Bovine serum albumin interacts with bacterial luciferase

Bovine serum albumin (BSA) affects the amount of light obtained from bacterial luciferase by competing with luciferase for one of the luciferase substrates, the aldehyde. At low aldehyde concentrations BSA behaves as an inhibitor, but at high aldehyde concentrations BSA relieves substrate inhibition. BSA reversibly binds decanal with a K_si = 3.36 μmol/l, approximately half the affinity of luciferase for decanal (K_M = 1.5 μmol/l). BSA also increased the rate of intermediate II dark decay. The data suggest that this involves a direct protein-protein (BSA-luciferase) interaction.     

血清蛋白与4,5-二溴荧光素相互作用及其分析应用的研究

在 0 .10mol/mL的醋酸溶液中 ,4,5 二溴荧光素能与血清蛋白形成稳定的复合物 ,最大吸收波长 482nm ,与试剂比较 ,红移了 12nm。据此建立了测定血清蛋白的方法 ,用于BSA和HSA的测定 ,分别在 2～ 14mg·L-1有线性关系 ,表观摩尔吸光系数分别为 3.12× 10 5L·mol-1·cm-1和 3.2 7× 10 5L·mol-1·cm-1。应用该法测定了人血清样品总蛋白含量 ,结果令人满意。     

羧甲基化壳聚糖季铵盐与牛血清白蛋白的相互作用研究

应用荧光光谱研究了羧甲基化壳聚糖季铵盐(CMCQA)与牛血清白蛋白(BSA)的相互作用.研究表明:CMCQA对BSA内源性荧光猝灭机制属于CMCQA和BSA形成复合物所引起的静态猝灭.在室温下,二者的结合常数为2.45×104 L/mol,结合位点数为1.04.二者主要靠静电引力相互作用.     

光谱及分子模拟法对HSA和BSA与酪氨酸激酶抑制剂Imatinib相互作用的比较分析

研究一种酪氨酸激酶抑制剂（tyrosine kinase inhibitor, TKI）伊马替尼（imatinib, IMA）与人血清清蛋白（HSA）及牛血清清蛋白（BSA）的相互作用,比较分析HSA和BSA与IMA相互作用机制的差异. 模拟生理条件下,计算机模拟技术结合荧光光谱和紫外光谱法,研究IMA与蛋白质的作用机制. 分子模建IMA与血清清蛋白的结合模型,表明伊马替尼与蛋白质的相互作用力为疏水作用力,兼有氢键作用. 光谱结果表明,IMA与HSA和BSA的相互作用表现为静态结合过程,结合强度较强,IMA与HSA和BSA分子的结合距离r值较小,说明发生了能量转移现象. IMA对HSA和BSA的结构域微区构象产生影响,使结合位域的疏水性发生改变. 荧光相图技术解析出IMA与HSA和BSA反应构象型态的变迁为“二态”模型. HSA与IMA相互作用的热力学参数表明,IMA与HSA之间是以疏水作用为主的分子间作用,而IMA与BSA之间的作用力为氢键和范德华力,兼有少量的疏水作用力. 光谱实验与计算机模拟结果基本一致,可为研究IMA与HSA和BSA相互作用本质提供一定参考.     

残余牛血清白蛋白含量检测试剂盒抗干扰性研究

为了对目前使用的残余牛血清蛋白(BSA)含量检测试剂盒的抗干扰性进行评价,选用19个企业的12个品种,共计28份样品进行检测,包括冻干疫苗和液体疫苗两种剂型。分别检测15ng/ml BSA对照样品、二倍稀释的疫苗样品和添加15ng/ml BSA的疫苗样品。将添加BSA的疫苗样品的检测结果减去未添加BSA的疫苗样品的结果,其数值应当位于BSA对照样品均值的95%可信区间内。多数品种的疫苗添加BSA后回收率在85%和115%之间。个别制品的回收率在82%~83%之间。实验研究结果证明目前使用的BSA检测试剂盒具有较好的抗干扰作用。     

A simple hydrogenase-linked assay for ferredoxin and flavodoxin.

Ferredoxin or flavodoxin mediates electron flow from H₂-hydrogenase to metronidazole[1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole] to cause the reduction of the latter compound. The reduction of metronidazole in solution is irreversible because the reduced compound further decomposes. Since metronidazole loses its absorption peak at 320 nm upon reduction, the rate of reduction can be monitored spectrophotometrically. When a solution of metronidazole at 0.1 to 0.5 mm is supplemented with ferredoxin- andflavodoxin-free hydrogenase and placed under H₂, the rate of metronidazole reduction is proportional to the amount of ferredoxin or flavodoxin added. This forms the basis for an assay that can measure 10 to 1000 ng of ferredoxin or 100–1000 ng of flavodoxin/ml of assay mixture.     

Detection of squalene in alpha-fetoprotein and fetal serum albumin from bovine

Alpha-fetoprotein and fetal serum albumin have been simultaneously purified from fetal bovine serum by mild procedures utilizing ammonium sulfate, hydrophobic interaction, immobilized metal (nickel) affinity chromatography, and isoelectric focusing. The lipidic extract from each protein was analyzed by gas chromatography and the peak appearing just after the arachidonic acid was identified as squalene by gas chromatography-mass spectrometry. This isoprenoid was not detected formerly in these proteins from human, rat, bovine, and pig. Until recently, in the analysis of the fatty acid composition of the alpha-fetoprotein and serum albumin from mammals, a peak has been assigned in the last part of the chromatographic profile, after arachidonic acid, to docosahexaenoic acid. In the present work, it was found that the peak corresponds to squalene instead of docosahexaenoic acid. Furthermore, we conclude that bovine alpha-fetoprotein and fetal serum albumin carry squalene, but not docosahexaenoic acid. These results agree with others obtained analyzing the same proteins from chick embryo.     

Inclusion of bovine serum albumin in semen extenders to enhance maintenance of stallion sperm viability

Semen from seven mature stallions was used to test the motility response of sperm cells when 3% bovine serum albumin (BSA) was added to seminal plasma and skim milk diluents. A total of 45 ejaculates was collected by artificial vagina and immediately evaluated for percent motile spermatozoa (PMS), rate of forward movement (RFM) and sperm cell concentration. Aliquots (four from each ejaculate) of raw semen containing 500x10(6) sperm cells were exposed to each of the following treatments: (1) seminal plasma (SP), (2) SP+BSA, (3) skim milk (SKM), (4) SKM+BSA; and incubated in 50-ml tubes at 37 C. The sperm cell characteristics, PMS and RFM, of each treatment suspension were reevaluated at 0, 0.5, 1, 2, 6, 12, 18 and 24 hr post-treatment. Inclusion of BSA and the type of extender, either seminal plasma or skim milk, significantly (P<0.05) affected the PMS and RFM of spermatozoa. Analysis of means within evaluation times showed that PMS maintenance was enhanced (P<0.05) when BSA was included in extenders at all incubation intervals except 24 hr. SKM+BSA maintained the highest (P<0.05) PMS for the first 2 hr with SP+BSA sustaining the highest (P<0.05) PMS from 12 to 24 hr. Skim milk alone sustained higher (P<0.05) PMS than the SP diluent for the first 6 hr of incubation, whereas SP maintained a higher (P<0.05) PMS than SKM from 18 to 24 hr. The RFM of spermatozoa was greatest (P<0.05) for the first 6 hr of incubation when exposed to SKM+BSA. Seminal plasma + BSA sustained a higher (P<0.05) RFM for the first 6 hr of incubation than SP alone, but not higher than SKM at this interval. Skim milk sustained a higher (P<0.05) RFM of spermatozoa for the first 6 hr of incubation than SP. These data support the hypothesis that BSA protects spermatozoa from the harmful effects of lipid peroxidation. Including this substance in semen extenders may prolong maintenance of sperm motility.     

Inhibition of ATPases by gymnemic acid

A specially prepared and partially fractionated preparation of gymnemic acid compounds were found to be inhibitory to the ATPase system from housefly brain and labellum, and fish brain. Enzyme activity in a homogenate fraction from labellum showed greatest sensitivity to the gymnemic acid preparation. Na⁺-K⁺ ATPase activity from the labellum, which contains the sweet taste sensory receptors, was inhibited by over 92% at a concentration of 4 middot; 10^?6M gymnemic acid. Because gymnemic acid compounds are specific suppressants of sweet receptors, the evidence presented in this paper implies that a portion of the ATPase system may be biochemically important in the sweet-sensing mechanism.