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.