Stereospecific formation of a ternary complex of (S)-α,β-fluoromethylene-dATP with DNA pol β

The influence of water: crystallization of (R/S)-α,β-CHF-dATP with the preorganized pol β-DNA complex shows that (S)-α,β-CHF-dATP is preferentially bound to the active site with the C=F fluorine proximal to a structural water bound to Asp276.     

Insight into the rescue of oxidized soluble guanylate cyclase by the activator cinaciguat

Nitric oxide (NO) signaling mediates many important physiological processes through the receptor soluble guanylate cyclase (sGC). Under disease conditions sGC heme can be oxidized resulting in NO insensitivity. Here, we show that the therapeutic compound cinaciguat (Cin) rescues dysfunctional sGC by direct displacement of the oxidized heme.     

Concentration of Umami Compounds in Pork Meat and Cooking Juice with Different Cooking Times and Temperatures

This study examined the concentrations of umami compounds in pork loins cooked at 3 different temperatures and 3 different lengths of cooking times. The pork loins were cooked with the sous vide technique. The free amino acids (FAAs), glutamic acid and aspartic acid; the 5′‐nucleotides, inosine‐5′‐monophosphate (IMP) and adenosine‐5′‐monophosphate (AMP); and corresponding nucleoside inosine of the cooked meat and its released juice were determined by high‐performance liquid chromatography. Under the experimental conditions used, the cooking temperature played a more important role than the cooking time in the concentration of the analyzed compounds. The amino acid concentrations in the meat did not remain constant under these experimental conditions. The most notable effect observed was that of the cooking temperature and the higher amino acid concentrations in the released juice of meat cooked at 80 °C compared with 60 and 70 °C. This is most likely due to the heat induced hydrolysis of proteins and peptides releasing water soluble FAAs from the meat into the cooking juice. In this experiment, the cooking time and temperature had no influence on the IMP concentrations observed. However, the AMP concentrations increased with the increasing temperature and time. This suggests that the choice of time and temperature in sous vide cooking affects the nucleotide concentration of pork meat. The Sous vide technique proved to be a good technique to preserve the cooking juice and the results presented here show that cooking juice is rich in umami compounds, which can be used to provide a savory or brothy taste.     

Bacterial and Autolytic Changes in Water Retention and Adenosine Nucleotides of Cod Mince

Water uptake ability (WUA), expressible moisture (EM), hypoxanthine (Hx), and inosine (HxR) were monitored in cod mince stored at 0, ?2, ?3°C, with or without bacterial inactivation using NaOCl. Hx and HxR increased (p < 0.05) in all samples during the first 9-10 days. Bacterial inactivation reduced Hx and HxR build up. Beyond day 10, Hx and HxR decreased in all samples. The decrease was slower in samples in which bacterial had been inactivated. Bacterial inactivation deterred WUA increases and EM decrease.     

核苷酸对斑点叉尾鮰幼鱼生长、 体成分和胃肠道形态的影响

研究外源核苷酸——5’-腺苷酸、5’-尿苷酸二钠、5’-胞苷酸二钠、5’-鸟苷酸二钠和5’-肌苷酸二钠对斑点叉尾鮰幼鱼生长性能、体成分和胃肠道形态的影响。结果表明:基础饲料中添加外源核苷酸没有显著提高斑点叉尾鮰幼鱼的增重率和特定生长率,但显著改善了鱼体的干物质和粗蛋白质含量,同时对胃肠道形态的发育具有显著地促进作用,其中以0.10%核苷酸混合物添加水平较佳。     

海产鲜味物质及海产品特征滋味的研究进展

素有"海鲜"之称的海产品,以其味道鲜美而备受人们的喜爱。迄今为止,人类所发现的氨基酸、核苷酸、有机酸三类鲜味物质在海产品中都广泛存在,这是海产品鲜味形成的共同物质基础。然而,不同的海产品又呈现出各具特色的特征滋味,这主要归因于各鲜味物质的不同比例以及多种呈味物质的存在。总结了主要海产鲜味物质的研究概况,综述了贝、鱼、虾、蟹等典型海产品特征滋味及其构成的研究进展。并在此基础上预测了今后海产鲜味物质的研究与开发趋势。     

热风微波联合干燥过程中南美白对虾滋味物质变化研究

为研究热风微波联合干燥过程中南美白对虾滋味物质的变化,测定了其呈味核苷酸与游离氨基酸含量,同时根据干燥过程中虾肉水分含量计算两者的干基含量变化,并计算虾肉味精当量.研究结果表明:虾肉干燥过程中,呈味核苷酸中肌苷酸含量最高,干制虾肉肌苷酸含量为405.96 mg/100 g,且始终高于阈值,对干制虾肉的鲜味形成有显著贡献;相比鲜样,干制南美白对虾中肌苷酸与单磷酸腺苷干基含量均显著下降;在虾肉中谷氨酸对鲜味形成有显著贡献,甘氨酸、丙氨酸与精氨酸对甜味形成有贡献,苯丙氨酸、赖氨酸与组氨酸能产生苦味;而在干燥过程中鲜、甜味氨基酸相对含量不断上升,分别从3.77％和17.03％上升到4.29％和35.84％;游离氨基酸总干基含量始终下降,但甘氨酸、丙氨酸、精氨酸与脯氨酸4种可以形成良好滋味的游离氨基酸干基含量上升;虾肉中肌原纤维蛋白与肌浆蛋白的干基含量均不断下降,部分分解为游离氨基酸;虾肉味精当量整体呈显著上升趋势,但在微波干燥初期(前40 s)显著下降,干制南美白对虾味精当量为3.50 g/100 g,远高于鲜虾(0.53 g/100 g),且虾肉味精当量始终远高于阈值.研究结果表明,由热风微波联合干燥引起的水分挥发与物质变化能够促进南美白对虾滋味形成.     

高效液相色谱法测定母乳及牛乳中总核苷酸含量

建立高效液相色谱测定母乳和牛乳中总核苷酸含量和组成的分析方法。总核苷酸包括游离核苷酸、游离核苷、核苷聚合物及加合物等不同来源的可利用核苷总量。利用酶解法释放出母乳中的核苷,以硼化聚丙烯酰胺凝胶（Affi-Gel 601）作为固相萃取介质进行样品净化,用反相高效液相色谱仪检测,内标法定量,检测结果以核苷酸计。且针对母乳样品的特性,增加高温灭活步骤进行样品前处理,以检测母乳中核苷酸的天然含量及组成。对所建方法进行全面验证,结果表明其具有良好的线性,相关系数（r2）均在0.999以上;母乳中各核苷酸的检出限和定量限分别在0.18～0.45 mg/L和0.60～1.51 mg/L之间;母乳基质中3 种不同加标水平下总核苷酸的回收率均在99%～108%之间,连续3 d 6 次检测结果的相对标准偏差在0.8%～7.8%之间,显示了良好的准确性及精密度。然后进一步利用所建检测方法,评估母乳及5 种市面常见的牛乳中的核苷酸总量及组成用以验证该方法的适用性。该方法的灵敏度、准确性及精密度均可满足对母乳和牛乳样品中天然的核苷酸含量及组成的测定要求。本研究为今后大样本量调查母乳及牛乳样品中核苷酸的含量和组成提供了更加科学准确的方法。     

反复卤煮对老汤品质的影响研究

传统酱卤肉制品因老汤的使用而深受消费者喜爱,卤汤在连续的使用过程中不断积累较多的可溶性滋味物质,使其本身具有鲜醇浓厚独特的美味,进而赋予卤煮制品特有的滋味。本研究以白羽肉鸡鸡腿为原料,对传统卤煮工艺不同卤制次数卤汤中的营养物质如蛋白质、游离氨基酸、呈味核苷酸、味精当量等和有害物质中的杂环胺的变化进行研究。结果表明:与对照组第0锅卤汤相比,当卤制次数达到第9锅时,卤汤中蛋白质含量由0.09%增加至3.86%,总游离氨基酸含量由68.57 mg/100g上升至601.92 mg/100 g,呈味核苷酸含量由0.78 mg/100 g达到了22.97 mg/100 g,味精当量(EUC)值由0.0068 g MSG/100 g升高至1.32 g MSG/100 g,但有害物质中杂环胺含量由12.29 ng/g上升至28.64 ng/g。因此,传统卤煮工艺中随着卤制次数的增加,卤汤中营养物质的含量呈不断上升的趋势,同时有害物质中杂环胺的含量也不断富集。