Isotope-Labelling of Methyl Groups for NMR Studies of Large Proteins - Recent Developments in Biomolecular NMR - page 7

Figure 1.3 Location of different methyl groups in 2D ( 1 H, 13 C) correlation spectra.

Average ( 1 H, 13 C) chemical shifts were taken from the BioMagResBank
(BMRB, http://www.bmrb.wisc.edu/). The x and y boundaries of the solid
and semi-transparent coloured ellipses demonstrate the first and second
standard deviations, respectively, associated with each chemical shift.

modified depending on the particular system and the question(s) being asked.
The basis of many of these labelling strategies lies in the biosynthesis of
methyl-group containing amino acids (Figure 1.4).
The objective of this chapter is not to provide detailed labelling protocols
but rather to give an introductory summary. Relevant references are cited
and the reader is encouraged to read these for a more detailed explanation.
Unless otherwise stated, the procedures and examples described below refer
to the over-expression of recombinant proteins from E. coli grown in 100 %
deuterated minimal medium. In order to avoid a great deal of confusion with
nomenclature, the chemical name used in the original publication is given
together, in parentheses, with the IUPAC name and Chemical Abstract

Services (CAS) number of the unlabelled molecule.

1.2.2.1 Alanine
Alanine is the smallest residue that contains a methyl group and is one of the
most common amino acids found in proteins. The b-methyl group of alanine is
directly connected to the polypeptide backbone and therefore it can provide
information about local backbone structure using the chemical shift index 24 as
well reporting on dynamics. 25 Alanine is frequently found on the protein
surface and can thus be used to detect and characterise biomolecular
interactions. 26,27 Furthermore, alanine is commonly used as a replacement in
mutagenesis studies.