acidic is ~2, basic is ~8.5

 Thanks Dear Gangamani, But i found pKa value of NADH in biochemistry book that is  ~ -4 !!! can you please suggest me reference article??

The pKa value depends on the solvent used for determination. Therefore these may differ.The original question was whether phosphate group in NADH can donate proton? All evidence shows that it can.

Dear Mahmood,

I do not know where the values given by Gangamani S Beligere come from. I it would be very helpful to know a citation for these data.

You can look at the theoretical values provided by ChemAxon and available at Drugbank:

https://www.drugbank.ca/drugs/DB00157

According to these calculations, the lowest one is very acid and probably will be very difficult to measure experimentally, but the highest one is ~5, that one can be calculated experimentally.

The closest molecule I have seen reported on handbooks of experimental data on aqueous ionization equilibria is phosphoribosil pyrophosphate, because I could not find data for ADP, though it is possible, this has been analysed experimentally, and data can be found in old handbooks, such as:

Kotrly, S., and Sucha, L. (1985) Handbook of Chemical Equilibria in Analytical Chemistry, pp. 111, 176. Ellis Horwood, London.

Serjeant, E. P., and Dempsey, B. (1979) Ionisation Constant of Organic Acids in Aqueous Solutions, IUPAC Chemical Data Series No. 3., p. 221, Pergamon Press. New York.

Best wishes

Rogelio