Rheological Properties of Chitosan and its Interaction with Porcine Myofibrillar Proteins as Influenced by Chitosan's Degree of Deacetylation and Concentration

ABSTRACT Rheological and gelation characteristics of a specific degree of deacetylation (dd 50 to 99) and concentration (0.5% to 1.5%) of chitosan and chitosan/SSP (salt-soluble protein) mixtures were studied. Results suggested that SSP thermal gelation was interfered with by the positive charges of amino groups of the chitosan molecule. Regardless of degree of deacetylation, increasing chitosan concentration caused stronger interference on SSP gelation and lowered complex modulus [G*]. Loss tangent of chitosan/SSP gel decreased with increasing temperature. Higher level (1.5%) of dd 99 chitosan had the lowest G*, which resulted from ionic interaction with SSP. SDS-PAGE revealed protein aggregation, indicating possible covalent bond formation.     

不同工艺条件对大豆分离蛋白7S和11S组分影响的探讨

利用碱提酸沉的工艺，通过改变温度和离子强度得到不同参数条件下的大豆分离蛋白。经过凝胶电泳分析得到蛋白质的各个条带组分图，用图像捕捉成像技术以及相关软件，分析出分离蛋白各个组分的详细情况（包括组分数、分子量和各个组分所占的百分含量）。由实验可知，分离蛋白的7S和11S组分随温度和离子强度的改变而发生变化，分析其变化规律，从而确定合适的工艺参数。     

Proteomic analysis of responses of a new probiotic bacterium Lactobacillus casei Zhang to low acid stress

Tolerance to acid is an important feature for probiotic bacteria during transition through the gastrointestinal tract. Proteomics analysis of a new probiotic bacterium, Lactobacillus casei Zhang, was performed upon 30-min exposure to low acid stress (pH 2.5 vs. pH 6.4) using two-dimensional electrophoresis. Out of 33 protein spots that showed changes of expression between the two pHs, 22 showed 1.5-fold higher expression at pH 2.5 than at pH 6.4, whereas five spots had expression decreased by 1.5-fold at pH 2.5. There were also six protein spots that were exclusively present on different pH maps. Further analysis showed that eight of the enhanced proteins, NagA, NagB, PGM, GlmM, LacC, TDP, GALM and PtsI, were involved in carbohydrate catabolism. Moreover, quantitative RT-PCR showed that the mRNA expression levels of dnaK, nagB, galm, estC, tuf and luxS were consistent with changes in protein expression. We postulate that there might be some relationship between differentially expressed proteins and acid tolerance in L. casei Zhang.     

雅安罐罐肉加工与贮藏过程中肌肉蛋白质的变化

为了探明雅安罐罐肉蛋白质的变化规律,以不同加工与贮藏阶段的罐罐肉为对象,采用常规理化检测方法以及SDS-PAGE电泳法分析其蛋白质的变化情况。结果显示:罐罐肉在油炸结束后蛋白酶活性为零;非蛋白氮(NPN)与游离氨基酸(FAA)含量在油炸结束时显著上升(P<0.01),FAA达到最大值(219.2 mg/100 g),在贮存的前期与中期缓慢下降,后期又有所回升,NPN达到最高值(0.616%);肌浆蛋白和肌原纤维蛋白经过高温油炸,蛋白质含量(干基)下降为4.18 mg/g和4.70 mg/g,大于66ku的蛋白质条带完全消失,积累大量小于16ku的条带,肌浆蛋白贮藏后期还出现了51ku和42ku的新条带。研究结果表明,雅安罐罐肉蛋白质的变化主要发生在油炸阶段,贮藏过程中的变化非常缓慢。     

Enzymatic Hydrolysis of Shrimp Head Waste: Functional and Biochemical Properties

Shrimp head of Penaeus kerathurus obtained from industrial processing, were hydrolyzed by commercial trypsin (0.1%). Hydrolysis reaction was terminated by heat inactivation of the enzyme (95°C) followed by centrifugation. The produced protein hydrolysates were characterized by biochemical analysis for protein content, total free amino acids (FAA), total volatile basic nitrogen (TVB-N) and electrophoresis SDS-PAGE profile. Functional properties such as emulsifying capacity, fat adsorption and foaming property were assessed. Compared to the raw shrimp head protein, results from enzymatic hydrolysis showed a significant increase (p?<?0.05) in protein content and FAA (17.22%). The low level of trypsin used in this study was sufficient to solubilize the substrate, resulting in substantial protein contents and TVB-N levels (< 6mg/100g), which was significantly lower than the acceptable limits established for marine products.     

均匀试验设计优化酶法提取燕麦全粉蛋白质研究

采用酶法从燕麦全粉中提取燕麦蛋白.先对提取所用的酶进行筛选,选定提取率最高的碱性蛋白酶为提取酶类,在单因素试验基础上用五因素十水平均匀试验设计对酶法提取燕麦蛋白的工艺进行优化.结果表明:碱性蛋白酶提取燕麦蛋白的最佳工艺为:加酶量(E/S) 100.358 U/g,pH 10.5,温度53.49℃,液料比18∶1,时间60 min,在此条件下,提取率为84.09％,纯度达89.16％,得到的燕麦蛋白的等电点为4.4,分离率达93.33％.SDS-PAGE电泳分析显示,酶法制备的燕麦蛋白在65.2 ～ 12.5 ku上都有条带分布,其中74.3％的条带集中在31.3 ～40.0 ku和21.0 ～21.9 ku两个区间,与碱法相比,有条带缺失.     

Comparative investigations of gluten proteins from different wheat species I. Qualitative and quantitative composition of gluten protein types

In contrast to the hexaploid common (bread) wheat, little information is available on the qualitative and quantitative compositions of gluten proteins from other cultivated wheat species. Therefore, representatives of hexaploid spelt, tetraploid durum wheat and emmer, and diploid einkorn were compared with three classes of common wheat (winter wheat, spring wheat, wheat rye hybrid). The flours were extracted to yield total endosperm proteins and the gluten protein fractions (gliadins and glutenin subunits). The extracts were characterised using sodium dodecyl sulfate polyacrylamide gel electrophoresis and reversed-phase HPLC; both methods revealed that gluten protein groups and types known from common wheat (ω-, α-, γ-gliadins, HMW and LMW subunits of glutenin) were present in all species. The HPLC platterns of gliadins and glutenin subunits from species with the same genome composition (common wheat/spelt or durum wheat/emmer) were related, and those of einkorn quite different. According to the quantities determined by reversed-phase HPLC, α-gliadins were predominant in most cases, followed by γ-gliadins and LMW subunits; ω-gliadins and HMW subunits were generally minor components. Common wheats were characterised by the highest proportions of total glutenins and HMW subunits, which are known to be important for breadmaking quality. Moreover, the lower ratio of gliadins to glutenins was typical. Emmer had the lowest proportions of total glutenins and of HMW and LMW subunits, together with einkorn the highest proportion of α-gliadins, and, by far, the highest ratio of gliadins to glutenins. The values for spelt and durum wheat were mostly in a medium range between common wheats, emmer, and einkorn, respectively. Amongst common wheats, spring wheat was characterised by more balanced quantities of α- and γ-gliadins, and wheat rye hybrid by the highest proportions of ω-gliadins. Received: 26 November 1999     

SDS-聚丙烯酰胺凝胶电泳法鉴定动物肌肉蛋白热变性的研究

分别对鸡、牛、猪、羊、鱼等五种新鲜动物肌肉组织进行不同温度的热处理,对处理前后的样品进行SDS-聚丙烯酰胺凝胶电泳,结果显示五种动物肌肉组织经不同温度处理,所得电泳图谱具有显著差异,反映蛋白质变性与温度存在密切相关性.因此,可采用SDS-聚丙烯酰胺凝胶电泳法鉴定动物组织蛋白的热变性程度,从而应用于肉制品加工过程中热熟程度的判定.该方法特异性和敏感性较强,操作简单,结果判定直观可靠.     

聚乙二醇化学修饰的重组L-门冬酰胺酶对小鼠白血病细胞P388的抑制作用

目的 考察聚乙二醇(polyethylene glycol,PEG)化学修饰的重组L-门冬酰胺酶(recombinant Lasparaginase, rL-ASP)的抗肿瘤活性。 方法 PEG 化学修饰rL-ASP, 获得的化学修饰酶(polyethylene glycolmodified recombinant L-asparaginase, rL-ASP-PEG)利用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳法(sodium dodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE)观察其分子大小变化, 四甲基偶氮唑盐(3-(4, 4-dimcthylthioazol-2-yl)-2, 5-diphenyl-tetrazolium bromide, MTT)法和流式细胞仪(flow cytometer, FCM)检测rL-ASP-PEG 对体外培养的小鼠白血病细胞P₃₃₈增殖作用的抑制作用, 腹腔给药考察rL-ASPPEG对小鼠移植性实体瘤P₃₃₈ 抑瘤效果, 透射电镜(transmission electron microscopy, TEM)观察rL-ASPPEG引起的肿瘤组织超微病理变化。 结果 SDSPAGE显示, rL-ASP-PEG 的分子量大于rL-ASP;MTT实验表明, rL-ASP-PEG 能抑制体外培养的小鼠P₃₈₈白血病细胞的增殖, 半数有效浓度(inhibitory concentration50 %, IC₅₀)为2.056 IU·ml^-1。FCM 结果表明, rL-ASP-PEG 主要将肿瘤细胞P₃₈₈ 抑制在G₀ +G₁期,S 期细胞减少。DBA/2 荷瘤小鼠的抑瘤实验表明rL-ASP-PEG 对移植性实体瘤P₃₃₈ 有显著抑制作用, P 值<0.001。超微病理切片显示rL-ASP-PEG引起肿瘤组织坏死。 结论 rL-ASP 经过聚乙二醇化学修饰后, 具有肿瘤抑制作用。     

γ-聚谷氨酸对带鱼鱼糜凝胶特性的影响

γ-聚谷氨酸作为一种新型可食用的食品添加剂,可显著提高带鱼鱼糜的凝胶强度(P<0.05),且对鱼糜的白度值影响较小。响应面优化试验结果表明,采用两段加热方式,γ-聚谷氨酸添加量0.54‰、第1段加热温度52.6℃,加热时间39min时,鱼糜凝胶强度最高,为281.66g.cm。在各影响因素中,γ-聚谷氨酸添加量对凝胶强度的影响最大,其次是第1段加热温度,加热时间影响最小。SDS-PAGE电泳图谱和扫描电镜图谱显示γ-聚谷氨酸与鱼糜蛋白质可相互作用,从而提高鱼糜凝胶强度。经两段式加热的鱼糜凝胶强度显著高于一段加热方式(P<0.05),但二者在肌原纤维蛋白SDS-PAGE电泳图谱上无明显差异,说明γ-聚谷氨酸对二者肌原纤维蛋白质的组成没有影响。