[理学]北大生物化学完整课件Chapter3 2.ppt

Amino Acids, Peptides and Proteins 氨基酸、肽及蛋白质 Nelson, D. L., and Cox, M. M. (2005) Lehninger Principles of Biochemistry, 4th edition. Protein sequences and Evolution！ Introduction to Bioinformatics: Sequence alignment; Homologs; Paralogs; orthologs; Blosum (blocks substitution matrix) ; Signature sequences;   Current phylogeny tree of life (by Carl Woese)  Characteristic titration curves of amino acids The principal components a spectrophotometer Levels of structure in proteins Proteins And Prosthetic groups (辅基) Analytical versus Preparative; Sources of proteins: Blood (serum); Tissue cells and microbial cells; Extraction, fractionation, separation and purification. Working with Proteins Methods for separating proteins take advantage of the physical properties such as charge, size, and solubility, which vary from one protein to the next. Because many proteins bind to other biomolecules, proteins can also be separated on the basis of their binding properties. Proteins can be separated and purified Centrifugation; Electrophoresis; Liquid Chromatography; Edman degradation; Mass spectrometry; Other Physical means: X-ray, NMR, Electron Microscopy; light scattering methods; different spectrophotometries; Thermo measurements; etc… Many ways to work with Proteins based on their physical and chemical properties Svedberg studied proteins with the methods of ultra-centrifugation (超速离心), and defined sedimentation coefficient (s). e.g. Hemoglobin: The(odor) Svedberg Uppsala University Born 1884 Ph.D. 1908 Professor 1912 Nobelprice 1926 蛋白质可以通过各种生物化学技术纯化 利用蛋白质的溶解度、净电荷、大小以及与配体结合特异性上的微小差异。有透析、凝胶过滤、离子交换层析、亲和层析、电泳（垂直板电泳、等电聚焦电泳、双向电泳）等分离纯化方法。透析 Salting out and dialysis(透析) Column chromatography  Ion-exchange chromatography Size-exclusion chromatography Hydrophobic interaction chromatography Isoelectric focusing chromatography Affinity chromatography: Antibodies, His-tags, Protein-A, Protein-G, GST-, MBP-fusion proteins etc…, Ion