FLUORESCENCE STUDIES OF PEPTIDE STRUCTURE & DYNAMICS

生长抑素、蛙皮素和其他柔性肽激素采用 在溶液中有多种构象，但具有高特异性结合 到膜受体。 实证结构-活性研究 发现了活性增强的更刚性的类似物，这表明 只有天然肽的构象异构体的一个子集 由受体识别。 适合受体的分子 结合位点应具有更高的亲和力和特异性， 受体的 尽管结合以外的因素影响生物学特性， 活性，肽设计的统一结构方法是 关键的重要性。 目前，很少有技术用于 确定这种复杂系统中的肽结构。 该研究的长期目标是开发 荧光方法来探测结构和动力学 柔性肽 荧光是一种敏感的技术， 芳香族氨基酸是肽结构的内在报道分子。 然而，在大多数情况下， 多指数荧光衰减的肽，即使是一个单一的 芳族残基不被理解。 我们的策略是设计 色氨酸和酪氨酸衍生物，其荧光发射 可以直接用结构术语来解释。 拟议 修饰将限制侧链键的旋转， 芳环系统。 激发态属性将为 通过稳态和时间分辨荧光测定。 地面- 状态属性将通过X射线衍射、分子 力学和核磁共振。 这种方法的成功是显而易见的， 限制色氨酸衍生物的初步研究。 的 肽环境对这种荧光的影响 衍生物将以简单的模型肽和刚性肽为特征， 生长抑素类似物。 最后，约束导数将为 掺入半刚性生长抑素类似物和柔性生长抑素类似物中， 蛙皮素类似物，用于探测溶液结构和 与生物活动有关的动力学特征。 未来的工作将集中在肽的结构和动力学复杂 环境，包括可溶性蛋白和膜受体 配合物 此外，一些拟议的衍生品可能具有 作为蛋白质构象的荧光探针 转换以及用于肽设计的工具。

Somatostatin, bombesin, and other flexible peptide hormones adopt multiple conformations in solution, yet bind with high specificity to membrane receptors. Empirical structure-activity studies have discovered more rigid analogs with enhanced activity, suggesting that only a subset of conformers of the natural peptide are recognized by the receptor. Molecules tailored to fit the receptor binding site should have higher affinity and specificity for the receptor. Although factors other than binding affect biological activity, a unifying structural approach to peptide design is of key importance. Presently, there are few techniques for determining peptide structure in such complex systems. The long term goal of the proposed research is to develop fluorescence methods to probe the structure and dynamics of flexible peptides. Fluorescence is a sensitive technique and the aromatic amino acids are intrinsic reporters of peptide structure. However, in most cases the structural and chemical basis of the multiexponenrial fluorescence decays of peptides with even a single aromatic residue are not understood. Our strategy is to design tryptophan and tyrosine derivatives, whose fluorescence emission may be directly interpreted in structural terms. The proposed modifications will constrain side chain bond rotations and extend the aromatic ring system. Excited-state properties will be determined by steady-state and time-resolved fluorescence. Ground- state properties will be determined by X-ray diffraction, molecular mechanics, and NMR. The success of this approach is apparent from preliminary studies of a constrained tryptophan derivative. The effects of peptide environment on the fluorescence of this derivative will be characterized in simple model peptides and rigid somatostatin analog. Finally, the constrained derivative will be incorporated into semi-rigid somatostatin analogs and flexible bombesin analogs and used to probe solution structural and dynamical features relevant to biological activity. Future work will focus on peptide structure and dynamics in complex environments, including soluble protein and membrane receptor complexes. In addition, some of the proposed derivatives may have applications as fluorescence probes for protein conformational transitions as well as tools for peptide design.