查询词典 hydantoin

In the first part, chemical synthesis, including by acraldehyde, malonic ester, ami no lactone and others were discussed and synthesis by hydantoin was emphasized.

第一部分讨论了DL-蛋氨酸及其衍生物的化学合成，包括丙烯醛法、丙二酸酯法，氨基内酯法等，并着重介绍了海因法。

hydantoin was synthesized from diethyl malonate comprising condensation with 1, 2-dichloroethane, ammonolysis to diamide, Hoffmann degradation to give 5-cyclopropanespirohydantoin, and ring-opening with 40% hydrobromic acid.

以丙二酸二乙酯为原料，先与1， 2-二氯乙烷缩合生成1， 1-环丙烷二羧酸二乙酯，再经氨解生成1， 1-环丙烷二甲酰胺，然后在次氯酸钙溶液中进行Hoffmann降解成环生成5-环丙螺海因，最后在40%氢溴酸中开环得到5-溴乙基海因。

On the basis of insoluble hydantoin bactericide prepared,the hydrophilic groups,such as trimethylamine group and triethylamine group,were introduced to the loading resin,such as chloromethyl polystyrene and formyl polystyrene.

在制成水不溶性海因类杀菌剂的基础上，在其载体树脂如氯球和醛基树脂上引入亲水基，如三甲胺基或三乙胺基。

A simple and rapid method for the spectrophotometric determination of hydantoin with chromotropic acid has been reported.

本文建立了简单、迅速地利用变色酸光度测定海因的方法。

As so far, there is just a little of literature of L252 monosubstituted hydantoin, and the details of the racemization of hydantoin are not revealed.

目前关于 52单取代海因的消旋的文献非常少，海因消旋的细节问题也没有被完全揭示。

If the ratio of the auto racemization of the hydantoin is Multi-purpose water bath ch lower than the hydrolytic ratio of hydantoin hydrolase?

若海因的自发消旋速率远低于海因水解酶的水解速率，则海因的消旋将成为D2N2氨甲酰氨基酸生产中的一个限速步骤。

If the ratio of the auto racemization of the hydantoin is much lower than the hydrolytic ratio of hydantoin hydrolase, the racemization of hydantoin will be a speed limited step of the production of D2N2 carbamoylase.

若海因的自发消旋速率远低于海因水解酶的水解速率，则海因的消旋将成为D2N2氨甲酰氨基酸生产中的一个限速步骤。

The hydantoin convert enzyme used in this essay is D2 hydantoinase, which has very high convert activity for D2 hydantoin. Therefore, if the used process of conversion do not occur the enzyme, the racemizatoin of hydantoin will be a speed limited step for the process that hydantoinase produce optical active amino acid.

本文采用的海因转化酶系中所含为 D2海因酶，对D2海因的转化活性非常高，由此可见，如若采用的转化体系中没有消旋酶的存在，则海因的消旋成为海因酶转化生产光学活性氨基酸的一个限速步骤。

Isolation, purification and characteristics of D-hydantoinase were carried out. The experiment results showed that the optimal pH and temperature of pure D-hydantoinase were pH 8. 5 and 35℃, respectively. D-hydantoinase activity could be increased significantly by Mn〓 and Fe〓. Substrate specificity of D-hydantoinase on various hydantoin derivatives showed the optimal substrate of D-hydantoinase was 5-phenylhydantoin, but hydantoin, 5-methylthioehylhydantoin, 5-hydroxyphenylhydantoin, 5-methylhydantoin, 5-benzylhydantoin could also be hydrolyzed by D-hydantoinase.

本文还进行了海因酶的分离纯化及性质研究，发现酶的最适反应温度为35℃，最适pH为8.5，金属离子Mn〓和Fe〓能显著提高D-海因酶活力。D-海因酶的特异性实验表明，D-海因酶的最适底物为D，L-苯海因，其次为海因，D，L-对羟基苯海因和D，L-甲硫乙基海因，对D，L-甲基海因和D，L-苯甲基海因也有一定的作用。

D2 hydantoinase (EC3151212) can change the D type racemates of the racemic D,L252 monosubstituted hydantoin to D2N2 carbamoylase, and the leftover L252 monosubstituted hydantoin due to never reacted with D2 hydantoinase, shown as figure 1, firstly racemizing, thus makes the D,L2 hydantoin completely changes to pure optical D2N2 carbamoylase, and then be changed to D2 amino acid.

海因酶具有底物特异性，D2海因酶(EC 3151212)可转化外消旋的D ，L252单取代海因中的D型消旋体成为D2N2氨甲酰氨基酸，剩余的L252单取代海因由于完全不被 D2海因酶所作用，如图 1所示，先进行消旋，从而使得 D ，L2海因完全转化为光学纯的 D2N2氨甲酰氨基酸，并进一步被转化为D2氨基酸。

Now, however, all children continue in "comprehensive" schools, and the eleven-plus determines which courses of study the child will follow.

然而现在，所有的孩子都要在综合学校继续学习，所以这次考试只是决定他们将要学习哪些课程。

Cultivatable land , and led to a general recognition that development must not be carried at the cost of agriculture .

城区的迅速扩大在很多情况下侵占了宝贵的可耕地，使人们普遍认识到发展不能以牺牲农业为代价。