Publication year: 2010
Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 6 March 2010
Stephen, Kadlecek , Kiarash, Emami , Masaru, Ishii , Rahim, Rizi
Intramolecular spin-order transfer is a useful technique for signal enhancement of insensitive and low-concentration molecular species. We present a closed-form, optimized pulse sequence which maximizes the efficiency of transfer between a singlet (para) nuclear pair and a vicinal heteronucleus. Neglecting the decay of coherences while the nuclei are in the transverse plane, the scheme is unity efficient for all combinations of internuclear scalar couplings. Efficiency loss due to T2-like decay is also minimized by keeping the sequence as short as possible. We expect this result to be useful for hyperpolarization experiments in which the spin-order originates in parahydrogen, as well as studies of singlet state decay aimed at longer-term storage of spin-order in hyperpolarized Magnetic Resonance Imaging.
Publication year: 2010
Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript,Dmytro Kotsyubynskyy, Jozef Kowalewski, Pekka Tallavaara, Ville-Veikko Telkki, Jukka Jokisaari,and Evgeny Polyakov
We have shown that proton-coupled carbon-13 2D NOESY experiments, performed on degenerate spin systems, can provide unique quantitative information about anisotropic reorientational motions and molecular geometry. Relevant theory for AX2 and AX3 spin systems is presented, assuming the dipole–dipole and random field relaxation mechanisms of 13C nucleus, and demonstrated on methyl iodide solution in chloroform. Agreement with experimental intensities of all the six independent peaks is very good in the whole range of mixing times (up to 45 s).
Quantitative determination of NOE rates in perdeuterated and protonated proteins: practical and theoretical aspectsPublication year: 2010
Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 15 March 2010
Beat, Vögeli , Michael, Friedmann , Dominik, Leitz , Alexander, Sobol , Roland, Riek
Precision and accuracy are the limiting factors in extracting structural and dynamic information from experimental NOEs. In this study, error sources at all stages of such an analysis are identified and errors are estimated. The data set of HN-HN cross-relaxation rates obtained from triple labeled ubiquitin presented in [Vögeli, B.; Segawa, T.F.; Leitz, D., Sobol, A.; Choutko, A.; Trzesniak, D.; van Gunsteren, W.; Riek, R., J. Am. Chem. Soc. 131 (47), 17215–17225, 2009] is extended to rates obtained from a double labeled sample. Analog data sets are presented for GB3. It is shown that quantitative NOE rates can be determined with high accuracy from both triple-labeled as well as double-labeled samples. The quality of experimental cross-relaxation rates obtained from 3D HXQC-NOESY and NOESY-HXQC experiments is discussed. It is shown that NOESY-HXQC experiments provide rates of the same quality as HXQC-NOESY if both diagonal and cross peaks for a spin pair can be resolved. Expressions for cross-relaxation rates for anisotropically tumbling molecules exhibiting fast and slow motion are derived. The impact of anisotropy on the prediction of cross-relaxation rates and on the conversion of experimental rates into effective distances is discussed. For molecules with anisotropy DII/D up to 5 the distance error is smaller than 2%. Finally, “averaged order parameters” are calculated for specific secondary structural elements showing similar trends for ubiquitin and GB3.
Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 19 March 2010
Nirbhay N., Yadav , Allan M., Torres , William S., Price
NMR q-space imaging is a powerful non-invasive technique used to determine structural characteristics of pores in applications ranging from medical to material science. To date, the application of q-space imaging has primarily been limited to microscopic pores in part because of limitations of the effective observation time due to relaxation. Here we report on the use of singlet spin states for NMR q-space imaging, which allow significantly greater observation times. This opens the way for studying larger pores in materials such as biological tissue, emulsions, and rocks.
Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 21 March 2010
Richard W., Quine , George A., Rinard , Sandra S., Eaton , Gareth R., Eaton
Experimental data obtained with an electron paramagnetic resonance (EPR) rapid scan spectrometer were translated through the reverse transfer functions of the spectrometer hardware to the sample position. Separately, theoretical calculations were performed to predict signal and noise amplitudes at the sample position for specified experimental conditions. A comparison was then made between the translated experimental values and the calculated values. Excellent agreement was obtained.