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首页> 美国卫生研究院文献>Biophysical Journal >Saturation transfer continuous wave saturation and saturation recovery electron spin resonance studies of chain-spin labeled phosphatidylcholines in the low temperature phases of dipalmitoyl phosphatidylcholine bilayers. Effects of rotational dynamics and spin-spin interactions.
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Saturation transfer continuous wave saturation and saturation recovery electron spin resonance studies of chain-spin labeled phosphatidylcholines in the low temperature phases of dipalmitoyl phosphatidylcholine bilayers. Effects of rotational dynamics and spin-spin interactions.

机译：链旋转标记的磷脂酰胆碱双层低温相中自旋标记的磷脂酰胆碱的饱和转移连续波饱和和饱和恢复电子自旋共振研究。旋转动力学和自旋-自旋相互作用的影响。

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摘要

The saturation transfer electron spin resonance (STESR) spectra of 10 different positional isomers of phosphatidylcholine spin-labeled in the sn-2 chain have been investigated in the low temperature phases of dipalmitoyl phosphatidylcholine (DPPC) bilayers. The results of continuous wave saturation and of saturation recovery measurements on the conventional ESR spectra were used to define the saturation properties necessary for interpreting the STESR results in terms of the chain dynamics. Spin labels with the nitroxide group located in the center of the chain tended to segregate preferentially from the DPPC host lipids in the more ordered phases, causing spin-spin interactions which produced spectral broadening and had a very pronounced effect on the saturation characteristics of the labels. This was accompanied by a large decrease in the STESR spectral intensities and diagnostic line height ratios relative to those of spin labels that exhibited a higher degree of saturation at the same microwave power. The temperature dependence of the STESR spectra of the different spin label isomers revealed a sharp increase in the rate of rotation about the long axis of the lipid chains at approximately 25 degrees C, correlating with the pretransition of gel phase DPPC bilayers, and a progressive increase in the segmental motion towards the terminal methyl end of the chains in all phases. Prolonged incubation at low temperatures led to an increase in the diagnostic STESR line height ratios in all regions of the spectrum, reflecting the decrease in chain mobility accompanying formation of the subgel phase. Continuous recording of the central diagnostic peak height of the STESR spectra while scanning the temperature revealed a discontinuity at approximately 14-17 degrees C, corresponding to the DPPC subtransition which occurred only on the initial upward temperature scan, in addition to the discontinuity at 29-31 degrees C corresponding to the pretransition which displayed hysteresis on the downward temperature scan.
机译：在二棕榈酰磷脂酰胆碱（DPPC）双层低温相中研究了sn-2链中自旋标记的磷脂酰胆碱的10种不同位置异构体的饱和转移电子自旋共振（STESR）光谱。常规ESR谱图上连续波饱和度和饱和度恢复测量的结果用于定义链动力学方面解释STESR结果所需的饱和度特性。具有位于链中央的氮氧化物基团的自旋标记物倾向于优先从DPPC宿主脂质中分离出更多有序相，从而引起自旋-自旋相互作用，从而产生光谱展宽并对标记的饱和特性产生非常明显的影响。相对于在相同微波功率下表现出更高饱和度的自旋标记物，STESR光谱强度和诊断线高度比大大降低。不同自旋标记异构体的STESR光谱的温度依赖性显示，在大约25摄氏度时，围绕脂质链长轴的旋转速率急剧增加，这与凝胶相DPPC双层的预转变有关，并逐渐增加在所有阶段都朝着链的末端甲基末端进行分段运动。在低温下长时间孵育会导致光谱的所有区域中诊断性STESR谱线高度比的增加，反映出伴随亚凝胶相形成的链迁移率下降。扫描温度时连续记录STESR谱图的中心诊断峰高，发现在大约14-17摄氏度时出现了不连续性，这与仅在初始向上温度扫描时发生的DPPC子转变相对应，除了在29-对应于向下温度扫描显示迟滞的预转变温度为31摄氏度。

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