J. L. Dallas

Conformational flexibility of bleomycin-A2: a carbon-13 spin-lattice relaxation time study.

Summary The extent of segmental motion of the backbone and sidechain carbons of the glycopeptide antibiotic, bleomycin-A 2 in aqueous solution, has been determined from the natural abundance carbon-13 spin-lattice relaxation times (T 1 ) measured at 67.89 MHz. The backbone carbons of the central residues have an average T 1 of 163 msec, corresponding to an isotropic rotational correlation time of 3.9×10 −10 sec. The backbone and sidechain carbons exhibit varying degrees of motional freedom. The solution conformation of bleomycin-A 2 is discussed in terms of the conformational flexibility available to these carbons.

Synthesis and properties of a fluorine-containing sulfhydryl reagent for 19F NMR studies

Nuclear magnetic resonance (NMR) spectroscopy provides a unique, non-destructive method for the study of biochemical processes. The advent of NMR spectroscopy using nuclei other than protons has permitted the extension of such studies to systems using “C, “N, 19F, ‘*P and other nuclei. Of these nuclei, 19F and 3rP are the predom~~t naturally occurring isotopes of these elements and studies using these nuclei have the advantage of not requiring the higher concentrations or isotope enrichment often necessary for the carbon and nitrogen NMR experiments. Several fluorine-containing probes have been described for the modification of proteins for NMR studies. These include the trifluoroacetyl group to label lysine amino groups [I ] and trifluorobromopropanone [2,3] , S,S-(2,2,2-trifhroro-1 ,l-dideuteroethyl)~-methyl~t~operoxycarbonate [4] and the ~.tr~fluoromethy~ercuri-group [5] for sulthydryl residues. Each of these suffers from some disadvantages, including non-specificity of reaction and difficulty in the synthesis or introduction of the label into proteins. We would like to describe properties of a maleimide derivative for use in fluorine NMR studies which is simple to prepare and shows a good deal of specificity for sulfhydryl groups.