面粉中过氧化苯甲酰紫外分光光度测定法

本论文利用原子态氢将面粉中过氧化苯甲酰还原成苯甲酸并提取出来,采用紫外分光光度法对其进行测定。该方法的最低检出浓度为６．５ｍｇ／ｋｇ,加标回收率在８９．３～９７．７之间,６次重复测定的变异系数为３．４％,与本实验室研究的气相色谱法相比时,采用ｔ检验法对实际样品进行了分析,结果表明两方法没有显著差异。     

紫外分光光度法测定饲料添加剂苯甲酸钠的研究

研究了苯甲酸钠的紫外分光光度法测定，实验证明：该方法可以快速、准确地测定饲料中的苯甲酸钠的含量。样品最小检出量为0.001 4mg/ml，回收率达96%。为饲料工业中快速检测苯甲酸钠提供了一种新的方法。     

紫外分光光度法测定红曲中酸式Lovastatin的含量

研究紫外分光光度计测定红曲中酸式Lovastatin的方法。将内酯型Lovastatin全部转化为酸式形式后用硅胶柱层析进行分离，再用双波长紫外分光光度法测定样品中总Lovastatin（以酸式存在）含量，同时用本室报道的实验方法测定内酯型Lovastatin的含量，二之差为红曲样品中酸式Lovastatin的含量。实验探索了样品中Lovastatin转化和洗脱的最佳条件，对总Lovastatin测定方法的准确度、精密度及最低检测限进行了研究，并且运用这一方法实测了五种红曲样品中酸式Lovastatin的含量。结果表明该方法具有良好的实用性，适用于中小企业对Lovastatin产品的科研开发及质量控制。     

双波长紫外分光光度法测定红曲中洛伐他汀（Lovastatin）的含量

：对紫外分光光度计测定组曲中洛伐他汀（Ｌｏｖａｓｔａｔｉｎ）的方法进行研究。采用７５％乙醇对红曲中的Ｌｏｖｉｓｔａｔｉｎ超声提取２０ｍｉｎ。离心后用中性氧化铝柱层析吸附上清液中的色素．一定条件下Ｌｏｖａｓｔａｔｉｎ不被吸附而随着洗脱液流出．由于Ｌｏｖａｓｔａｔｉｎ在２４６ｎｍ、 ２５４ｎｍ两波长下其吸光度之差（Ａ２４６—Ａ２５４）正好能够代表一个特征吸收峰的峰高,并且经实验测定与其浓度的关系符合比尔定律．而红曲色素在此波长下△Ａ值极小,因此采用双波长紫外分光光度法能够排除样品经吸附层析分离后残存色素的干扰,完成对样品中Ｌｏｖａｓｔａｔｉｎ含量的定量测定．在本实验条件下６次重复测定加标样品的回收率为９７．５±１．３８％,变异系数为１．４％．样品中Ｌｏｖａｓｔａｔｉｎ的最低检测下限为０．６５μｍ／ｍｌ．利用本实验条件成功测定了三种红曲发酵制品中Ｌｏｖａｓｔａｔｉｎ的含量．同时测定加标回收率．结果看到实测样品的回收率都在９５％以上,标准偏差小于０．２．说明该方法具有良好的实用性．适用于中小企业对Ｌｏｖａｓｔａｔｉｎ产品的科研开发及产品质量控制．     

食品添加剂苯甲酸的紫外分光光度法测定研究

本文建立了苯甲酸的紫外分光光度法，该方法简便准确。样品检验结果：最小检出量为０．００１２ｍｇ／ｍｌ，回收率达９７％，可以满足食品工业的生产和科研需要。     

紫外分光光度法快速测定葡萄糖

应用紫外分光光度法分析技术建立了快速测定葡萄糖的检测方法。利用样品中葡萄糖在葡萄糖氧化酶的催化作用下生成的过氧化氢具有强氧化性,可以将还原性的草酸钛钾氧化生成稳定的黄色络合物。该络合物在最大吸收波长382nm处的吸光值与样品中葡萄糖的质量浓度成比例。结果显示葡萄糖质量浓度在0.05～0.75mg/mL的范围内具有良好的线性关系,相关系数为0.996,相对标准偏差为1.67%,加标回收率为99.87%～100.39%。方法操作简便、可靠,可以用于样品中葡萄糖的快速测定。     

食品添加剂NaFeEDTA测定方法研究

根据ＮａＦｅＥＤＴＡ在２５６ｎｍ处的强紫外吸收与浓度的线性关系,测定了酱油样品中的ＮａＦｅＥＤＴＡ含一,同时做了样品测定的重现性及回收率实验,结果表明,线性范围在０．４￣４．０μｇ／ｍｌ之间,相关系数为０．９９９９,样品中测定ＮａＦｅＥＤＴＡ报回收率在９５－１０７％之间,此法简便,快速、准确、是测定强化食品中ＮａＦｅＥＤＴＡ含量的行之有效的方法     

紫外分光光度法测定食品添加剂苯甲酸的研究

本文研究了苯甲酸的紫外分光光度法,实验证明：样品中苯甲酸的最小检出量为0.0012mg/ml,回收率达97%。该方法灵敏、快速、准确。     

巯基棉富集－分光光度法测定食品及药物中的痕量硒

本文提出了巯基棉分离富集，硫氰酸盐－丁基若丹明Ｂ－吐温４０体系分光光度法测定痕量硒的方法。当ｐＨ为４．０时，在吐温４０存在下，硒与过量的ＳＣＮ－形成稳定的铬阴离子［Ｓｅ（ＳＣＮ）＿６］￣（２－），再与丁基罗丹明Ｂ形成三元配合物，该配合物的最大吸收波长为６０６ｎｍ，ε＝３．１６×１０￣５。硒含量在０～６μｇ／２５ｍｌ范围内服从比尔定律。方法的相对标准偏差为１．４％，回收率１０２％。将该法应用于实际样品中硒的测定，结果满意。     

紫外分光光度法同时测定饮料中山梨酸钾和苯甲酸钠

介绍了饮料中山梨酸钾和苯甲酸钠的紫外分光光度法同时测定方法。实验表明该方法可快速准确地测定饮料中的山梨酸钾和苯甲酸钠，样品中山梨酸钾最小检出限为0．00067g/L，回收率为92％-94％；苯甲酸钠最小检出限为0．0014g／L，回收率为94％-96％。     

面粉中添加葡萄糖氧化酶后巯基变化的研究

为研究葡萄糖氧化酶氧化面粉中的巯基生成二硫键,从而改善面团流变性质的作用机理,采用GB/T14614-93方法测定面粉试验仪的性质;用重铬酸钾氧化法检测不同葡萄糖氧化酶作用条件下巯基的含量,结果表明:面粉中巯基减少量与葡萄糖氧化酶酶活力和浓度相关,但并不是简单的正向变化,还受到外界条件的影响,说明葡萄糖氧化酶氧化面粉中的巯基生成二硫键是一个复杂的过程。     

Sensitive detection of sulfhydryl groups in surface-confined metallothioneins and related species via ferrocene-capped gold nanoparticle/streptavidin conjugates

Metallothionein (MT), a cysteine-rich metalloprotein that is purported to play an important role in heavy metal accumulation and detoxification, and its related peptidic species were attached onto dithiobissuccinimidyl propionate self-assembled monolayers. The spatially accessible sulfhydryl groups present in these immobilized biomolecules, tagged with N-biotinoyl-N'-[6-maleimidohexanoyl]hydrazide, were detected voltammetrically at a sensitive level via the use of ferrocene (Fc)-capped gold nanoparticle/streptavidin conjugates. The method was established first by examining relatively simple peptides (e.g., glutathione). For the hexapeptidic species that resembles the N-terminus of MT with a sequence of Lys-Cys-Thr-Cys-Cys-Ala, concentration levels as low as 0.050 nM can be determined. Such a remarkable sensitivity is attributed to the presence of a large number of Fc caps present at each gold nanoparticle, which enhances the detection of a small number of surface-bound sulfhydryl groups. Microgravimetric measurements, performed with a quartz crystal microbalance, were used in tandem with voltammetry to quantify the number of tagged sulfhydryl groups. Through extraction of the metals present in MT adsorbate, it is demonstrated that this amplified voltammetric detection is also suitable for the investigation of the variation of the number of sulfhydryl groups present at an electrode and sensitive to the change of surface structure of an immobilized biomolecule. This work represents a new method for the determination of sulfhydryl groups inherent in surface-bound proteins or peptides and can facilitate the study on the environmental issues related to MTs.     

Potassium Bromate Effects on Gel-forming Ability of Pacific Whiting Surimi

Physical and chemical analyses defined the reinforced oxidation of sulfhydryl groups on the myofibrillar proteins to disulfide bonds by bromate. Electrophoretic studies demonstrated myosin degradation during heat-setting and its protection from proteinase attack by bromate. A bromate level of 0.075% inactivated 89.9% of the proteinase activity in surimi sols. Maximum gel hardness was 0.15%. Major increases in cohesiveness and elasticity were achieved at levels s 0.075%, brittle-ness occurred at levels a0.1%. Surimi gels with AA folding test grade was achieved with 0.15%. Potassium bromate probably improved surimi gelation through proteinase inactivation and reinforced disulfide formation during heat-setting.     

Alkali treatment of proteins. I. Behavior of sulfhydryl and disulfide groups in alkali-treated beta-lactoglobulin and alpha-lactalbumin]

The alkali treatment of beta-lactoglobulin and alpha-lactalbumin results in the splitting of disulphide bonds in the protein molecules. When a 0.8-10(4) M beta-lactoglobulin solution in a 0.022 N sodium hydroxide solution (pH = 12) is heated at 90 degrees C for 30 min, 0-4 M disulphide groups, 2.2 M sulfhydryl groups and 1.8 M sulphide ions/M dimeric beta-lactoglobulin are detectable of the total of 4 M disulphide groups and 2 M sulfhydryl groups/M dimeric beta-lactoglobulin. The sulphide ions can be determined directly in the form of hydrogen sulphide or by calculating the difference between the values from the amperometric-argentometric titration and those from the method of ELLMAN (reaction with DTNB). The disulphide groups are determined with the aid of DTNB after reduction with sodium borohydride. The sulfhydryl groups obtained by reduction with sodium borohydride re-oxidize, the reaction velocity being of the second order. If the disulphide groups are reduced with sodium borohydride, the argentometric-amperometric determination of the sulfhydryl groups by means of the platinum rotating-disk electrode is disturbed by the presence of boric acid.     

Requirement for a sulfhydryl group for sulfhydryl oxidase activity

Sulfhydryl oxidase was isolated from bovine skim milk membranes using a transient covalent affinity chromatographic method. This preparation exhibited two chemically reactive sulfhydryl groups in the native enzyme and three in the denatured form, based on a subunit weight of 85 kdaltons. The kinetics of inactivation by carboxymethylation with iodoacetate indicated that modification of one sulfhydryl group per enzyme subunit caused complete loss of activity. These results, together with the enzyme's attachment to cysteinylsuccinamidopropyl-glass and the observed initial rate enzyme kinetics, strongly implicate a substituted-enzyme kinetic mechanism with a mixed disulfide as the intermediate enzyme form.     

The effects of ultra-high-pressure treatments combined with heat treatments on the antigenicity and structure of soy glycinin

Glycinin is one of the important allergens found in soybeans, which can potentially cause severe allergic reactions. Therefore, reducing the antigenicity of glycinin is of major significance to the research of soybean allergies. In order to detect the relationships between the antigenicity and structure of glycinin, samples were extracted from defatted soybean and then processed by ultra-high-pressure combined heat treatments. The processed proteins were determined using SDS-PAGE, enzyme-linked immunosorbent assay (ELISA), immunoblotting, exogenous fluorescence, free sulfhydryl groups and Fourier transform methods. The results revealed that the antigenicity of the processed soy glycinin had decreased. In addition, the content levels of the hydrophobic groups, free sulfhydryl groups, α-helix, β-turn and random coils had increased, and the content of β-sheets had decreased. The results indicated that the reduction in the antigenicity of the glycinin was due to the processing treatments, which effectively destroyed the spatial structure of the glycinin.     

新型蛋氨酸测定方法的建立

本文建立了一条快速、简便、精确度高的蛋氨酸测定方法。蛋氨酸与过量氯铵-T反应生成蛋氨酸亚砜,过量的氯铵-T与NTB发生氧化反应生成DTNB,一定范围内剩余的NTB的量与蛋氨酸量成正比,412nm测定其OD值;同时加入掩蔽剂DEPC可有效消除其他氨基酸尤其是含硫氨基酸的干扰。该方法适用于大量的蛋氨酸菌种的筛选工作。     

磷酸二氢钾的生产工艺

简要介绍了生产磷酸二氢钾各种工艺方法及其各自特点,同时提出了以海水为原料,以天然沸石为离子交换剂制取磷酸二氢钾的工艺方法,该工艺方法原料来源广泛,价格低廉,中间物料可最大限度的进行循环操作,具有工艺简捷、成本低、无污染的特点,工业化前景十分广阔。     

常温储存和干热处理对豆粕蛋白质氧化的影响

研究常温储存和干热处理对豆粕中蛋白质氧化的影响。取新鲜豆粕200 g装入自封袋,置于室温下保存不同时间(1、10、20、30和60 d);另取豆粕20 g于烘箱中100℃加热不同时间(0、1、2、4和8 h),测定分析2种处理方式对豆粕中的蛋白质羰基、巯基、总巯基基团及氨基酸含量的影响。结果表明,与新鲜豆粕(对照)相比,室温储存和干热处理不同时间后蛋白质羰基含量均显著增加(P0.05);随储存和干热处理时间的增加,豆粕蛋白质巯基和总巯基基团含量均逐渐降低,蛋白质巯基被氧化成非二硫键的含硫化合物,导致蛋白质巯基和总巯基与二硫键含量均降低;随加热时间的延长豆粕中苏氨酸、酪氨酸、赖氨酸及组氨酸含量在数值上逐渐降低。结果提示,蛋白质羰基、巯基及氨基酸含量的变化与蛋白质氧化密切相关,室温储存和干热处理均会导致豆粕中蛋白质发生氧化。     

Positive interaction between amino and sulfhydryl groups for acrylamide removal

The reaction of acrylamide with glutamic acid (Glu), N-acetylcysteine (AcCys), glutamic acid/N-acetylcysteine mixture, glutathione (GSH), and cysteine was studied to analyze the combined action of amino and sulfhydryl groups on acrylamide reduction. Their reactivities for decreasing acrylamide content were inversely correlated (r = − 0.975, p = 0.025) to the E_a of the reaction and acrylamide disappearance decreased in the following order: Cys > GSH > AcCys >> Glu. In addition, E_a of acrylamide/nucleophile reactions seemed to be determined not only by the simultaneous presence of amino and sulfhydryl groups but also by the distance among them. Thus, when both groups were present in different molecules, an interaction between the protective effects of amino and sulfhydryl groups was only observed when small concentrations of AcCys and Glu were employed. However, this interaction was always positive when amino and sulfhydryl groups were simultaneously present in the same molecule and the closer the position of both groups, the higher the positive interaction observed. All these results suggest that, in the search of potential acrylamide-mitigating substances, nucleophiles should have both amino and sulfhydryl groups and these groups should be as close as possible in the molecule.