ORIENTATION-DEPENDENT STUDIES OF ALIGNED MEMBRANES

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。在膜的研究中，排列膜有几个光谱上的优势。一个优点是提高了光谱分辨率，因为排列的膜将光谱权集中在有限数量的明确定义的光谱区域，而囊泡光谱代表相对于外部磁场的膜法向的不同方向的光谱叠加（MOMD模型）。排列膜的另一个优点是减少了光谱模糊性。在许多情况下，大量不同的模拟参数集给出了非常相似的实验MOMD谱近似值。排列膜中ESR光谱的模拟，特别是在几个方向同时拟合的情况下，不存在这种模糊性。排列膜的研究可以提供氮氧化物部分相对于膜正常取向的特别有价值的信息。由于在MOMD囊泡光谱中，膜相对于磁场的所有方向都是平均的，所以关于氮氧化物部分方向的信息分辨得很差。然而，高频/高场光谱要求薄（100微米）的平面样品，B0方向严格垂直于样品的平面。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），我们将显微镜技术应用于ISDU对准的样品。将水合良好的ISDU排列膜样品切成薄（~ 80微米）的薄片，其中薄片的法线处于用户控制的角度。其中的2到4块被封闭在两个石英显微镜盖卡瓦之间，以用户控制的方向形成一个对准的样品，用于高场ESR。我们已经成功地在95和170/240GHz频段实现了这种技术。

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.