T1ρ of protein solutions at very low fields: Dependence on molecular weight, concentration, and structure
✍ Scribed by Anette Virta; Markku Komu; Martti Kormano
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 590 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
The effect of molecular weight, concentration, and structure on 1/T~1~ρ, the rotating frame relaxation rate, was investigated for several proteins using the on‐resonance spin‐lock technique, for locking fields B~1~ < 200 μT. The measured values of 1/T~1~ρ, were fitted to a simple theoretical model to obtain the dispersion curves 1/T~1~ρ(ω~1~) and the relaxation rate at zero B~1~ field, 1/T~1~ρ,(O). 1/T~1~ρ, was highly sensitive to the molecular weight, concentration, and structure of the protein. The amount of intra‐ and intermolecular hydrogen and disulfide bonds especially contributed to 1/T~1~ρ. In all samples, 1/T~1~ρ(O) was equal to 1/T~2~ρ measured at the main magnetic field B~o~ = 0.1 T, but at higher locking fields the dispersion curves mono‐tonically decreased. The results of this work indicate that a model considering the effective correlation time of molecular motions as the main determinant for 1/T~1~ρ relaxation in protein solutions is not valid at very low B~1~ fields. The underlying mechanism for the relaxation rate 1/T~1~ρ at B~1~ fields below 200 μT is discussed.