You need to choose a buffer to use at pH 6.4. Which buffers from this table (Tab

Question

You need to choose a buffer to use at pH 6.4. Which buffers from this table (Table 2.8) would be acceptable choices? Check all that apply TABLE 2.8 Acid and Base Form of Some Useful Biochemical Buffers Acid Formm Base Form pK, TRIS-H TRIS (free amine) (HOCH),CNH TES (anionic form) (HOCH CNHCH,CH SO, HEPES (anionic form) N trislhydroxymethylJaminomethane (TRIS) 8.3 (protonated form) (HOCH,),CNH; TES-H (zwitterionic form) (HOCH2),CNH,CH,CH SO, HEPES-H (zwitterionic form) Ntris[hydroxymethyl]methyl-2- aminoethane sulfonate (TES) 7.55 N- 2 hydroxyethylpiperazine-N'2 ethane sulfonate (HEPES) 7.55 HocH,CHN NCH,CH,SO HOCH,CH,N NCH,CH.SO MOPS-H (zwitterionic form) 3-[N-morpholino] propane. sulfonic acid (MOPS) MOPS (anionic form) 7.2 O NCH CH CH SO O NCH,CH CHSO PIPES (dianion) 6.8 PIPES-H (protonated dianion) Piperazine-N.N bis[2-ethanesulfonic acid] (PIPES) OSCH,CH,NN NCH,CH,SO OSCH,CHN NCH,CH SO TRIS TES HEPES MOPS PIPES

Explanation / Answer

A buffer substance is useful around its pKa, also by a range of + or - 1 in terms of pH, this means, that to maintain a pH of 6.4, the pKa of the buffer that is chosen, should not be more than 1 (pH) away from this value.

MOPS and PIPES are two buffer substances that can be used to maintain this pH value.

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