Table 1.
Physical properties of the Good [1, 2, 3] buffers. The maximum distance between atomic centers of each buffer was measured from a 3-D model and used as an estimate of its molecular Stokes radius (a). The same was done for weak electrolytes with known diffusion coeficients (D). Linear regression of D vs 1/a for the weak electrolytes was used to predict the expected value of the Ds (E[D]) of the Good buffers. Atomic distances were measured using the Chem-3D plugin from CambridgeSoft Corporation (www.camsoft.com) in combination with 3-D data models of the compounds available from the online ChemFinder Database.
Buffer |
pKa |
Atomic dist |
2a [Å ] |
E [D] |
MES |
6.15 |
O7-H20 |
7.08 |
0.820 |
ACES |
6.90 |
H12-H13 |
10.03 |
0.668 |
MOPS |
7.15 |
H14-H21 |
10.15 |
0.664 |
HEPES |
7.55 |
O14-H16 |
11.41 |
0.618 |
TRICINE |
8.15 |
H13-H16 |
8.56 |
0.731 |
TRIS |
8.30 |
H11-H15 |
6.28 |
0.886 |