PHOTOPHYSICS OF FLUORESCENT NON-NATURAL AMINO ACIDS

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。 近年来，对氰基苯丙氨酸(PheCN)已成为研究蛋白质结构和动力学的一种有用的光谱探针。例如，它的CN伸展频率对环境很敏感，因此被用来探测与模型膜结合的多肽的各个侧链的取向和水化状态，以及淀粉样纤维的结构。此外，PheCN在水中的荧光量子产率约为苯丙氨酸的5倍，脱水后荧光量子产率下降，是一种有吸引力的蛋白质构象变化的荧光探针。更重要的是，它通过荧光能量转移(FRET)机制激发色氨酸(Trp)荧光的能力，进一步增加了它作为光谱探针的用途。最后，也许最重要的是，在蛋白质构象研究中使用PheCN的主要优势是，作为一种非天然氨基酸，它对所讨论的天然蛋白质的物理性质的干扰最小，因为它的尺寸很小，特别是当它取代天然序列中的Phe或Tyr(酪氨酸)残基时。 虽然之前的研究已经确定了PheCN作为一种有价值的荧光探针的实用性，但其光物理的许多细节尚不清楚，这在许多情况下限制了其应用于定性背景下。在这里，我们建议研究PheCN在不同溶剂中的荧光寿命和量子产率，试图了解环境因素，如氢键和极性，如何决定其荧光性质

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. Recently, p-cyanophenylalanine (PheCN) has emerged as a useful spectroscopic probe of protein structure and dynamics. For example, its CN stretching frequency is sensitive to environment and thus has been used to probe the orientation and hydration status of individual sidechains of a peptide that is bound to model membranes , as well as the structure of amyloid fibers. In addition, the fluorescence quantum yield of PheCN in water is about five times larger than that of phenylalanine and decreases upon dehydration, making it an attractive fluorescent probe of protein conformational changes. What is more, its utility as a spectroscopic probe is further increased by its ability to excite tryptophan (Trp) fluorescence via the mechanism of fluorescence energy transfer (FRET). Finally, and perhaps most importantly, the major advantage of using PheCN in protein conformational studies is that as a non-natural amino acid, it minimally perturbs the physical properties of the native protein in question because of its small size, especially when it replaces either a Phe or Tyr (tyrosine) residue in the native sequence. While previous studies have established the utility of PheCN as a valuable fluorescent probe, many details of its photophysics are not known, which, in many cases, limits its application to a qualitative context. Herein, we propose to investigate the fluorescence lifetime and quantum yield of PheCN in a variety of solvents, attempting to understand how environmental factors, such as hydrogen bonding and polarity, determine its fluorescence properties