碱性pH对马鲛鱼肌球蛋白热聚集行为的影响

为探究碱性条件下pH对马鲛鱼肌球蛋白热聚集行为的影响,以马鲛鱼肌球蛋白为研究对象,探究在加热条件下pH（7.0、8.0、9.0）对肌球蛋白的结构和理化性质（溶解度、浊度、二级结构、总巯基含量、表面疏水性）的影响,未加热组作为空白对照组。结果表明：对照组肌球蛋白在pH（7.0、8.0、9.0）下溶解度从68.00%升高到82.00%、浊度变化不明显;加热组则有较大差异,溶解度从30.00%增加到94.00%,浊度吸光值从0.49降低到0.23;加热组pH 9.0的肌球蛋白α-螺旋含量减少,在所有组中含量最低,为45.60%,β-折叠含量增加,为10.60%;加热组的巯基含量呈下降趋势,由70.45 nmol/mg减少到50.11 nmol/mg,碱性pH下的蛋白质有助于巯基向分子间和分子内二硫键的转化;随着pH值的增加,对照组肌球蛋白的表面疏水性系数依次增加,而加热组下降,但加热组肌球蛋白的表面疏水性系数仍然远高于对照组。综上所述,通过探究碱性条件下肌球蛋白热聚集体的性质,有助于对其热聚集进行调控,获得一种热稳定性较好的肌球蛋白溶液,对以后研究其作为乳化剂添加到食品中有重要意义。     

Isolation and identification of procyanidins in apple pomace

The chemical nature of the procyanidin components in apple pomace was investigated as part of a programme seeking alternative uses of the large quantity of pomace that is being generated from the apple juice industry. The homogeneous nature of the procyanidin fractions was demonstrated by the isolation and identification of a range of epicatechin oligomers, namely epicatechin-(4β-6) epicatechin, epicatechin (4β-8) epicatechin, epicatechin (4β-8) epicatechin (4β-8) epicatechin and epicatechin (4β-8) epicatechin (4β-8) epicatechin (4β-8)-epicatechin. The procyanidin polymers were also isolated and purified by a Sephadex LH20 column and shown to consist exclusively of epicatechin units. The chemical structures of these procyanidins were established by ¹³C-NMR spectroscopy, by acid-catalysed degradation reaction with phloroglucinol and by electrospray mass spectrometry.     

Closed-loop diesel engine combustion phasing control based on crankshaft torque measurements

Methods for closed-loop combustion phasing control in a diesel engine, based on measurements of crankshaft torque, are developed and evaluated. A model-based method for estimation of cylinder individual torque contributions from the crankshaft torque measurements is explained and a novel approach for identification of crankshaft dynamics is proposed. The use of the combustion net torque concept for combustion phasing estimation in the torque domain is also described. Two different control schemes, one for individual cylinder control and one for average cylinder control, are studied. The proposed methods are experimentally evaluated using a light-duty diesel engine equipped with a crankshaft integrated torque sensor. The results indicate that it is possible to estimate and control on a cylinder individual basis using the measurements from the crankshaft torque sensor. Combustion phasing is estimated with bias levels of less than 0.5 crank angle degrees (CAD) and cycle-to-cycle standard deviations of less than 0.7 CAD for all cylinders and the implemented combustion phasing controllers manage to accurately counteract disturbances in both fuel injection timing and EGR fraction.     

Synthesis and characterizations of oligomeric (4,4′-dialkyl-2,2′-bithiazole) carboxylic acids and their LB-film behavior

The synthesis of series of 4,4′-dialkyl-2,2′-bithiazole oligomers, (ABTz)_1,2, and their 5-carboxylic acid derivatives is described. The Langmuir–Blodgett film-forming behavior of the several of the bithiazole dimer carboxylic acids was explored. The compounds form LB films with areas per molecule increasing from 32 to 40 Å² as the length of the alkyl side chain increases from ethyl to hexyl.     

Enhanced electrochemical performance of a promising anode material FeVO4 by tungsten doping

FeVO₄ is considered to be a promising anode material due to its high specific capacity and abundant resource. However, cyclic stability and rate capability of FeVO₄ need to be improved. W doped FeVO₄ is prepared by a sol-gel method in this work. The sol-gel method plays a key role in obtaining nanometer materials. W doping not only further reduces the particle size, but also improves the conductivity of FeVO₄. The combined effects of sol-gel method and W doping are in favor of enhancing electrochemical performance, because both small particle size and superior conductivity are all beneficial to improving the reaction kinetics of FeVO₄. W doped FeVO₄ shows better electrochemical performance than pure FeVO₄. It delivers 410 mA h/g after 300 cycles at the current density of 500 mA/g. W doped FeVO₄ shows great potential applications as an anode material for Li ion batteries.     

20(R)-ginsenoside Rg3, a product of high-efficiency thermal deglycosylation of ginsenoside Rd,exerts protective effects against scrotal heat-induced spermatogenic damage in mice

Heat stress (HS) reaction can lead to serious physiological dysfunction associated with cardiovascular and various organ diseases. Ginsenoside Rg3 (G-Rg3) is a representative component of ginseng rare saponin and can protect against multiple organs, also used as functional food to adjust the balance of the human body, but the therapeutic effect and molecular mechanism of G-Rg3 on male diseases under HS are underexplored. The aim of the present study, G-Rg3 was prepared through the efficient conversion of ginsenoside Rd and investigate the contribution of G-Rg3 to testicular injury induced exposure to HS. All mice were divided into four groups as follows: normal group, HS group, and HS+G-Rg3 (5 and 10 mg/kg) groups. G-Rg3 was administered orally for 14 days, then exposed to a single scrotal heat treatment (43°C, 18min) on the 7th day. After HS treatment, the morphology of testis and epididymis changes, and caused a significant loss of multinucleated giant cells, desquamation of germ cells in destructive seminiferous tubules, and degenerative Leydig cells, further destroying the production of sperm. After administration G-Rg3 (5 and 10 mg/kg/day) for 2 weeks, the spermatogenic-related indexes of testosterone levels and superoxide dismutase (SOD) activity, glutathione (GSH) content significantly (p < 0.01) increase compared with the HS group. Moreover, G-Rg3 treatment effectively ameliorated the production of malondialdehyde (MDA) (p < 0.05 or p < 0.01). Importantly, G-Rg3 exhibited the protective potential against HS-induced injury not only suppressing the protein levels of heme oxygenase-1 (HO-1), hypoxia-inducible factor-1α (HIF-1α), and heat shock protein 70 (HSP70) but also modulating the Bcl-2 family (p < 0.01 or p < 0.001) and activation of mitogen-activated protein kinase (MAPK) signaling pathways (p < 0.01). For most of the parameters tested, the HS+G-Rg3 (10 mg/kg) group exhibited potent effects compared with those exhibited by the low dose (5 mg/kg) group. In conclusion, the present study demonstrated that G-Rg3 exerted protective effects against HS-induced testicular dysfunction via inhibiting the MAPK-mediated oxidative stress and apoptosis in mice.     

玉米醇溶蛋白核壳结构微粒的制备及应用研究进展

玉米醇溶蛋白是一种来自玉米的储存蛋白,因其良好的成膜性、独特的溶解性和自组装性能在食品、制药和生物技术等领域具有广泛的应用。基于玉米醇溶蛋白在不同溶剂体系的溶解特性和自组装特性,可采用多种方法制备具有核壳结构特征的玉米醇溶蛋白微粒,该微粒可作为生物活性物质的递送载体、乳液稳定剂和纳米纤维材料等。本文综述了玉米醇溶蛋白核壳结构微粒的不同制备方法及其功能特性,旨在为玉米醇溶蛋白核壳结构微粒的制备及其在食品领域的应用提供理论依据和实际指导。     

马鲛鱼中精氨酸脱羧酶的基因克隆及生物信息学分析

本研究以马鲛鱼贮藏期内腐败产胺菌-霍氏肠杆菌(Enterobacter hormaechei)为研究对象,通过基因工程和生物信息学多种分析方法,探究马鲛鱼种霍氏肠杆菌精氨酸脱羧酶的理化性质。通过T-A克隆并测序得到ADC基因,将其翻译成蛋白序列,然后预测蛋白质一级结构、二级结构以及三维构象,分析ADC蛋白质的理化性质及其功能。结果显示:ADC蛋白由93个氨基酸构成,预估分子量大小约为10.82 ku、理论等电点是8.64、原子组成为C₄₉₂H₇₄₆N₁₃₆O₁₃₅S₃、半衰期>10 h(大肠杆菌,体内)、脂肪系数是86.02;总平均亲水性是-0.35整体表现为亲水性,是可溶性蛋白;不稳定系数为48.57,且ADC蛋白不存在信号肽,不是分泌蛋白。这些结果以及同时预测的ADC蛋白的二级结构和三维构象,为后续的深入研究提供参考,今后在基因克隆的基础上,将进行蛋白质的表达、分离纯化和性质研究,进一步解析精氨酸脱羧酶。