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固载杂多酸催化合成富马酸二甲酯 总被引:2,自引:0,他引:2
以富马酸与甲醇为原料,固载杂多酸PW12/C为催化剂合成了富马酸二甲酯。详细探讨了影响酯化反应的各种因素,得出了富马酸与甲醇反应的最佳条件,即m(催化剂)∶m(富马酸)8∶100,n(富马酸)∶n(甲醇)=1∶8,回流搅拌反应3h。在该条件下,酯化产率为91.6%。结果表明,此法催化剂用量少,催化活性高,反应时间短,酯收率高,反应工艺简单。 相似文献
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Gemma Janer Sonia Mesia-Vela Margy L. Wintermyer Keith R. Cooper Fred C. Kauffman Cinta Porte 《Marine environmental research》2004,58(2-5):481
The esterification of two model vertebrate steroid hormones – estradiol (E2) and dehidroepiandrosterone (DHEA) – was studied in the oyster Crassostrea virginica. The activity of acyl-CoA:steroid acyltransferase was characterized in microsomal fractions isolated from oyster digestive glands. The apparent Km and Vmax values changed with the fatty acid acyl-CoA used (C20:4, C18:2, C18:1, C16:1, C18:0 or C16:0), and were in the range of 9–17 μM, and 35–74 pmol/min/mg protein for E2, and in the range of 45–120 μM, and 30–182 pmol/min/mg protein for DHEA. Kinetic parameters were also assessed in gonadal tissue. The enzyme saturated at similar concentrations, although conjugation rates were lower than in digestive gland. Preliminary data shows that tributyltin (TBT) in the low μM range (1–50) strongly inhibits E2 and DHEA esterification, the esterification of E2 being more sensitive to inhibition than that of DHEA. Overall, results indicate that apolar conjugation occurs in oysters, in both digestive gland and gonads, at a very similar rate to mammals, suggesting that this is a well conserved conjugation pathway during evolution. Esterification, together with other mechanisms, can modulate endogenous steroid levels in C. virginica, and might be a target for endocrine disrupters, such as TBT. 相似文献
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Mussels Mytilus galloprovincialis were exposed to different concentrations of estradiol (20, 200, and 2000 ng/l) in a semi-static regime (1-day dosing intervals) for up to 7 days in an attempt to see how mussels dealt with exogenous estrogenic compounds. Sex hormone levels were determined in whole tissue. Free-estradiol was only significantly elevated at the highest exposure dose (up to 10-fold). Most of the estradiol was in the tissues as fatty acid esters (>78%), which sharply increased in a dose-dependent manner (from 4 ng/g in controls to 258 ng/g at the high exposure group). In contrast, neither free nor esterified testosterone levels showed significant differences between control and exposure groups. The results suggest the existence of mechanisms that allow mussels to maintain their hormonal status, and the important role that fatty acid esterification may play within those mechanisms. Synthesis and conjugation rates of estradiol were further investigated by measuring the activity of P450 aromatase, and palmitoyl-CoA:estradiol acyltransferase, in digestive gland microsomal fractions. Overall, the study contributes to the better knowledge of molluscan endocrinology, and defines new mechanisms of regulation of free steroid-levels in mussels. 相似文献
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