十二烷基硫酸钠对不锈钢在循环冷却水中的缓蚀作用

研究了在50℃含有氯离子的模拟循环冷却水溶液中,表面活性剂十二烷基硫酸钠对不锈钢点蚀行为的影响。实验结果表明,十二烷基硫酸钠对不锈钢的点蚀具有一定的缓蚀作用,且随其浓度的增大,缓蚀效果越好;当十二烷基硫酸钠的浓度为6mmol/L,θ为50℃时缓蚀效果最佳。     

The effects of sodium hexametaphosphate addition on the physicochemical properties and microstructure of the milk fat globule membrane (MFGM) in liquid milk after freezing

This research examined the effects of sodium hexametaphosphate on the physicochemical properties and the microstructure of the milk fat globule membrane (MFGM) after freezing. The particle size distribution showed that the peak of the MFGM in the controlled sample was higher than the peak in the frozen sample. The MFGM sample that contained the highest concentration of sodium hexametaphosphate displayed the highest peak. The MFGM samples with the highest concentrations of sodium hexametaphosphate were more stable than the samples with the lowest concentrations. Sodium dodecyl sulfate Polyacrylamide gel electrophoresis and scanning electron microscopy showed sizeable destruction of the MFGM after freezing.     

羊毛角蛋白的提取

将生化用新型精细二硫键还原剂TCEP(三羧乙基膦)应用于羊毛角蛋白的提取.探讨了在羊毛角蛋白的提取过程中,温度和十二烷基硫酸钠(SDS)对羊毛的最终溶解时间和最终溶解率的作用.温度对羊毛溶解所需时间和最终溶解率的影响非常大.SDS可以加快羊毛溶解速度,但对羊毛的最终溶解率影响不大.当温度较低(＜70℃)时,SDS对羊毛的最终溶解率有很大影响;当温度较高(＞70℃)时,SDS对羊毛的最终溶解率无明显影响.羊毛溶解所需时间几乎不受SDS量的影响,可见随着SDS量的增加,其起到的助溶作用增加不明显.通过显微镜观察,羊毛溶解是溶胀溶解的过程.     

Effect of grain hardness,fractionation and cultivars on protein,pasting and dough rheological properties of different wheat flours

Coarse flour fractions (CFFs) and fine flour fractions (FFFs) obtained from flour milled from twelve different wheat cultivars varying in grain hardness index (GHI) were evaluated for particle size distribution, pasting and protein characteristics. Cultivars with greater hardness produce flour with high protein content had more proportion of large size particles. FFF had higher unextractable polymeric protein, solvent retention capacity (SRC), sedimentation value (SV) and dough stability (DS) than their corresponding CFF. Both FFF and CFF from cultivars with lower hardness showed lower sodium SRC. CFF showed higher pasting viscosities than their corresponding FFF, and difference in these properties was greater amongst soft cultivars. DS increased with decrease in grain hardness, but medium hard cultivars showed exceptionally higher value. The concentration of HMW‐GS in the CFF was higher than FFF of hard wheat cultivars, whereas the concentration of LMW‐GS in the CFF and FFF was not influenced by the fractionation of flour.     

底物亲和法分离纯化蕲蛇胃蛋白酶

利用酶(胃蛋白酶)与其底物(酪蛋白)的亲和性,从蕲蛇胃中提取得到一种胃蛋白酶.让底物和酶在pH 2.5的乳酸缓冲液中充分结合,然后调pH至4.0(底物的等电点)沉淀底物和酶的结合物,随后让沉淀物再溶解于乳酸缓冲液中,添加低浓度的SDS将底物和酶分离,最后用DEAE离子交换色谱柱进行纯化,经SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)鉴定,分离得到的胃蛋白酶为电泳纯,其分子量为33KD.酶的最适pH值小于3.0,最适温度为50℃.该结果证明胃蛋白酶能利用其与酪蛋白的亲合性及SDS沉淀作用有效地分离,这种胃蛋白酶能在食品生产的加热、强酸处理过程中应用.     

重组小分子多肽的SDS-PAGE分析方法

比较了小分子多肽SDS PAGE的各种显色方法 ,结果表明 ,考马斯亮蓝R 2 5 0染色需要 3μg以上的样品 ,相对分子质量 30 0 0左右的肽才能得到清晰条带 ,而对含量低的基因工程产物不能显色 .银染可用于检测微量的分子多肽 ,银染过程中用戊二醛和甲醛进行敏化而减少固定时间 ,可显著提高检测灵敏度 ,是检测微量基因工程产物的好方法     

十二胺与十二烷基磺酸钠组合捕收剂对赤铁矿浮选的优化及其泡沫性能调控北大核心

采用十二胺进行微细粒级赤铁矿反浮选时具有泡沫产品黏、难消泡的问题。选取赤铁矿和石英两种纯矿物,分别在十二胺(DDA)以及十二胺与十二烷基磺酸钠(SDS)的组合捕收剂体系下,研究了pH值、捕收剂用量及其配比、淀粉用量等对赤铁矿和石英单矿物和混合矿浮选的影响,并进行了泡沫稳定性试验。研究表明,不加入矿物颗粒时,十二胺溶液的气泡平均尺寸小于组合捕收剂(DDA∶SDS=2∶1)的气泡平均尺寸;采用十二胺作捕收剂浮选赤铁矿和石英时,泡沫量更多,气泡小且密集,气泡破裂速度较慢,泡沫更黏更稳定。与单一十二胺捕收剂相比,十二胺和十二烷基磺酸钠组合捕收剂在浮选指标和泡沫性能均体现出了优势。在适宜的药剂制度条件下,十二胺与十二烷基磺酸钠在一定比例条件下组合使用,不仅能够提高浮选指标,还能优化泡沫性能,大幅度降低泡沫黏性。研究对克服阳离子浮选工艺存在的泡沫问题和微细粒级赤铁矿石的浮选具有一定的参考价值。