| MOLECULAR DYNAMICS, MATRIX RELAXATION | TWO STARTING STRUCTURES WERE GENERATED BY MANUALLY DOCKING THE DRUG ONTO A- AND B-FORM DNA USING INSIGHT II AND WERE SUBSEQUENTLY REFINED BY DISTANCE-RESTRAINED MOLECULAR DYNAMICS USING A SET OF INTER-PROTON DISTANCE RESTRAINTS DERIVED FROM THE 2-D NMR DATA. ONE INITIAL VELOCITY SEED WAS USED FOR EACH STARTING STRUCTURE WHICH YIELDS TWO DISTANCE-REFINED STRUCTURES. THEY WERE REFINED FURTHER WITH TWO INITIAL VELOCITIES USING RELAXATION-MATRIX BASED NOE INTENSITY-RESTRAINED MOLECULAR DYNAMICS TO GENERATE THE FINAL FOUR STRUCTURES. THE FINAL FOUR STRUCTURES WERE OBTAINED BY TAKING THE AVERAGE COORDINATES OF THE LAST 1.0 PS OF THE DYNAMICS DURING RELAXATION MATRIX REFINEMENT AND ENERGY MINIMIZED. THE R(1/6) VALUE WAS USED TO REFINE THE STRUCTURE DURING RELAXATION MATRIX REFINEMENT. THE SUMMATIONS RUN THROUGH ALL OBSERVED, QUANTIFIABLE NOE CROSSPEAKS IN NOESY SPECTRA RECORDED IN D2O AND MIXING TIMES OF 40, 80, 120 AND 160 MS. THE R(1/6) FACTOR AND THE RMS DEVIATIONS FROM IDEAL GEOMETRY FOR THE FOUR FINAL STRUCTURES ARE: MODEL1-MODEL4 R(1/6) FACTOR 0.042-0.045 BOND (ANG) 0.009-0.010 ANGLES (DEG) 3.078-3.780 IMPROPERS (DEG) 0.310-0.321. THE STRUCTURE HAS APPROXIMATE TWO-FOLD SYMMETRY RELATING THE TWO STRANDS OF THE DNA WITH THE SYMMETRY AXIS PERPENDICULAR TO THE HELICAL AXIS. THE TRANSFORMATION MATRIX WAS CALCULATED FOR THE AVERAGED STRUCTURE OF THE FOUR MODELS. | X-PLOR |
