FLUORESCENCE STUDIES OF PEPTIDE STRUCTURE & DYNAMICS

生长抑素、蛙皮素和其他灵活的多肽激素采用 溶液中的多种构象，但具有高度的特异性 到膜上的受体。经验性结构-活性研究 发现了更多活性增强的刚性类似物，这表明 只有天然多肽的一部分构象是 由受体识别。为适应受体而量身定制的分子 结合部位应具有较高的亲和力和特异性 受体。尽管约束性以外的因素会影响生物 活性，多肽设计的统一结构方法是 关键的重要性。目前，几乎没有什么技术可以 在这样的复杂体系中确定多肽结构。 拟议研究的长期目标是发展 用荧光方法探测分子的结构和动力学 有弹性的多肽。荧光是一种敏感的技术，而 芳香氨基酸是多肽结构的内在报告者。 然而，在大多数情况下，结构和化学基础 单链多肽的多指数荧光衰变 芳香残留物是不被理解的。我们的战略是设计 色氨酸和酪氨酸的衍生物，它们的荧光发射 可以直接用结构术语来解释。建议数 修饰将约束侧链的键旋转并延伸 芳香环系统。激发态性质将是 由稳态和时间分辨荧光测定。地面- 态性质将由X射线衍射、分子 力学和核磁共振。这种方法的成功从以下方面看是显而易见的 一种限制性色氨酸衍生物的初步研究。这个 多肽环境对其荧光的影响 将衍生物表征为简单的模型多肽和刚性 生长抑素类似物。最后，受约束的导数将是 并入半刚性生长抑素类似物和柔性 蛙皮素类似物，用于探测溶液的结构和 与生物活动相关的动力学特征。 未来的工作将集中在复合体中的多肽结构和动力学 环境，包括可溶性蛋白和膜受体 复合体。此外，一些拟议的衍生品可能会 蛋白质构象荧光探针的应用 转换以及多肽设计的工具。

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.