Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Quantifying hydrogen-bonding strength
T2 - The measurement of 2hJNN couplings in self-assembled guanosines by solid-state 15N spin-echo MAS NMR
AU - Pham, Tran N.
AU - Griffin, John M.
AU - Masiero, Stefano
AU - Lena, Stefano
AU - Gottarelli, Giovanni
AU - Hodgkinson, Paul
AU - Fillip, Claudiu
AU - Brown, Steven P.
PY - 2007/7/14
Y1 - 2007/7/14
N2 - 2hJNN hydrogen-bond mediated J couplings are measured in the solid state for two synthetic deoxyguanosine derivatives by 15N MAS NMR spin-echo experiments. The use of rotor-synchronised Hahn-echo pulse train (RS-HEPT) 1H decoupling, with a duty cycle of 6%, allows spin-echo durations out to 200 ms, hence enabling the accurate determination of J couplings as small as 3.8 Hz. A single-crystal X-ray diffraction structure exists for the shorter alkyl chain derivative dG(C3)2: the observation of significantly different 2hJNN couplings, 6.2 ± 0.4 and 7.4 ± 0.4 Hz, for the two resolved N7 resonances is to be expected given the NH…N hydrogen-bonding distances of 2.91 and 2.83 Å for the two distinct molecules in the asymmetric unit cell. For the longer alkyl chain derivative, dG(C10)2, for which there is no single-crystal diffraction structure, a 15N refocused INADEQUATE spectrum (Pham et al., J. Am. Chem. Soc., 2005, 127, 16018-16019) has demonstrated the presence of N2-H…N7 intermolecular hydrogen-bonds indicative of a quartet-like structure. The 2hJNN hydrogen-bond mediated J coupling of 5.9 ± 0.2 Hz is at the lower end of the range (5.9-8.2 Hz) of 2hJNN couplings determined from solution-state NMR of guanosine quartets in quadruplex DNA. A full discussion of the determination of error bars on the fitted parameters is given; specifically, error bars determined by a non-linear fitting (using the covariance matrix) or in a Monte-Carlo fashion are found to give effectively identical results.
AB - 2hJNN hydrogen-bond mediated J couplings are measured in the solid state for two synthetic deoxyguanosine derivatives by 15N MAS NMR spin-echo experiments. The use of rotor-synchronised Hahn-echo pulse train (RS-HEPT) 1H decoupling, with a duty cycle of 6%, allows spin-echo durations out to 200 ms, hence enabling the accurate determination of J couplings as small as 3.8 Hz. A single-crystal X-ray diffraction structure exists for the shorter alkyl chain derivative dG(C3)2: the observation of significantly different 2hJNN couplings, 6.2 ± 0.4 and 7.4 ± 0.4 Hz, for the two resolved N7 resonances is to be expected given the NH…N hydrogen-bonding distances of 2.91 and 2.83 Å for the two distinct molecules in the asymmetric unit cell. For the longer alkyl chain derivative, dG(C10)2, for which there is no single-crystal diffraction structure, a 15N refocused INADEQUATE spectrum (Pham et al., J. Am. Chem. Soc., 2005, 127, 16018-16019) has demonstrated the presence of N2-H…N7 intermolecular hydrogen-bonds indicative of a quartet-like structure. The 2hJNN hydrogen-bond mediated J coupling of 5.9 ± 0.2 Hz is at the lower end of the range (5.9-8.2 Hz) of 2hJNN couplings determined from solution-state NMR of guanosine quartets in quadruplex DNA. A full discussion of the determination of error bars on the fitted parameters is given; specifically, error bars determined by a non-linear fitting (using the covariance matrix) or in a Monte-Carlo fashion are found to give effectively identical results.
KW - X-RAY-DIFFRACTION
KW - CARBON-CARBON CONNECTIVITIES
KW - C-13-C-13 J-COUPLINGS
KW - SCALAR COUPLINGS
KW - CROSS-POLARIZATION
KW - DISORDERED SOLIDS
KW - LIPOPHILIC DEOXYGUANOSINE
KW - CORRELATION SPECTROSCOPY
KW - PHOSPHINE COMPLEXES
KW - SHIFT CORRELATION
U2 - 10.1039/b703513f
DO - 10.1039/b703513f
M3 - Journal article
C2 - 17664965
VL - 9
SP - 3416
EP - 3423
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 26
ER -