Download or read book Directed Evolution of and with Expanded Genetic Codes written by Chang C. Liu and published by . This book was released on 2009 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: By expanding the genetic code to allow the cotranslational incorporation of unnatural amino acids, one can site-specifically introduce unique chemical functionality into proteins in vivo. By using such expanded genetic codes in directed evolution, one can impose selection for novel protein function wherein variants containing unnatural amino acids will be selected should the unnatural amino acids confer a functional advantage. I first describe the expansion of E. coli 's genetic code for the site-specific incorporation of the unnatural amino acid sulfotyrosine and the subsequent use of this expanded genetic code for the expression and study of several proteins including sulfo-hirudin and sulfated anti-HIV antibodies. I then describe the development of a phage-based system for evolution with expanded genetic codes and the application of this system for directed evolution, through which proteins that use unnatural amino acids for enhanced function can emerge from selection. This work demonstrates the value of genetically encoding more than the 20 natural amino acids for protein engineering applications and shows that these expanded genetic codes can confer a selective advantage.