New chemical methods for the synthesis of proteins and their application to the elucidation of protein structure by racemic protein crystallography.

摘要

My thesis research aimed to address: (1) the expansion of chemical tactics available for the rapid and efficient preparation of larger and more complex proteins; and, (2) the use of racemic mixtures to crystallize and determine the Xray structure of proteins. The new tactics allow for the convergent synthesis and selective desulfurization of proteins. Convergent synthesis of proteins increases the yields and size of proteins targets accessible to total chemical synthesis. The same method developed for the convergent synthesis of proteins allows for the preparation of cyclic proteins from more than one polypeptide. Selective desulfurization is a chemical tactic that allows for ligations at Ala residues, in the presence of protected Cys residues, thereby increasing synthetic versatility. Some of the new methods described were used to prepare the minor image forms of proteins needed for racemic protein crystallography. The minor image form of a protein can only be prepared by chemical synthesis. Moreover, we document the exploration of racemic protein mixtures as an avenue to determine novel Xray structures that are difficult to crystallize. We also show, for the first time, that direct methods and racemic crystallography can be used in a simple fashion to determine the Xray structure.