title: Intramolecular hydrogen bonding in flavin adenine dinucleotide.
abstract: Data obtained by means of proton magnetic resonance spectroscopy indicate that specific association of FMN occurs with AMP in aqueous solution, because much weaker interaction is observed with FMN of either GMP or CMP. A comparison of FAD with a 1:1 mixture of FMN and AMP suggests that the flavin is involved in an intramolecular hydrogen bonding with the adenine moiety of FAD. The temperature dependence of chemical shifts would seem to indicate that the pyrophosphate linkage acts to reinforce stacking interactions as well as hydrogen bonding in the coenzyme. The linkage also limits the number of cyclic hydrogen bonding configurations, and a model is proposed to describe a fraction of unstacked FAD in aqueous solution.A parallel study was made of NAD(+) and its analogues; in contrast to FAD, no clear evidence of cyclic hydrogen bonding was obtained with the pyridine coenzymes.
mesh_terms: D000249:Adenosine Monophosphate; D005486:Flavin Mononucleotide; D005182:Flavin-Adenine Dinucleotide; D006150:Guanine Nucleotides; D006859:Hydrogen; D009682:Magnetic Resonance Spectroscopy; D008961:Models, Structural; D008968:Molecular Conformation; D009243:NAD
chemical_list: D006150:Guanine Nucleotides; D009243:NAD; D005182:Flavin-Adenine Dinucleotide; D000249:Adenosine Monophosphate; D005486:Flavin Mononucleotide; D006859:Hydrogen