LINEAR ELECTRIC FIELD EFFECT (LEFE) IN ESR

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。 静电相互作用影响蛋白质的结构、功能和与其他生物分子的相互作用。因此，探测静电学的方法提供了对动力学敏感的方法的补充信息，并将有助于构建解释光谱的模型。 高场/高频电子自旋共振(HFHF-ESR)的出现使得氮氧化物自旋标记可以作为生物分子中局部静电的准确探针。当电子能级通过与局部电场的相互作用而移动时，氮氧化物的g张量出现二阶移动。在高场下出色的g因子辨别能力允许测量这些在标准ESR场中无法检测到的微小移位。在较强的外加电场作用下，可大大提高对局部静电效应的敏感性。利用HFHF-ESR的高g因子分辨率来观察有机自由基中的这种效应的可能性大大扩展了可以检测的体系的范围。在高频样品谐振器中施加强局域电场所需的探头是我们为研究液晶中的电场效应而发展的技术的自然延伸。我们正在优化我们的标准法布里-珀罗(FP)谐振器的薄膜电极几何形状，以允许在E平行配置下进行研究。利用该中心开发的时域分析方法，正在开发一系列用于95 GHz、170 GHz和240 GHz可变耦合的并联FP谐振器。这些新的谐振器将允许我们在E垂直构型下进行实验。我们在该中心的95 GHz脉冲光谱仪上获得的经验使我们对成功进行LEFE实验所需的样品夹要求有了重要的了解。

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. Electrostatic interactions influence the structure, function, and interaction of proteins with other biomolecules. Thus, methods that probe electrostatics provide complementary information to methods sensitive to dynamics and will aid in the construction of models for interpreting spectra. The availability of high-field/high-frequency-ESR (HFHF-ESR) allows the use of nitroxide spin labels as an accurate probe of local electrostatics in biomolecules. When the electronic energy levels are shifted by interactions with a local electric field, second-order shifts appear in the nitroxide's g-tensor. The excellent g-factor discrimination at high field permits the measurement of these small shifts that are not detectable at standard ESR fields. The sensitivity to local electrostatic effects may be greatly enhanced by the application of a strong external electric field. The possibility of exploiting the high g-factor resolution of HFHF-ESR to observe such effects in organic radicals greatly extends the range of systems that can be examined. The probe necessary for applying a strong local electric field in a high-frequency sample resonator is a natural extension of techniques we have developed for studying electric-field effects in liquid crystals. We are optimizing the thin-film electrode geometry for our standard Fabry-P¿rot (FP) resonator, to permit studies in the E parallel configuration. Development work on a series of shunt FP resonators for use at 95, 170 and 240GHz with variable coupling is underway utilizing time-domain analysis methods developed in the center. These new resonators will allow us to perform experiments in the E perpendicular configuration. The experience we have gained with the center's 95GHz pulse spectrometer has given us important insights into the sample holder requirements that will be necessary for the success of the LEFE experiments.