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Module „NMR“ (MSc): Practical exercises Sheet 03 3.1
3.2
3.2 (continuation) Explain the J-coupling pattern and determine the J-coupling constant
3.3 Read the following publication and explain the relevance of the following NMR data:
S. Li and M. Hong (2011) Protonation, tautomerization, and rotameric structure of histidine:
A comprehensive study by magic-angle-spinning solid-state NMR. J. Am. Chem. Soc. 133,
1534–1544. Supporting Information is available online.
• Histidine—a functionally important histidine in proteins (e.g., act as a proton pump),
knowledge about the protonation state and tautomeric structure of histidine (imidazole
side-chain).
Q1: How the histidine behaves over a pH range between 4.5 and 11, e.g., in terms of 1H, 13C, 15N chemical shifts, the hydrogen-bonding properties, and rotameric conformations?
Q2: How the authors demonstrated the measurement of the side-chain torsional angles χ1 and
χ2 of histidine? How accurate is their measurement?
Q3: The 15N chemical shift anisotropy (CSA) was measured which tautomeric structure (or
protonation state) has the largest CSA span (Δσ)? Why?
Q4: The 15N–1H dipolar couplings were measured using DIPSHIFT experiment, what
information can be obtained from this measurement? And how?
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