Lanthanide-induced shift fluorescence

The hydration number q-. this parameter influences strongly the IS contribution (equations (3) and (4)). If this number increases from 1 to 2, the relaxivity increases by about 30%, but most of the Gd-complexes have a q number equal to one. This number can be measured by fluorescence study of europium or terbium complexes or by NMR measuring the lanthanide induced shift (LIS). 

In principle, paramagnetic ions also may be used to induce hyperfine shifts in nucleic acids to aid detection of binding sites. Ions with high relative magnetic anisotropy and short unpaired electron relaxation times (i.e., Co Fe and trivalent lanthanide ions except for Gd ) are candidates for such studies. Indeed, Tb and Eu ions have been used as fluorescent probes of nucleic acid structures it is expected that NMR studies also would be informative. " ... 

Of particular interest in the study of effects of metal ion binding on the conformation of a-lactalbumin are the contributions of Berliner and co-workers. Murakami etal. (1982), in a study of bovine, caprine, human, and guinea pig a-lactalbumin, observed metal ion-induced conformational change resulting in a unique hypsochromic shift and quenching of tryptophan fluorescence. They found that Ca(II) and the lanthanides Tb(III), Eu(III), Gd(III), Yb(III), Pr(III), and Dy(III) could be bound extremely strongly to a specific site. They also found that Mn(II), Ca(II), and Mg(II) could be weakly bound to the same site. 

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