BioPHYSICAL chemistry

detailed analysis since the contribution from each atom of the molecule must be considered in the analysis. Each type of atom pr ...

Because protein crystals have such a significant amount of the crystal- lization solution, there is a dark ring due to the solve ...

326 PART 2 QUANTUM MECHANICS AND SPECTROSCOPY Complex numbers can be considered to be vectors in a complex plane with the com- p ...

CHAPTER 15 X-RAY DIFFRACTION AND EXAFS 327 according to its atomic scattering factor, fi(hkl), which has both an amplitude fi(hk ...

Phase determination In a diffraction experiment, the intensity of each diffraction peak, that is |F(hkl)|^2 , is measured. To de ...

protein. Also, amino acid residues that are not conserved can be replaced with alanine. Computers are used to place the resultin ...

and the location of the metal can be identified. This approach is now com- monly used to provide phase information by incorporat ...

CHAPTER 15 X-RAY DIFFRACTION AND EXAFS 331 Model building Once the phases have been determined then it is possible to calculate ...

Experimental measurement of X-ray diffraction X-rays can be generated in the laboratory by bombarding a metal with high-energy e ...

CHAPTER 15 X-RAY DIFFRACTION AND EXAFS 333 Experiment endstations Storage ring Accelerating chamber Undulators Injection 15 metr ...

The bremsstrahlung radiation is 100 –1000 times more intense than what is available in the laboratory, with significant improvem ...

Examples of protein structures All of this work is done so that the three-dimensional structure of pro- teins can be determined. ...

In addition to trapping proteins in different functional states it is now possible to monitor protein structure as it undergoes ...

exothermic but kinetically is extremely slow due to the initial step of breaking the triple bond of N 2. Despite this unfavorabl ...

338 PART 2 QUANTUM MECHANICS AND SPECTROSCOPY negative ripple that obscures the electron density of any light atom. In the highe ...

CHAPTER 15 X-RAY DIFFRACTION AND EXAFS 339 rates (Chapter 10). The spatial arrangement of these docking geometries may reflect l ...

For a free metal, as the energy of the X-rays is varied, the intensity of the beam undergoes an abrupt shift when it matches a t ...

CHAPTER 15 X-RAY DIFFRACTION AND EXAFS 341 SSR Fe S SR RS Fe RS SR SR RS Fe RS 123 EXAFS signal Distance (Å) 123 EXAFS signal Di ...

342 PART 2 QUANTUM MECHANICS AND SPECTROSCOPY Problems 15.1 Why are X-rays needed to determine the structure of proteins in diff ...

15.15Explain how the lack of all reflections in the diffraction data analysis changes the calculated electron density. 15.16 Wha ...