具酯酶活性的温敏型分子印迹微凝胶

以双醛葡聚糖-组氨酸偶连物(PAD-His)为功能大单体、过渡态类似物p-硝基苯磷酸酯(NPP)为模板分子、Co2+为中心离子,采用油包水反相乳液法首次制得具有酯酶活性的温敏型分子印迹微凝胶(MIGs).催化水解实验表明,MIGs催化活性受模板分子用量的影响,并可通过温度进行有效调控.MIGs催化p-硝基乙酸苯酯(NPA)水解反应行为可用Michaelis-Menten方程进行描述,其最大催化水解反应速率和Michaelis-Menten常数分别为2.04×10-8mol/h和2.2×10-5mol/L,且具有较好的催化选择性.     

分子印迹微凝胶模拟酶的研究

采用油包水反相乳液法, 以马来酸酐酯化葡聚糖-氨基吡啶偶联物(Dex-MA-AP)为功能大单体、过渡态类似物p-硝基苯磷酸酯(NPP)为模板分子、Co2+为中心离子, 制得分子印迹微凝胶模拟酶(MIGs). 用紫外光谱研究了Dex-MA-AP上吡啶功能基团与NPP之间的相互作用. 用SEM观察了MIGs的形貌和大小. 研究发现, MIGs催化活性受模板分子和交联剂用量的影响,MIGs催化p-硝基乙酸苯酯(NPA)水解反应行为可用Michaelis-Menten方程进行描述, 其最大催化水解反应速率(Vm)和Michaelis-Menten常数(Km)分别为25.1 nmol/h和0.030 mmol/L, 且具有较好的催化选择性.     

含5-氟尿嘧啶的氨基酸衍生物的合成及其抗肿瘤活性研究

5-氟尿嘧啶乙酸对硝基苯酯和5-氟尿嘧啶丙酸对硝基苯酯与一系列氨基酸反应,制备了12个新的含5-氟尿嘧啶的氨基酸衍生物,并确定了化合物的结构。初步动物试验表明某些化合物有一定的抗肿瘤活性。     

Expression and Characterization of a Novel Lipase from Aspergillus fumigatus with High Specific Activity

A novel lipase gene from Aspergillus fumigatus, afl1-1, was cloned and expressed with a molecular mass of 38 kDa in Escherichia coli for the first time. The recombinant lipase had a preference for short carbon chain p-nitrophenyl esters, especially toward C2 p-nitrophenyl ester and exhibited potent hydrolysis activity that had not been observed. The optimum pH and temperature of this new enzyme were 8.5 and 65 °C, respectively. The recombinant lipase (AFL1-1) is an alkaline enzyme which was stable in the pH range 6.0～8.5 for 16 h (at 4 °C) and at 30～50 °C for 1 h. It is an intracellular enzyme which was purified approximately 8.47-fold with an overall yield of 86.1% by single-step Ni-NTA affinity purification, with a very high specific activity of approximately 1.00?×?10(3) U mg(-1) on a standard substrate of p-nitrophenyl acetate. The Michaelis-Menten kinetic parameters V (max) and K (m) of the lipase were 1.37 mM mg(-1) min(-1) and 14.0 mM, respectively. Ca(2+) and other metal ions could not activate the lipase. According to the homology analysis and site-directed mutagenesis assay, the catalytic triad of the recombinant lipase was identified as Ser-165, Asp-260, and His-290 residues.     

亲水梳状环氧聚合物载体柔性固定化脂肪酶

以氯乙酰化聚苯乙烯微球载体为大分子引发剂,以甲基丙烯酸缩水甘油酯和亲水性丙烯酰胺为共聚接枝单体,以氯化亚铜及2,2'-联吡啶为催化体系,采用原子转移自由基聚合法接枝合成了具有柔性链的亲水梳状环氧聚合物载体PS-acyl-P(AM-co-GMA),并将其用于耐有机溶剂YCJ01脂肪酶的共价柔性固定化.结果表明,固定化酶催...     

The thermodynamics of phosphate versus phosphorothioate ester hydrolysis

Phosphorothioate esters are phosphate esters in which one of the nonbridging oxygen atoms has been replaced by sulfur. In the comparative hydrolysis reactions of phosphorothioate and phosphate esters, the sulfur substitution accelerates the rates of the monoesters while slowing the rates of diesters and of triesters. Previously measured enthalpies and entropies of activation for the hydrolysis reactions of the monoesters, p-nitrophenyl phosphate and p-nitrophenyl phosphorothioate, were compared to the activation parameters measured herein for the diesters, ethyl p-nitrophenyl phosphate and ethyl p-nitrophenyl phosphorothioate, and the triesters, diethyl p-nitrophenyl phosphate and diethyl p-nitrophenyl phosphorothioate. A consistent trend of a greater DeltaH++ for the phosphorothioate analogue was found in all three classes of ester. In the monoester case, a more positive DeltaS++ arising from a mechanistic difference (D(N) + A(N) for the phosphorothioate versus A(N)D(N) for the phosphate) compensates, resulting in a lower DeltaG++ for the phosphorothioate monoester. Spectroscopic investigations indicate there is no significant difference in bond order to the leaving group in phosphates, as compared to their phosphorothioate analogues, ruling this out as a contribution to the consistently higher enthalpies of activation.     

Hofmeister series: the hydrolytic activity of Aspergillus niger lipase depends on specific anion effects

The specific activity of lipase A (Aspergillus niger) toward the hydrolysis of p-nitrophenyl acetate (p-NPA) is shown to increase as a result of sodium salt addition according to specific ion effects of the Hofmeister series. This shows explicitly that the Hofmeister effect is due to the different specific interactions between anions and the enzymatic surface.     

Reduction of tris (p-nitro phenyl) methyl bromide as a model reaction for the study of the electron-donating ability of nucleophilic compounds

Conclusions The reaction of tris(p-nitrophenyl)methyl bromide with various nucleophiles yields a stable radical, viz., tris(p-nitrophenyl)methyl, which is also generated by the reaction of tris(p-nitrophenyl)methyl anion with various electrophiles.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1669–1670, July, 1972.     

Catalytic hydrolysis of phosphate diester （BNPP） and plasmid DNA by mononuclear macrocyclic polyamine metal complexes

The activities of the catalytic hydrolysis of phosphate diester(BNPP)[bis(p-nitrophenyl)phosphate diester]and plasmid DNA (pUC18)by mononuclear macrocyclic polyamine metal complexes have been investigated in this paper.The results showed that the highest activity in hydrolysis of BNPP was obtained with 1e-Zn(Ⅱ)complex(composed of lipophilic group)as catalyst.The hydrolysis rate enhancement is up to 3.64×10~4 fold.These metal complexes could effectively promote the cleavage of plasmid DNA(pUC18)at physiol...     

Esterase-like activity of human serum albumin. VIII. Reaction with amino acid p-nitrophenyl esters.

The reactions of human serum albumin (HSA) with optically active amino acid p-nitrophenyl esters (substrate, S) were examined kinetically at 25 degrees C. The rate data were analyzed in terms of a mechanism involving 1:1 complexing (S.HSA) between S and HSA. The dissociation constant (Ks in M) and the catalytic rate constant (k2 in s-1) of S.HSA were determined. Among ten substrates examined, the reactions with N-carbobenzoxy-D(L)-alanine p-nitrophenyl esters (N-CBZ-D(L)-AlaNP) were most accelerated by HSA. Results of the reaction in the presence of excess N-CBZ-D(L)-AlaNP over HSA indicated the existence of one strong reactive site on HSA. The effects of the reversible binding of the site-specific drug and the chemical modification by site-specific reagents on the HSA activity showed that the reactive site towards N-CBZ-D(L)-AlaNP is the R site located near tyrosine-411 residue of HSA.     

多羟乙基双核大环多胺La(III)配合物对双对硝基苯酚磷酸二酯和DNA 催化水解作用研究

合成了一类新型多羟乙基双核大环多胺La(III)配合物, 其结构经1H NMR, MS, 元素分析等表征. 通过紫外分光光谱法和琼脂糖凝胶电泳技术, 研究了双核大环多胺La(III)配合物催化双对硝基苯酚磷酸二酯的水解反应和对质粒DNA(pUC18)的催化水解作用. 结果表明: 双核大环多胺La(III)配合物可以有效催化双对硝基苯酚磷酸二酯水解和促进质粒DNA在生理条件下的水解裂解. 双对硝基苯酚磷酸二酯的水解速率提高了2.36×104倍. 讨论了配合物结构对水解反应的影响.     

Research in the isoxazole series

The 4-nitro derivative is formed in the nitration of 3,5-diphenylisoxazole (I) in acetic anhydride. Mononitration of isoxazole I in concentrated H₂SO₄ gave 3-phenyl-5-(p-nitrophenyl)isoxazole, while polynitration gave a mixture of dinitro derivatives, among which 3- (m-nitro-phenyl)-5-(p-nitrophenyl)isoxazole was identified. The structures of the isolated products were established by means of the spectra, by reaction-chromatography methods, and gasliquid chromatography, as well as by a comparison with genuine samples of the two mononitro and four dinitro derivatives of isoxazole I.     

Measurement of alpha-amylase activity in white wheat flour,milled malt,and microbial enzyme preparations,using the Ceralpha assay: collaborative study

This study was conducted to evaluate the method performance of a rapid procedure for the measurement of alpha-amylase activity in flours and microbial enzyme preparations. Samples were milled (if necessary) to pass a 0.5 mm sieve and then extracted with a buffer/salt solution, and the extracts were clarified and diluted. Aliquots of diluted extract (containing alpha-amylase) were incubated with substrate mixture under defined conditions of pH, temperature, and time. The substrate used was nonreducing end-blocked p-nitrophenyl maltoheptaoside (BPNPG7) in the presence of excess quantities of thermostable alpha-glucosidase. The blocking group in BPNPG7 prevents hydrolysis of this substrate by exo-acting enzymes such as amyloglucosidase, alpha-glucosidase, and beta-amylase. When the substrate is cleaved by endo-acting alpha-amylase, the nitrophenyl oligosaccharide is immediately and completely hydrolyzed to p-nitrophenol and free glucose by the excess quantities of alpha-glucosidase present in the substrate mixture. The reaction is terminated, and the phenolate color developed by the addition of an alkaline solution is measured at 400 nm. Amylase activity is expressed in terms of Ceralpha units; 1 unit is defined as the amount of enzyme required to release 1 micromol p-nitrophenyl (in the presence of excess quantities of alpha-glucosidase) in 1 min at 40 degrees C. In the present study, 15 laboratories analyzed 16 samples as blind duplicates. The analyzed samples were white wheat flour, white wheat flour to which fungal alpha-amylase had been added, milled malt, and fungal and bacterial enzyme preparations. Repeatability relative standard deviations ranged from 1.4 to 14.4%, and reproducibility relative standard deviations ranged from 5.0 to 16.7%.     

采用SFAD将碳酸酐酶偶联至无活性官能团聚合物表面的新方法

摘 要 采用异双官能团光偶联剂－Sulfosuccinimidyl (perfluoroazidobenzamido) ethyl-1,3-dithio propionate,SFAD),将碳酸酐酶（Carbonic anhydrase,CA)接枝在无活性官能团聚合物－聚甲基戊烯（Polymethyl-pentene,PMP)膜式氧合器表面,以对硝基苯酚乙酸酯(p-nitrophenyl acetate,p-NPA)为底物,采用紫外分光光度计测定了接枝CA的活性、浓度、重复利用性、储存稳定性。结果表明,采用SFAD为交联剂能将酶成功地偶联在无活性官能团聚合物表面,在保持酶活性的同时获得较高的接枝效率;共价接枝CA（Covalently immobilized CA,CACI）的浓度随SFAD浓度的增加而增加,最大可达理论单分子层接枝量的85.86％;CACI比物理吸附的CA（Physically adsorbed CA,CAPA）具更好的重复利用性;37°C下, CACI 比CA溶液表现出更好的储存稳定性。     

铈(Ⅲ)-巴比妥钠配合物催化双(对硝基苯基)磷酸酯水解性能

研究了Ce(Ⅲ)离子与巴比妥钠形成的配合物对双(对硝基苯基)磷酸酯(BNPP)的催化水解作用。 结果表明, Ce(Ⅲ)与巴比妥钠形成的配合物对BNPP的水解具有很高的催化活性,可使BNPP水解速率提高至自发水解时的1.52×10⁸倍。 体系的pH值和温度对催化水解反应的影响,发现在温度为25 ℃和pH值为8.50的条件下,催化效果最佳。     

Sugar-amide surfactant micelles as effective reaction fields for enantioselective hydrolysis of alpha-amino acid esters

The enantioselective hydrolysis of p-nitrophenyl esters of alpha-amino acids (Phe, Leu, Ala) was accomplished in micelles formed with the surfactants bearing one or two sugar-amide headgroups. The effect of structural variations in such sugar-amide surfactants on the rates and enantioselectivity (kD/kL) for hydrolysis of p-nitrophenyl esters of D- and L-phenylalanine hydrogen bromides (D- and L-PheONp) was studied. Both the hydrolysis rate of D-PheONp and the enantioselectivity increased with an increase in the alkyl chain length as well as an increase in the number of the alkyl chains in the maltobionamide-type surfactants. Enantioselectivity also increased with an increase in the sugar chain length from bisgluconamide to bismaltobionamide (by one glucose unit per each sugar chain) in the double-sugar-chain surfactants, but enantioselectivity was no longer influenced by a further increase to bismaltotrionamide. The stereochemistry of the linkage between the sugar units in the sugar chain remarkably affected the enantioselectivity: the maltobionamide-type surfactant, in which the two sugar units are connected by an alpha-1,4-glucosidic linkage, showed high enantioselectivity (kD/kL = 5.5), whereas the surfactant bearing cellobionamide headgroups (beta-1,4-glucosidic linkage) showed no enantioselectivity. Similar trends were observed when p-nitrophenyl esters of D- and L-leucine hydrogen bromides were used as substrates. On the other hand, the rates and enantioselectivity for hydrolysis of p-nitrophenyl esters of D- and L-alanine hydrogen bromides were not so largely affected by the structural variations in the sugar-amide surfactants. Additionally, the effects of the surfactant concentration and the reaction temperature on the rates and enantioselectivity for the hydrolysis of D- and L-PheONp were examined.     

Fairly marked enantioselectivity for the hydrolysis of amino acid esters by chemically modified enzymes

The hydrolysis (deacylation) of enantiomeric substrates by the chemically modified enzymes decanoyl-alpha-chymotrypsin and decanoyl-trypsin was studied. Reaction activity for decanoyl-alpha-chymotrypsin was lower than that for the native enzyme, although intriguingly the enantioselectivity was markedly enhanced as compared with the native enzyme. In particular, the apparently complete enantioselective catalysis was attained for the hydrolytic cleavage of p-nitrophenyl N-dodecanoyl-D(L)-phenylalaninates. The enhancement of enantioselectivity, however, was not observed for decanoyl-trypsin. These results suggest that the chemically modified alpha-chymotrypsin by addition of hydrophobic groups has promoted enantioselectivity for the hydrolysis of hydrophobic esters.     

Solvent effects and alkali metal ion catalysis in phosphodiester hydrolysis

The kinetics of the alkaline hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) have been studied in aqueous DMSO, dioxane, and MeCN. In all solvent mixtures the reaction rate steadily decreases to half of its value in pure water in the range of 0-70 vol % of organic cosolvent and sharply increases in mixtures with lower water content. Correlations based on different scales of solvent empirical parameters failed to describe the solvent effect in this system, but it can be satisfactorily treated in terms of a simplified stepwise solvent-exchange model. Alkali metal ions catalyze the BNPP hydrolysis but do not affect the rate of hydrolysis of neutral phosphotriester p-nitrophenyl diphenyl phosphate in DMSO-rich mixtures. The catalytic activity decreases in the order Li+ > Na+ > K+ > Rb+ > Cs+. For all cations except Na+, the reaction rate is first-order in metal ion. With Na+, both first- and second-order kinetics in metal ions are observed. Binding constants of cations to the dianionic transition state of BNPP alkaline hydrolysis are of the same order of magnitude and show a similar trend as their binding constants to p-nitrophenyl phosphate dianion employed as a transition-state model. The appearance of alkali metal ion catalysis in a medium, which solvates metal ions stronger than water, is attributed to the increased affinity of cations to dianions, which undergo a strong destabilization in the presence of an aprotic dipolar cosolvent.     

含水杨酸的缩聚物对P-硝基苯酚乙酸酯水解反应的催化作用(Ⅰ)

通过Mannich反应,由水杨酸、甲醛和甲胺合成了一种在主链上含有水杨酸基和叔胺基的新型聚电解质SFMA。用SFMA作为聚合物催化剂催化P-硝基苯酚乙酸酯(PNPA)的水解反应。动力学研究结果表明,在较高的pH值下,SFMA比水杨酸及其与甲醛的缩聚物具有较高的加速作用。缩聚物主链上的胺基能与水杨酸基的羟基发生协同作用。对缩聚物的组成及其在水溶液中的构象对催化活性的影响也进行了研究。     

Synthesis, structure and cytostatic activity of a series of N-substituted 3,4-diphenyl-1H-pyrrole-2,5-diones

A series of N-substituted 3,4-diphenyl-1H-pyrrole-2,5-diones (diphenylmaleimides) (IV) were synthesized and tested for cytostatic activity. Compounds IVa--k were prepared from diphenylmaleic anhydride or its dinitro derivative (V or VI) and the corresponding amine. Compounds IVl--n were obtained by reaction of 3-(p-nitrophenyl)-4-phenyl-1H-pyrrole-2,5-dione potassium salt with the appropriate chloroalkylamine. Hydrogenation of IVl,n gave the the corresponding cis-3-(p-aminophenyl)-4-phenylsuccinimides (VIIIa,b). The structure-cytostatic activity relationship of these compounds is discussed.