Vincent J S, Levin I W
Chemistry Department, University of Maryland Baltimore County, Catonsville 21228.
Biochemistry. 1988 May 3;27(9):3438-46. doi: 10.1021/bi00409a047.
The vibrational Raman spectra of both pure L-alpha-dipalmitoylphosphatidylcholine (DPPC) liposomes and DPPC multilayers reconstituted with ferricytochrome c under varying conditions of pH and ionic strength are reported as a function of temperature. Total integrated band intensities and relative peak height intensity ratios, two spectral scattering parameters used to determine bilayer disorder, are invariant to changes in pH and ionic strength but exhibit a sensitivity to the bilayer concentration of the ferricytochrome c. Protein concentrations were estimated by comparing the 1636 cm-1 resonance Raman line of known ferricytochrome c solutions to intensity values for the reconstituted multilayer samples. Temperature-dependent profiles of the 3100-2800 cm-1 C-H stretching, 1150-1000 cm-1 C-C stretching, 1440 cm-1 CH2 deformation, and 1295 cm-1 CH2 twisting mode regions characteristic of acyl chain vibrations reflect bilayer perturbations due to the weak interactions of ferricytochrome c. The DPPC multilamellar gel to liquid-crystalline phase transition temperature, TM, defined by either the C-H stretching mode I2935/I2880 or the C-C stretching mode I1061/I1090 peak height intensity ratios, is decreased by approximately 4 degrees C for the approximately 10(-4) M ferricytochrome c reconstituted DPPC liposomes. Other spectral features, such as the increase in the 2935 cm-1 C-H stretching mode region and the enhancement of higher frequency CH2 twisting modes, which arise in bilayers containing approximately 10(-4) M protein, are interpreted in terms of protein penetration into the hydrophobic region of the bilayer.
报道了在不同pH值和离子强度条件下，纯L-α-二棕榈酰磷脂酰胆碱（DPPC）脂质体以及用铁细胞色素c重构的DPPC多层膜的振动拉曼光谱随温度的变化情况。用于确定双层无序度的两个光谱散射参数——总积分带强度和相对峰高强度比，对pH值和离子强度的变化不敏感，但对铁细胞色素c的双层浓度敏感。通过将已知铁细胞色素c溶液的1636 cm-1共振拉曼线与重构多层样品的强度值进行比较来估算蛋白质浓度。3100 - 2800 cm-1 C-H伸缩振动、1150 - 1000 cm-1 C-C伸缩振动、1440 cm-1 CH2变形振动以及1295 cm-1 CH2扭曲振动模式区域的温度依赖性曲线特征反映了由于铁细胞色素c的弱相互作用导致的双层扰动。由C-H伸缩振动模式I2935/I2880或C-C伸缩振动模式I1061/I1090峰高强度比定义的DPPC多层凝胶向液晶相转变温度TM，对于约10(-4) M铁细胞色素c重构的DPPC脂质体降低了约4℃。其他光谱特征，如在含有约10(-4) M蛋白质的双层中出现的2935 cm-1 C-H伸缩振动模式区域的增加以及高频CH2扭曲振动模式的增强，被解释为蛋白质渗透到双层疏水区域的结果。
