(13)C shielding tensors of crystalline amino acids and peptides: Theoretical predictions based on periodic structure models.
Precise theoretical predictions of NMR parameters are helpful for the spectroscopic identification of complicated biological molecules, especially for the carbon shielding tensors in amino acids. The (13)C shielding tensors of various crystalline amino acids and peptides have been calculated using the gauge-including projector augmented wave (GIPAW) method based on two different periodic structure models, namely that deduced from available crystallographic data and that from theoretically optimized structures. The incorporation of surrounding lattice effects is found to be crucial in obtaining reliable predictions of (13)C shielding tensors that are comparable to the experimental data. This is accomplished by refining the experimental crystallographic data of the amino acids and peptides at the GGA/PBE level by which more accurate intramolecular C--H bond lengths and intermolecular hydrogen-bonding interactions are obtained. Accordingly, more accurate predictions of (13)C shielding tensors comparable to the experimental results (within a maximum deviation of +/-10 ppm) were achieved, rendering more explicit (13)C shielding tensors assignments for solid biological systems particularly for amino acids with multiple carboxyl carbons, such as asparagine, glutamine, and glutamic acid.
Zheng
Anmin
A
State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, The Chinese Academy of Sciences, Wuhan 430071, China.
Liu
Shang-Bin
SB
Deng
Feng
F
D000596:Amino Acids / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D002247:Carbon Isotopes / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D055672:Static Electricity
D000596:Amino Acids; D002247:Carbon Isotopes; D010455:Peptides; D002244:Carbon