脂肪酶GZEL及其C-端截断突变体对磷脂单分子膜的吸附动力学研究

基于单分子层技术研究了禾谷镰孢菌脂肪酶GZEL对不同磷脂单分子膜的吸附动力学。同时,采用截断突变方法分析C-端肽段(编号为269-319的氨基酸)缺失后对脂肪酶GZEL界面吸附动力学参数的影响。研究发现,脂肪酶GZEL对不同磷脂单分子层的吸附动力学参数(吸附常数k_a,解离常数k_d,吸附平衡常数K_(Ads))与磷脂单分子膜的种类及初始表面压力密切相关。尽管如此,相比于野生型GZEL,269-319肽段缺失后导致酶蛋白对不同磷脂单分子膜的吸附常数k_a均显著降低,而解离常数k_d则显著升高,两者共同导致酶蛋白对于磷脂单分子膜的亲和力K_(Ads)显著降低。野生型GZEL对不同磷脂单分子膜的选择性顺序为磷脂酰丝氨酸磷脂酰胆碱磷脂酰乙醇胺。而269-319肽段缺失后,酶蛋白对于这三种磷脂单分子膜的亲和力则表现为无显著差异。以上结果表明269-319肽段在脂肪酶GZEL的界面吸附及对磷脂选择性方面均发挥有重要作用。     

人乳的磷脂组成与脂肪球结构

采用核磁共振磷谱(~(31)P-NMR)测定不同泌乳期、不同胎龄的人乳磷脂组成,结果显示足月儿和早产儿人乳中,磷脂的主要组成均为鞘磷脂(SM)、磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE)、磷脂酰乙醇胺缩醛磷脂(EPLAS)、磷脂酰肌醇(PI)和磷脂酰丝氨酸(PS),其中SM含量最高,其次为PC和PE,PS和PI含量最低。总磷脂含量在相同胎龄不同泌乳期以及相同泌乳期不同胎龄间均无显著性差异。在磷脂组成上,足月儿人乳中PI在初乳和过渡乳中的含量分别为(4.14±0.42)%和(3.66±0.66)%,显著高于成熟乳中的(2.79±0.09)%;早产儿人乳中PC在初乳和过渡乳中的含量分别为(30.74±2.03)%和(29.40±2.37)%,显著高于成熟乳的(27.55±2.42)%,此外EPLAS含量随泌乳期的延长逐渐降低,PE含量逐渐升高,PE+EPLAS在不同的泌乳期无显著性差异。另外,足月儿和早产儿的脂肪球结构无明显差异,磷脂构成的膜包裹体积平均粒径约为5μm的脂肪球。     

油菜、菊花和荷花蜂花粉中磷脂的色谱分析

以油菜、菊花、荷花蜂花粉为原料,采用薄层层析法(thin layer chromatography,TLC)法分离纯化蜂花粉中的磷脂,并用高效液相色谱法(high-performance liquid chromatography,HPLC)法测定磷脂酰肌醇(PI)、磷脂酰丝氨酸(PS)、脑磷脂(PE)、卵磷脂(PC)及溶血卵磷脂(LPC)的含量。结果表明：3种蜂花粉中总磷脂含量为1.19～3.98g/100g,3种花粉存在极显著差异(P＜0.01);PC是蜂花粉磷脂的主要成分,占总磷脂的34.30%～59.69%;在油菜蜂花粉中检测到PI、PS、PE、PC、LPC,菊花蜂花粉未测出PI,荷花蜂花粉未测出PI、LPC。结论：油菜蜂花粉中磷脂种类最丰富、总含量最高,是花粉磷脂的较好来源。     

UPLC-Triple-TOF-MS/MS法分析中国东北地区人乳磷脂的组成

借助超高效液相色谱联用质谱(UPLC-Triple-TOF-MS/MS)分析法,对不同泌乳期人乳中的磷脂进行定性和相对定量,为中国人乳磷脂组成的研究提供参考。本研究从哈尔滨(黑龙江省)、齐齐哈尔(黑龙江省)和吉林(吉林省)地区采集到汉族人初乳(1~5 d)、过渡乳(6~20 d)和成熟乳(21 d~)共计73份。LipidView 1.2用于检索磷脂分子式,PeakView 2.2及其插件MasterView 1.1用于磷脂定性分析,MultiQuant用于磷脂相对定量分析(基于色谱峰面积)。结果显示,人乳中检出磷脂共计60种。其中,磷脂酰胆碱(PC)17种,磷脂酰乙醇胺(PE)25种,磷脂酰丝氨酸(PS)4种,磷脂酰肌醇(PI)5种,鞘磷脂(SM)9种。磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE)、鞘磷脂(SM)、磷脂酰丝氨酸(PS)和磷脂酰肌醇(PI)在总磷脂中的相对含量分别为38.12%、26.97%、29.54%、4.43%和0.94%,各种磷脂的相对含量随泌乳期变化表现出不同的变化趋势,但大多数磷脂的相对含量差异并不显著。     

柱层析法分离大豆磷脂

通过实验探讨了使用低压制备色谱柱在等度洗脱方式下分离大豆磷脂中的磷脂酰肌醇(PI)、磷脂酰乙醇胺(PE)、磷脂酰胆碱(PC)等成分.结果表明,在使用100cm×26 mm规格的色谱柱、氯仿-甲醇(2∶1)作为流动相、流速控制在3.0 mL/min,负载量为0.25 g/150 g硅胶(100～200目)的条件下可以分离得到PI纯度在90%以上、PE纯度在80%以上、PC纯度在95%以上的各种产品.     

卵磷脂的制备及其应用(二)

一、绪言 卵磷脂是天然的乳化剂,作为食品用的乳化剂具有多种的用途。工业上称谓的卵磷脂,是指磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE))磷脂酰肌醇(PI)等磷脂和甘三酯(中性油)的混合脂质。在化学术语中,称磷脂酰胆碱为卵磷脂,称磷脂酰乙醇胺为脑磷脂。 卵磷脂在自然界分布广泛,动物的脑、肝脏、肾脏、骨髓、肌肉等组织含量较多,植物的种子、果实,谷物中含量较多。     

大豆卵磷脂的生产及其在食品中的应用

大豆油是我国主要食用油脂之一。毛大豆油中一般含有1.1～3.2％(一般约为1.8％左右)大豆磷脂,经水化脱胶,即可从毛油中分离出磷脂,精制后得到大豆卵磷脂。大豆卵磷脂包括磷脂、植物甘油类脂化合物、甘油三酸酯、甾醇、生育酚、游离脂肪酸等,其中磷脂化合物的组成是:磷脂酰胆碱(PC)15％、磷脂酰乙醇胺(PE)13％,磷脂酰肌醇(PI)9％、磷脂酸(PA)5％、磷脂酰丝氨酸(PS)2％。     

固定化磷脂酰胆碱水相酶催化合成磷脂酰丝氨酸

本文构建了一种固定化底物磷脂酰胆碱(phosphatidylcholine,PC)水相催化体系,磷脂酶D转化PC合成磷脂酰丝氨酸(phosphatidylserine,PS)新技术。探讨了沉淀剂种类、载体类型和底物初始添加量等主要因素,对固定化底物PC过程中PC吸附率的影响,获得了最佳工艺参数。在此基础上,进一步研究了固定化底物PC酶法合成PS的时间反应动力学和酶重复利用特性。结果表明,催化反应24 h后,PS得率为98.74%,磷脂酶D重复使用10次,PS得率仍然大于60%。文章还比较了固定化底物水相催化体系和双液相催化体系酶法合成PS效果,结果发现,固定化底物水相催化体系中PS得率和酶循环利用特性均优于双液相催化体系。本文研究结果为今后酶法改性PC合成PS提供了一种新的催化反应体系。     

国际粮油近讯

<正> 大豆磷脂系精炼大豆油脱胶时副产品,若以2％含量计,日本现有油厂约有1.34万吨生产能力,但实际上全日本仅有6～7家公司生产大豆磷脂、每年回收磷脂约1万吨左右。大豆磷脂制品主要以磷脂酰胆碱(PC)含量为分,包括从15％含量粗制糊状品至98％以上高纯度粉末状精制品。日本工业生产大多为粗制磷脂,主要作食品乳化剂之用,日本年需求量予计约7000～8000吨,其余绝大部份直接作饲料添加剂。大豆磷脂系由磷脂酰胆碱(PC),磷脂酰乙醇胺(PE),磷脂酰肌醇(PI)和磷脂酸(PA)为主成份组成磷脂质混合物。其结构含有疏水性脂肪酸基和亲水性磷酸酯基,PI和PA具有阴离子,而PC与PE     

直接进样HPLC-ELSD法测定花生中磷脂含量

建立了直接进样高效液相色谱-蒸发光检测器(HPLC-ELSD)法测定花生中磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE)、磷脂酰肌醇(PI)和磷脂酸(PA)的方法。采用改良Folch方法提取样品总脂肪,然后将提取出的总脂肪直接溶于流动相进行液相色谱分析,以L-Si型正相硅胶色谱柱(250 mm×4.6 mm,5μm)为固定相,以正己烷-异丙醇(体积比2∶3)为流动相A,正己烷-异丙醇-25 mmol/L乙酸铵溶液(体积比3.6∶5.4∶1)为流动相B进行二元梯度洗脱,蒸发光检测器检测。PC、PE、PI和PA 4种磷脂色谱峰面积与其质量浓度的线性相关系数(R2)大于0.995,4种磷脂的平均回收率在93.59%108.57%之间,RSD均小于10%。该方法具有重现性好、稳定性高、前处理简单的特点,可应用于磷脂的分离检测。     

Characterisation of the glycerophospholipid fraction in flaxseed oil using liquid chromatography–mass spectrometry

A high-performance liquid chromatographic method coupled with mass spectrometry was used to characterise the natural phospholipid (PL) classes and molecular species in flaxseed oils. The PL fraction included phosphatidylethanolamine (PE) (27–40%), phosphatidylinositol (PI) (29–32%), phosphatidylcholine (PC) (7–18%), lysophosphatidylcholine (LPC) (8–21%), phosphatidylglycerol (PG) (1–4%) and phosphatidic acid (PA) (1–9%). The distribution of fatty acids was found to differ between phospholipids. Stearic acid was mainly present in the form of PC and LPC. Palmitic acid was present in the most abundant molecular species in PI, PG and PA whereas linoleic acid formed the most abundant molecular species in PE.     

杯芳烃/还原氧化石墨烯纤维的制备及其选择性吸附性能

为提升杯芳烃纤维对Pt(Ⅱ)的平衡吸附量,依次通过酰胺化、还原法和静电纺丝法制备了杯芳烃/还原氧化石墨烯(CrGO)纤维.借助扫描电子显微镜、红外光谱仪、拉曼光谱仪和热重分析仪分析了纤维的结构与性能,并采用吸附实验研究了纤维的吸附选择性、吸附动力学及吸附等温模型.结果表明:CrGO纤维直径为(2±0.5)μm,具有褶皱...     

Molecular species of phosphatidylethanolamine from continuous cultures of Saccharomyces pastorianus syn. carlsbergensis strains

Saccharomyces pastorianus syn. carlsbergensis strain 34/70 is well known to be the most used strain for lager beer production. The difference between this strain and very closely related strain 34/78 is the latter's greater flocculating character. This single physiological trait can cause technical difficulties in beer production. The aim of this study was to determine whether lipid analysis by a combination of thin layer chromatography (TLC) with electrospray ionization mass spectrometry (ESI-MS) could be used as a strain-typing technique in order to distinguish S. pastorianus syn. carlsbergensis strain 34/70 from strain 34/78. Both strains (34/70 and 34/78) were harvested after continuous culture under standard conditions. Polar lipids were then extracted from lyophilized cultures and analysed by TLC in order to separate phospholipid families. Phosphatidylethanolamine (PE) was extracted and investigated using ESI-MS, to gain further information on individual molecular species. Using TLC analysis, lipids were separated corresponding to standards for PE, phosphatidylcholine (PC), phosphatidylglycerol (PG), cardiolipin (CL), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidic acid (PA) and sphingomyelin (SM). ESI-MS of the PE band, separated by TLC, showed that electrospray mass spectra were highly reproducible for repeat cultures. Novel findings were that both brewing strains displayed major phospholipid peaks with m/z 714, PE (34 : 2) m/z 742, PE (36 : 2) and m/z 758, PE (37 : 1). However, strain 34/78 had additional peaks of m/z 700, PE (33 : 2) and m/z 728, PE (35 : 2). Strain 34/70 had an extra peak with m/z 686 PE (32 : 2). We conclude that combined TLC/ESI-MS can distinguish between S. pastorianus syn. carlsbergensis 34/70 and 34/78 and may be a useful typing technique for differentiation of closely related yeast strains. This novel approach may aid quality assurance and could be suitable for yeast collections and larger industrial companies.     

超声强化亚硫酸钙吸附糖汁中非糖分

为考察超声波强化亚硫酸钙沉淀吸附糖汁中非糖分过程的作用,采用超声波作用方式、超声功率以及超声时间对糖汁简纯度的影响,对超声强化亚硫酸钙沉淀吸附糖汁中非糖分的动力学和吸附等温线进行研究。结果表明：超声处理能够明显提高糖汁的简纯度,超声波最佳的处理阶段是在糖汁加入聚丙烯酰胺(PAM)之后,最佳的超声功率为260W、超声作用时间为90s,在此条件下糖汁简纯度提高了2.13%。亚硫酸钙沉淀对糖汁中非糖分的吸附符合颗粒扩散方程,吸附等温线符合Freundlich 方程。     

采用离子交换吸附对蛹虫草中虫草素的提取研究

采用超声波法对蛹虫草中虫草素进行粗提,筛选得到了最佳吸附介质阳离子树脂001×16,该介质对虫草素的吸附特性,包括吸附等温线、吸附动力学条件等进行了探讨。结果表明,001×16对虫草素的吸附等温线符合Langmuir方程,最佳吸附条件为pH值为4.0,温度15℃,吸附时间3 h。在此优化条件下,虫草素最大吸附量可达到1.3 mg/g。     

高粱壳色素上染毛织物的动力学和热力学

为研究高粱壳色素上染毛织物的染色机制,给优化染色工艺提供理论指导,应用动力学、热力学模型对高粱壳色素上染毛织物的实验数据进行拟合。结果表明,高粱壳色素上染毛织物符合准二级动力学模型。染色温度在80~100℃范围内,随着温度升高,染色速率、半染时间及扩散系数均增大。高粱壳色素上染毛织物的吸附等温线符合朗格缪尔型,属于单分子层吸附。染色温度在80~100℃范围内,随着染色温度的升高,上染到毛织物上的高粱壳色素量增加,吸附饱和值升高;并且染色热和染色焓变均为正值。     

明胶吸附单宁酸的机理探讨及其在蓝莓汁脱涩中的应用

分别用0.01～0.11 g的明胶吸附25 mL 900 mg/L单宁酸模拟溶液,根据明胶吸附量和单宁酸去除率得到明胶的最佳用量,然后研究最佳用量的明胶对25 mL 900 mg/L单宁酸模拟溶液的吸附动力学方程和吸附等温线方程,最后研究明胶对单宁酸质量浓度为900 mg/L的25 mL蓝莓汁的脱涩效果。结果表明：吸附25 mL 900 mg/L单宁酸模拟溶液时,明胶最佳用量为0.03 g,其明胶吸附量为527.5 mg/g,单宁酸去除率为70.33%。明胶吸附单宁酸的过程符合准二级动力学方程,其吸附等温线符合Langmuir吸附方程,为单分子层吸附。当脱除单宁酸含量为900 mg/L的25 mL蓝莓汁的涩味时,明胶用量0.03 g、温度15 ℃、振荡时间20 min,在该条件下,其明胶吸附量为420.8 mg/g,单宁酸去除率为56.11%,脱涩效果良好。     

磁性壳聚糖改性对高岭土吸附蔗糖溶液中咖啡酸性能的影响

目的:研究磁性壳聚糖改性高岭土对模拟蔗汁中咖啡酸的吸附特性。方法:通过共沉淀法将壳聚糖、纳米四氧化三铁与高岭土结合制备成磁性壳聚糖改性高岭土,通过FT-IR、VSM和SEM表征高岭土改性前后表面结构和基团变化,采用吸附试验研究磁性壳聚糖改性高岭土对咖啡酸的吸附特性。结果:改性后壳聚糖和纳米Fe₃O₄成功地负载到了高岭土上并提升了其对咖啡酸的吸附性能,磁性壳聚糖改性高岭土的等电点为4.54,酸性条件有利于咖啡酸的去除,并在240 min时达到吸附平衡。磁性壳聚糖改性高岭土对咖啡酸的吸附过程更符合准二级动力学和Langmuir等温线吸附模型,其吸附过程主要为化学吸附和单分子层吸附,热力学研究表明吸附过程为自发吸热过程。结论:磁性壳聚糖改性高岭土对蔗汁中咖啡酸具有较强吸附性能,可作为糖用澄清剂用于蔗汁中咖啡酸的吸附处理。     

Effect of acidification and heating on the rheological properties of oil-water interfaces with adsorbed milk proteins

The behavior of casein and whey proteins at the oil-water interface was studied using a dynamic drop tensiometer (DDT). The dilational modulus of the interface was measured for aqueous solutions of skim milk powder (SMP) and whey protein concentrate (WPC) with various additions (salt, calcium, lactose) and (order of) various processing steps. Acidification or heating was performed before or after creation of the interface. The elastic properties of oil-water interfaces with adsorbed milk proteins could partly determine the rate of partial coalescence and resulting product instability.For WPC, preacidification slows down the adsorption, but the modulus is not affected. This is probably because, although the whey proteins change conformation more slowly at the interface, still a homogeneous film is formed. If postacidification is applied, coarsening of the protein film leads to loss of interfacial rigidity. Preheating of the aqueous phase with WPC leads to denaturation and aggregation, but the aggregates formed are still surface active and give high moduli. If preheating of a WPC solution is followed by postacidification, the resulting modulus is high (approximately 60 mN/m).The oil-water interfacial properties of SMP are only minimally affected by preheating or by choice of powder (low, medium, or high heat). At low pH, however, aggregates are formed that are less surface active, and interfacial moduli are lower.If measurements are performed at high temperature (i.e., if postheating is applied), for both SMP and WPC systems, moduli became much lower (approximately 10 mN/m). This is probably because of accelerated rearrangements, leading to the formation of inhomogeneous film structures.