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BIOCHEM 4300 EXAM 5 QUESTIONS WITH CORRECT DETAILED ANSWERS 100% VERIFIED
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BIOCHEM 4300 EXAM 5 QUESTIONS WITH CORRECT DETAILED ANSWERS 100% VERIFIED...
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BIOCHEM 4300 EXAM 5 QUESTIONS WITH CORRECTDETAILED ANSWERS 100% VERIFIED
What is the bell analogy for NMR? - ANSWER each atom has its own tumbling frequency
What is the tumbling frequency of an atom affected by? - ANSWER its environment
When does NMR occur? - ANSWER when the nucleus changes its spin status
What is the nucleus changing its spin status driven by? - ANSWER absorption of a
quantum of energy
What is the energy required for NMR applied as? - ANSWER electromagnetic radiation
What is the equation for NMR? - ANSWER N(Beta)/N(alpha) = e ^ (-deltaE/kt)
For a proton, is there slightly more population in alpha or beta state? - ANSWER alpha
How does difference in NB/Na or delta population relate to NMR signal? - ANSWER
larger difference = better NMR signal
What nuclei are visible to NMR? - ANSWER 1H, 13C, 15N, 19F, 31 P
What nuclei are slightly visible to NMR? - ANSWER 29Si, 107Ag, 119Sn, 199 Hg
What is the half spin for a NMR active nuclei? - ANSWER I = 1/2
,How many possible orientations are there for a nucleus spin? - ANSWER 2l + 1
For I=1/2 spin, how is the energy level affected when a magnetic field is applied? -
ANSWER it splits
What is the classic view of NMR? - ANSWER using the coordinate grid
What is the quantum mechanic view of NMR? - ANSWER the lines with one on top and
one on bottom
What is T1 relaxation? (spin-lattice relaxation) - ANSWER gain and loss of magnetization
in the z-relaxation
What is T2 relaxation (spin-spin relaxation)? - ANSWER Heisenberg uncertainty principle
broadening due to lifetime of spin coherence -- gain and loss of magnetization in the x,y
direction
How is tissue contrast determined by MRI? - ANSWER differences in T1 and T2
relaxation
What is the most abundant nucleus in the body? - ANSWER 1H from water
How does the brain show up on MRI with T1 weighting? - ANSWER CSF - dark
white matter - bright
gray matter - gray
How does the brain show up on MRI with T2 weighting? - ANSWER CSF = bright
white matter -gray
gray matter -dark
, How do resonances compare in folded and unfolded proteins on a 1D proton spectrum?
- ANSWER resonances in folded proteins are better dispersed than in unfolded ones
Why is there a need for a 2nd dimension of proton spectrum? - ANSWER - peaks are
crowded
- 2nd dimension can separate peaks to relieve crowding
- 2nd dimension can establish spatial or covalent proximity of neighboring chemical
groups
Scalar coupling (J) - ANSWER - through bonds
- used to determine connectivity
Dipolar coupling - ANSWER - through space
- exhibited in magnetization transfer
- fundamentally different from scalar coupling
- used to determine spatial relationships
How close should nuclei be for dipolar coupling? Why? - ANSWER within 5 A
bc dipolar coupling falls off with 1/r^6
What corresponds to a stiff spring/large J constant? - ANSWER fast energy exchange
What corresponds to a loose spring/ small J constant? - ANSWER slow energy exchange
What are the 4 basic steps of 1h-15N experiment for connecting the chemical shift of an
amide hydrogen with chemical shift of is covalently attached nitrogen? - ANSWER 1.
ring the nitrogen
2. record the nitrogen's signal
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