TY - JOUR
T1 - Tryptophan Chemical Shift in Peptides and Proteins
T2 - A Solid State Carbon-13 Nuclear Magnetic Resonance Spectroscopic and Quantum Chemical Investigation
AU - Sun, Haihong
AU - Oldfield, Eric
PY - 2004/4/14
Y1 - 2004/4/14
N2 - We have obtained the carbon-13 nuclear magnetic resonance spectra of a series of tryptophan-containing peptides and model systems, together with their X-ray crystallographic structures, and used quantum chemical methods to predict the 13C NMR shifts (or shieldings) of all nonprotonated aromatic carbons (Cγ, Cδ2, and Cε2). Overall, there is generally good accord between theory and experiment. The chemical shifts of Trp Cγ in several proteins, hen egg white lysozyme, horse myoglobin, horse heart cytochrome c, and four carbonmonoxyhemoglobins, are also well predicted. The overall Trp C γ shift range seen in the peptides and proteins is 11.4 ppm, and individual shifts (or shieldings) are predicted with an rms error of ∼1.4 ppm (R value = 0.86). Unlike Cα and NH chemical shifts, which are primarily a function of the backbone φ,ψ torsion angles, the Trp Cγ shifts are shown to be correlated with the side-chain torsion angles χ1 and χ2 and appear to arise, at least in part, from γ-gauche interactions with the backbone C′ and NH atoms. This work helps solve the problem of the chemical shift nonequivalences of nonprotonated aromatic carbons in proteins first identified over 30 years ago and opens up the possibility of using aromatic carbon chemical shift information in structure determination.
AB - We have obtained the carbon-13 nuclear magnetic resonance spectra of a series of tryptophan-containing peptides and model systems, together with their X-ray crystallographic structures, and used quantum chemical methods to predict the 13C NMR shifts (or shieldings) of all nonprotonated aromatic carbons (Cγ, Cδ2, and Cε2). Overall, there is generally good accord between theory and experiment. The chemical shifts of Trp Cγ in several proteins, hen egg white lysozyme, horse myoglobin, horse heart cytochrome c, and four carbonmonoxyhemoglobins, are also well predicted. The overall Trp C γ shift range seen in the peptides and proteins is 11.4 ppm, and individual shifts (or shieldings) are predicted with an rms error of ∼1.4 ppm (R value = 0.86). Unlike Cα and NH chemical shifts, which are primarily a function of the backbone φ,ψ torsion angles, the Trp Cγ shifts are shown to be correlated with the side-chain torsion angles χ1 and χ2 and appear to arise, at least in part, from γ-gauche interactions with the backbone C′ and NH atoms. This work helps solve the problem of the chemical shift nonequivalences of nonprotonated aromatic carbons in proteins first identified over 30 years ago and opens up the possibility of using aromatic carbon chemical shift information in structure determination.
UR - http://www.scopus.com/inward/record.url?scp=1842688079&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=1842688079&partnerID=8YFLogxK
U2 - 10.1021/ja030612u
DO - 10.1021/ja030612u
M3 - Article
C2 - 15070392
AN - SCOPUS:1842688079
SN - 0002-7863
VL - 126
SP - 4726
EP - 4734
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 14
ER -