PHOTOPHYSICS OF FLUORESCENT NON-NATURAL AMINO ACIDS

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 最近，对氰基苯丙氨酸（PheCN）已成为一个有用的光谱探针的蛋白质结构和动力学。例如，其CN伸缩频率对环境敏感，因此已用于探测与模型膜结合的肽的单个侧链的取向和水合状态，以及淀粉样蛋白纤维的结构。此外，PheCN在水中的荧光量子产率约为苯丙氨酸的五倍，并且在脱水后降低，使其成为蛋白质构象变化的有吸引力的荧光探针。 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实用性。最后，也许是最重要的，在蛋白质构象研究中使用PheCN的主要优点是，作为一种非天然氨基酸，由于其尺寸小，它对所讨论的天然蛋白质的物理性质的干扰最小，特别是当它取代天然序列中的Phe或Tyr（酪氨酸）残基时。 虽然以前的研究已经建立了PheCN作为一种有价值的荧光探针的效用，但其荧光物理学的许多细节尚不清楚，这在许多情况下将其应用限制在定性范围内。在此，我们打算研究PheCN在各种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. 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. 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