Order Magnetic Resonance Techniques Assignment

Order Magnetic Resonance Techniques Assignment
5.1 Explain why higher magnetic field strengths result in a better resolution
of magnetic resonance spectrometers.
5.2 Discuss the advantages of pulsed NMR methods over NMR methods in
which the absorption of continuous radiowaves is measured.
5.3 Figure 5.4 illustrates the reasons for the splitting and the intensities of the
signals for the methyl group protons of ethanol (shown in Figure
5.3,c). Explain in the same way the line splitting and intensities for
the methylene protons marked by b in Figure 5.3.
individual nuclei sum to the total magnetization. Sketch graphically how
the magnetic moments of individual nuclei can sum to a total magnetization that points in the direction of the half-diagonal between the z- and
the y-axis.
Order Magnetic Resonance Techniques Assignment
5.5 In the rotating frame coordinate system a 90x° pulse corresponds to the
rotation of the total magnetization around the x-axis by 90°. Sketch
graphically the trajectory of the total magnetization vector during a 90x°
pulse in the laboratory frame.
5.6 In a multidimensional NMR experiment a protein sample is first irradiated with a radiowave pulse that results in a zero population difference of
α and β proton spins. An identical second radiowave pulse is applied after
a time that corresponds to 1/8 of a full Larmor rotation of the α-carbon
hydrogen spin of a distinct amino acid. After about 1 s a third identical
radiowave pulse is applied. Now the FID is measured.
a) What kind of NMR experiment does this situation correspond to?
b) How much signal does the α-carbon hydrogen contribute to the
observed FID? Discuss various scenarios.
5.7 A protein with an unknown structure is investigated in a NOESY experiment. Extremely strong NOESY correlations are found between α-carbon
hydrogens, Hα
, and hydrogens bound to nitrogens, HN, three amino acids
further in the primary sequence [Hα
5.9 Explain why in EPR spectroscopy the magnetic field is scanned rather
than the microwave frequency?
146 5 Magnetic Resonance Techniques
5.10 Explain how rotational correlation times can be derived from EPR spectra. Discuss the advantages and disadvantages of determining rotational
correlation times with EPR and fluorescence polarization measurements.