超声作用植物细胞膜振动的理论研究

运用声学基本理论并结合植物种子细胞膜结构特点,提出单层平面矩形薄膜模型.推导出细胞膜振动的频率方程,在一定的细胞膜表面张力、面密度和膜大小的情况下,得到了计算植物种子细胞膜的共振频率的方法.此方法对超声育种中声参数的确定有一定参考价值.

细胞膜振动的物理模型

目的提出细胞膜振动的物理模型,以探讨超声波育种的机理。方法通过建立植物种子细胞膜的椭圆振动理论模型,在测量和计算细胞膜表面张力、面密度和膜大小的情况下,得出细胞膜的共振频率。结果理论计算的细胞膜的共振频率与实验结果符合较好。结论建立的超声育种细胞膜振动模型具有一定的合理性,对超声波育种有一定的指导意义。

Effects of BYHW Decoction and Its Effective Constituents on the Fluidity of the Cell Membrane in a Stroke-Modeled Rat Brain

With in vitro spin labeling electron spin resonance (ESR) spectroscopy, we have studied the effects of Bu Yang Huan Wu (BYHW) decoction and its effective constituents such as astragaloside IV ferulic acid, chuanxiongzine, rutin, chlorogenic acid, 9,10 dimethoxy pterocarpane 7 O β D glucoside, calycosin, formononetin, calycosin 7 O glucoside, paeoniflorin, paeonal and quercein on the cell membrane fluidity of a rat brain which was modeled after the dual cervical arteries were intercepted and released for realizing an ischemia reperfusion injury which was selected as a brain stroke model. Our results indicated that the cell membrane fluidity in the model group decreased approximately 8% compared with the control group, and after brain cells were incubatied with species, the membrane fluidity could be recovered closely to the control level depending on the BYHW decoction and its different constituents. As the membrane fluidity is a very sensitive biological index which reflectsd the cell status, our method will be useful to study the molecular mechanism of tradition Chinese medicine (TCM) and its combination recipe.

Sum Frequency Spectroscopy Studies on Cell Membrane Fusion Induced by Divalent Cations

Cell membrane fusion is a fundamental biological process involved in a number of cellular living functions. Regarding this, divalent cations can induce fusion of the lipid bilayers through binding and bridging of divalent cations to the charged lipids, thus leading to the cell membrane fusion. However, the elaborate mechanism of cell membrane fusion induced by divalent cations is still needed to be elucidated.Here, surface/interface sensitive sum frequency generation vibrational spectroscopy(SFG-VS) and dynamic light scattering(DLS) were applied in this research to study the responses of phospholipid monolayer to the exposure of divalent metal ions i.e.Ca^(2+)and Mg^(2+). According to the particle size distribution results measured by DLS experiments, it was found that Ca^(2+)could induce inter-vesicular fusion while Mg^(2+)could not. An octadecyltrichlorosilane self-assembled monolayer(OTS SAM)-lipid monolayer system was designed to model the cell membrane for the SFG-VS experiment. Ca^(2+)could interact with the lipid POO_(2)^(-)head groups more strongly, resulting in cell membrane fusion more easily, in comparison with Mg^(2+). No specific interaction between the two metal cations and the C=O groups was observed. However, the C=O orientations changed more after Ca^(2+)-PO2-binding than Mg^(2+)mediation on lipid monolayer. Meanwhile, Ca^(2+)could induce dehydration of the lipids(which should be related to the strong Ca^(2+)-PO_(2)^(-)interaction), leading to the reduced hindrance for cell membrane fusion.

The dehydration dynamics of a model cell membrane induced by cholesterol analogue 6-ketocholestanol investigated using sum frequency generation vibrational spectroscopy

Dehydration of a surface is the first step for the interaction between biomolecules and the surface. In this study, we systemati- cally investigated the influence of cholesterol analog 6-ketocholestanol （6-KC） on the dehydration of model cell membrane, using sum frequency generation vibrational spectroscopy. In pure DI water environment, two separate dehydration dynamic components were observed in neutrally charged and isotopically labeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine （DMPC） and positively charged 1,2-dimyristoyl-sn-glycero-3-ethylphosphocholine（chloride salt） （DMEPC） bilayer： a large-amplitude fast component and a small-amplitude slow component, which originated from the water molecules with a weak and a strong water-membrane bound strengths, respectively. Dehydration of a negatively charged mixed DMPC/DMPG bilayer lead to the membrane-bound water being reorganized to ordered structures quickly. It is evident that the water-membrane bound strengths depend largely on the charge status of the lipid and has an order of neutrally charged membrane〈〈positively charged mem- brane〈〈negatively charged membrane. In an ionic environment, KC1 solution can not only dehydrate DMPC bilayer, but also prevent the 6-KC fiom further dehydrating this model cell membrane. We observed that the dehydration dynamics behavior of DMPC bilayer in the presence of the chaotropic anions is similar to that of the negatively charged DMPG bilayer because of the penetration of chaotropic anions into the DMPC bilayer. The degree of dehydration difficulty in kosmotropic anions fol- lows a Hofmeister series and linearly correlates with the hydration Gibbs free energy of the anions. Our results provide a molecular basis for the interpretation of the Hofmeister effect of kosmotropic anions on ion transport proteins.