THE DESIGN OF SPIN PROBES FOR ELECTRON MAGNETIC-RESONANCE SPECTROSCOPY AND IMAGING

The problems that have to be addressed in designing suitable spin prob es are manifold. In this article it will be shown that some the proper ties the probes need to possess are (i) a simple EMR spectrum (in some types of imaging or oximetry a single line is desirable), (ii) sharp lines with no unresolved splittings, to provide maximum sensitivity to detection, (iii) chemical, metabolic and thermal stability, (iv) easy possible synthesis to permit substitution with isotopes, prosthetic g roups or groups to control the partition coefficients in lipid/water s ystems, and (v) electronic anisotropy, if rotational correlation times are to be determined, for example for the measurement of local viscos ity.