柠檬酸改性聚乙二醇/丝胶蛋白复合膜的性能

为提高丝胶膜的实际应用价值，采用水蒸气提取的丝胶为基质，添加聚乙二醇400及柠檬酸进行改性，以普通的流延法将其制备成膜，并以纯丝胶膜为对照，通过傅里叶红外光谱(FTIR)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)及力学性能等测试表征其结构与性能变化。结果表明：添加聚乙二醇400能制得完整、难溶于水且具备较好力学性能的聚乙二醇400/丝胶复合膜；采用柠檬酸对聚乙二醇400/丝胶复合膜进行交联后，其耐水溶失及力学性能得到进一步提升，当柠檬酸浓度为0.8%时，复合膜应变增加了3.5倍左右，且表面平整，亲水性能提升，结构有明显改变，具有一定的防紫外线能力。本文通过对丝胶进行改性制备了丝胶复合膜，在医用材料方面有一定的应用前景。     

以柠檬酸作交联剂改善丝胶/聚乙烯醇热固化膜的性能

交联、接枝和共混等是改善纯丝胶膜耐溶失与力学性能的重要技术方法。以柠檬酸作为交联剂制备的丝胶/聚乙烯醇/柠檬酸共混固化膜的表面结构形态得到改善,耐溶失性能以及力学性能显著提高。成膜条件对丝胶/聚乙烯醇/柠檬酸共混固化膜结构及其性能产生影响,适当升高干燥温度有助于提高柠檬酸与丝胶和聚乙烯醇的交联程度,在干燥温度为120℃、柠檬酸质量分数为0.6%的条件下,制备的共混固化膜表现出最佳的力学性能和耐溶失性能。用柠檬酸作交联剂的丝胶/聚乙烯醇/柠檬酸共混固化膜材料培养L929细胞,测试其对细胞毒性的分级为一级(细胞为圆形,偶见裂解细胞),具有良好的生物医用价值。     

多酚氧化酶对蚕丝及丝蛋白生物材料的改性与应用研究进展

多酚氧化酶能催化氧化酚类结构生成醌类活性中间体,引发酚类单体之间聚合。家蚕丝素蛋白和丝胶蛋白大分子肽链上均含一定数量的酪氨酸残基,酪氨酸的酚羟基能被多酚氧化酶催化氧化,生成醌类活性基,不仅可促成丝蛋白大分子交联,而且可与外源氨基功能化合物发生迈克尔加成或席夫碱反应,实现底物分子改造。本文讨论了多酚氧化酶的催化氧化机制,侧重阐述了近年来国内外应用多酚氧化酶(漆酶和酪氨酸酶)进行丝蛋白生物材料加工的研究,包括丝纤维制品酶法抗菌和防皱整理、丝素或丝胶酶促交联与接枝改性、再生丝蛋白膜及功能性生物材料制备等,为蚕丝及丝蛋白基材料的生物改性研究及开发利用提供参考。     

丝胶的分子结构与胶粘强度的相关研究

通过仪器分析和数理统计表明 ,丝胶的胶粘特性依存于分子结构的变化 ,丝胶的胶粘强度与丝胶分子 β结构比率 ( % )的变化呈“S”型曲线 ,其关系式为 :　　y[丝胶分子　β结构比率 ( % ) ]=59 701 +4 0 0 2e- 0 0 0 1X[胶粘强度 (N/mm2 ) ] 。     

不同柞蚕品种茧层的丝胶含量及对缫丝成绩的影响

为了明确将茧层丝胶含量作为柞蚕新品种选育性状的必要性,用称量法和紫外光谱法测定多丝4号、多丝3号、柞杂9号、青6号4个柞蚕品种的蚕茧茧层丝胶含量及分布,并通过缫丝试验分析茧层丝胶含量对缫丝成绩的影响。测定结果表明不同柞蚕品种蚕茧的丝胶含量以及不同茧层的丝胶含量有较大差异:多丝4号的茧层丝胶含量较低(11.9%),青6号的茧层丝胶含量较高(14.2%);各茧层丝胶含量由高到低依次为内层、外层和中层,外茧层和内茧层的丝胶含量在品种间有差异。缫丝试验结果表明柞蚕茧茧层的丝胶含量对缫丝成绩有明显的影响:中茧层和内茧层的练减率在品种间有显著差异;茧层丝胶含量高,解舒性状优,生丝回收率高。从蚕茧的缫丝性能考虑,柞蚕新品种选育应将茧层丝胶含量作为目标性状之一。     

丝胶的分离与用作食品胶凝剂效果初探

利用丝胶作为胶凝剂应用于食品的研究报道极少。本实验用水煮法将丝胶从茧丝中分离出来,以分光光度法在波长280nm处测定其不同浓度溶液的吸光度,结果表明丝胶液浓度、丝胶干物得率与水煮时间的长短呈正相关关系,而丝胶的凝胶化过程也因水煮时间不同产生不同的速度和效果,从而确定以水煮3h所得丝胶液作为制作丝胶果冻的最佳胶凝剂,配以一定比例的果汁、糖及酸,即可制得风味独特的丝胶果冻。     

用热水解法制备不同分子质量丝胶粉的溶解性差异及其成因探讨

用沸水法和高温高压热水法提取丝胶溶液,分别在90℃热水中进行二次降解处理,获得具有不同分子质量分布范围的各种热水解丝胶溶液,经冷冻干燥制成丝胶粉。对各种丝胶粉的热水溶解性差异比较和成因探讨表明,热水二次降解能够提高丝胶的水溶性,降解处理时间越长,其水溶性越大;丝胶的分子质量大小能显著影响其溶解性,而丝胶的结晶结构含量对其溶解性的影响较小。研究结果有助于对不同溶解性丝胶的有效利用。     

关于桑蚕茧层丝胶含量的调查

丝胶是一种球状蛋白质,亲水性大,易溶于水。丝胶的溶解度随着水温、PH值及水质不同而有大小,并由于时间和压力的增加而提高,国内外均有文献记载。本调查就现行蚕品种(各原种及交杂种)、茧层层次(外、中、内层)及上簇条件(温湿度、通风等)不同与丝胶含量和溶解速度的关系作了分析比较,以探索其间的规律及趋向,为煮茧及缫丝采用工艺,便于合理掌握丝胶的膨润和溶解,为有利于解舒提供依据。现将调查结果报告如下     

丝胶溶解条件、组分及结构特性的研究

探讨了H_2O、1％SDS高温极短时间抽提丝胶和LiBr、NaSCN、CaCl_2浓溶液溶解丝胶对丝胶的破坏性。用SDS—聚丙烯酰胺凝胶电泳法分析了丝胶的肽链组分和分子量,归纳出丝胶含有约25种肽链,它们的分子量约从14000到256000。指出丝胶分子中含有两条肽链通过二硫键连结的结构。     

丝胶的凝胶化及其结构、性质的研究

试验对丝胶的凝胶化和凝胶的结构、性质进行了较系统的测定分析。丝胶的凝胶化一般在60°C以下的温度范围内发生,并随着温度的上升和pH值的降低而加剧。丝胶凝胶的分子结构为无规卷曲和β构象,丝胶凝胶的颗粒较大,分布粗疏。丝胶凝胶在水和热的作用下即行溶解,丝胶的凝胶和胶溶的转化过程温度在50—70°C范围。     

丝胶凝胶物理性状的研究

丝胶在凝胶化时,强力增加,而表面张力减小。丝胶凝胶,在30～40℃热水处理时,溶解量很小;50一70℃热水处理时,溶解量增多,溶解速度呈恒定状态;80℃以上,呈快速溶解。根据丝胶凝胶的DTA分析,其吸热分解峰向高温侧移动,这表明丝胶分子的有序性、结晶度提高了。丝胶凝胶在热水处理时,转化为液胶,同时丝胶分子也由β构象转化为无视卷曲结构。并且,丝胶液胶又可重新凝胶化。     

家蚕茧解舒机理的研究

丝胶的胶着性与胶凝有密切的关系。在一定的条件下，丝胶分子相互藉氢键的结合而发生凝集，形成束状的网络结构，分子结构由无规卷曲转化为β构象，失去流动性而发生胶凝作用，随着胶凝作用的进行胶着力增强并固化。高温多湿环境中蚕儿吐丝时由于水分发散难，长时间处于多湿环境中，丝胶分子由无现卷曲转化为β构象，丝胶发生胶凝作用，干燥固化而被覆于茧丝表面。丝胶的强度、胶着力相对增加，茧丝剥离抵抗强，蚕茧解舒就变劣。因此，相对优良的营茧环境是控制丝胶分子不发生构象转化、胶凝作用，生产优质蚕茧的有效途径。     

丝胶/海藻酸钠复合凝胶粒的制备及其结构性能表征

为了改良丝胶型药物载体的结构性能,将丝胶粉末与海藻酸钠溶液均匀混合后,采用氯化钙胶凝法制备了粒径为1.88 mm±0.15 mm的丝胶/海藻酸钠复合凝胶粒。红外光谱检测表明该复合凝胶粒中的丝胶与海藻酸钠之间以物理方式混和;差示扫描量热分析发现丝胶与海藻酸钠复合后,其结构稳定性有所提高;机械性检测表明丝胶/海藻酸钠复合凝胶粒具有更好的力学性能;溶胀性检测表明丝胶/海藻酸钠复合凝胶粒具有pH敏感溶胀性。研究结果表明丝胶/海藻酸钠复合凝胶粒使丝胶作为药物固定化载体的结构与性能得到改善,更有利于开发利用。     

绢纺精练液中丝胶蛋白的氨基酸组成、相对分子量及溶解性的测定

利用氨基酸自动分析仪对从桑蚕丝条吐精炼液中回收的丝胶蛋白的氨基酸组成进行分析,采用聚丙烯凝胶电泳法对其相对分子质量进行测定,利用紫外分光光度计对其溶解性进行探究。结果表明:丝胶蛋白含有18种氨基酸,其中极性氨基酸占80.39%,丝氨酸占27.52%,天门冬氨酸占15.91%,苏氨酸7.41%;丝胶蛋白的相对分子质量集中分布于17~75 KD;丝胶蛋白溶解性优于大豆分离蛋白。     

蓖麻蚕丝胶的溶解特性与组成结构关系的探讨

对蓖麻蚕丝胶的化学组成与聚集态结构进行了研究，认为蓖麻蚕茧丝中丝胶的难溶性与其丝胶包含着丰富的茧丝蜡和单宁物质有密切关系，而蓖麻蚕丝胶分子的聚集态结构的存在形式对其丝胶溶解性关系不大。     

Effect of Sericin Supplementation During In Vitro Maturation on the Maturation,Fertilization and Development of Porcine Oocytes

This study aimed to examine the effects of sericin supplementation during in vitro oocyte maturation on the nuclear maturation, fertilization and development of porcine oocytes. Cumulus‐oocyte complexes (COCs) were cultured in maturation medium supplemented with 0 (control), 0.1, 0.5, 1.0, 2.5 or 5.0% sericin and were then subjected to in vitro fertilization and embryo culture. More COCs matured with 1.0% sericin underwent germinal vesicle breakdown and reached metaphase II compared with the control COCs matured without sericin (p < 0.01). The proportions of oocytes with DNA‐fragmented nuclei did not differ between the groups, regardless of the sericin level. The total fertilization rate of oocytes matured with 1.0% sericin was higher (p < 0.05) than that of oocytes matured with 0.1%, 2.5% and 5.0% sericin. Supplementation with more than 1.0% sericin decreased the DNA fragmentation index of the blastocysts compared with the control group (p < 0.05). However, the supplementation of the maturation medium with sericin had no beneficial effects on the cleavage, development to the blastocyst stage and the total cell number of the embryos. Our findings indicate that supplementation with 1.0% sericin during maturation culture may improve the nuclear maturation and the quality of the embryos but does not affect blastocyst formation.     

In vitro development of OPU‐derived bovine embryos cultured either individually or in groups with the silk protein sericin and the viability of frozen‐thawed embryos after transfer

The optimization of single‐embryo culture conditions is very important, particularly in the in vitro production of bovine embryos using the ovum pick‐up (OPU) procedure. The purpose of this study was to examine the development of embryos derived from oocytes obtained by OPU that were cultured either individually or in groups in medium supplemented with or without sericin and to investigate the viability of the frozen‐thawed embryos after a direct transfer. When two‐cell‐stage embryos were cultured either individually or in groups for 7 days in CR1aa medium supplemented with or without 0.5% sericin, the rates of development to blastocysts and freezable blastocysts were significantly lower for the embryos cultured individually without sericin than for the embryos cultured in groups with or without sericin. Moreover, the rate of development to freezable blastocysts of the embryos cultured individually with sericin was significantly higher than that of the embryos cultured without sericin. When the frozen‐thawed embryos were transferred directly to recipients, the rates of pregnancy, abortion, stillbirth and normal calving in the recipients were similar among the groups, irrespective of the culture conditions and sericin supplementation. Our findings indicate that supplementation with sericin during embryo culture improves the quality of the embryos cultured individually but not the viability of the frozen‐thawed embryos after transfer to recipients.     

Effect of supplemented sericin on the development,cell number,cryosurvival and number of lipid droplets in cultured bovine embryos

Sericin was investigated as an alternative to fetal bovine serum (FBS) for bovine embryo culture. In vitro matured oocytes were developed using 0.05%, 0.1% or 0.15% sericin. The developmental rate, cryosurvival rate and blastulation time of these embryos were compared with those of embryos developed using 5% FBS. The number of lipid droplets was compared among the blastocysts developed using 5% FBS, using 0.05% sericin and in vivo. The rate of cleavage and blastocyst formation was similar among all groups. Blastulation occurred significantly earlier in the embryos developed using 5% FBS than in those developed using sericin at any concentration (P < 0.05). At 72 h after thawing, the cryosurvival rate of the blastocysts developed using 5% FBS and 0.05% sericin were significantly higher compared with those developed using 0.1% and 0.15% sericin (P < 0.05). The blastocysts developed using 0.05% sericin and in vivo produced a significantly fewer number of medium and large lipid droplets than those developed using 5% FBS. These results suggest that the blastocysts developed using 0.05% sericin show characteristics similar to those of the blastocysts developed in vivo and that the use of sericin as an alternative to FBS is feasible.