyl or 17α-(2-iodoethenyl) substituent, were prepared, and their relative binding affinities (RBAs) for androgen-binding protein (ABP) were compared with those of 5α-Androstan-17β-ol-3-one, androst-4-en-17β-ol-3-one, Androsta-4, 6-dien-17β-ol-3-one, and Androsta-1,4,6-trien-17β-ol-3-one. These binding studies indicate that the iodine[125I] analogues of 17α-iodoethynyl and 17α-[(E)-2-iodoethenyl] derivatives of Androsta-4,6-dien-17β-ol-3-one and Androsta-1,4,6-trien-17β-ol-3-one will have RBAs at least twice as great as that of 5α-Androstan-17β-ol-3-one. They can be prepared from 17α-ethynylAndrosta-4-en-17β-ol-3-one, the final synthetic step using N-[125I]iodosuccinimide, and are potential radioiodinated, active site-directed photoaffinity ligands for ABP and testosterone-binding globulin.

Richard A Decreau - One of the best experts on this subject based on the ideXlab platform.

  • production of malodorous steroids from Androsta 5 16 dienes and Androsta 4 16 dienes by corynebacteria and other human axillary bacteria
    The Journal of Steroid Biochemistry and Molecular Biology, 2003
    Co-Authors: Richard A Decreau, Charles M Marson, Kelvin E Smith, John Martin Behan
    Abstract:

    Abstract The biotransformations of a number of steroids, chiefly 5,6,16,17-tetradehydro-Androstanes, are reported. The strains investigated were Corynebacteria sp. G38, G40, G41, B, Brevis sp. CW5 and Micrococcus sp. M-DH2. Corynebacterium sp. G41 proved remarkably efficient in effecting oxidative isomerisation of 5-ene-3-sterols into the corresponding 4-en-3-ones. The main biochemical reactions involved were oxidation at C-3; no reduction processes were observed. Conversions of 3β-sterols into the C-3 oxo-steroids were high, but were correspondingly low for the 3α-sterol epimers. Androsta-4,16-dien-3-one and 5β-Androsta-16-en-3-one are crucial to the formation of malodour. The rate of formation of these compounds was measured over 72 h incubation periods using three substrates: Androsta-5,16-dien-3β-ol, Androsta-4,16-dien-3β-ol and Androsta-5,16-dien-3-one. Induction studies of the transformation of the Androsta-5,16-dien-3β-ol into the very odorous compound Androsta-4,16-dien-3-one showed that cells incubated with a mixture of antibiotics displayed the same extent of biotransformation as normal cells if the concentration of antibiotic was low (1, 3, 5 and 7 μg/ml), although at concentrations higher than 10 μg/ml, biotransformation yields were reduced. Pre-incubation with a 3β-fluoro-steroid inhibited the formation of the odorous Androsta-4,16-dien-3-one.