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Esterification of borate with NAD + and NADH as studied by electrospray ionization mass spectrometry and 11 B NMR spectroscopy
Author(s) -
Kim Danny H.,
Marbois Beth N.,
Faull Kym F.,
Eckhert Curtis D.
Publication year - 2003
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.476
Subject(s) - chemistry , electrospray ionization , nad+ kinase , boric acid , boron , mass spectrometry , nicotinamide , electrospray , nuclear chemistry , medicinal chemistry , inorganic chemistry , stereochemistry , organic chemistry , chromatography , enzyme
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 µ 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. Copyright © 2003 John Wiley & Sons, Ltd.