title: H nuclear magnetic resonance study of restricted internal rotation of N-6,N-6-dimethyladenine in aqueous solution.
abstract: Kinetics of internal rotation about the C(6)-N(6) bond of N-6,N-6-dimethyladenine (M2-6A) was investigated by -1H nuclear magnetic resonance line-shape analysis of the methyl resonances (220 MHz). Rates of rotation were determined for M2-6A deuterated at N(1) and for neutral M2-6A. Activation parameters for monodeuterated M2-6A at 22 degrees are Ea = 13.8kcal/mol, log A = 12.6, incrementG++=14.9 kcal/mol, incrementH++ = 13.1 kcal/mol, incrementS++ = minus 5.8 eu; for neutral M2-6A: Ea = 15.5 kcal/mol, log A = 14.9, incrementG++ = 12.6 kcal/mol, incrementH++ = 14.9 kcal/mol, incrementS++ =7.8 eu. Vertical stacking of bases interferes with internal rotation of the dimethylamino group.
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives*; D002151:Calorimetry; D003903:Deuterium; D049671:History, 18th Century; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008697:Methane; D008968:Molecular Conformation; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D003903:Deuterium; D000225:Adenine; D008697:Methane