Protein Sequencing Protocols

If the development of techniques for the labeling of a polypeptide- terminus and for repetitive N-terminal sequencing mark the beginning of the science of protein structure determination, then the field has just about reached its half century. In more recent times, recombinant DNA techniques have pro- vided powerful means by which to obtain long protein sequences (by theoreti- cal translation from nucleic acid sequences), but rather than replacing the direct, chemical, protein sequencing approach, they have instead added further impe- tus to the drive towards a better understanding of posttranslational processing and modification events, as well as identification of novel proteins. Recent years have also seen the advent of "e;biopharmaceuticals"e; (i. e. , pharmaceutical products that are proteins, such as monoclonal antibodies), and this has meant that protein sequencing has found an important new application as a quality control tool. Over the decades of protein sequencing many new techniques have been introduced, with the basic aim of generating more information from less material. Some techniques have come and gone, but others have been with us for many years. Edman chemistry is perhaps the best example of the latter class, with its basic principles still being applied today in the newest protein sequencer design. Methods for cleaving and modifying peptides are also long- standing, having been adapted over the years to suit progressively smaller amounts of sample.