structures if the structures are not too large. Although NMR techniques
are being developed to overcome this limitation, the upper boundary
for normal NMR spectroscopy is a molecular mass of about 50,000 Da.
Therefore, an active area of research is the development of novel tech-
niques that can be used for larger structures (Riek et al. 2000; Hakumaki
& Brindle 2003; Tugarinov et al. 2004; Vaynberg & Qin 2006). In con-
ventional two-dimensional NMR, the spectra of large proteins typically
CHAPTER 16 MAGNETIC RESONANCE 353
(a)
3
2
1
4
4
CαH
CβH 3
321
ppm
ppm
Alanine
1.3
4.35
CβH 3
H
Cα COO
ND 2
(b)
3
2
1
4
4321
ppm
ppm
CδH 3
CδH 3
CδH 3
L-Leucine
H Cγ CβH 2
H
Cα
CαH
CβH 2
COO CγH
ND 2
(c)
3
2
1
4
4321
ppm
ppm
H
Threonine
DO Cβ
CγH 3
CγH 3
H
Cα
CβH
CαH
COO
ND 2
(d)
3
2
1
4
4
CαH
CβH
CγH 3
CγH 3
321
ppm
ppm
Valine
H
Cα COO
ND 2
CγH 3
H
Cβ
CγH 3
Figure 16.9Examples of NMR spectra of (a) alanine, (b) leucine, (c) threonine, and (d) valine.