Paramagnetic line broadening

Plus 52 upper distance limits from the cluster for protons that could not be detected, 126 lower distance limits from the cluster for protons without any appreciable paramagnetic line broadening, and 42 distance constraints derived from hydrogen... 

Characterization of the modified plastocyanins was by Inductively Coupled Plasma Emission Spectroscopy to analyze for Ru and Cu (1 1 ratio), and by HNMR spectroscopy. In the HNMR characterization the C2H resonance of His59 at 8.2 ppm is seen to be lost due to paramagnetic line broadening effect of the attached Ru(III), Fig. 13 [50]. In a further test it is known that the His59 s of both native plastocyanins react with diethyl pyrocarbonate (DEPC) to give an JV-ethoxyhistidine derivative, (12), which absorbs strongly at 238 nm (e 2750M- cm-i), Fig. 14 [133]. 

Further determinations of intramolecular distances have been made by Musci et al. (1987). Met-90 in a-lactalbumin was spin-labeled. Paramagnetic line broadening of the spin-laheled ESR lines by Gd(III), substituted at the high-affinity site, yielded a distance of 8 1 A between the spin label and the metal binding site. Distances between the Met and several resolvable protons were also determined from paramagnetic line broadening, with the use of NMR. 

Xiang, T.-X. Anderson, B. D., Development of a combined NMR paramagnetic ion-induced line-broadening dynamic light scattering method for permeability measurements across lipid bilayer membranes, J. Pharm. Sci. 84, 1308-1315 (1995). 

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