类酶催化反应机理的量子化学的研究

研究了癸酰基－Ｌ－组氨酸催化下的苄酯基－Ｎ－苯丙氨酸对硝基苯酚的类酶催化反应。用ＩＮＤＯ程序计算了底物和催化剂的电荷分布。通过分析，得到了底物和催化剂的活性中心，并提出了一个合理的反应机理。     

内硝基冠醚中间体的合成

研究了作为制备新型内硝基冠醚原料的中间体２－硝基－１，３－苯二酚（ＮＢ）及多甘醇双对甲苯磺酸酯（ＯＥＤＴ）的合成．通过改进ＮＢ的合成条件，使磺化、硝化、水解三步总收率由１２．９％提高到３７．５％；以吡啶为溶剂和ＨＣｌ的束缚剂，控制反应物摩尔比为ＴｓＣｌ∶ＯＥＧ＝２．０６∶１．００，在０℃～５℃反应２ｈ后，加入适量水静置过夜，可明显提高ＯＥＤＴ的收率和纯度．     

PVC/CPE-g-VC/LDPE共混体系研究

研究了ＰＶＣ／ＣＰＥ－ｇ－ＶＣ／ＬＤＰＥ和ＰＶＣ／ＣＰＥ－ｇ－ＶＣ／ＬＬＤＰＥ三元共混体系．对不同配比的共混物的物理机械性能进行了测试．考察了ＬＤＰＥ,ＬＬＤＰＥ用量分别对ＰＶＣ／ＣＰＥ－ｇ－ＶＣ／ＬＤＰＥ和ＰＶＣ／ＣＰＥ－ｇ－ＶＣ／ＬＬＤＰＥ三元共混体系冲击强度和拉伸强度的影响．结果表明,ＣＰＥ－ｇ－ＶＣ与ＬＤＰＥ（或ＬＬＤＰＥ）并用增韧ＰＶＣ时,能产生显著的协同效应     

BTEAC相转移催化TA残渣中芳香酸合成苄酯的研究

本文采用苄基三乙基氯化铵（ＢＴＥＡＣ）作相转移催化剂，对对苯二甲酸（ＴＡ）残渣中有机酸苄酯的合成进行了研究。有机酸转化率达到９９％以上，酯的酸值低于０．３ｍｇＫＯＨ／ｇ。     

L—异亮氨酸产生菌的选育

以黄色短矸菌（Ｂｒｅｖｉｂａｃｔｅｒｉｕｍｆｌａｖｕｍ）ＡＴＣＣ１４０６７为出发菌株，经硫酸二乙酯（ＤＥＳ），紫外线（ＵＶ）和亚硝基胍（ＮＴＧ）逐级诱发处理，α－氨基－β－羟基戊酸（ＡＨＶ），Ｓ－２－氨基乙基－Ｌ－半胱氨酸（ＡＥＣ）磺胺胍（ＳＧ），乙硫氨酸（Ｅｔｈ）α－氨基丁酸（α－ＡＢ），异亮氨酸氧肟酸（ＩｌｅＨｘ）等氨基酸结构类似物及琥珀酸主碳源平板定向筛选，获得一株Ｌ－异亮氨酸高产菌ＺＱ－４     

沙田柚饮料的降血脂作用研究

以８周龄ＢＡＬＢ／Ｃ雄性小白鼠为实验动物，饲以高脂饲料造成实验性高血脂模型，分别灌胃不同浓度的沙田柚汁各１ｍｌ，高脂对照组和空白对照组则灌胃１ｍｌ的生理盐水，饲喂常规饲料，５０天后采尾血测定血清总胆固醇（ＴＣ）、甘油三酯（ＴＧ）、高密度脂蛋白胆固醇（ＨＤＬ－Ｃ）含量和卵磷脂胆固醇酰基转移酶（ＬＣＡＴ）的相对活性，并计算出低密度脂蛋白胆固醇（ＬＤＬ－Ｃ）和极低密度脂蛋白胆固醇（ＶＬＤＬ－Ｃ）浓度及动脉硬化指数ＡＩ（ＴＣ－ＨＤＬ－Ｃ／ＨＤＬ－Ｃ）。结果表明，沙田柚汁饮料能够明显降低实验性高血脂小鼠血清ＴＣ、ＴＧ、ＬＤＬ－Ｃ、ＶＬＤＬ－Ｃ和ＡＩ（Ｐ＜０．０５或Ｐ＜０．０１），并能使ＨＤＬ－Ｃ含量及ＬＣＡＴ相对活性显著升高（Ｐ＜０．０１），由此说明沙田柚汁具有降低血脂、防止动脉粥样硬化的作用。     

对硝基苯酚法对雅致放射毛霉脂肪酶特性的研究

以不同碳链长度的对硝基苯酚酯为底物对雅致放射毛霉（Actinomucor elegans AS3.27）脂肪酶的酶学特性和其发酵的腐乳在发酵过程中脂肪酶活力的变化进行研究,结果表明：分别以对硝基苯酚正辛酸酯（pNPC）和对硝基苯酚棕榈酸酯（pNPP）为反应底物所测得的脂肪酶酶学特性有所不同。以pNPC和pNPP为反应底物时,雅致放射毛霉脂肪酶的最适作用温度分别为30、35℃,最适作用pH为7.5、7.0,最适盐浓度都为0.20mol/L。以两种底物分别测定雅致放射毛霉接种的腐乳在发酵过程中的脂肪酶活力,均显示在后期发酵过程中脂肪酶活力呈现出不断下降的趋势,然而在第20～25d脂肪酶活力呈现出小幅度的反复。使用碱滴定法以聚乙二醇-橄榄油为底物进行验证,得到相同的趋势。     

第八届北京木工机械展主要厂商及展品简介

公司名称产品及业务（续） ＩＴＡＬＹ意大利Ａ ＣＯＳＴＡ Ｓ．Ｐ．Ａ．封边机、横切机、木地板生 产线ＡＬＦＡＭＡＣＣＨＩＮＥ Ｄ ＲＡＦ－框架装配机、双横切锯ＦＯＮＩ ＧＩＵＳＥＰＰＥＡＮＧＥＬＯ ＣＲＥＭＯＮＡ原木制备设备Ｓ．Ｐ．Ａ．ＡＲＴＵＲＯ ＳＡＬＩＣＥ Ｓ．Ｐ、Ａ．家俱自动关闭铰链ＡＵＴＥＣＯ Ｓ．Ｒ．Ｌ．多轴四面铣刨机ＢＡＬＥＳＴＲＩＮＩ ＲＥＮＺＯ实木餐椅生产机械Ｓ．Ｐ．Ａ．ＢＩＥＳＳＥ ＧＲＯＵＰ木工机械ＢＭＡ ＡＢＲＡＳＩＶＥＳ砂纸ＢＲＥＶＥＴＴＩＭＡ双锯斜角切割机、固定、涂 胶、基砖材料接…     

顺智公司更名迁址

原瑞典顺智公司的母公司－劳马集团已于１９９９年９月与芬兰维美德集团合并。 顺智公司（ＳＵＮＤＳ ＤＥＦＩＢＲＡＴＯＲ ＡＢ）目前已更名为 维美德纤维技术公 司（ＶＡＬＭＥＴ ＦＩ－ＢＥＲ ＴＥＣＨ ＡＢ）,继续致力于制浆领域的业务。 原顺智公司北京办事处已于２０００年６月３０日迁至维美德公司北京代表处,即：北京朝阳门北大街２号,港澳中心写字楼７６０室。 电话：０１０－６５０１１５９５ 传真：０１０－６５０１２５８８ 邮编：１０００２７顺智公司更名迁址@刘翃翃     

APMP制浆中的化学药品及应用实践

ＡＰＭＰ是英文ＡＬＫＡＬＩＮＥ ＰＥＲＯＸＩＤＥ ＭＥＣＨＡＮＩＣＡＬ ＰＵＬＰ四个单词第一个字母的缩写,中文名即为碱性过氧化物机械浆。它是ＡＮＤＲＩＴＺ ＳＰＲＯＵＴ－ＢＡＵＥＲ（ＡＳ－Ｂ）公司在１９８９年推出的一种高得率化学热磨机械浆的制备方法。可以看出,ＡＰＭＰ这一名称主要是根据其所使用的化学药品来命名的。可见化学药品在这一制浆方法中的重要性。笔者１９９７年曾专门到辽宁鸭绿江造纸厂学习ＡＰＭＰ制浆技术,后来参加云南保山造纸厂ＡＰＭＰ生产线的建设。２０００年该生产线建成后,有幸参加了其试车及生产…     

Vascular effects of egg white‐derived peptides in resistance arteries from rats. Structure–activity relationships

BACKGROUND: The vasodilator properties of several peptide sequences derived from egg white proteins were screened in mesenteric resistance arteries from Wistar‐Kyoto rats. For this, third‐order branches of the mesenteric arteries from 6‐month‐old male rats were used. The vasodilator responses, with or without endothelium, to several peptides (0.1 mmol L^?1) were analysed in an isometric myograph. Moreover, the effect of nitric oxide (NO) synthase (L‐NAME, 100 µmol L^?1) and cyclooxygenase (indomethacin, 10 µmol L^?1) inhibitors on the vasodilator response was tested. RESULTS: The peptides Arg‐Ala‐Asp‐His‐Pro‐Phe‐Leu, Arg‐Ala‐Asp‐His‐Pro‐Phe, Arg‐Ala‐Asp‐His‐Pro, Tyr‐Arg‐Gly‐Gly‐Leu‐Glu‐Pro‐Ile‐Asn‐Phe, Arg‐Asp‐Ile‐Leu‐Asn‐Gln and Val‐Pro‐Pro showed a high endothelium‐dependent vasorelaxation, whereas Phe‐Arg‐Ala‐Asp‐His‐Pro‐Phe‐Leu was only partially endothelium‐dependent. The relaxation induced by Arg‐Ala‐Asp‐His‐Pro‐Phe‐Leu, Arg‐Ala‐Asp‐His‐Pro‐Phe, Arg‐Ala‐Asp‐His‐Pro, Arg‐Asp‐Ile‐Leu‐Asn‐Gln and Val‐Pro‐Pro was mainly mediated by NO, since the response was inhibited only by L‐NAME, while both L‐NAME and indomethacin inhibited the vasodilator response induced by Phe‐Arg‐Ala‐Asp‐His‐Pro‐Phe‐Leu and Tyr‐Arg‐Gly‐Gly‐Leu‐Glu‐Pro‐Ile‐Asn‐Phe. The presence of Arg or Tyr at the N‐terminal position could be related to the vasodilator activity of these compounds in this vascular bed. The well‐known angiotensin‐converting enzyme inhibitor captopril showed only a slight vasodilator effect. CONCLUSION: These peptides could reduce the vascular resistance and be used as functional ingredients in the prevention and/or treatment of hypertension and other associated disorders. Copyright © 2010 Society of Chemical Industry     

The role of pulsed electric fields treatment in enhancing the stability of amino acid – sugar complexes:‐ interactions between L‐Phenylalanine and β‐Cyclodextrin

In this work, the effect of pulsed electric fields (PEF) treatment on the interactions between amino acids (using L‐Phenylalanine: L‐Phe) and sugar (using β‐Cyclodextrin: β‐CD) complex was analysed by fluorescence spectroscopy, Raman spectroscopy and simultaneous thermal analyzer. Moreover, the molecular dynamics of β‐CD–L‐Phe inclusion complex treated by PEF was calculated by molecular modelling. The results indicated that β‐CD–L‐Phe complexes are formed by a molar ratio of 1:1, and the stability constant of such complexes increased from 147 to 614 M^?1 by PEF treatment. Thermal characterisations of β‐CD–L‐Phe complexes indicated that the PEF treatment could increase the yield of complexes. The PEF treatment resulted in an increase in the reaction enthalpy of β‐CD–L‐Phe inclusion complexes by DSC curve. These results show that PEF treatment has the potential to promote the chemical processing, especially the small organic molecules participate in inclusion or cross‐linking reaction.     

ENZYMATIC PROPERTIES OF A PROTEASE FROM THE HEPATOPANCREAS OF SHRIMP, PENAEVS OMENTAIM

The protease purified from hepatopancreas of shrimp, Penaeus orientals, had high proteolytic activity in the pH range of 7.0 to 9.5. Temperature optimum for hydrolysis of casein was 70C. The protease was stable at neutral and alkaline pH and unstable at acidic pH. The apparent Michaelis‐Menten constant (K_m) and the turnover number (V_max) of the protease on hydrolysis of N‐CBZ‐L‐tyrosine p‐nitrophenyl ester (CBZ‐Tyr‐NE) and N‐CBZ‐L‐phenylalanine p‐nitrophenyl ester (CBZ‐Phe‐NE) ‐were similar, however, those for N‐CBZ‐L‐cysteine p‐nitropher.yl ester (CBZ‐Cys‐NE) were different. K_m and V_max for hydrolysis of casein by the protease were determined to be 0.31% and 5.21s^‐1, respectively. The N‐terminal sequence of the protease showed higher homology with the collagenase of crab and trypsins from Crustacea. Myosin heavy chain (MHC) was the primary substrate during proteolysis with the protease. Actin/tropomyosin were degraded progressively during 2 h incubation but to a lesser extent than MHC.     

Photochemical fate of carbamazepine in surface freshwaters: laboratory measures and modeling

It is shown here that carbamazepine (CBZ) would undergo direct photolysis and reaction with (?)OH as the main phototransformation pathways in surface waters. Environmental lifetimes are expected to vary from a few weeks to several months, and predictions are in good agreement with available field data. Acridine (I) and 10,11-dihydro-10,11-trans-dihydroxy-CBZ (V) are the main quantified phototransformation intermediates upon direct photolysis and (?)OH reaction, respectively. The photochemical yield of mutagenic I from CBZ is in the 3-3.5% range, and it is similar for both direct photolysis and (?)OH reaction: it would undergo limited variation with environmental conditions. In contrast, the yield of V would vary in the 4-8.5% range depending on the conditions, because V is formed from CBZ by (?)OH (9.0% yield) more effectively than upon direct photolysis (1.4% yield). Other important photointermediates, mostly formed from CBZ upon (?)OH reaction, are an aromatic-ring-dihydroxylated CBZ (VI) and N,N-bis(2-carboxyphenyl)urea (VII). Compounds VI and VII are formed by photochemistry and are not reported as human metabolites; thus, they could be used as tracers of CBZ phototransformation in surface waters. Interestingly, VI has recently been detected in river water.     

Transformation of the recalcitrant pharmaceutical compound carbamazepine by Pleurotus ostreatus: role of cytochrome P450 monooxygenase and manganese peroxidase

Carbamazepine (CBZ) is an environmentally recalcitrant compound highly stable in soil and during wastewater treatment. In this study, we examined the mechanisms by which the white-rot fungus Pleurotus ostreatus metabolizes CBZ in liquid culture using a physiological approach. P. ostreatus PC9 was grown in media known to support different levels of a multiplicity of enzyme systems such as cytochrome P450 (CYP450) and manganese peroxidase (MnP). When both CYP450 and MnP systems were active, 99% of the added CBZ was eliminated from the solution and transformed to 10,11-epoxycarbamazepine. High removal of CBZ was also obtained when either MnP or CYP450 was active. When both CYP450 and MnP were inactivated, only 10 to 30% of the added CBZ was removed. In this latter system, removal of CBZ might be partially attributed to the activity of versatile peroxidase. P. ostreatus was able to eliminate CBZ in liquid culture even when CBZ was added at an environmentally relevant concentration (1 μg L(-1)). On the basis of our study, we suggest that two families of enzymes are involved in the oxidation of CBZ in liquid culture: MnP in a Mn(2+)-dependent or independent manner and CYP450. Our study also highlights the potential of using P. ostreatus for bioremediation systems.     

Identification and quantitation of nonylphenol ethoxylates and nonylphenol in fish tissues from Michigan

Nonylphenol (NP) and its lower ethoxylates, nonylphenol monoethoxylate (NPE1) and nonylphenol diethoxylate (NPE2), can be present in aquatic environments at total concentrations of more than 10 microg/L. They are metabolites of nonylphenol polyethoxylates (NPE) and have been found to be weakly estrogenic. To evaluate bioaccumulation potential and identify potential risks posed by these chemicals, concentrations of NP, NPE1, NPE2, and nonylphenol triethoxylate (NPE3) were determined in the tissues of fish inhabiting various waters in Michigan. This method involves extraction of samples using exhaustive steam distillation with concurrent liquid extraction. Concentrations of NP among all sites and species ranged from <3.3 to 29.1 ng/g, ww and varied little among sites. NPE1 was detectable in some samples but at concentrations less than the method detection limit (16.8 ng/g). Concentrations of NPE2 and NPE3 in all samples were less than their respective MDLs of 18.2 and 20.6 ng/g.     

Tyrosine and phenylalanine catabolism by Lactobacillus cheese flavor adjuncts

Bacterial metabolism of Tyr and Phe has been associated with the formation of aromatic compounds that impart barny-utensil and floral off-flavors in cheese. In an effort to identify possible mechanisms for the origin of these compounds in Cheddar cheese, we investigated Tyr and Phe catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts under simulated Cheddar cheese-ripening (pH 5.2, 4% NaCl, 15 degrees C, no sugar) conditions. Enzyme assays of cell-free extracts indicated that L. casei strains catabolize Tyr and Phe by successive, constitutively expressed transamination and dehydrogenation reactions. Similar results were obtained with L. helveticus strains, except that the dehydrogenase enzymes were induced during incubation under cheese-ripening conditions. Micellar electrokinetic capillary chromatography of supernatants from L. casei and L. helveticus strains incubated under simulated cheese-ripening conditions confirmed that Tyr and Phe transamination and dehydrogenation pathways were active in both species and also showed these reactions were reversible. Major products of Tyr catabolism were phydroxy phenyl lactic acid and p-hydroxy phenyl acetic acid, while Phe degradation gave rise to phenyl lactic acid, phenyl acetic acid, and benzoic acid. However, some of these products were likely formed by nonenzymatic processes, since spontaneous chemical degradation of the Tyr intermediate p-hydroxy phenyl pyruvic acid produced p-hydroxy phenyl acetic acid, p-hydroxy phenyl propionic acid, and p-hydroxy benzaldehyde, while chemical degradation of the Phe intermediate phenyl pyruvic acid gave rise to phenyl acetic acid, benzoic acid, phenethanol, phenyl propionic acid, and benzaldehyde.     

Metabolism of phenylalanine and biosynthesis of styrene in Penicillium camemberti

The occurrence of styrene in food may be an important aroma defect (celluloid odour), even at very low concentrations (Miltz et al. 1980) causing consumer rejection and is therefore a problem for the food industry. We examined the biosynthetic pathway leading to styrene formation by Penicillium camemberti using labelled compounds. As styrene is strongly hydrophobic and volatile, we first had to develop a continuous extraction process. Using resins XAD2 it was reasonable to suspect phenylalanine (Phe) as the precursor. The addition of Phe marked with 13C on the ring provokes the accumulation of labelled styrene. The enzyme activities involved were also tentatively measured. Styrene appears to be synthesized from phenylalanine by phenylalanine ammonia-lyase activity followed by a decarboxylation catalysed by a cinnamic acid decarboxylase.     

Umami Taste Enhancement of MSG/NaCl Mixtures by Subthreshold L-α-Aromatic Amino Acids

l ‐Phenylalanine (l ‐Phe) and l ‐tyrosine (l ‐Tyr) are L‐α‐aromatic amino acids that have recently been discovered to be important components of the savory fractions of soy sauce in addition to l ‐glutamate. Their effects are evaluated on the umami or savory taste of monosodium L‐glutamate (MSG), with or without sodium chloride (NaCl). Because l ‐Phe at subthreshold concentration (1.0 mM) significantly enhances an umami taste of a MSG/NaCl mixture (P= 0.000), combinations of 4 subthreshold concentrations (0, 0.5, 1.5, and 5.0 mM) of l ‐Phe with a weakly suprathreshold MSG (4.0 mM) and NaCl (80 mM) mixture were then rated for salty and umami intensities relative to those of standard solutions. L‐Phe was found to significantly enhance the umami tastes of the MSG/NaCl mixtures when it was added in a concentration range of 0.5 to 5.0 mM (P= 0.000). However, neither the umami taste of MSG alone nor the salty taste of NaCl alone was intensified. In a further experiment, l ‐Tyr at the 3 subthreshold concentrations (0, 0.5, and 1.5 mM) studied was shown to have the same activity as L‐Phe. The phenomenon of umami or savory enhancement by subthreshold aromatic amino acids in the soy sauce system has been established.