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From what I understand, NADH does not contain any sodium, so why is it being referred to as a sodium salt? Were sodium ions added to NADH? If so, why were they added? On a related note, why is its oxidized correspondent NAD+ referred to as "free acid"?

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http://upload.wikimedia.org/wikipedia/commons/thumb/0/02/NAD%2B_phys.svg/363px-NAD%2B_phys.svg.png

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The two phosphate groups each carry a negative charge at physiological pH.

NADH (sodium salt) means that at least one of the two negative charges are counterbalanced by Na+. If both are counterbalanced with Na+, it would be better to say "disodium salt".

http://www.scbt.com/datasheet-205762-nadh-disodium-salt.html

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    $\begingroup$ Good answer, although note that (i) the structure drawn is of NAD+, and (ii)in that structure there is a positive charge that would balance out one of the phosphates. So there's only a need for one Na+ to reach neutrality. In practice, the actual amount of sodium can vary considerably, because depending on the pH of the solution, there can be varying proportions of the 2- ion, the 1- ion, and the neutral ion. A good supplier with include the amount of sodium per mol of NAD(H) as well as the amount of water per mol of NAD(H) in a certificate of analysis. $\endgroup$ – Curt F. Apr 9 '15 at 21:51

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