Erythrocytes, proton relaxation

Proton relaxation dispersion data for representative suspensions of washed and oxygenated AA and SS erythrocytes at 35 C. 

All of the authors imply that separation of water phases probably occurs at the cellular level. The semi-permeable nature of the cell membrane towards ions and solutes which are capable of relaxing water protons provides compartments in which relaxation rates can be significantly different, even when water transport across the membrane is very rapid. Indeed this property of whole tissue has been used in the development of an NMR method of determining water transport across erythrocyte membranes (11). 

T-90°-data acquisition [9] in which the time interval, x, is chosen such that the water resonance, which is expected to have the longest T, in the sample, has zero magnetization after the 90° pulse [113, 114], The CPMG spin-echo pulse sequence 90°-(t-180°-t) n-data acquisition (n = number of repetitions), has been used with the pulse interval, r, adjusted to attenuate the water signal, for example, from erythrocyte and protein suspensions [113], The technique is improved by the addition of ionic species such as ammonium chloride which increases the chemical exchange of the water protons and thus shortens T2 relative to the compounds of interest. This method is known as WATR (Water Attenuation by T2 Relaxation) [114]. Solvent suppression can also be achieved by selective excitation of the spectrum with special pulses such that the water resonance occurs at a point of null excitation [115-119]. However, distortion of peaks near the null point may occur. 

Gillis, P. Koenig, S. H. Transverse relaxation of solvent protons induced by magnetized spheres application to ferritin, erythrocytes, and magnetite. Magn. Reson. Med, 1987,5,323-345. 

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