Understanding Enzyme Mechanism through Protein Chimeragenesis -- Chemical Protein Engineering: Synthetic and Semisynthetic Peptides and Proteins -- Native Chemical Ligation: SemiSynthesis of Post-translationally Modified Proteins and Biological Probes -- Chemical Methods for Mimicking Post-Translational Modifications -- Noncanonical Amino Acids in Protein Science and Engineering -- Fidelity Mechanisms of the Aminoacyl-tRNA Synthetases -- Specialized Components of the Translational Machinery for Unnatural Amino Acid Mutagenesis: tRNAs, Aminoacyl-tRNA Synthetases, and Ribosomes -- In Vivo Studies of Receptors and Ion Channels with Unnatural Amino Acids -- Synthesis of Modified Proteins Using Misacylated tRNAs -- Cell-Free Synthesis of Proteins with Unnatural Amino Acids. The PURE System and Expansion of the Genetic Code -- Engineering Nucleobases and Polymerases for an Expanded Genetic Alphabet -- Understanding Membrane Proteins. How to Design Inhibitors of Transmembrane Protein-Protein Interactions. Site-specific mutagenesis of DNA, developed some thirty years ago, has proven to be one of the most important advances in biology. By allowing the site-specific replacement of any amino acid in a protein with one of the other nineteen amino acids, it ushered in the new era of "Protein Engineering". The field of protein engineering has, however, evolved rapidly since then and the last fifteen years have witnessed remarkable advances through the use of new chemical, biochemical and molecular biological tools towards the synthesis and manipulation of proteins. The chapters included in this book reflect the rapid evolution of protein engineering and its many applications in basic research, biotechnology, material sciences and therapy. This book will provide the reader with an introduction to state-of the-art concepts and methods and will be of use to anyone interested in the study of proteins, in academia as well as in industry.