ORIENTATION-DEPENDENT STUDIES OF ALIGNED MEMBRANES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 在膜的研究中，当有取向膜可供研究时，有几个光谱优势。一个优点是提高了光谱分辨率，因为对准的膜将光谱权重集中在光谱的有限数量的明确定义的区域中，而囊泡光谱表示对应于相对于外部磁场(MOMD模型)的膜法线的不同取向的光谱的叠加。取向膜的另一个优点是减少了光谱模糊性。在许多情况下，基本上不同的模拟参数集给出了与实验MOMD谱非常相似的近似。在取向膜中的ESR谱的模拟，特别是在几个取向同时拟合的情况下，没有这种模糊性。对取向膜的研究可以提供关于氮氧化物部分相对于膜法线的取向的特别有价值的信息。由于在MOMD囊泡光谱中，膜法向相对于磁场的所有取向都是平均的，所以关于氮氧化物部分的取向的信息分辨率很差。然而，高频/高场光谱学要求薄(100微米)平板样品的B0严格垂直于样品平面。为了获得不同于0°取向的高场光谱(这里，膜法线对应于样品法线)，我们对ISDU排列的样品应用显微切割机技术。一个水合良好的ISDU排列的膜样品被切割成薄的(~80微米)切片，其中切片的法线处于用户控制的角度。其中2到4块被密封地限制在两个石英显微镜盖片之间，形成用户控制的取向的对准样品，用于高场ESR。我们已经在95 GHz和170/240 GHz成功地实现了这一技术。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In the study of membranes, there are several spectroscopic advantages when aligned membranes are available for study. One advantage is improved spectral resolution since the aligned membrane concentrates the spectral weight in a limited number of well-defined regions of the spectrum, whereas a vesicle spectrum represents a superposition of spectra corresponding to different orientations of the membrane normal relative to the external magnetic field (MOMD model). Another advantage of aligned membranes is a reduction in spectral ambiguity. In many cases substantially different sets of simulation parameters give very similar approximations of an experimental MOMD spectrum. The simulation of ESR spectra in aligned membranes, especially in the case of simultaneous fits for several orientations, is free from this ambiguity. The study of aligned membranes may provide particularly valuable information on the orientation of the nitroxide moiety relative to the membrane normal. Because all orientations of the membrane normal relative to the magnetic field are averaged in MOMD vesicle spectra, information about the orientation of the nitroxide moiety is poorly resolved. High frequency/high field spectroscopy, however, requires thin (100 micron) flat samples with B0 directed strictly perpendicular to the plane of the sample. To obtain high field spectra in an orientation different from 0¿ (here, the membrane normal corresponds to the sample normal) we apply microtome technique on ISDU aligned samples. A well-hydrated ISDU aligned membrane sample is cut into thin (~ 80 micron) slices where the slice normal is at a user controlled angle. 2 to 4 of these pieces, hermitically confined between two quartz microscope cover slips, form an aligned sample at a user-controlled orientation for high field ESR. We have successfully implemented this technique at 95 and 170/240GHz.