The effects of lanthanide ions and their complexes of citrate and DTPA ligandson the fluldity of dipathetoylphosphatidylethanolamine (DPPE) bilayers have been studiedby FT-Raman spectroscopy. The results show that lan...The effects of lanthanide ions and their complexes of citrate and DTPA ligandson the fluldity of dipathetoylphosphatidylethanolamine (DPPE) bilayers have been studiedby FT-Raman spectroscopy. The results show that lanthanide ions oflower concentrationndecrease the nuldity of acyl chains of DPPE bilayers and change the conformation of c C-C backbone from gauche to the trans lanthanide ions of higher concentration, however,increase the fluldity of acyl chains and increase the gauche population of C-C-C backbone.Lanthainde complex of citrate have no effect on the fluidity of acyl chains of DPPE bilayersin the region of experdriental concentration, but La-DTPA complex increase slightly thefluidity of acyl chains. The results also indicated that lanthainde ion of lower concentrationchanged the lattice packing of hydrocarbon chains from hexagonal form to orthorhombicform, but it is still in hexagonal or distorted hexagonal lattice cell in the gel state in thepresence of metaJ ions and lanthanide complexes of higher展开更多
Rutin was acylated with stearic acid in esterification reaction catalyzed by immobilized Candida antarctica lipase B(Novozym 435).The results suggested that the regioselectivity of the lipase-catalyzed esterification ...Rutin was acylated with stearic acid in esterification reaction catalyzed by immobilized Candida antarctica lipase B(Novozym 435).The results suggested that the regioselectivity of the lipase-catalyzed esterification of rutin was specific at the C4’’’ position of the rhamnose moiety.The monolayer of dioleoylphosphatidylcholine(DOPC) was used as the model membrane to study their molecular interaction with RS.The miscibility of DOPC/RS mixed monolayers has been investigated by Langmuir film balance to yield quantitative information on the nature of the molecular interaction,which could provide valuable insights to reveal the antioxidative activity mechanism of flavonoids.Pure RS and pure DOPC were capable of forming monolayers with liquid-phase at the air/water interface.The two components of DOPC/RS monolayer were miscible throunghout the mixture composition range.The effects of the temperature of the subphase on the miscibility and molecular interaction of DOPC/RS monolayers were investigated.The miscibility was more excellent at higher temperature.The condensing effect of RS,which represented the attractive forces between DOPC and RS,could be ascribed to the match of molecular shapes of RS and DOPC on the monolayers packing.展开更多
文摘The effects of lanthanide ions and their complexes of citrate and DTPA ligandson the fluldity of dipathetoylphosphatidylethanolamine (DPPE) bilayers have been studiedby FT-Raman spectroscopy. The results show that lanthanide ions oflower concentrationndecrease the nuldity of acyl chains of DPPE bilayers and change the conformation of c C-C backbone from gauche to the trans lanthanide ions of higher concentration, however,increase the fluldity of acyl chains and increase the gauche population of C-C-C backbone.Lanthainde complex of citrate have no effect on the fluidity of acyl chains of DPPE bilayersin the region of experdriental concentration, but La-DTPA complex increase slightly thefluidity of acyl chains. The results also indicated that lanthainde ion of lower concentrationchanged the lattice packing of hydrocarbon chains from hexagonal form to orthorhombicform, but it is still in hexagonal or distorted hexagonal lattice cell in the gel state in thepresence of metaJ ions and lanthanide complexes of higher
文摘对磷脂酶D(phospholipase D,PLD)在有机溶媒-水两相体系中催化磷脂酰胆碱(phosphatidylcholine,PC)和乙醇胺(ethanolamine,EA)合成磷脂酰乙醇胺(phosphatidylethanolamine,PE)的反应条件进行优化,并对反应动力学机制进行了研究。确定最佳反应条件为:温度28℃,p H 5.5,底物摩尔比(EA/PC)20∶1,在此条件下PE产率达87.2%。通过研究底物浓度对反应速率的影响,确定反应符合单底物抑制的Ping-Pang机制。分别以Matlab软件的Fminsearch函数与Lineweaver-Burk双倒数作图法求取动力学参数,结果基本一致,底物乙醇胺EA的抑制常数为Ki B=1.50mmol/L。抑制机理为两分子EA同时结合到一分子磷脂酰基-PLD中间体上,生成磷脂酰基-PLD-(EA)2死端复合物,符合竞争性抑制反应动力学规律。该动力学模型预测与实验数据吻合良好,对PLD催化合成PE反应过程的操作及反应器选型设计具有指导作用。
文摘Rutin was acylated with stearic acid in esterification reaction catalyzed by immobilized Candida antarctica lipase B(Novozym 435).The results suggested that the regioselectivity of the lipase-catalyzed esterification of rutin was specific at the C4’’’ position of the rhamnose moiety.The monolayer of dioleoylphosphatidylcholine(DOPC) was used as the model membrane to study their molecular interaction with RS.The miscibility of DOPC/RS mixed monolayers has been investigated by Langmuir film balance to yield quantitative information on the nature of the molecular interaction,which could provide valuable insights to reveal the antioxidative activity mechanism of flavonoids.Pure RS and pure DOPC were capable of forming monolayers with liquid-phase at the air/water interface.The two components of DOPC/RS monolayer were miscible throunghout the mixture composition range.The effects of the temperature of the subphase on the miscibility and molecular interaction of DOPC/RS monolayers were investigated.The miscibility was more excellent at higher temperature.The condensing effect of RS,which represented the attractive forces between DOPC and RS,could be ascribed to the match of molecular shapes of RS and DOPC on the monolayers packing.
文摘为了揭示二酰甘油酰基转移酶(DGAT)在小球藻油脂合成过程中的作用,对单细胞小球藻Chlorella variabilis NC64A的二酰甘油酰基转移酶进行原核克隆表达及功能初步研究。结果表明,其编码序列为894bp,编码297个氨基酸,表达蛋白的表观分子量为33 k Da,p I 9.48。保守结构域分析表明,该蛋白属于Lysophospholipid acyltransferases(LPLATs)超家族,具有二酰甘油酰基转移酶活性,序列位点H68,L71,F76,R94,I97和GAA(144?146)组成特定的酰基受体结合口袋,能够结合酰基?酰基载体蛋白(ACP)或者酰基辅酶A上的酰基,催化三酰甘油合成的最后一步。表达蛋白与Ss PDAT和At PDAT的序列相似性分别为32%和24%,表明该蛋白可能具有磷脂酰甘油酰基转移酶(PDAT)活性,能利用磷脂上的酰基合成三酰甘油。因此,采用薄层层析方法以L-α-磷脂酰胆碱和1,2-二油酰-sn-甘油为底物,检测到其确实具有PDAT活性,表明限氮条件下NC64A中DGAT的PDAT活性可能促进了膜脂降解耦合三酰甘油的合成。
