BioPHYSICAL chemistry

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.