On the Hydration State of Amino Acids and Their Derivatives at Different Ionization States: A Comparative Multinuclear NMR and Crystallographic Investigation
Table 1
14 N (at 28.9 MHz) and 17O (at 48.8 MHz) linewidths, , of protein amino acids in different ionization states*a.
Amino Acid
MWf
, Hzb,c
pH 0.5
pH 6.0
14N
17O
14N
17O
Gly
75.07
55 (67)
205 (233)
36 (40)
132 (131)
Ala
89.10
71 (79)
276 (274)
45 (49)
194 (172)
Sar
89.10
83 (80)
272 (274)
60 (49)
170 (172)
N,N-dimethyl-Gly
103.10
329 (314)
198 (212)
Ser
105.09
97 (94)
359 (320)
57 (58)
249 (218)
Pro
115.13
87 (104)
286 (349)
60 (64)
197 (247)
Val
117.15
102 (105)
376 (355)
72 (65)
280 (253)
Thr
119.12
118 (107)
410 (360)
71 (66)
300 (259)
Cys
121.26
104 (109)
e
59 (67)
254 (265)
4-hydroxy-Pro
131.13
366 (395)
275 (293)
Ile
131.18
115 (118)
453 (395)
65 (73)
335 (294)
Leu
131.18
124 (118)
397 (395)
71 (72)
298 (294)
Asn
132.12
d
e
d
274 (296)
Asp
133.11
140 (120)
d
65 (74)
285 (299)
Gln
146.15
d
e
d
330 (337)
Lys
146.19
d
443 (439)
d
354 (337)
Glu
147.13
146 (133)
d
89 (82)
316 (340)
Met
149.21
133 (135)
397 (448)
78 (83)
297 (346)
His
155.16
169 (140)
438 (465)
99 (86)
359 (363)
Phe
165.19
143 (150)
485 (494)
88 (93)
376 (392)
Arg
174.20
165 (159)
482 (520)
111 (98)
394 (418)
Tyr
181.19
134(164)
558 (540)
102 (102)
457 (438)
O-Methyl-Tyr
195.19
622 (581)
525 (479)
Trp
204.23
180 (186)
602 (607)
108 (115)
508 (505)
*Adapted, with permission, from J. Magn. Reson. [11]. Copyright 2003, by Elsevier Inc.
a0.1 M solutions in H2O containing 10-5 M EDTA (ethylenediamine-N,N,N′,Ν′-tetraacetate); °C.
b Linewidths at half-height, estimated errors <±5%.
cValues into parenthesis correspond to line widths resulting from regression analysis assuming isotropic molecular motion and linear approximation.
dOverlapping resonances.
eNot measured because of degradation.
fMW of the zwitterionic form.
