Buffer Bistris

FIGURE 12 Plots of the approach distance a (in angstroms) versus k for the protein human serum albumin (HSA) (pi = 5.85, Mr = 69,000) measured with the strong anion exchange sorbent, Mono-Q, under conditions of varying NaCI concentration to achieve smaller kf values at a flow rate of I mL/min and at a temperature of 298 K with (I) 20 mM piperazine buffer, pH 9.6 (2) 20 mM triethanolamine, pH 7.5 (3) bistris buffer, pH 6.5 and (4), 20 mM piperazine buffer, pH 5.5, as the eluents. Data selected from Ref. 542. 

Figure 3 Effect of Zn + binding on the CD spectrum of the hemopexin (Hx)-heme complex the Hx-heme complex (thick black curve), additions of 3-15 equiv of Zn + (thin black curve), and addition of 18 equiv of Zn + (red curve). The Hx-heme concentration is 8 xM, with 50 mM bisTris buffer and 50 mM sodium chloride (pH 7.0, 25 °C). (Reprinted with permission from Mauk, Rosell, Lelj-Garolla, Moore and Mauk. 2005 American Chemical Society)...

With 80 mM Tris-HCl buffers, the activity was measured at comparable rates between pH 7.5 and pH 9.0, although some inhibitory effects were observed below pH 7.0, probably due to the lower buffering activity of the Tris buffer. Indeed, no inhibitory effect was observed with 80 mM BisTris-HCl buffer between pH 6.5 and pH 7.0, and the maximum activity was measure at pH 7.0 with this buffer system. However, at pH 6.0 with both 80 mM BisTris-HCl and 60 mM Histidine-HCl buffers the activity was... 

Tris is one of the most popular buffers used in biochemical studies probably because its buffer region encompasses the physiological to slightly alkaline pH range [212]. The same is true for Bistris which buffers in the pH range 6 to 7.5 [213]. Another widely employed buffer is Bicine [214,215] which is employed in the pH range 7.5 to 9. The structures of the three mentioned buffers are shown in Figure 15. 

Because Bicine is derived from glycine, it was expected already nearly 50 years ago that this buffer forms complexes with metal ions [216]. For Tris and Bistris the awareness of metal ion interactions is much lower, and the fact that also mixed ligand complexes may form [212,213], has hardly been reaUzed. Therefore, the stabilities of the ternary Cd " and some other metal ion complexes formed between these buffers and ATP are briefly summarized. The stability constants according to equilibria (28) and (29) are listed in Table 13 together with the stability differences defined in equation (30). 

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