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豆浆凝固过程中大豆蛋白质二级结构的研究 总被引:2,自引:0,他引:2
用变温ATR-FT-IR测定了豆浆加热、豆浆凝固过程中蛋白质二级结构的变化,结果显示:随着温度的升高,熟豆浆中蛋白质分子间强相互作用氢键(1β)和总相互作用氢键(1β 2β)明显下降,豆浆从20℃升温到80℃时,1β由29.2%下降到16.1%,表明蛋白质分子间的相互作用减弱;豆腐的核心结构(β α)约38.0%变化不大。随豆腐凝胶强度增加,1β由17.4%上升到43.3%,而维持蛋白质紧密结构的氢键(β α)由38.8%下降到17.4%。豆浆凝固过程中1β的变化与其凝胶特性G*变化完全一致,说明蛋白质分子间强相互作用氢键与豆腐的硬度有关。 相似文献
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通过探究菠菜、葱与豆腐是否可以一起吃,使学生深刻理解化学与生活的密切联系。分别检验菠菜、葱中的钙、铁、镁和草酸;检验豆腐中的钙、铁、镁;菠菜与葱中草酸能否与豆腐中的钙生成不溶性草酸钙。 相似文献
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天然胶乳离子沉积过程中若干因素的研究 总被引:1,自引:0,他引:1
本文研究了凝固剂的种类和浓度等因素对天然胶乳离子沉积过程的影响。就沉积能 力而言氯化钙>硝酸钙>醋酸钙>氯化钡>醋酸钡。其中以醋酸钡的凝胶及胶膜性能较好,其他几种凝固剂之间差异不大。钙盐对胶膜老化的影响大于钡盐,其中尤以氯化物为甚。 随着凝固剂浓度的增加橡胶沉积量、凝胶起始浓度及凝胶物理性能均增加。但当使用氯化钙时,在15%左右凝胶抗张力达到最大。 在沉积过程中凝胶浓度起始稍高,随后逐渐下降至一定程度后又缓慢上升,凝胶性能也有类似的变化。 沉积方法与凝固剂的附型剂对沉积过程有明显影响。 由以上结果:我们认为天然胶乳的离子沉积过程可以分成三个阶段:(a)凝结、(b)过渡、(c)胶凝。由以上试验数据证明了所提出的离子沉积动力方程式基本上是正确的。但整个离子沉积过程用q=q_0(kt)/(1+kt)来表示,可能要更好一些。 相似文献
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为确定以不同硒含量的大豆为原料生产豆腐过程中硒分布特性,用石墨炉原子吸收分光光度法对该过程中各种产物的硒含量进行了分析研究。结果表明,以硒含量分别为0.692、2.561、2.801 mg/kg的大豆为原料生产得到的豆腐、黄浆水、豆渣的硒含量分别为:0.089、0.250、0.138 mg/kg,0.462、0.760、0.507 mg/kg和0.532、0.764、0.524 mg/kg。豆腐生产过程中,以低硒大豆为原料生产豆腐,硒总回收率为75.59%;采用富硒大豆为原料生产,硒的回收率分别达到87.37%、87.20%;生产过程中豆腐、黄浆水和豆渣中硒含量占总回收硒的比率分别为39.01%~49.97%、23.92%~29.89%、26.11%~30.92%。 相似文献
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天然无序蛋白质是一类新发现的蛋白质,它们在天然条件下没有确定的三维结构,却具有正常的生物学功能,广泛参与信号传递、DNA转录、细胞分裂和蛋白质聚集等重要的生理与病理过程.无序蛋白质的发现是对传统的蛋白质"序列-结构-功能"范式的挑战.在这篇综述里,我们首先回顾了蛋白质的传统范式以及无序蛋白质的发现过程,然后介绍无序蛋白质在结构、序列、功能等方面的特征与相互作用,并以分子识别过程为例,进一步阐述目前国际上对无序蛋白质所具有优势的一些认识与观点.我们还分析了无序蛋白质研究在生命科学和医学等领域的应用前景,并介绍了国内在无序蛋白质领域的研究现状. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献
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Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described. 相似文献
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用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在. 相似文献
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Jona Mirnik Eva Pušavec Kirar Sebastijan Ričko Uroš Grošelj Amalija Golobič Franc Požgan Bogdan Štefane Jurij Svete 《Tetrahedron》2017,73(24):3329-3337
A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu0 as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than CuI in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT). 相似文献
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George E. Magoulas Thomas Garnelis Constantinos M. Athanassopoulos Dionissios Papaioannou George Mattheolabakis Konstantinos Avgoustakis Dimitra Hadjipavlou-Litina 《Tetrahedron》2012,68(35):7041-7049
(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C60, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine. 相似文献