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?