Table 2.

Acid dissociation constants of buffer molecules used in the peptide array binding experiments at 25 °C in aqueous solutions.

Substance	pKa(1)	pKa2	pKa3	Source	Charge of dominant species			Chemical structure at pH 7
					At pH 6	At pH 7.4	At pH 8
Tris	8.07			55	+ 1	+ 1	+ 1
Phosphate	2.16	7.21	12.33	68	−1	−2	−2
Citrate	3.13	4.76	6.40	69	−2	−3	−3