冷冻-解冻循环对鳞鲀(Abalistes Stellaris)鱼糜蛋白变性的影响

研究了冷冻-解冻循环对鳞鲀鱼糜蛋白变性的影响,测定指标为蛋白质盐溶性、Ca2+ -ATPase活性及鱼糜凝胶的破断强度、凹陷深度、压出水分和白度.结果表明:随冷冻-解冻循环次数增加,鳞鲀白肉鱼糜及全肉鱼糜蛋白的盐溶性和Ca2+ -ATPase活性均下降,表明鱼糜蛋白发生了变性;鱼糜凝胶的破断强度、凹陷深度及持水性也下降(白度除外).因此,在加工中应避免反复冷冻-解冻,以保证鳞鲀鱼糜质量.     

两种蛋白类添加剂对鳙鱼鱼糜凝胶特性的改良

通过检测鱼糜凝胶的质构及微观结构,研究了鸡蛋清蛋白和谷朊粉两种蛋白类添加剂对鳙鱼鱼糜凝胶特性的影响,并采用SDS-聚丙烯酰胺凝胶电泳(SDS—PAGE)对相关作用机理进行分析．结果表明：这两类添加剂可明显提高鳙鱼鱼糜的凝胶特性,使其形成致密、均匀的凝胶网络结构,且浓度越大,作用越强;鸡蛋清蛋白还可增加鳙鱼鱼糜凝胶的白度,但谷朊粉则使白度降低．SDS—PAGE实验表明,鸡蛋清蛋白和谷朊粉对鳙鱼鱼糜凝胶肌球蛋白重链(MHC)带的强度影响不大．     

白姑鱼鱼糜的化学组成及冻藏稳定性的研究

以舟山产的冷冻小规格白姑鱼为对象,研究了鱼肉和鱼糜蛋白在-30℃、-20℃和-10℃下的冻藏稳定性和冷冻变性特点,并考察了不同抗冻剂对白姑鱼鱼糜低温变性的保护作用。结果表明:白姑鱼鱼肉在不同温度下冻藏时,肌原纤维蛋白都容易发生变性,并且冻藏温度越高变性速度越快,而凝胶强度则随着冻藏时间的延长呈明显下降趋势。添加各种抗冻剂可较好地抑制其冷冻变性,其中海藻糖和乳酸钠的抗冻效果可与商业抗冻剂比拟,可以在工业化生产中单独应用或复配使用。     

猪血肠制作工艺的响应面法优化

以猪血及其他辅料为原料,探讨了猪血肠的制作工艺.在分析大豆分离蛋白(SPI)、黄原胶、变性淀粉、谷氨酰胺转胺酶(TG酶)、卡拉胶及魔芋胶对猪血肠凝胶性能影响的基础上,以SPI、黄原胶、淀粉及TG酶为影响因子,以破断力及凝胶强度最大为优化目标,对猪血肠的制作工艺进行优化.实验显示:SPI和黄原胶均对猪血肠的破断力及凝胶强度有显著(p0.05)影响,淀粉及TG酶对猪血肠的破断力及凝胶强度影响不显著(p0.05);各因素对猪血肠破断力及凝胶强度的影响程度依次为SPI黄原胶变性淀粉TG酶;对各因素与破断力及凝胶强度进行拟合分析,所得拟合模型具有较好的可靠性;以所得拟合模型对猪血肠的制作工艺进行优化,得出:SPI添加量4%、黄原胶添加量0.2%、淀粉添加量0.5%、TG酶添加量0.01%时,所得凝胶的破断力及凝胶强度最高.     

生物保鲜剂对中国对虾蛋白质生化特性的影响

采用茶多酚和壳聚糖对中国对虾进行冷藏保鲜处理,以虾肉蛋白质组成、肌动球蛋白盐溶性、巯基含量、Ca2+-ATPase活性及SDS-PAGE图谱为指标,分析了两种保鲜剂对中国对虾肌肉蛋白特性的影响.结果显示,与对照组相比,保鲜处理组肌动球蛋白质的盐溶性、巯基含量和Ca2+-ATPase活性下降速度减慢,SDS-PAGE分析亦可发现蛋白质降解速度有一定程度的降低,说明茶多酚和壳聚糖能够在一定程度上减缓蛋白质的变性.壳聚糖和茶多酚两种保鲜剂处理之间相比,发现壳聚糖对蛋白质的保护作用优于茶多酚,这与前期得到的壳聚糖用于中国对虾保鲜效果优于茶多酚的研究结果一致.     

6-姜酚对草鱼鱼糜凝胶特性及贮藏稳定性的影响

为了研究6-姜酚对鱼糜凝胶特性及贮藏稳定性的影响,分析了添加不同浓度的6-姜酚后,草鱼鱼糜在4℃冷藏过程中凝胶强度、持水性、色泽、挥发性盐基氮(TVB-N)、硫代巴比妥酸反应物(TBARS)、总巯基含量和细菌总数的变化规律。结果表明,添加6-姜酚的鱼糜凝胶强度和持水性显著高于对照组,且随着添加量的增加呈现先上升后下降的趋势,在添加量为1%时达到最大值。在冷藏过程中,6-姜酚可明显延缓凝胶强度、持水性、白度和总巯基含量的下降,同时抑制TVB-N、TBARS和细菌总数的升高。因此,在鱼糜生产中,添加1%的6-姜酚可改善鱼糜凝胶特性,并延长其保质期。     

鲫鱼（Carassius auratus）肌原纤维蛋白生化特性在冻藏过程中的变化

以肌动球蛋白的盐溶性、肌原纤维蛋白ATPase活性以及肌原纤维蛋白的疏基含量为指标，研究了鲫鱼（Carassius auratus)肌原纤维蛋白在－10℃，－20℃，－30℃和－40℃下冻藏时的变性情况。结果表明，在不同温度下冻藏时，鲫鱼肌动球蛋白的盐溶性、肌原纤维蛋白的ATPase活性以及巯基含量随着冻藏时间的延长，均呈下降趋势。且鲫鱼蛋白质的变性速度在不同冻藏温度下的差异是极其显著的（P＜0．01），冻藏温度越低，变性越缓慢。     

猪血超氧化物歧化酶纯化与分析─—一种铜盐沉淀新工艺

本文建立铜盐沉淀、选择热变性、ＳｅｐｈａｄｅｘＧ—１００层析方法从猪血中提纯超氧化物歧化酶，纯化倍数１８６．５．该酶在聚丙烯酰胺凝胶电泳中呈一蛋白带．纯酶的比活性为９３２５ｕ／ｍｇ—ｐｒ（邻苯三酚—３２５法）．通过ＳＤＳ—ＰＡＧＥ法测出分子量为３００００．该酶对热稳定，纯酶液的最大吸收波长为２６０ｕｍ．     

猪血超氧化物歧化酶纯化与分析─—一种铜盐沉淀新工艺

本文建立铜盐沉淀、选择热变性、ＳｅｐｈａｄｅｘＧ—１００层析方法从猪血中提纯超氧化物歧化酶，纯化倍数１８６．５．该酶在聚丙烯酰胺凝胶电泳中呈一蛋白带．纯酶的比活性为９３２５ｕ／ｍｇ—ｐｒ（邻苯三酚—３２５法）．通过ＳＤＳ—ＰＡＧＥ法测出分子量为３００００．该酶对热稳定，纯酶液的最大吸收波长为２６０ｕｍ．     

维生素B_(12)对牛冷冻精液精子质量的影响

牛精液冷冻前于精液稀释液中添加ＶＢ１２为试验组，不添加ＶＢ１２的为对照组。冷冻结果表明：试验组冻精解冻后精子活力、顶体完整率分别比对照组提高１６．１１％（Ｐ＜０．０１），１５．９％（Ｐ＜０．０１）；精子畸形率与ＧＯＴ活性均明显下降；精子存活时间延长。说明ＶＢ１２在牛精液冷冻中对牛精子形态结构具有保护作用。     

过度训练对红细胞膜结构和功能影响的实验研究

为进一步探讨过度训练的发生机制,采用建立一般训练和过度训练动物模型,应用荧光法和比色法分别测定了过度训练后红细胞膜MDA含量、红细胞变形性、Na~+-K~+-ATPase、Ca~(2+)-ATPase活性以及红细胞膜总磷脂、胆固醇含量及其比值.结果显示:与对照组相比,MDA含量在运动后即刻显著升高(P<0.01);红细胞变形性显著下降(<0.05;P<0.01),Na~+-K~+-ATPase和Ca~(2+)-ATPase活性显著下降(P<0.05),红细胞膜总磷脂显著下降(P<0.05),红细胞膜上胆固醇在运动后即刻显著低于对照组(P<0.01),红细胞膜上胆固醇/磷脂比值在运动后即刻显著低于对照组(P<0.05),相关分析表明,红细胞的变形性与红细胞膜上MDA含量呈显著负相关(P<0.05).结果揭示:过度训练运动引发的自由基产生的脂质过氧化对红细胞膜结构有损害,使Na~+-K~+-ATPase和Ca~(2+)-ATPase活性下降,红细胞膜上的磷脂和胆固醇含量以及其比值降低,致使红细胞变形性下降,可能是造成过度训练后红细胞功能下降的重要原因之一.     

Crystal structure of the plasma membrane proton pump

A prerequisite for life is the ability to maintain electrochemical imbalances across biomembranes. In all eukaryotes the plasma membrane potential and secondary transport systems are energized by the activity of P-type ATPase membrane proteins: H+-ATPase (the proton pump) in plants and fungi, and Na+,K+-ATPase (the sodium-potassium pump) in animals. The name P-type derives from the fact that these proteins exploit a phosphorylated reaction cycle intermediate of ATP hydrolysis. The plasma membrane proton pumps belong to the type III P-type ATPase subfamily, whereas Na+,K+-ATPase and Ca2+-ATPase are type II. Electron microscopy has revealed the overall shape of proton pumps, however, an atomic structure has been lacking. Here we present the first structure of a P-type proton pump determined by X-ray crystallography. Ten transmembrane helices and three cytoplasmic domains define the functional unit of ATP-coupled proton transport across the plasma membrane, and the structure is locked in a functional state not previously observed in P-type ATPases. The transmembrane domain reveals a large cavity, which is likely to be filled with water, located near the middle of the membrane plane where it is lined by conserved hydrophilic and charged residues. Proton transport against a high membrane potential is readily explained by this structural arrangement.     

Study on the effect of doxorubicin on expressions of genes encoding myocardial sarcoplasmic reticulum Ca^2＋ transport proteins and the effect of taurine on myocardial protection in rabbits

To investigate the effect of doxorubicin(DOX) on gene expression of the myocardial sarcoplasmic reticulum (SR)Ca^2 transport proteins and the mechanism of taurine(Tau) protecting cardiac muscle cells, 9 rabbits were injected with DOX , 8 rabbits with DOX and Tau, and 9 rabbits with normal saline. Cardiac function , concentration of calcium in cardiomyocytes ( Myo [ Ca^2 ]i ), activity of SR Ca^2 -ATPase (SERCA2a) , level of SERCA2a mRNA and Ca^2 released channels(RYR2) mRNA were detected. The left ventricle tissues were observed by electron microscopy. The results showed that cardiac index, left ventricular systolic pressure, activity of SR Ca^2 -ATPase and level of SERCA2a mRNA decreased , while Myo[ Ca^2 ]i increased in DOX-treated rabbits. DOX could not affect the level of RYR2 mRNA. Tau intervention could alleviate the increase of left ventricular diastolic pressure, Myo[ Ca^2 ] i and the decrease of SERCA2a mRNA induced by doxorubicin. Tile results suggested that downregulation of SERCA2a gene expression was an important mechanism of DOX-induced cardiomyopathy and that Tau could partially improve the heart function by reducing calcium overload and alleviating downregulation of SERCA2a mRNA.     

冻融循环后大理岩单轴压缩破坏特性及规律研究

为研究大冶铁矿高边坡广泛分布的大理岩在冻融循环后单轴压缩破坏特性及规律,对岩样进行不同冻融次数和不同冻融温度下的冻融试验后,再进行单轴压缩试验。对比分析其单轴压缩应力-应变曲线及破裂面宏观形态,结果表明:经历冻融循环后的大理岩岩样,随冻融次数的增加和冻融温度的降低,岩样内部损伤趋重,弹性变形减弱而塑性增强;破裂面由张破裂向剪破裂转变,由多断面破裂转变为单一断面破裂;破坏模式由轴向劈裂拉伸破坏模式向轴向拉剪破坏模式逐渐过渡。     

下肢静脉功能不全时下肢腓肠肌细胞病理生理学改变的研究

探讨腓肠肌细胞病理形态学和细胞代谢变化与下肢静脉功能不全相互关系及其临床意义 .依据血管造影和多普勒超声检查结果分为对照组 (A组 )及单纯下肢浅静脉曲张 (B组 )、原发性下肢深静脉瓣膜功能不全(C组 ) 3组 ,每组 1 0例 .分别取大腿长收肌 (对照 )和小腿腓肠肌标本检测肌肉中的SOD、NO、Na+ _K+ _ATP酶、Ca2 + _ATP酶、乳酸等各项指标 ;HE染色、ATP酶染色、SDH/COX双重染色后光镜、电镜观察 .结果显示 :A及B组肌组织结构和生化指标均正常 ,C组腓肠肌可见散在肌纤维萎缩、变性和坏死 ,炎性细胞浸润 ;同型肌纤维群化 ;COX/SDH染色可见单根或多根肌纤维酶活性增高 .肌丝间可见脂肪空泡聚集 ,部分线粒体空泡化或髓鞘样改变 .C组腓肠肌乳酸显著高于其他组别 (P <0 .0 1 ) ,而其Na_K_ATP酶、Ca2 + _ATP酶活性、NO、SOD等与其他组比较有显著下降 (P <0 .0 1 ) .表明下肢深静脉功能不全者患肢腓肠肌在肌纤维类型、超微结构和肌肉组织多项生化指标等均发生明显变化 ,推测小腿腓肠肌超微结构的病变是手术后远期效果不佳的病理基础 .如果从骨骼肌营养和抗氧化处理等角度进行治疗 ,可能会改善小腿肌肉泵功能     

岩石冻融循环及抗拉特性试验研究

通过开放饱水状态下的冻融循环试验研究了红砂岩和页岩2种岩石的冻融损伤劣化及破坏行为,将经历不同冻融次数后的岩样进行抗拉试验,分析了冻融循环作用对岩石损伤及抗拉特性的影响。研究表明:由于岩性及初始损伤状态不同,红砂岩的冻融损伤劣化模式为剥落模式和断裂模式,而页岩为裂纹模式;岩石抗拉压特性的冻融效应具有相同的规律性,2种岩石的劈裂抗拉强度均随冻融循环次数的增大而减小,但其抗拉特性对冻融循环反映更敏感,损伤劣化更显著;红砂岩受冻融循环次数影响引起的损伤较页岩大;寒区岩体工程稳定性评价中必须考虑应力状态对岩石冻融损伤的影响。     

Distribution of two distinct Ca2+-ATPase-like proteins and their relationships to the agonist-sensitive calcium store in adrenal chromaffin cells

Many cellular functions are regulated by activation of cell-surface receptors that mobilize calcium from internal stores sensitive to inositol 1,4,5-trisphosphate (Ins(1,4,5)P3). The nature of these internal calcium stores and their localization in cells is not clear and has been a subject of debate. It was originally suggested that the Ins(1,4,5)P3-sensitive store is the endoplasmic reticulum, but a new organelle, the calciosome, identified by its possession of the calcium-binding protein, calsequestrin, and a Ca2+-ATPase-like protein of relative molecular mass 100,000 (100K), has been described as a potential Ins(1,4,5)P3-sensitive calcium store. Direct evidence on whether the calciosome is the Ins(1,4,5)P3-sensitive store is lacking. Using monoclonal antibodies raised against the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum, we show that bovine adrenal chromaffin cells contain two Ca2+-ATPase-like proteins with distinct subcellular distributions. A 100K Ca2+-ATPase-like protein is diffusely distributed, whereas a 140K Ca2+-ATPase-like protein is restricted to a region in close proximity to the nucleus. In addition, Ins(1,4,5)P3-generating agonists result in a highly localized rise in cytosolic calcium concentration ([Ca2+]i) initiated in a region close to the nucleus, whereas caffeine results in a rise in [Ca2+]i throughout the cytoplasm. Our results indicate that chromaffin cells possess two calcium stores with distinct Ca2+-ATPases and that the organelle with the 100K Ca2+-ATPase is not the Ins(1,4,5)P3-sensitive store.     

The structural basis of calcium transport by the calcium pump

The sarcoplasmic reticulum Ca2+-ATPase, a P-type ATPase, has a critical role in muscle function and metabolism. Here we present functional studies and three new crystal structures of the rabbit skeletal muscle Ca2+-ATPase, representing the phosphoenzyme intermediates associated with Ca2+ binding, Ca2+ translocation and dephosphorylation, that are based on complexes with a functional ATP analogue, beryllium fluoride and aluminium fluoride, respectively. The structures complete the cycle of nucleotide binding and cation transport of Ca2+-ATPase. Phosphorylation of the enzyme triggers the onset of a conformational change that leads to the opening of a luminal exit pathway defined by the transmembrane segments M1 through M6, which represent the canonical membrane domain of P-type pumps. Ca2+ release is promoted by translocation of the M4 helix, exposing Glu 309, Glu 771 and Asn 796 to the lumen. The mechanism explains how P-type ATPases are able to form the steep electrochemical gradients required for key functions in eukaryotic cells.