BioPHYSICAL chemistry
Magnetic resonance is widely used for spectroscopic measurements of biological systems. The concept of magnetic resonance can be ...
Electromagnetic radiation interacts with dipole moments. For example, a radio and television antenna responds to a broadcast sig ...
These energies can be expressed in terms of the Larmor frequency,νL, by: (16.5) For a nucleus with a spin of 1/2, this interacti ...
Chemical shifts Every dipole of a protein will interact with the external magnetic field. The magnetic field experienced by each ...
shielding. Electronegative groups withdraw electron density from the pro- tons, give less shielding, and hence have larger shift ...
a proton. The spins of the H 2 may be up/up, up/down, down/up, or down/down. Since the up/down and down/up configurations lead t ...
at different frequencies and start to separate. The magnetization vector decreases with a time constant, T 2 , resulting in an e ...
Two-dimensional NMR: nuclear Overhauser effect The nuclear Overhauser effect is a specific NMR tool for the determination of whi ...
pulse is applied to the system that has an energy matching the energy dif- ference for one of the spins, the populations of thos ...
structures if the structures are not too large. Although NMR techniques are being developed to overcome this limitation, the upp ...
display broad lines and the poor resolution limit imposes a fundamental limitation. In the new approaches, such as transverse re ...
bonds in proteins, the approach has been extended to methyl groups resulting in sharp NMR signals for very large proteins exceed ...
A second approach is to use solid-state NMR (McDermott 2004). The protein is no longer in solution and so does not tumble, and a ...
determine the structures of the proteome; that is, all the proteins that are found in an organism (Stauton et al. 2003). In addi ...
358 PART 2 QUANTUM MECHANICS AND SPECTROSCOPY Table 16.2 (^1) H Chemical shifts of the amino acid residues (see Figure 1.8) in t ...
found in many different cell types but the mutations lead to termination of growth only for motor neurons. The protein plays a r ...
surface of the structure is Glu-134. The mutation Glu to Lys at 134 had been found previously in a patient with spinal muscular ...
CHAPTER 16 MAGNETIC RESONANCE 361 magnetic field strength, as the tube on the right-hand side has a much stronger magnetic field ...
Improvements in the resolution of the result- ing images have led to their application as a tool for studying physiological resp ...
Just as for the nuclear spins, the electronic spins will split the atomic energy levels in the presence of an external magnetic ...
«
14
15
16
17
18
19
20
21
22
23
»
Free download pdf