关于添加金属离子对国产大麦芽酶系酶活力影响的研究

国产大麦芽的酶活力不如进口大麦芽的酶活力强,其中原因之一是国产大麦中某些金属离子含量低,而这些离子对大麦中的某些酶有抑制和激活作用。实验发现:当添加Na+、K+、Mg2+、Zn2+和Cu2+浓度分别达到80×10-6、60×10-6、40×10-6、20×10-6、20×10-6时,制麦酶系中的α-淀粉酶、β-淀粉酶、蛋白酶和纤维素酶活力都达到最大值,提高幅度明显。故可通过添加某些金属离子来强化制麦酶系的酶活力,提高其生产性能。     

诱抗剂对烟草组织培养过程影响的研究

供试诱抗剂对烟草愈伤组织脱分化,再分化及试管苗生根过程均有明显的影响。其中,诱抗剂A在所试浓度下(10×10-6~1000×10-6),均强烈抑制愈伤组织细胞的生长发育和分化;诱抗剂G在低浓度下(1×10-6~10×10-6)促进愈伤组织生长分化,高浓度下(≥30×10-6)则表现抑制作用;诱抗剂F和H对愈伤组织细胞的生长发育及分化也有一定的抑制作用;诱抗剂P在低浓度下(10×10-6~100×10-6)对愈伤组织细胞的影响不很明显,高浓度下(400×10-6)明显抑制愈伤组织细胞的生长发育。经电子显微镜观察,发现所用诱抗剂对愈伤组织细胞的结构均有不同程度的影响。      

乙酰胆碱酯酶生物传感器法测定蔬菜水果中有机磷农药残留

研究一种快速简便测定蔬菜水果中有机磷农药残留的方法。利用乙酰胆碱酯酶生物传感器技术,以苹果、黄瓜为样品,采用标准加入法进行分析,测定蔬菜水果中有机磷农药残留。实验结果表明,该方法回收率在96.45%～100.12%,相对标准偏差为2.76%～3.09%,对马拉硫磷和甲基对硫磷的检出限分别为4.80×10-11、2.93×10-10mol/L。     

人工矿泉水的动态离子交换研究(英文)

本实验采用动态离子交换法生产“碱性”人工矿泉水。结果表明,当用6%NaHCO3再生氯型阴离子交换树脂时,再生剂用量为140ml/8g干树脂;配制人工矿泉水时,用100ml1.24%CaCl2和1.06%MgCl2混合溶液过8g干树脂,可得到最佳交换效果。另需加入Sr2+、Li+、Zn2+、柠檬酸、VC等成分,组成人工矿泉水的底料。人工矿泉水成品含Ca2+200×10-6,Mg2+120×10-6,Sr2+0.5×10-6,Li+0.21×10-6,Zn2+0.5×10-6,Cl-292×10-6,HCO3-732×10-6,CO20.21%,pH6.26。     

柚皮提取物抗氧化作用和对正常小鼠免疫功能的影响

研究了柚皮提取物的抗氧化作用和对正常小鼠免疫功能的影响,结果表明柚皮提取物在一定浓度下可以有效的抑制菜油的氧化,但是不具有剂量-效应关系。500×10-6的柚皮提取物抗氧化效果最好,并强于1000×10-6的VC和BHT,但柚皮提取物在高浓度时 (1000×10-6、2000×10-6)反而有轻微的助氧化作用。抗坏血酸对柚皮提取物抗氧化效果具有明显的协同增效作用;柚皮提取物可明显增强正常小鼠细胞免疫和非特异性免疫功能,能显著地提高正常小鼠血清SOD的活性、降低血清MDA的含量,且呈明显的剂量-效应关系。     

壳聚糖固定化单宁酸酶的特性研究

研究了以壳聚糖为载体交联-吸附单宁酸酶后的化学特性。结果表明：固定化单宁酸酶（简称“ITA”）的最适反应pH为3.0,原酶（简称“TA”）为5．5;ITA最适反应温度为50℃,TA为40℃;ITA的Km（app）为1．3845×10(-1)mol／L,TA为6．7500×10(-5)mol/L;ITA在pH3．0～8．0的范围内残存酶活大于60％,ITA在pH3．0～6.0范围内残存酶活大于60％;ITA在80℃的水浴中保温1h,酶活力仍未见下降,而TA在60℃水浴中保温30min酶已失活;ITA和TA在4℃和30℃的条件下,贮藏20d后,ITA的残存活性大于40％,TA的残存活性小于20％。     

熏硫处理荔枝贮藏过程中二氧化硫残留研究

研究了经熏硫处理荔枝在贮藏过程中二氧化硫残留的变化。采用相同的处理方法,对不同的品种而言,果皮和果肉中的二氧化硫残留会相差较大。对于适量熏硫的荔枝,在2℃下贮藏,2d后果皮中的二氧化硫含量不超过200×10-6,而且在2℃下贮藏,10d以后果肉中的二氧化硫含量才能降至10×10-6以下。对于过量熏硫荔枝,在2℃下贮藏,26d内果皮中的二氧化硫含量仍然超出150×10-6,果肉中的二氧化硫含量在16d后才能降到10×10-6以下。     

紫甘薯花色素与胰蛋白酶相互作用特性

测定紫甘薯花色素与胰蛋白酶反应前后酶的催化活性、催化反应动力学并采用紫外光谱法、荧光光谱法和红外光谱法研究紫甘薯花色素与胰蛋白酶相互作用特性。结果表明：紫甘薯花色素对胰蛋白酶催化活性有明显的抑制作用,抑制类型为可逆的竞争性抑制,抑制常数Ki＝6.16×10－4 mmol/L,当紫甘薯花色素与胰蛋白酶的物质的量比为140∶1,在 37 ℃反应 15 min,抑制率达到38.61%,而反应时间对催化活性的影响不明显;紫甘薯花色素可使胰蛋白酶的内源荧光猝灭,猝灭类型为静态猝灭,室温下猝灭常数Kq为1.73×1012 L/（mol·s）,结合常数KA为3.88×104 L/mol,结合位点数n为0.86;热力学参数确定两者之间的作用力主要为氢键和范德华力;根据Förster能量转移理论得出它们的结合距离为3.56 nm;红外光谱经过去卷积、二阶导数处理得知与紫甘薯花色素作用后胰蛋白酶的α-螺旋含量降低,β-折叠含量升高。     

一种新的食品中亚硝酸盐含量测定方法研究

酸性条件下利用亚硝酸盐具有氧化性的特性氧化KI 生成I2,I2 和淀粉作用灵敏地生成I2- 淀粉蓝色络合物的特效反应,建立光度法测定食品中亚硝酸盐含量的新分析方法。研究表明,I2- 淀粉蓝色络合物最大吸收波长为540nm,在试液pH5、50ml 试液中加入1.0 × 10-2g/ml KI 10ml、0.3% 的淀粉4ml、反应时间6min 的最佳实验条件下,新建方法线性范围为8.0 × 10-4～7.0 × 10-6g/ml,检出限5.0 × 10-8g/ml,相对标准偏差0.7%。新方法具有选择性高、简单、准确和灵敏的优点。     

流动注射化学发光法测定面粉中过氧化苯甲酰

目的：建立面粉中过氧化苯甲酰含量测定的化学发光新方法。方法：过氧化苯甲酰氧化KI 生成I2,该反应和luminol-H2O2 化学发光体系相耦合,进而对面粉中的过氧化苯甲酰进行测定。结果：方法的线性范围为3.0 × 10-8～4.0 × 10-6g/mL,检出限为4.0 × 10-9g/mL, RSD 为2.2%(质量浓度5.0 × 10-8g/mL,11 次平行测定)。结论：该方法具有简单、灵敏、线性范围宽的优点。     

Inhibition of lipase from rice (Oryza sativa) by diethyl-p-nitrophenyl phosphate

The inhibition of rice bran lipase (RBL) by diethyl-p-nitrophenyl phosphate was studied with reference to kinetics, nature of inhibition and also elucidate the effect of the inhibitor on the structure—function of the enzyme. Enzyme activity measurements shows that the inhibitor is more effective at 0.050 mM concentration of diethyl-p-nitrophenyl phosphate and the activity is 50% at this level of inhibitor concentration. The affinity of substrate for the enzyme was observed by the increase in the velocity of the reaction with increase in the substrate concentrations and double reciprocal plot indicates that the inhibition followed a competitive in nature and inhibition constant K _i is found to be 0.016 mM at pH 7.0. The decrease in apparent thermal denaturation temperature to 4 °C compared to control indicates the destabilization of enzyme in the presence of inhibitor. Fluorescence spectral measurements suggests that pronounced quenching of fluorescence intensity of RBL occurs at higher concentrations of diethyl-p-nitrophenyl phosphate and ‘K _a’ value was found to be 2.4 × 10⁴ M⁻¹ with free energy change ΔG^o—26 kJ/mol at 30 °C suggesting strong binding between the enzyme and the inhibitor with microenvironmental changes occur at the active site or in the neighbourhood of active site. The far UV-CD data suggest that there is no significant changes in the conformation of the enzyme as a result of binding of diethyl-p-nitrophenyl phosphate. These results indicate that diethyl-p-nitrophenyl phosphate is a inhibitor of RBL and binds to the enzyme in brining about inhibition without any structural alterations.     

柿叶乙醇提取物在猪油中的抗氧化性研究

研究了柿叶乙醇提取物在猪油中的抗氧化作用。结果表明 ,柿叶乙醇提取物的抗氧化性随着在猪油中添加量的增大而增强。使用浓度为 60 0 mg kg时 ,其抗氧化性比 1 0 0 mg kg橙皮甙和 1 0 0 mg kg茶多酚略强。柠檬酸的增效作用比硬脂酰 L 抗坏血酸酯明显。     

Conversion of glucose in lactase-hydrolyzed whey permeate to fructose with immobilized glucose isomerase

The maximum conversion of glucose to fructose in lactase-hydrolyzed whey permeate by glucose isomerase was approximately 52% at .1 g enzyme/ml substrate after 7 h incubation at 60 degrees C. Removal of minerals from the substrate was essential for enzyme activity. The dependence of the enzyme on Mg++ and Co++ for activity in the presence of high ash concentration was demonstrated. Optimum Mg++ and Co++ additions were 250 and 100 ppm, respectively. The isomerization reaction was enhanced more when both 100 ppm Mg++ and 50 ppm Co++ were added. Hydrolyzed isomerized lactose whey syrup with sweetness equivalent to sucrose was successfully produced through enzymatic isomerization of glucose in lactase-hydrolyzed whey permeate after supplementation with pure glucose. Fructose in hydrolyzed isomerized lactose whey syrup was effectively separated from other sugars by Dowex 1X8-200 anion exchange resin in the bisulfite form.     

Purification and Characterization of β-Glucosidase from Aspergillus niger

Aspergillus niger, an isolate of soil contaminated with effluents from cotton ginning mill was grown in Czapek-Dox medium containing sawdust, Triton-X 100 and urea for production of an extracellular β-glucosidase. β-Glucosidase enzyme was purified (86-fold) from culture filtrate of A. niger by employing ammonium sulphate precipitation and gel filtration on sephadex G-75. The molecular mass of the purified enzyme was estimated to be 95 kDa by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The enzyme had an optimal activity on p-nitrophenyl β-D-glucopyranoside at 50°C and pH 5.0. The K_m and V_max of the enzyme on p-nitrophenyl β-D-glucopyranoside at 50°C and pH 5 were 8.0 mM and 166 µmol/min/mg of protein, respectively. The enzyme could hydrolyze cellobiose and lactose but not sucrose. Heavy metals like Hg²⁺, Al³⁺, and Ag⁺ inhibited the activity, whereas Zn²⁺ and detergents such as Triton-X 100 and Tween-80 increased the activity at 0.01%. The enzyme activity increased in the presence of methanol and ethanol.     

稠李花色苷的纯化及体外抗氧化活性

目的：建立AB-8大孔树脂纯化稠李花色苷的方法,并检测稠李花色苷体外抗氧化活性。方法：通过AB-8大孔树脂对稠李花色苷的动态吸附与解吸条件优化,确定最佳纯化条件;采用四唑氮蓝（nitroblue tetrazolium,NBT）光化还原法测定花色苷体外抗氧化活性,2’,7’-二氢二氯荧光素二乙酸酯（2’,7’-dichlorodihydrofluorescein diacetate,DCFH-DA）法观察花色苷对H2O2诱导的N2A细胞氧化损伤的保护作用。结果：稠李花色苷的最佳动态纯化条件是：吸附流速0.01 mL/s,粗提液质量浓度8 mg/mL,过柱次数2 次;解吸剂乙醇体积分数70%,流速0.01 mL/s,pH 3,纯化之后稠李花色苷的色价为57.1,纯化了16.31 倍;NBT实验结果表明,稠李花色苷具有清除超氧阴离子自由基的能力,且具有较好的剂量-效应关系;0.025 mg/mL的稠李花色苷能够保护H2O2损伤的N2A细胞,0.05 mg/mL的稠李花色苷能够降低细胞内活性氧水平。结论：AB-8大孔树脂是纯化稠李花色苷的一种有效方法,稠李花色苷在一定质量浓度范围内具有较好的体外抗氧化活性。     

Purification and characterisation of a soluble nucleotide pyrophosphatase/phosphodiesterase from prickly pear (Opuntia ficus indica) fruits

A glycosylated metallo-protein, nucleotide pyrophosphatase/phosphodiesterase, in a soluble form was purified to homogeneity from prickly pear (Opuntia ficus indica) fruits. The native protein had a molecular mass of 105 ± 8 kDa and was formed by two apparently identical subunits each containing 1 Ca²⁺ and 1 Mg²⁺ ion. The Opuntia enzyme exhibited hydrolytic activities toward pyrophosphate/phosphodiester bonds of a broad range of natural substrates, but among these, only NAD(P) and NAD(P)H were hydrolysed very efficiently. Moreover, Opuntia pyrophosphatase/phosphodiesterase hydrolysed the artificial substrate thymidine 5′-monophosphate 4-nitrophenyl ester, whereas it did not show any catalytic activity toward bis-4-nitrophenyl phosphate, which is a substrate of other pyrophosphatase/phosphodiesterase enzymes. We observed an increase of enzyme activity from the green to the red stage of fruits development, suggesting that ONPP activity might be related to the ripening of prickly pears. The protein was shown to be resistant to 75 °C for 30 min. Other biochemical characteristics were investigated and are reported here.     

INT reduction as a basis for determining bakers' yeast viability

Two rapid and simple methods for determining the reduction of 2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyltetrazolium chloride (INT) to INT-formazan by bakers' yeast were compared. The first method involves counting with a light microscope the number of yeast cells containing INT-formazan crystals. In the second method, INT-formazan is extracted from cells retained on membrane filters, using dimethyl sulphoxide. The INT-formazan is then quantitated by absorption spectrophotometry. Several brands of bakers' yeast of various ages were tested. Results obtained with the two methods were closely correlated. The extraction method is the more rapid and convenient of the two assays investigated and may be used to follow change in activity with time, compare various yeast brands or investigate the effect of various environmental conditions on yeast INT-dehydrogenase activity.     

一种用于汞检测的三联吡啶钌配合物的分子设计与合成

设计合成一种具有延长共轭体系的三联吡啶钌配合物：4’-（p-硝基苯基）-2,2’6’∶2’’-三联吡啶基-三异硫氰 基钌Ru(tpy)(NCS)3,该配合物与汞离子作用后由墨蓝色变为粉红色,如以肉眼可见粉红色作为检测灵敏度,则对汞 离子的检测限约为0.03 μg/g。通过密度泛函理论B3LYP方法优化得到了Ru(tpy)(NCS)3以及Ru(tpy)(NCS)3与Hg2+离子 结合形成的配离子[Ru(tpy)(NCS)3·HgCl]+的几何构型,通过对其前线分子轨道成分的分析,探讨钌配合物作用于 汞离子检测的基本机理。     

Pathogen Reduction and Quality of Lettuce Treated with Electrolyzed Oxidizing and Acidified Chlorinated Water

ABSTRACT: The efficacy of electrolyzed oxidizing (EO) and acidified chlorinated water (45 ppm residual chlorine) was evaluated in killing Escherichia coli O157:H7 and Listeria monocytogenes on lettuce. After surface inoculation, each leaf was immersed in 1.5 L of EO or acidified chlorinated water for 1 or 3 min at 22 °C. Compared to a water wash only, the EO water washes significantly decreased mean populations of E. coli O157:H7 and L. monocytogenes by 2.41 and 2.65 log10 CFU per lettuce leaf for 3 min treatments, respectively (p < 0.05). However, the difference between the bactericidal activity of EO and acidified chlorinated waters was not significant (p > 0.05). Change in the quality of lettuce subjected to the different wash treatments was not significant at the end of 2 wk of storage.     

乳清蛋白肽美拉德反应产物的抗氧化活性与稳定性

以乳清蛋白碱性蛋白酶水解物为原料与葡萄糖发生美拉德反应,制备得到乳清蛋白肽美拉德反应产物（whey protein peptide Maillard reaction products,WPP-MRPs）,并研究其抗氧化活性以及温度、pH值、光照、金属离子和过氧化氢对其抗氧化活性的影响。结果表明,WPP-MRPs具有较强的总还原力、羟自由基（·OH）清除能力和2,2’-连氮基-双-（3-乙基苯并二氢噻唑啉-6-磺酸）二铵盐自由基（ABTS+·）清除能力,且抗氧化活性随着WPP-MRPs质量浓度的增加而加强。WPP-MRPs在90～100 ℃时具有较高的活性;在碱性环境中的抗氧化活性大于在中性及酸性环境中;室外自然光照射会降低WPP-MRPs抗氧化活性;金属离子Cu2+、Fe2+、Fe3+和氧化剂--过氧化氢能够显著降低WPP-MRPs的抗氧化活性。