CONFORMATIONALLY CONSTRAINED PROTEIN POLYMERS

这项拟议的研究将涉及含有非天然氨基酸的重复多肽序列的设计、建模、合成和表征。特别强调的是蛋白质聚合物的体内表达，包括蛋氨酸类似物高烯丙基甘氨酸，或“HAG”。这些聚合物中存在的烯烃化学官能团将被用来创造具有定制性能的新型高分子材料。编码α-螺旋蛋白聚合物的人工基因将在大肠杆菌蛋氨酸营养缺陷体中表达，该聚合物包括重复的I到I+4模式的Hag残基。纯化后，HAG侧链的端烯基团将发生闭环歧化反应。这个反应将产生19个成员的环大环，这将系住蛋白质的二级结构。预期的产品是单分散刚性棒状聚合物。将研究这种聚合物的生物物理和材料性质，特别是α-螺旋结构的热稳定性。聚合物的行为将通过分子动力学模拟来模拟。这些聚合物的表征将通过对新的化学功能的精确空间构图来促进材料科学的进步，并将通过加强对控制蛋白质二级结构形成的作用力的了解来促进蛋白质生物物理学的进步。

The proposed research will entail the design, modeling, synthesis, and characterization of repeating polypeptide sequences incorporating non-natural amino acids. A particular emphasis will be the in vivo expression of protein polymers that include the methionine analog homoallylglycine, or "Hag". The presence of the alkene chemical functionality in these polymers will be exploited to create novel macromolecular materials with tailored properties. Artificial genes encoding alpha-helical protein polymers that include Hag residues in a repeating i to i + 4 pattern will be expressed in an E. coli methionine auxotroph. Following purification, the terminal alkene groups of the Hag sidechains will be subjected to ring-closing metathesis. This reaction will generate 19-membered ring macrocycles that will tether the protein secondary structure. The anticipated product is a monodisperse rigid-rod polymer. The biophysical and materials properties of this polymer will be investigated, with particular attention to the thermal stability of the alpha- helical structure. The behavior of the polymers will be modeled by molecular dynamics simulations. Characterization of these polymers will provide advances in materials science through the precise spatial patterning of novel chemical functionalities, and will provide advances in protein biophysics through an enhanced understanding of the forces that control the formation of protein secondary structure.