基因,蛋白,免疫 课程之蛋白组学 4.ppt

Proteomics 4 Principles of Proteomics “Life in the post-genomic era” With the completion of the sequencing of the human genome we have now entered the “post-genomic” era. The challenge is now to: Identify the genes encoded in the genome Identify the factors that control protein synthesis Determine the number of proteins expressed in a cell In particular, the control of the interaction between proteins is governed by post tanslational modifications such as phosphorylation and glycosylation which can never be understood from the sequence of a gene. Proteomics The “proteome” is the term coined to described the proteins expressed in any one particular cell type at any one particular time. However proteomics has become synonymous with the procedure for the analysis and identification of proteins in complex mixtures. Overview Proteomics can be used to answer many different types of question. Eg identification of proteins whose expression is regulated by hormones or drugs Differences in protein expression between normal and malignant cells. Identification of proteins present in biological fluids. This contrasts with techniques based on the use of nucleic acids such as array technology and differential display. The Mass Spectrum In mass spectrometry, molecules are bombarded with a beam of energetic electrons. The molecules are ionized and broken up into many fragments, some of which are positive ions. Each kind of ion has a particular ratio of mass to charge, m/e value. For many ions, the charge is 1 so that the m/e is simply the mass of the ion. Determination of peptide sequence by Mass Spectrometry Two approaches: Post source decay Tandem Mass Spectrometry * Currently, proteomics involves the display of as many proteins as possible using the technique of two dimensional gel electrophoresis coupled to the analysis and identification of the proteins. Two dimensional electrophoresis was developed 20 years ago. It was not highly reproducible at this time but this has