ORIENTATION-DEPENDENT STUDIES OF ALIGNED MEMBRANES

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。在膜的研究中，当对齐的膜可用于研究时，存在几个光谱优势。一个优点是改进的光谱分辨率，因为对齐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膜法线相对于外部磁场的不同取向的光谱的叠加（MOMD模型）。对齐膜的另一个优点是减少光谱模糊性。在许多情况下，基本上不同的模拟参数集给出了实验MOMD谱的非常相似的近似。在对齐膜的ESR谱的模拟，特别是在同时适合几个方向的情况下，是免费的这种模糊性。对齐的膜的研究可以提供特别有价值的信息，相对于膜正常的氮氧部分的取向。由于所有的取向的膜正常相对于磁场的平均MOMD囊泡光谱，氮氧自由基部分的取向的信息是很差的解决。然而，高频/高场光谱学需要薄（100微米）的平坦样品，其中B 0严格垂直于样品的平面。为了在不同于0 °的方向上获得高场光谱（这里，膜法线对应于样品法线），我们在ISDU对准的样品上应用切片机技术。 将充分水合的ISDU对准的膜样品切割成薄（~ 80微米）切片，其中切片法线处于用户控制的角度。2至4个这些片，密封限制在两个石英显微镜盖玻片，形成一个对齐的样品在用户控制的方向高场ESR。我们已经在95和170/240 GHz成功地实现了这种技术。

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.