Proteolytic-Based Method for the Identification of Human Growth Hormone

Human growth hormone (HGH) is a relatively small protein consisting of 191 amino acids and has an average mass of 22,125 amu. The forensic analysis of proteins such as HGH must meet the analytical sufficiency requirements for the laboratory and consists of a binary approach. A suspected sample is analyzed as the whole protein for retention time and mass determination using high performance liquid chromatography equipped with a photodiode array and liquid chromatography mass spectrometry. Further fragmentation of the protein using a proteolytic enzyme adds another dimension to the specificity of the analysis. Porcine trypsin digests proteins in a very predictable manner and yields peptide fragments of the original protein that can be used as a means for fingerprinting the larger biomolecule. In silico, or theoretical, digestion of HGH by trypsin yields 21 peptides ranging in size from 1 to 23 amino acids in length. The larger fragments containing higher numbers of amino acids give more specificity to identifying a protein based on a fragment produced by the digestion of trypsin. Herein, the analysis of HGH using a proteolytic approach is presented that meets the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) recommendations for the identification of unknown substances.