ON THE USE OF THE PHASE MEMORY TIME T-2 FOR THE QUANTITATIVE CHARACTERIZATION ION OF THE ROTATIONAL MOTIONS OF PROTEINS IN LIPID BILAYER SYSTEMS

Numerical simulations of the echo responses from a nitroxide label rig idly attached to a large protein undergoing ultraslow rotational motio ns in a lipid bilayer are presented, The echoes are formed by the appl ication of Hahn, COSY, and 2D-ELDOR sequences utilizing both soft and hard microwave pulses. The simulations address the question of whether the echo responses elicited by these sequences are affected by restri cted angular excursions of the long axis of the protein relative to th e normal to the bilayer plane, The results indicate that all three pul se sequences yield the same quantitative motional information regardle ss of the nature of the microwave pulses and there is no theoretical r eason for preferring one sequence above the others. (C) 1988 Academic Press.