血影膜及脂质体的融合及其与膜流动性的关系

本文采用Tb/DPA荧光方法研究了血影膜及磷脂酰丝氨酸脂质体在不同Ca~(2 )浓度诱导下的融合动力学过程,并通过改变温度研究了血影膜、PS脂质体的融合与膜流动性的关系.血影膜、PS脂质体的最大融合程度在一定范围内随膜流动性增加而增大,超出此范围则随膜流动增加而减小.对此结果进行了讨论.     

声波刺激对菊花愈伤组织膜脂物理状态和膜脂代谢的影响

以蔗糖梯度法纯化的菊花(Dendranthema morifolium (Ramat.) Tzvel.)愈伤组织质膜微囊为材料,研究了声波刺激下质膜膜脂代谢和物理状态的变化.结果表明, 一定强度(100 dB)和频率(1 000 Hz)的声波刺激使质膜磷酸二脂含量和二苯己三烯(DPH)荧光偏振值降低,质膜光散射值、MC540荧光强度和磷酸单脂含量增加.表明一定强度和频率的声波刺激使质膜变疏松,膜的流动性增加,膜表面电荷密度和疏水性降低,膜脂合成代谢增加,分解代谢减弱.由此可见,膜脂物理状态和膜脂代谢对声波刺激极为敏感.     

声波刺激对菊花愈伤组织膜脂物理状态和膜脂代谢的影响

以蔗糖梯度法纯化的菊花 (Dendranthemamorifolium (Ramat.)Tzvel.)愈伤组织质膜微囊为材料 ,研究了声波刺激下质膜膜脂代谢和物理状态的变化。结果表明 ,一定强度 (10 0dB)和频率 (10 0 0Hz)的声波刺激使质膜磷酸二脂含量和二苯己三烯 (DPH)荧光偏振值降低 ,质膜光散射值、MC5 40荧光强度和磷酸单脂含量增加。表明一定强度和频率的声波刺激使质膜变疏松 ,膜的流动性增加 ,膜表面电荷密度和疏水性降低 ,膜脂合成代谢增加 ,分解代谢减弱。由此可见 ,膜脂物理状态和膜脂代谢对声波刺激极为敏感。     

竹红菌甲素对红细胞膜和几种磷脂脂质体膜的流动性的光敏损伤

本文以荧光探针为手段,通过测量膜偏振度的变化,探讨了竹红菌甲素光敏作用对红细胞膜和几种磷脂脂质体膜的流动性的损伤。结果表明,甲素光敏作用使不同种类的磷脂(DPPC,DPPC/DPPE,红细胞膜磷脂)脂质体的流动性增加,其对光敏作用的敏感程度为红细胞膜磷脂脂质体显著小于DPPC/DPPE脂质体及DPPC脂质体。对红细胞膜来说,甲素光敏作用使其流动性呈现先降低而后增加的现象。去除膜上的spectrin以及用胰蛋白酶处理可使这种流动性变化的幅度受到抑制。据此,我们认为,膜磷脂,膜蛋白对甲素光敏作用中膜流动性的变化有着不同的影响,膜蛋白,特别是spectrin,是其中极重要的因素。     

红细胞膜上结合水的萤光与红外研究

水是生物膜上重要的结构与功能分子。本实验以20℃红细胞膜对水的等温吸附曲线为定量根据,研究了不同水化水平的水化效应。DPH的萤光偏振测量证明:脱水将破坏脂双层的有序结构,大约20%的水化度是维持膜结构所必需的;在膜结构完整的条件下结合水的增加会使膜流动性增大,水分子对双层类脂分子的“松弛效应”和水分子的运动对于膜脂分子的活动性可能有重要贡献。ANS的萤光发射谱说明水化效应增加了膜表面的极性,也提示在高水化水平膜上存在着一部份活动性较大的水分子。红外差示谱表明膜上存在着两类结合水——紧密结合水与松弛结合水,也说明脱水将造成磷脂与胆固醇的相分离现象。     

硒拮抗超氧阴离子导致的心肌线粒体膜损伤

由黄嘌呤和黄嘌呤氧化酶体系产生的超氧阴离子作用于心肌线粒体后,其膜脂双层内产生了脂类自由基。在一定时间内,脂类自由基与自旋捕捉剂形成的加合物的ＥＳＲ信号强度随着孵育时间的增加而加强。１．０μｍｏｌ／Ｌ硒代蛋氨酸（Ｓｅ－Ｍｅｔ）或２．３μｍｏｌ／ＬｍＮａ２ＳｅＯ３可显著清除并抑制脂类自由基的产生。在的影响下,荧光探针ＤＰＨ在膜脂双层中的荧光寿合和膜脂流动性发生了明显改变。一定浓度的Ｓｅ－Ｍｅｔ或Ｎａ２ＳｅＯ３可明显拮抗的上述影响,前者的作用更为显著。     

脂肪族类两亲物对肌浆网膜脂区结构的影响

C18饱和脂肪酸和胺可增加DPH标记肌浆网(SR)的荧光偏振度,而C18单不饱和脂肪酸。胺和醇则使其偏振度下降。加入MgATP,可除去单不饱和脂肪胺引起的DPH标记的荧光偏振度下降,并使之高于未加脂肪胺的对照水平。饱和酸及相应胺可使标记于膜脂中层和深层的TAS和12AS的荧光偏振度上升,不饱和酸及相应胺和醇仅使12AS荧光偏振下降。说明脂肪族类两亲物对SR膜流动性的影响与脂肪链饱和程度有关。饱和者主要使膜中、深层流动性下降.不饱和者主要使膜深层流动性升高。     

膜脂状态在Mg~2+对线粒体H~+-ATP酶影响中的作用

对猪心线粒体H-ATP酶体系中膜脂在Mg~(2 )的激活功能中起极重要的作用。通过DPH外源荧光探针和5-NSESR探针测膜脂表层Mg~(2 )作用影响的研究表明Mg~(2 )首先对膜脂作用,增加膜脂的有序性。TU颗粒和复合体的酶、色氨酸残基内源荧光偏振度测定的结果表明Mg~(2 )可进而影响内嵌蛋Fo,最终导致F_1上功能位点的构象和功能的变化。但膜脂的原始状态对Mg~(2 )起作用是重要的。     

稀土离子对带3蛋白阴离子转运活性及血影膜流动性的影响

测定了Ｌａ２＋、Ｇｄ３＋、Ｔｂ３＋及Ｙｂ３＋四种稀土离子对带３蛋白阴离子转运活性及对血影膜脂流动性的影响。结果如下：（１）稀土离子可强烈抑制带３蛋白的阴离子转运活性,抑制程度随稀土离子浓度增加而增加,最高达到６３．７％。（２）不同的稀土离子对带３蛋白的抑制程度不同,抑制程度从大到小的顺序为Ｙｂ＞Ｔｂ＞Ｇｄ＞Ｌａ。（３）稀土离子可显著降低血影膜流动性,并且在脂双层的全部厚度内都降低,降低的程度随稀土浓度的增大而增大。（４）不同的稀土离子对血影膜流动性的影响不同,作用从大到小的顺序与它们对带３蛋白活性抑制程度大小的顺序一致。（５）稀土离子对血影膜流动性的影响特征与稀土离子抑制带３蛋白活性的特征完全相符,带３蛋白中承担阴离子转运功能的部分是贯穿性膜蛋白,并且在阴离子转运过程中要发生显著的构象变化,因此稀土离子可能是通过作用于膜脂再影响带３蛋白活性的。     

外源脂肪酸对莱氏衣原体膜流动性的影响——电子自旋共振与荧光偏振研究

生物膜类脂的物理性质直接影响膜的生理功能,膜的流动动性是反映膜脂物理状态的一个重要特征.本文采用电子自旋共振波谱及荧光偏振技术研究油酸,硬脂酸以及油酸和棕榈酸的混合物渗入莱氏衣原体膜后对膜流动性的影响.结果表明,上述外源脂肪酸均能增加膜的流动性,其中以油酸渗入膜后最为显著.油酸中双键的作用不仅仅局限于双键所在碳原子附近,而且能使整个膜脂双层各个层次上流动性都有增加.对于用荧光偏振和自旋标记顺磁共振二种技术所获得结果的异同也进行了初步讨论.     

精胺对脂质体及细胞膜融合的作用

本文通过共振能量转移法与三氯化铽荧光法探讨了精胺及其与Ca~(2 )对脂质体及人红细胞膜融合的诱导作用.结果表明,精胺能诱导PS脂质体的凝聚,但不能诱导其融合.精胺能诱导血影膜的融合.精胺与Ca~(2 )一起使用.对脂质体及血影膜的融合都分别有协同增效作用.     

没食子酸丙酯和没食子酸异丁酯对人红细胞膜结构与功能的影响

本文应用荧光探剂ANS(1—苯胺—8萘磺酸)、NPN(N—苯基—1—萘胺)和DPH(1.6—二苯基—1.3.5—已三烯)观察没食子酸丙醋和没食子酸异丁酯对人红细胞膜流动性和相变温度以及Na~ -K~ ATP酶活性的影响.实验结果指出该两种化合物均能:(1)降低与膜结合的荧光探剂强度但不改变探剂在水相与膜相的分配比例:(2)降低膜脂的相变温度,增加膜的流动性;(3)抑制红细胞膜Na~ -K~ ATP酶活性;(4)标记红细胞膜的DPH偏振度随化合物浓度的增加而降低,膜的流动性增加.在给定的浓度范围内,两种化合物的效应表现为明显的量效关系与构效关系.从上述结果推测该两种化合物可能是通过改变膜脂结构、膜蛋白的脂类环境而调节膜的功能,成为其治疗疾病的机理之一.     

Effects of alcohols on fluorescence anisotropies of diphenylhexatriene and its derivatives in bovine blood platelets: relationships of the depth-dependent change in membrane fluidity by alcohols with their effects on platelet aggregation and adenylate cyclase activity.

The effects of three short-chain alkyl alcohols and benzyl alcohol on the membrane fluidity of bovine blood platelets were investigated by studies on the fluorescence anisotropies of diphenylhexatriene (DPH), its cationic trimethylammonium derivative (TMA-DPH) and its anionic propionic acid derivative (DPH-PA). These alcohols decreased the fluorescence anisotropy of DPH, which is thought to be located within the hydrophobic core of the membrane, in concentration ranges that inhibited platelet aggregation. On the other hand, they had little or no effects on the fluorescence anisotropy of DPH-PA which is thought to be located in the interfacial region of the lipid bilayer. Likewise, they had little or no effects on the fluorescence anisotropy of TMA-DPH, which is also thought to be located in the interfacial region of the lipid bilayer, either when the probe was located in the outer layer of the plasma membrane or when the probe was located in the inner membrane compartment. These results suggest that alcohols mainly increase the fluidity in the central region of the lipid bilayer. Consistent with their effects on the fluorescence anisotropy of DPH, these alcohols increased the intracellular cyclic AMP concentration. Thus alcohols may inhibit platelet function due to stimulation of adenylate cyclase, which is mediated by perturbation of the central region of the membrane lipid bilayer.     

Membrane actions of water-soluble fusogens: Effect of dimethyl sulfoxide,glycerol and sucrose on lipid bilayer order and fluidity

The effect of three water-soluble fusogens: dimethyl sulfoxide (DMSO), glycerol and sucrose on the structural properties of model lipid membranes has been studied by electron spin resonance (ESR) using 5-doxylstearic acid as a spin probe and by fluorescence spectroscopy using pyrene as an excimer forming fluorescent probe. All three fusogens tested produce a marked increase in the order parameter of the region close to the polar surface of the lipid bilayer. The ordering effect of DMSO, but not of glycerol and sucrose, is much stronger with respect to membranes prepared from acidic than from neutral phospholipids. The membrane-perturbing action of glycerol and sucrose manifests itself also in the reduced lateral mobility of membrane incorporated pyrene, indicating thus a decreased fluidity of the bilayer hydrophobic region. The structural perturbations produced in model membranes by DMSO, glycerol and sucrose are discussed in relation to the mechanism by which these substances promote cell fusion.     

Changes Caused by Fruit Extracts in the Lipid Phase of Biological and Model Membranes

The aim of the study was to determine changes incurred by polyphenolic compounds from selected fruits in the lipid phase of the erythrocyte membrane, in liposomes formed of erythrocyte lipids and phosphatidylcholine liposomes. In particular, the effect of extracts from apple, chokeberry, and strawberry on the red blood cell morphology, on packing order in the lipid hydrophilic phase, on fluidity of the hydrophobic phase, as well as on the temperature of phase transition in DPPC liposomes was studied. In the erythrocyte population, the proportions of echinocytes increased due to incorporation of polyphenolic compounds. Fluorimetry with a laurdan probe indicated increased packing density in the hydrophilic phase of the membrane in presence of polyphenolic extracts, the highest effect being observed for the apple extract. Using the fluorescence probes DPH and TMA-DPH, no effect was noted inside the hydrophobic phase of the membrane, as the lipid bilayer fluidity was not modified. The polyphenolic extracts slightly lowered the phase transition temperature of phosphatidylcholine liposomes. The studies have shown that the phenolic compounds contained in the extracts incorporate into the outer region of the erythrocyte membrane, affecting its shape and lipid packing order, which is reflected in the increasing number of echinocytes. The compounds also penetrate the outer part of the external lipid layer of liposomes formed of natural and DPPC lipids, changing its packing order.     

Receptor-mediated interaction of ricin with the lipid bilayer of ganglioside GM1-liposomes

The interaction of ricin with ganglioside GM1 or glycoprotein containing liposomes was investigated. At neutral pH, ricin bound to galactose moieties on the surface of the liposomes to form ricin-liposomes complexes, but did not associate with their lipid bilayers. When these ricin-liposomes complexes were exposed to a pH below 5, ricin bound to GM1-liposomes became associated with the lipid bilayer, whereas ricin bound to glycoprotein-liposomes (containing human erythrocyte Band 3) was only rarely associated. Association of ricin with the lipid bilayer of GM1-liposomes did not occur in the presence of lactose, which inhibits the binding of ricin to ganglioside GM1. Using a hydrophobic probe, 8-amino-1-naphthalene sulfonic acid (ANS), it was revealed that an acidity below pH 5 resulted in exposure of hydrophobic regions on the ricin molecule. These results strongly suggest that association of ricin with the lipid bilayer of GM1-liposomes at acidic pH is mediated by the binding of ricin to ganglioside GM1 at neutral pH and occurs through interaction between the exposed hydrophobic region on the ricin molecule and the lipid bilayer of GM1-liposomes at low pH.     

缺锌对大鼠红细胞膜生物物理性质的影响

利用激光衍射仪,荧光分光光度法,ＥＳＲ等牲物理技术和缺锌大鼠模型,研究缺锌对大鼠红细胞膜生物物理性质的影响,实验结果表明缺锌使大鼠红细胞的变形能力增大,稳定性降低,红细胞膜脂的流动性和膜蛋白的运动性增加,支持了锌具有维持膜结构和功能和生理作用的理论;为膜结构和功能的改变是缺锌病理变化主要原因的假说提供了实验依据。     

汞化合物对红细胞膜作用的研究

本文研究了汞化合物对红细胞膜作用的光谱变化,观察了膜蛋白的荧光和磷光,膜上DPH的荧光偏振和ANS与红细胞膜的结合,以及他们与汞产生红血球溶血的关系。 在5P7.5缓冲液中红细胞膜蛋白的荧光随HgCl_2 Hg(AC)_2和PCMB的浓度加大而降低,表现为快和慢双相变化的过程,其淬灭作用的大小为HgCl_2>Hg(AC)_2PCMB,这是由于膜上形成了不发荧光的R—Trp—Hg~ 络合物以及能量从Trp转移到R—S—Hg~ 络合物上。HgCl_2对膜蛋白磷光的作用也是随汞离子浓度加大而降低,但磷光/荧光比则是增加的。标记红细胞膜的DPH偏振度是随HgCl_2浓度增加,表明膜流动性是随汞离子浓度加大而降低。标记膜上的ANS的荧光强度随HgCl_2和Hg(AC)_2的浓度加大而增加,这是由于ANS与膜的结合数随汞离子浓度加大而增加的缘故。上述各种变化是与汞离子对红血球溶血的作用一致的。     

Profile of changes in lipid bilayer structure caused by beta-amyloid peptide.

beta-Amyloid peptide (A beta) is the primary constituent of senile plaques, a defining feature of Alzheimer's disease. Aggregated A beta is toxic to neurons, but the mechanism of toxicity is uncertain. One hypothesis is that interactions between A beta aggregates and cell membranes mediate A beta toxicity. Previously, we described a positive correlation between the A beta aggregation state and surface hydrophobicity, and the ability of the peptide to decrease fluidity in the center of the membrane bilayer [Kremer, J. J., et al. (2000) Biochemistry 39, 10309--10318]. In this work, we report that A beta aggregates increased the steady-state anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) embedded in the hydrophobic center of the membrane in phospholipids with anionic, cationic, and zwitterionic headgroups, suggesting that specific charge--charge interactions are not required for A beta--membrane interactions. A beta did not affect the fluorescence lifetime of DPH, indicating that the increase in anisotropy is due to increased ordering of the phospholipid acyl chains rather than changes in water penetration into the bilayer interior. A beta aggregates affected membrane fluidity above, but not below, the lipid phase-transition temperature and did not alter the temperature or enthalpy of the phospholipid phase transition. A beta induced little to no change in membrane structure or water penetration near the bilayer surface. Overall, these results suggest that exposed hydrophobic patches on the A beta aggregates interact with the hydrophobic core of the lipid bilayer, leading to a reduction in membrane fluidity. Decreases in membrane fluidity could hamper functioning of cell surface receptors and ion channel proteins; such decreases have been associated with cellular toxicity.     

Partitioning and membrane disordering effects of dopamine antagonists: influence of lipid peroxidation, temperature, and drug concentration.

The effect of four dopamine antagonists (spiperone, haloperidol, pimozide, and domperidone) on the lipid order of caudate nucleus microsomal membranes and on liposomes from membrane lipid extracts was evaluated and related to the partition coefficients (Kp) of the drugs. Lipid membrane order was determined by fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe of the membrane core and 1-[4-(trimethylammonium)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) as a probe of the membrane surface. Dopamine antagonists decrease the fluorescence polarization of both probes, indicating that they disorder the membrane lipids at different depths. Pimozide and domperidone, the drugs with higher Kp values, are more effective at decreasing the polarization of DPH, a probe of the membrane core, than that of TMA-DPH. In contrast, spiperone and haloperidol, which have lower values for Kp, induce more significant decreases in TMA-DPH depolarization, a probe of the membrane surface. These findings indicate that higher partition coefficients of the drugs are directly correlated with an increase of fluidity in the hydrophobic core of brain membranes. Ascorbate/Fe(2+)-induced membrane lipid peroxidation increases membrane order. Membrane lipid peroxidation decreases the partition coefficients of the dopamine antagonists tested. Increasing temperature (4-37 degrees C) decreases membrane order, but temperature effect is less evident after lipid peroxidation. The disordering effect of dopamine antagonists increases with increasing drug concentrations (1-15 microM), a maximum being observed at 10 microM. However, this effect is also less evident after membrane lipid peroxidation. We can conclude that dopamine antagonists and membrane lipid peroxidation affect membrane lipid order and that the action of these drugs is dependent on initial bilayer fluidity. Membrane lipid peroxidation increases membrane order while dopamine antagonists show a disordering effect of membrane phospholipids. This disordering effect can indirectly influence the activity of membrane proteins and it is one of the mechanisms through which membrane function can be altered by these drugs.