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SOLUTION STRUCTURE OF THE MITHRAMYCIN DIMER-DNA COMPLEX
SOLUTION NMR
NMR Refinement
Method
Details
Software
MOLECULAR DYNAMICS, MATRIX RELAXATION
TWO STARTING MODELS WERE OBTAINED BY DOCKING THE MG2+ COORDINATED MITHRAMYCIN DIMER IN THE MINOR GROOVE OF A AND B FORM D(TCGCGA) DUPLEX. THESE MODELS WERE SUBSEQUENTLY REFINED BY DISTANCE RESTRAINED MOLECULAR DYNAMICS USING A SET OF INTER-PROTON DISTANCE RESTRAINTS DERIVED FROM THE NMR DATA. THE TWO DISTANCE-REFINED STRUCTURES WERE REFINED FURTHER USING RELAXATION-MATRIX BASED NOE INTENSITY-RESTRAINED MOLECULAR DYNAMICS. THE FINAL TWO STRUCTURES WERE OBTAINED BY TAKING THE AVERAGE COORDINATES OF THE LAST 1 PS OF THE DYNAMICS DURING RELAXATION MATRIX REFINEMENT AND MINIMIZED. THE R VALUE WAS USED TO REFINE THE STRUCTURE DURING RELAXATION MATRIX REFINEMENT. THE R FACTOR AND THE RMS DEVIATIONS FROM IDEAL GEOMETRY FOR THE TWO FINAL STRUCTURES ARE: MODEL 1 MODEL 2 R FACTOR 0.146 0.136 BOND (ANGSTROMS) 0.016 0.013 ANGLES (DEGREES) 3.410 3.369. THE STRUCTURE EXHIBITS APPROXIMATE TWO-FOLD SYMMETRY, PERPENDICULAR TO THE HELICAL AXIS AND PASSING THROUGH THE MAGNESIUM IN THE COMPLEX. THE TRANSFORMATION PRESENTED ON *MTRIX 1* RECORDS BELOW WILL YIELD APPROXIMATE COORDINATES FOR CHAIN B OF MODEL 1 WHEN APPLIED TO CHAIN A OF MODEL 1. THE TRANSFORMATION PRESENTED ON *MTRIX 2* RECORDS BELOW WILL YIELD APPROXIMATE COORDINATES FOR CHAIN B OF MODEL 2 WHEN APPLIED TO CHAIN A OF MODEL 2.
X-PLOR
NMR Ensemble Information
Conformer Selection Criteria
all calculated structures submitted
Conformers Calculated Total Number
2
Conformers Submitted Total Number
2
Additional NMR Experimental Information
Details
THE HYDROXYL PROTONS IN THE RELAXATION MATRIX REFINED STRUCTURES ARE NOT WELL DETERMINED. THE HYDROPHILIC SIDE CHAIN, THE B SUGAR RESIDUE DDA 1 AND DDA 7, AND RESIDUES T 1 AND C 2 ARE UNDETERMINED.