NATURE OF ESR SIGNAL IN MELANINS: A HIGH FIELD-HIGH FREQUENCY CW-ESR STUDY

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 黑色素是人类色素系统的关键成分。人类皮肤、眼睛或头发的色素沉着程度在很大程度上取决于细胞合成真黑素和褐黑素的能力。黑色素的各种功能是由它们的化学和物理性质决定的。这些性质又由分子、超分子结构和聚集层结构决定。其最终目标是构建这些物理效应的一致模型，以便理解分子和细胞尺度结构与黑色素的宏观可观察特性和功能之间的关系，以帮助设计适当的医疗模式。大多数天然黑色素在X波段表现出单一的、略微不对称的ESR信号，包含的结构信息非常少。从人视网膜色素上皮分离的天然黑色素颗粒的W波段CW-ESR初步测量表明，ESR光谱发生了明显的变化，表明眼睛黑色素可能存在随年龄变化的原位光氧化。我们的目标是使用更高的ESR频率/场来光谱地解决眼睛黑色素的这些微小的物理化学变化，这些变化可能是综合暴露在光和氧化应激下造成的。我们最初的CW研究是在170/240 GHz集中在合成黑色素上(Sigma Aldrich)。值得注意的是，其主要光谱特征与腐植酸非常相似。我们发现，腐植酸钠盐(Sigma-Aldrich)在241 GHz/9T处的光谱在实验不确定度内与合成黑色素的线宽和g因子相同。一个有趣的问题是，合成黑色素的宽阔线条中包含的细微而狭窄的特征的起源。由于黑色素以其不同寻常的电导行为而闻名，合成黑色素光谱中窄线的存在可能表明了半喹酮自由基(富含黑色素)之间的相关性。进一步的多频高频ESR，由于其优越的g因子分辨率，以及脉冲ESR研究，将有助于区分和分离频谱的两个宽和窄分量，并完善它们的解释。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Melanin is a key component of the human pigmentary system. The degree of pigmentation of the human skin, eyes or hair is to a large extent determined by the ability of cells to synthesize eumelanin and pheomelanin. The various functions of the melanins are defined by their chemical and physical properties. These properties in turn are defined by the molecular, supermolecular and aggregate-level structures. The ultimate goal is to construct a consistent model of these physical effects in order to engender understanding of how molecular and cellular scale structures relate to macroscopically observable properties and functions of melanins aiding the design of appropriate medical treatment modalities. Most natural melanin pigments exhibit a single, slightly asymmetric ESR signal at X-band that contains very little structural information. Preliminary W-band cw-ESR measurements of natural melanin granules, isolated from human retinal pigment epithelium, indicate distinct changes of the ESR spectrum that suggest possible age-dependent in situ photo oxidation of the ocular melanin. Our aim is to use even higher ESR frequencies/fields to spectrally resolve these small physicochemical changes of ocular melanin that may result from integrated exposure to light and oxidative stress. Our initial cw study is at 170/240 GHz concentrated on synthetic melanin (Sigma Aldrich). Notably, the major spectral features are very similar to that of humic acid. We found that the spectrum of the sodium salt of humic acid (Sigma-Aldrich) at 241 GHz/9T has to within experimental uncertainty the same linewidth and g-factor as observed for synthetic melanin. The interesting question is the origin of the subtle, narrow features contained in the broad single line of the synthetic melanin. Since melanins are known for their unusual electric conductivity behavior, it is possible that the presence of the narrow line in the spectrum of synthetic melanin demonstrates correlations between semiquinone radicals (abundant in melanin). Further multifrequency HFHF ESR, due to its superior g-factor resolution, and pulse ESR investigation will help to distinguish and separate between the two broad and narrow components of the spectrum and refine their interpretation.