生物化学（英文版）Chapter4 Proteins Three-Dimensional Structures and Function-part 1.ppt

Chapter 4 Proteins: Three-Dimensional Structures and Function 4.1 Methods for determining protein structrue 4.2 The conformation of the peptide group 4.3 Secondary structures of proteins 4.4 Tertiary structure of proteins 4.5 Quaternary structure of proteins 4.6 Protein denaturation and renaturation 4.7 Fibrous protein 4.8 Structure and function of myoglobin 4.9 Structure and function of hemoglobin 4.10 Antibodies bind specific antigens 4.11 Measurement of protein 1. X-Ray Diffraction： 2. Nuclear Magnetic Resonance (NMR)： 3. Circular Dichroism (CD) ： 4.1 Methods for determining protein structrue (a) X-ray diffraction data is collected by sending a beam of collimated X-rays through a single protein crystal. The diffracted rays are detected on a piece of film. (b) Shown is the diffraction pattern of a crystal of adult human deoxyhemoglobin. Darker spots result from larger numbers of X-rays being diffracted to that location. The location and intensity of the spots on the film are used to determine the three dimensional structure of the protein. Diffraction is evaluated at many different angles of incidence of the X-ray beam. Film may be cylindrical (as shown in A) or possibly spherical. X-Ray Diffraction Ribonuclease A (RNase A) is a secreted enzyme that hydrolyzes RNA during digestion. This diagram utilizes the structure of the bovine RNAse A. (a) Shown is a space-filling model of RNAse A with a bound substrate (black stick model.) (b) The same enzyme is shown with a ribbon model of the protein backbone. (c) This close-up view of the substrate binding site depicts the substrate analog (5-diphosphoadenosine- 3-phosphate) in space-filling model. The side-chains of the amino acid residues in the active site are shown in ball-and-stick model while the remainder of the protein is represented in ribbon form. [PDB 1AFK] NMR (nuclear magnetic resonance) is used to analyze protein structure in solution Ribonuclease A determined by NMR (p