Search

A general approach for mapping local p[K.sub.a] values of protein side chains with spin labeling EPR is described. The results showed that the high accuracy of p[K.sub.a] determination for pH-sensitive nitroxides is achieved irrespective of the frequency of measurements or the regime of spin exchange.

Time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) and laser flash photolysis (LFP) methods are used to measure rate constants for coupling between acrylate-type radicals and a series of newly synthesized stable imidazolidine N-oxyl radicals. The carbon-centered radicals are generated in the presence of the stable nitroxides by laser flash photolysis of the corresponding ketone precursors RC(O)R.

A general method of measuring local pK values of peptides with high-field EPR using methane-thiosulphonate derivatives of imidazolidine nitroxides is described. Differentiating polarity and proton exchange effects using A(sub iso) versus g(sub iso) relationship plots generated from high-field EPR are reported.

An investigation was conducted to examine the synthesis of a spin-labeled stacking polymer from Ni(II) and Pd(II) complexes and to analyze the magnetic properties of these complexes. These metal complexes carried a stable nitroxide 2,2,5,5-tetramethyl-l-oxylpyrrolidine-3,4-dione dioxime. The investigation revealed a layered polymeric structure of the solids which could be attributed to the formation of exchange cluster which contained a diamagnetic metal ion property.

Tert-butyl diphenylmethyl nitroxide (compound L) is the first new metal-complex forming member of the alpha-H containing nitroxide group of chemicals. Its coordination properties are in line with other fully alpha-substituted analogs, but it is very stable and the coordination center is more accessible than the other analogs. When compound L is reacted with with bis (1,1,1,5,5,5,-hexafluoro-2,4-pentanedionato) copper(II) hydrate, or Cu(hfac)2H2O, a stable mixed-ligand complex of Cu(hfac)2L is produced. The complex forms needle-like crystals and is diamagnetic at room temperature.