Which of the buffers shown in Table 2.8 would you choose to make a buffer with a pH of 7.3? Explain why.

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Table 2.8 Acid and Base Form of Some Useful Biochemical Buffers Name Acid Form N-tris[hydroxymethyl] aminomethane (TRIS) N-tris[hydroxymethyl] methyl-2- aminoethane sulfonate (TES) N-2-hydroxyethylpiperazine-N-2- ethane sulfonate (HEPES) 3 [N-morpholino]propane- sulfonic acid (MOPS) Piperazine N,N- bis[2-ethanesulfonic acid] (PIPES) TRIS-H+ (protonated form) (HOCH₂),CNH; TES-H+ (zwitterionic form) (HOCH₂),CNH₂CH₂CH₂SO, HEPES-H* (zwitterionic form) HOCH CHINNCH.CH.SO, NCH₂CH₂SO, → HOCH₂CH₂N NCH₂CH₂SO, H MOPS-H+ (zwitterionic form) *NCH₂CH₂CH₂SO, H 2-PIPES-H+ (protonated dianion) O,SCH₂CH₂N Base Form TRIS (free amine) (HOCH₂),CNH₂ TES (anionic form) (HOCH₂),CNHCH₂CH₂SO, HEPES (anionic form) NCH.CH.S NCH.CH.SO, H MOPS (anionic form) NCH CH₂CH.SO, 2 PIPES (dianion) OSCH.CH.NNCH₂CH.SO, O,SCH₂CH₂N pk₂ 8.3 7.55 7.55 7.2 6.8