MICROTOME METHODS FOR ALIGNED SAMPLES FOR HIGH FIELD ESR

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。利用等电位自旋干燥离心（ISDU）和显微组技术相结合，记录了膜法向相对于磁场不同方向对应的高场/高频（HF/HF） ESR谱。在x波段（~ 9.5 GHz），只要在谐振腔中旋转样品，就可以得到膜法向相对于磁场不同方向的ESR谱。这种方法不适用于更高的频率。由于不可避免的介电损耗，成功的高频实验需要在毫米波e场的节点放置薄（100 mkm）的平面样品。对于标准的固定谐振器几何形状，样品法线平行于外加磁场B0。然而，将显微组技术应用于ISDU排列样品提供了一个机会，将优秀的定向分辨率（高场ESR的主要优点之一）与研究不同方向排列膜样品的能力结合起来。该技术用于制备各种膜取向可控的薄片，适用于HF/HF ESR。薄片的x波段光谱与在谐振腔中旋转相应的ISDU样品获得的光谱相同。自旋标记的Gramicidin A和胆甾烷自旋标记在排列DPPC膜上的例子说明了该技术的应用以及hhfhf ESR在排列膜上相对于x波段的一些优点。

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. A combination of isopotential spin-dry centrifugation (ISDU) and microtome techniques is used to record high field/high frequency (HF/HF) ESR spectra corresponding to different orientations of the membrane normal relative to the magnetic field. At X-band (~ 9.5 GHz) one can get ESR spectra for different orientations of the membrane normal relative to the magnetic field merely by rotating the sample in the resonator. The method is not applicable at higher frequencies. Due to unavoidable dielectric losses, a successful HF experiment requires thin ( 100 mkm) flat samples placed at a node of the millimeter wave E-field. For the standard fixed resonator geometry, the sample normal is parallel to the applied magnetic field B0. However, applying microtome techniques to ISDU aligned samples offers an opportunity to combine excellent orientational resolution, one of the main virtues of high-field ESR, with the ability to study aligned membrane samples in various orientations. The technique is used to prepare thin slices of various, controllable membrane orientations, suitable for HF/HF ESR. The X-band spectra of the slices are shown identical to the spectra obtained by rotating corresponding ISDU samples in the resonator. Examples of spin-labeled Gramicidin A and cholestane spin label in the aligned DPPC membrane illustrate applications of the technique and some virtues of HFHF ESR on aligned membranes vs. X-band.