硒化合物与脂质过氧自由基作用的研究

本文以卵磷脂、亚油酸和脂质体作为生物膜模型, 鼠红细胞膜作为生物膜实例, 通过ESR研究, 观察到包括RSe和RSeSeR在内的硒化合物在模拟的和真实的生物膜体系中对脂质过氧自由基的清除作用, 使得硒作为自由基清除剂的假说在体外模型体系实验中被初步证实, 提示占体内总硒量约2/3的非GSH-Px硒可能是通过直接清除过氧自由基而发挥其生理功能, 研究表明, 其清除作用是针对生物膜磷脂分子上的不饱和脂肪酸过氧自由基, 其作用部位处于膜磷脂双分子层中部疏水区(脂相)中, 在体外实验的清除效果上, 有机硒优于无机硒, 某些有机硒化合物表面出“奇偶规律"。CNDO/2计算表明, 硒化合物清除脂质过氧自由基可能是通过硒中心自由基而起作用的。     

简便合成二酰基二硒醚

芳基硒代酰胺与酰氯以1∶1的摩尔比在氯仿溶液中作用, 可以较高的产率得到二酰基二硒醚, 而芳基硒代酰胺与酰氯以1∶2的摩尔比反应时则生成二酰基硒醚. 提出了反应可能的机理.     

二碘化钐促进的硒代酯的合成

用SmI2/THF/HMPA体系在室温下使二芳基二硒醚中的Se-Se键还原断裂成硒负离子物种, 继而与酸酐作用得到硒代酯, 该反应条件温和中性, 产率良好, 提供了合成硒代酯的一个新途径。     

芳基硒代酰胺与α-卤代乙酸在醇中的硒转移反应——二烷氧羰基甲基二硒醚的简便合成

芳基硒代酰胺与氯乙酸在各种醇中无催化剂下以1∶1和1∶2的比例投入, 发生硒转移反应, 不同原料投入比下的反应生成了同一种C—Se—Se—C偶联产物——具有多功能团的二烷氧羰基甲基二硒醚, 提供了一种新的合成二烷氧羰基甲基二硒醚的简便方法, 且反应具有条件温和、产率高、原料易得和选择性好等优点. 为了研究该反应机理, 选择α-溴代乙酸甲酯或α-溴代乙酸乙酯在无催化剂、中性条件下, 乙醇溶液中与苯基硒代酰胺室温下反应, 投料比为1∶1和2∶1, 结果也都生成了同一类产物二甲氧羰基甲基二硒醚或二乙氧羰基甲基二硒醚, 同时还分离得到了相应的副产物苯甲酸乙酯. 对该C—Se—Se—C偶联反应发生的可能机理作了推测.     

杂元素冠醚研究（Ⅺ）：邻苯二硒型硒杂冠醚的合成

在碱性条件下，聚邻二硒代苯被硼氢化钾还原成双硒离子后与二卤代和缩后关环得到７个邻苯二硒型硒杂冠醚化合物，其结构经元素分析、ＭＳ、ＩＲ和ＨＮＭＲ证实。     

α-芳硒基羰基化合物的合成

茂钛硒化物分别与α－溴代酮和α－溴代酯反应生产了相应的α－硒酮和α－硒代酯，茂钛硒配合物由Ｃｐ２ＴｉＣｌ２／２ｉ－ＢｕＭｇＢｒ／ＴＨＦ体系还原二芳基二硒醚得到。     

CF3C(O)O2+HO2反应机理的理论研究

用量子化学密度泛函方法, 在CCSD(T)/cc-pVDZ//B3LYP/6-31+G(d,p)水平上研究了氟代乙酰过氧自由基[CF3C(O)O2]和氢过氧自由基(HO2)的反应机理. 研究结果表明, 反应物优先生成能量低的单态反应络合物, 进而经过相对较低的反应势垒生成臭氧和氟代羧酸, 即CF3C(O)O2+HO2→CF3C(O)OH+O3为主要反应. 该结论与实验结果一致.     

二碘化钐诱导的芳族二硒醚Se—Se键还原断裂导致芳基硒负离子:β-硒代酯(腈)的制备

报导了芳族二硒醚在SmI_2作用下,Se—Se键还原断裂成硒负离子。再与α,β-不饱和酯(腈)发生Michael加成反应,得到β-硒代酯(腈)。     

柱前衍生化-HPLC法测定恩施3种富硒蔬菜中硒氨基酸

采用HPLC与ICP-MS间隙联用的方法,以柱前衍生化-HPLC法进行定性定量分析,使用ICP-MS鉴定,建立一种富硒蔬菜中硒氨基酸的分离检测方法。结果表明:所测定的硒代氨基酸在其线性范围内呈现良好的线性关系(R2>0.999)。该方法中硒代蛋氨酸和硒代胱氨酸的检出限分别为0.204 mg/L和0.680 mg/L,加标回收率分别为97.4%和94.0%,RSD分别为2.1%和0.69%。检测恩施富硒蔬菜样品,白菜、萝卜叶和苋菜含有硒代蛋氨酸和硒代胱氨酸。此方法可用于富硒蔬菜中硒代氨基酸的含量检测。     

高效液相色谱-电感耦合等离子体质谱（HPLC-ICP-MS）联用测定富硒小麦中硒代氨基酸

为科学补硒和促进富硒小麦的种植推广,建立了高效液相色谱-电感耦合等离子体质谱联用技术(HPLC-ICP-MS)检测富硒小麦中硒代氨基酸的方法。用蛋白酶XIV辅助微波振荡提取富硒小麦中硒代氨基酸,采用C18 分离柱分离,以30.0mmol/L磷酸氢二铵+1.0%甲醇+2.0mmol/L四丁基溴化铵溶液(pH=6.5)为流动相,能在10min内实现5种硒代氨基酸的分离。在高能氦气模式（HEHe）下,用78Se的色谱峰积分面积作为定量依据,5种硒代氨基酸在1.0～200.0μg/L范围内线性相关性良好,检出限在 0.11~0.29μg/L之间。以富硒小麦为基体进行加标回收试验,除硒代胱氨酸（SeCys2）可能不稳定,易分解造成回收率偏低外,其他4种硒代氨基酸的加标回收率在92.34～102.46%之间,相对标准偏差为 1.6 %~4.2 %（n=7）。用该方法测定了农业科技工作者种植推广的富硒小麦,结果发现小麦中的硒赋存形态多为硒代蛋氨酸（SeMet）,此外,小麦中还含有少量硒代胱氨酸（SeCys2）、硒代半胱氨酸（SeCys）、甲基硒代半胱氨酸（MeSeCys）和硒代乙硫氨酸（SeEt)。该方法具有良好的精密度和准确度,适用于富硒小麦中硒代氨基酸的形态分析。     

油松籽油脂的提取及其脂肪酸组成与含量的评价

采用索氏提取法提取油松籽中的油脂,得油率为42.9%;对油脂进行甲酯化处理后用气相色谱-质谱联用仪检测其中的脂肪酸组成及含量。实验结果表明,油松籽油中含有7种脂肪酸,分别为肉豆蔻酸10.38%、硬脂酸3.05%、油酸21.98%、亚油酸(13,16-十八碳二烯酸)3.53%、亚油酸(9,12-十八碳二烯酸)38.38%、亚麻酸20.06%和二十碳三烯酸2.62%,其中饱和脂肪酸含量为13%,不饱和脂肪酸含量为87%。     

Determination of peroxides by capillary zone electrophoresis with amperometric detection

The combination of cathodic amperometric detection with capillary zone electrophoresis is demonstrated to be a versatile method for the quantification of organic and inorganic peroxides. A gold microelectrode, polarized at -600 mV against an Ag/AgCl reference electrode, is placed at the end of the capillary. Since the electroosmotic flow purges the detector electrode from oxygen, no degassing of the detector cell or the sample is necessary. With an injection volume of ca. 1 nl, hydrogen peroxide, peroxosulfate, peroxy alkanoic acids and the hydroperoxides of linoleic acid can be detected down to 10 micromol/l. Separation of the isomeric hydroperoxides of the unsaturated fatty acids is achieved by addition of beta-cyclodextrin to the electrolyte.     

Docosahexaenoic acid and eicosapentaenoic acid induce changes in the physical properties of a lipid bilayer model membrane

We investigated the effect of fatty acids such as stearic acid (SA, 18:0), oleic acid (OA, 18:1), eicosapentaenoic acid (EPA, 20:5), and docosahexaenoic acid (DHA, 22:6) on a dipalmitoylphosphatidylcholine (DPPC) bilayer by determining the phase transition temperature, fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH), and detergent insolubility. Treatment with unsaturated fatty acid broadened and shifted the phase transitions of the DPPC bilayer to a lower temperature. The phase transition temperature and the value of fluorescence anisotropy of DPH at 37 degrees C decreased progressively with increasing treatment amounts of unsaturated fatty acid. A large amount of the DPPC bilayer treated with unsaturated fatty acid was dissolved in Triton X-100, obtaining a low level of detergent insolubility. These modifications of the bilayer physical properties were most pronounced with DHA and EPA treatment. These data show that unsaturated fatty acids, particularly DHA and EPA, induce a marked change in the lipid bilayer structure. The composition of fatty acids in the DPPC bilayer was similar after treatment with various unsaturated fatty acids, suggesting that the different actions of unsaturated fatty acids are attributed to change in the molecular structure (e.g., kinked conformation by double bonds). We further explored the change in physical properties induced by fatty acids dispersed in a water-in-oil-in-water multiple emulsion and found that unsaturated fatty acids acted efficiently on the DPPC bilayer, even when incorporated in emulsion form.     

大果白刺游离脂肪酸的柱前衍生高效液相色谱-荧光检测法分析

采用2-（11H-苯[a]咔唑）乙基对甲苯磺酸酯（BCETS）为柱前荧光衍生试剂,通过梯度洗脱使得18种脂肪酸在BDS-C8柱上得到良好的分离.方法应用于大果白刺不同部位中游离脂肪酸的分析,结果表明大果白刺的果皮果肉和叶子中均含有大量的不饱和脂肪酸,其总不饱和脂肪酸含量分别为70.74%和73.47%.大果白刺种子中不饱和脂肪酸的含量相对较少,仅占总脂肪酸含量的57.21%,其不饱和脂肪酸组成主要是C18∶1（油酸）和C18∶2（亚油酸）.其中,大果白刺的果皮果肉中,不饱和脂肪酸主要是C18∶1、C18∶2和C18∶3（亚麻酸）.其叶子中的不饱和脂肪酸主要是C18∶3,所占总脂肪酸比例为48.34%.首次对大果白刺中的脂肪酸进行了分析,可以为大果白刺在食品、药品中的进一步开发应用和质量控制提供一定的数据支持.     

Highly Selective Process for Epoxidation of Fatty Acid Methyl Esters with Peroxyacetic Acid

Specific features of the double-stage process in which unsaturated compounds and, in particular, fatty acid methyl esters of vegetable oils are epoxidated with peroxyacetic acid obtained ex situ in aqueous solutions of acetic acid and hydrogen peroxide under catalysis with Amberlyst 15 Dry ion-exchange resin were examined. It was shown that the independently occurring processes in which the peroxy acid is heterogeneously catalytically formed and epoxy compounds are synthesized can substantially raise the formation selectivity of epoxides with respect to double bonds in fatty acid methyl esters and simplify the simulation of these processes and their technological implementation.     

南海Spirasterella中脂肪酸酯组分的鉴定

用色谱—质谱联用技术分析了中国南海海绵Spirasterella aurivilli Lindgren中脂肪酸酯组分。鉴定了29种脂肪酸酯,其中20种饱和脂肪酸乙酯,8种不饱和脂肪酸乙酯及1种饱和脂肪酸甲酯。并发现该海绵中含有自然界少见的10种奇数碳脂肪酸乙酯。     

植物油中脂肪酸不同定量方法的比较分析

比较峰面积归一化法与标准曲线法两种方法分析植物油中脂肪酸百分比含量的差异。利用气相色谱-质谱联用仪(GC-MS)检测10种市售食用植物油中的8种主要脂肪酸,峰面积归一化法和标准曲线法计算脂肪酸的百分比含量。结果表明,标准曲线法与峰面积归一化法相比,肉豆蔻酸、棕榈酸、十七烷酸、硬脂酸和棕榈油酸所占的百分比升高,而油酸、亚油酸和亚麻酸比例降低;饱和脂肪酸比例升高,不饱和脂肪酸百分比降低。利用峰面积归一化法计算植物油中脂肪酸百分比时,降低了饱和脂肪酸比例,升高了不饱和脂肪酸比例,可能对健康有潜在的不利影响。建议使用标准曲线法计算不同植物油中脂肪酸的百分比。     

Chemistry and Biochemistry of Unsaturated Fatty Acids

Although unsaturated fatty acids have long been known to accompany saturated fatty acids in most lipids, qualitative and quantitative determination of fatty acid patterns only became possible with the advent of modern analytical methods. Present day knowledge of the chemical structure, physical properties, and metabolism of unsaturated fatty acids provides the basis for the development of new concepts of their function. Thus unsaturated fatty acids crucially determine the properties of biological membranes. Moreover, essential fatty acids are precursors of prostaglandins.     

The Effects of Selenium on Polyunsaturated Fatty Acids of Diasporangium jonesianum

Fungi had become the main resource of polyunsaturated fatty acids, especially linoleic acid. The research studied the effects and mechanism of selenium on polyunsaturated fatty acids of Diasporangium jonesianum. The results showed that selenium could significantly increase the yields of linoleic acid. In contrast, the growth and γ-linolenic acid yield of D. jonesianum was decreased under selenium treatments. Δ6-Fatty acid desaturase gene of D. jonesianum was investigated in this research. Sequence analysis indicated that this cDNA sequence encoded 235 amino acids. The conserved region of Δ6-fatty acid desaturase included three conserved histidine-rich domain, hydropathy profile, and was rich in disulfide bonds. This study showed that selenium may in discriminatively substitute S and incorporate selenium-amino acids into the desaturase that the conformation of enzyme active sites was impacted which leaded to the inhibition of the convert of linoleic acid to γ-linolenic acid and the over accumulation of linoleic acid. Selenium might enhance the fatty acid contents of fungi through influencing the desaturase structure.     

Proton‐Coupled Electron Transfer of Unsaturated Fatty Acids and Mechanistic Insight into Lipoxygenase

A proton‐coupled electron transfer (PCET) process plays an important role in the initial step of lipoxygenases to produce lipid radicals which can be oxygenated by reaction with O₂ to yield the hydroperoxides stereoselectively. The EPR spectroscopic detection of free lipid radicals and the oxygenated radicals (peroxyl radicals) together with the analysis of the EPR spectra has revealed the origin of the stereo‐ and regiochemistry of the reaction between O₂ and linoleyl (= (2Z)‐10‐carboxy‐1‐[(1Z)‐hept‐1‐enyl]dec‐2‐enyl) radical in lipoxygenases. The direct determination of the absolute rates of H‐atom‐transfer reactions from a series of unsaturated fatty acids to the cumylperoxyl (= (1‐methyl‐1‐phenylethyl)dioxy) radical by use of time‐resolved EPR at low temperatures together with detailed kinetic investigations on both photoinduced and thermal electron‐transfer oxidation of unsaturated fatty acids provides the solid energetic basis for the postulated PCET process in lipoxygenases. A strong interaction between linoleic acid (= (9Z,12Z)‐octadeca‐9,12‐dienoic acid) and the reactive center of the lipoxygenases (Fe^III? OH) is suggested to be involved to make a PCET process to occur efficiently, when an inner‐sphere electron transfer from linoleic acid to the Fe^III state is strongly coupled with the proton transfer to the OH group.