Transferred cross-relaxation and cross-correlation in NMR: effects of intermediate exchange on the determination of the conformation of bound ligands.
Exchange transferred effects in solution-state NMR experiments allow one to determine the conformation of ligands that are weakly bound to macromolecules. Exchange-transferred nuclear Overhauser effect spectroscopy ('TR-NOESY') provides information about internuclear distances in a ligand in the bound state. Recently the possibility of obtaining dihedral angle information from a ligand in the bound state by exchange-transferred cross-correlation spectroscopy ('TR-CCSY') has been reported. In both cases the analysis of the signal amplitudes is usually based on the assumption that rapid exchange occurs between the free and bound forms of the ligand. In this paper we show that the fast exchange condition is not easily attained for observing exchange-transferred cross-correlation effects even in systems where exchange-transferred NOE can be observed. Extensive simulations based on analytical expressions for signal intensities corresponding to fast, intermediate, and slow chemical exchange have been carried out on a test system to determine the exchange regimes in which the fast exchange condition can be fulfilled for successfully implementing TR-NOESY and TR-CCSY.
Ravindranathan
Sapna
S
Institut de Chimie Moléculaire et Biologique, Ecole Polytechnique Fédérale de Lausanne, BCH, 1015 Lausanne, Switzerland.
Mallet
Jean-Maurice
JM
Sinay
Pierre
P
Bodenhausen
Geoffrey
G
D000465:Algorithms; D001665:Binding Sites; D003198:Computer Simulation; D003208:Concanavalin A / Q000737:chemistry*; D004735:Energy Transfer; D008024:Ligands; D046911:Macromolecular Substances; D008358:Mannose / Q000737:chemistry*; D008956:Models, Chemical; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry; D012815:Signal Processing, Computer-Assisted; D013223:Statistics as Topic
D008024:Ligands; D046911:Macromolecular Substances; D011506:Proteins; D003208:Concanavalin A; D008358:Mannose