Esterification of borate with NAD⁺and NADH as studied by electrospray ionization mass spectrometry and¹¹B 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.

Cellular changes in boric acid-treated DU-145 prostate cancer cells

“…There is no evidence supporting metabolism of BA in any animal species (EPA, 1991). BA does bind to molecules with cishydroxyl groups, as established through mass spectrometry and NMR analysis identifying a high affinity for the ribose moieties of NAD þ , and a somewhat lower affinity for mononucleotides (Kim et al, 2003). Nucleotide phosphorylation and loss of charge greatly reduces substrate affinity for BA .…”

Borate–nucleotide complex formation depends on charge and phosphorylation state

“…1 -4 Complex formation between boric acid and polyhydroxy compounds depends on the pH of the solution and the structure of the polyhydroxy compounds, and we have previously shown that this is true for boric acid and NAD C . 5 Van den Berg et al showed that in the case of diols, cis-1,2-are favored over trans-or 1,3-diols, and five-membered ring are preferred over six-membered ring 1,2-diols. 6 Therefore, a ribose ring with 2,3-cis-diol may be an important reactive site for interaction with boric acid.…”

“…At pH 10.3, all the boric acid-nucleotide complex detected by flow injection analysis with electrospray ionization mass spectrometry (ESI-MS) was a fragment of borate-nucleotide complex due to a loss of a hydroxyl group in the gas phase. 5 Henceforth, most of the nucleotide complexes in solution prior to ionization are assumed to be borate-nucleotide complexes.…”

“…21 -23 However, direct measurements by ESI-MS is superior to those methods. 5 Because of the sensitivity and resolution, it is possible to use concentrations that are physiologically more relevant to investigate the complexation. In the present study, we extended our previous work with a direct determination and comparison of the association constants K A of different borate-nucleotide complexes.…”

Broad-Spectrum Antibacterial Characteristics of Four Novel Borate-Based Bioactive Glasses

“…Borate alone has also been shown to have antimicrobial properties, and has actually been used as an ancient remedy to soothe skin infections and wounds [10]. While the antimicrobial capabilities of borate-based biomaterials are not well documented, borate chemistry in solution has been studied, and potential mechanisms include energy depletion by binding NAD and NADH [11] [12], and initiating DNA damage by binding to ribose groups [11]- [13].…”