title: Esterification of borate with NAD+ and NADH as studied by electrospray ionization mass spectrometry and 11B NMR spectroscopy.
abstract: This paper describes for the first time the direct measurement of boric acid (B(OH)(3)) and borate (B(OH)(4) (-)) adduction to NAD(+) and NADH by electrospray ionization mass spectrometry (ESI-MS) and (11)B NMR spectroscopy. The analysis demonstrates that borate binds to both cis-2,3-ribose diols on NAD(+) forming borate monoesters (1 : 1 addition), borate diesters (1 : 2 addition) and diborate esters (2 : 1 addition), whereas, only borate monoesters were formed with NADH. MS in the negative ion mode showed borate was bound to a cis-2,3-ribose diol and not to the hydroxyl groups on the phosphate backbone of NAD(+), and MS/MS showed that the 1 : 1 addition monoester contained borate bound to the adenosine ribose. Boron shifts of borate monoesters and diesters with NAD(+) were observed at 7.80 and 12.56 ppm at pH 7.0 to 9.0. The esterifications of borate with NAD(+) and NADH were pH dependent with maximum formation occurring under alkaline conditions with significant formation occurring at pH 7.0. Using ESI-MS, the limit of detection was 50 micro M for NAD(+) and boric acid (1 : 1) to detect NAD(+)-borate monoester at pH 7.0. These results suggest esterification of borate with nicotinamide nucleotides could be of biological significance.
authors.affiliation: Department of Environmental Health Sciences, University of California, 10833 Le Conte Avenue, Los Angeles, California 90095, USA.
authors.forename: Danny H
authors.initials: DH
authors.lastname: Kim
authors.forename: Beth N
authors.initials: BN
authors.lastname: Marbois
authors.forename: Kym F
authors.initials: KF
authors.lastname: Faull
authors.forename: Curtis D
authors.initials: CD
authors.lastname: Eckhert
mesh_terms: D001881:Borates / Q000737:chemistry*; D004951:Esterification; D006153:Guanosine Diphosphate / Q000032:analysis / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009243:NAD / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D001881:Borates; D009243:NAD; D006153:Guanosine Diphosphate