Specific interaction of isocytosine and amino acid carboxylic group shifts the base tautomeric equilibrium.
By 1H NMR, UV and IR spectroscopies in anhydrous DMSO and quantum-chemical calculations by MNDO/H in vacuum specific interactions of isocytosine with neutral and deprotonated carboxylic groups of amino acids were investigated. In vacuum interaction with carboxylate ion provokes in isoCyt transition from the ground-state enolic form to the high energy N3H-keto tautomer. In DMSO keto tautomer N3H of isoCyt is stabilized but interactions with carboxylate ion essentially shifts equilibrium to enolic form. Neutral carboxylic group forms the most stable complex with the ground-state enolic tautomer in vacuum but in DMSO it proves to shift the keto(N3H)-enolic equilibrium to the right.
Samijlenko
S P
SP
Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv.
Potyahaylo
A L
AL
Stepanyugin
A V
AV
Hovorun
D M
DM
D000596:Amino Acids / Q000378:metabolism*; D002264:Carboxylic Acids / Q000378:metabolism*; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014618:Vacuum
D000596:Amino Acids; D002264:Carboxylic Acids; D011522:Protons; C093270:isocytosine; D003596:Cytosine; D004121:Dimethyl Sulfoxide