Effects of β-cyclodextrins on the enzymatical hydrolysis of chiral dichlorprop methyl ester

The effect of β-cyclodextrins(β-CDs) on the enzymatical hydrolysis of chiral dichlorprop methyl ester (DCPPM) was studied. Four kinds of β-cyclodextrins(β-cyclodextrin, Partly methylated-CD(PM-β-CD), hydroxypropyl-cyclodextrin(HP-β-CD) and carboxymethyl-cyclodextrin(CM-β-CD)) were used. Compared with 100% DCPPM in the absence of β-cyclodextrins, the activity of lipase decreased with the increase of β-cyclodextrin and PM-β-cyclodextrin. However, CM-β-cyclodextrin stimulated the lipase activity. The inhibition effect of β-cyclodextrin and PM-β-cyclodextrin on the hydrolysis of DCPPM is affected by many factors other than degree of the methylation blocking the active site of lipase. UV-Vis and Fourier transform infrared(FTIR) spectroscopy studies of the complexation of aqueous DCPPM with β-CDs provide fresh insight into the molecular structure of the complex and explain the effects of β-CDs on enzymatical hydrolysis of chiral DCPPM. Data showed that inclusion complexes had formed by complexation of the CM-β-CD with DCPPM and the solubility of DCPPM was increased in water, which leaded to the increased lipase activity.

Influence of kaolinite on chiral hydrolysis of methyl dichlorprop enantiomers

The effect of kaolinite on the enzymatic chiral hydrolysis of methyl dichlorprop enantiomers ((R,S)-methyl-2-(2,4- dichlorophenoxy) propanoic acid, 2,4-DPM) was investigated using chiral gas chromatography. Compared with the control without kaolinite, the enantiomeric ratio (ER) increased from 1.35 to 8.33 and the residual ratio of 2,4-DPM decreased from 60.89% to 41.55% in the presence of kaolinite. Kaolinite likely had emotion influence on lipase activity and its enantioselectivity. Moreover, the amount of kaolinite added was also found to be a sensitive factor affecting the enantioselective hydrolysis of 2,4-DPM. Fourier transform infrared (FTIR) spectroscopy studies of the interaction of lipase with kaolinite provided insight into the molecular structure of the complex and offered explanation of the effects of kaolinite on enzymatic hydrolysis of 2,4-DPM. Spectra showed that the effect of kaolinite on the hydrolysis of 2,4-DPM was affected by adsorption of lipase on kaolinite and changes of adsorbed lipase conformation, which led to the modified enantioselectivity.

衍生化-手性毛细管色谱分离和测定水中的2,4-滴丙酸

建立了一种采用手性气相色谱分离、测定水中 2 ,4 滴丙酸 (DCPP)的分析方法。通过对样品的酯化处理降低了被测物的沸点 ,提高了其挥发性 ;利用手性气相色谱 ECD检测灵敏度高、量程宽的优点 ,实现了水中DCPP的手性分离、定量分析 ,平均回收率达 90 %。该方法安全、快速、准确 ,可用于水中 2 ,4 滴丙酸和 2 ,4 滴丙酸甲酯对映体定量分析。

淤泥优势菌对手性农药2,4-滴丙酸甲酯的对映体选择性降解

考察了手性农药2,4-滴丙酸甲酯(DCPPM)生物降解过程中的对映体选择性,通过驯化、培养分离了1株对其具有降解能力的菌株DP,并且运用手性毛细管气相色谱测定了DCPPM在降解过程中的对映体分数(EF),评价了DCPPM在水相中的对映体选择性生物降解.研究表明在菌株DP接种过的介质中,2个对映异构体均被迅速降解,但是R型DCPPM的逸散速度明显快于相对应的S型;EF值发生了显著的偏离,从一开始的0·5变化到最后的1.证实了该菌种对DCPPM的降解存在着对映体选择性.

手性溶剂-NMR法测定2,4-滴丙酸对映体纯度的定量分析

研究了手性溶剂法测定2,4-滴丙酸的1H、13C谱,在满足NMR准确定量所要求的分离度和信噪比的条件下,能准确测定手性化合物的对映体纯度。比较了以对映体百分含量(R%)和对映体过量(ee)表示手性农药的对映体纯度的差别,发现以对映体百分含量代替对映体过量来表示手性农药的对映体纯度更为准确。

紫外光谱法研究环糊精对2，4-滴丙酸甲酯对映体的包合作用

采用紫外光谱法研究β-环糊精（B-CD）、羧甲基-阻环糊精（CM-B-CD）和部分甲基化-β-环糊精（PM-G-CD）对2，4-滴丙酸甲酯包合作用的对映体差异．在298．15～318．15K的温度范围内，3种环糊精均能与2，4-滴丙酸甲酯形成1：1型的包合物，其包合常数值大小依次为KPM-β-CD》KcM-β-CD，且随着温度的升高而降低．经计算，热力学参数△G、△H和△S均为负值，说明包合反应是放热反应且能自发进行，焓变是形成包合物的主要驱动力．对于同-环糊精主体而言，R-2，4-滴丙酸甲酯比S-2，4-滴丙酸甲酯易于被包合，且KR/KS的顺序与包合常数K值的次序-致．

荧光光谱法研究2,4-滴丙酸及其手性对映体与牛血清白蛋白的相互作用

用荧光光谱法研究了手性除草剂2,4-滴丙酸及其两种手性异构体分别与牛血清白蛋白(BSA)的相互作用。结果表明:2,4-滴丙酸对BSA的荧光有较强的猝灭作用,且属于静态猝灭。实验获得了不同温度下2,4-滴丙酸及其对映体与牛血清白蛋白作用的结合常数,发现相同温度下S型2,4-滴丙酸比R型更易与BSA结合,其外消旋体的结合能力居于两者之间。通过计算反应热力学参数,推测它们之间的主要作用力为疏水作用力。同步荧光光谱法研究2,4-滴丙酸对BSA构象的影响,表明2,4-滴丙酸与BSA的结合位点位于色氨酸残基附近。

基于氧化石墨烯在大黄中有机氯的含量测定

目的:采用经典Hummers法自制氧化石墨烯材料,建立大黄中2,4-滴丙酸和2,4,5-三氯苯氧乙酸残留的高效液相色谱(high performance liquid chromatography,HPLC)测定方法。方法:含量测定采用色谱柱Inertsil ODS-3 C_(18)柱(4.60×250mm,5μm);流动相:甲醇-0.1%磷酸梯度洗脱,检测波长230 nm,流速1.0 mL/min,柱温30℃,进样量10μL,利用L_(9)(3^(4))正交试验法,从洗脱时间、氧化石墨烯用量和洗剂浓度三个因素开展考察,对氧化石墨烯萃取药材中有机氯的方法进行优化筛选。结果:2,4-滴丙酸进样量在0.04~0.40μg(R2=0.9998)范围和2,4,5-三氯苯氧乙酸进样量在0.02~0.20μg(R^(2)=0.9993)范围内均呈良好的线性关系。大黄中2,4-滴丙酸和2,4,5-三氯苯氧乙酸的加样平均回收率分别为99.78%(RSD=2.27%)、99.65%(RSD=2.78%);有机氯萃取的最佳工艺:25 g中药大黄的条件下,氧化石墨烯加入量为30 mg,洗脱时间为40 min,丙酮浓度为40%。采用HPLC法检测大黄药材中2,4-滴丙酸和2,4,5-三氯苯氧乙酸的平均含量分别为41.32μg/g和25.87μg/g,确定氧化石墨烯萃取技术在中药检测中的最优方法,为石墨烯复合材料固相萃取技术在中药农药富集分离的应用提供科学依据。

臭氧及催化臭氧化降解2,4-滴丙酸动力学研究

对臭氧及催化臭氧氧化降解2,4-滴丙酸(DCPP)的效率进行了研究,并利用竞争动力学法算得了DCPP与臭氧及羟基自由基的反应速率常数,参比有机物为硝基苯(NB).结果表明,DCPP与臭氧的反应速率常数kO3-DCPP为(0.733±0.163)L·mol-.1s-1,与羟基自由基的kOH-DCPP为2.367×109L·mol-.1s-1.在单独臭氧和Mn(II)催化臭氧化降解DCPP过程中,基于上述结果计算所得的速率常数与实际所测的表观反应速率常数具有较好的吻合度.以上结果对臭氧化处理含DCPP废水具有很好的理论指导意义.