The buffer contains Tris-HCl ph 8.8, which is to maintain the pH for the polymerase enzyme to be active optimally. I understand the role of MgCl2 or other Mg salts, for interactions with the dNTPs during polymerase reaction. But other components like KCl, (NH4)2 SO4, BSA, Triton-X has to play in PCR? Also we add MgCl2 as one of the reaction component in PCR. Then is it recommended to add MgSO4 in the buffer? Can anyone explain why these reagents are used in this buffer?
https://www.researchgate.net/post/Taq_Buffer_with_KCl_or_Taq_Buffer_with_NH42SO4
https://www.researchgate.net/post/Taq_Buffer_with_KCl_or_Taq_Buffer_with_NH42SO4
Two magnesium ions are involved in the nucleotidyl-transfer reaction:
A) 'catalytic' Mg2+ [lowers the pKa of 3'OH group of the 3'-terminal nucleotide of the primer DNA strand];
B) 'structural' Mg2+ [binds the triphosphate group of the dNTP substrate and the PPi product].
One Mg salt is probably sufficient. The concentration of ions might be more important. "Special" components are usually used only if standard conditions fail. Most of those components just interact with DNA somehow, increasing primer annealing temperature, relaxing secondary structures in DNA, etc. Some are used for historical reasons (someone used before, it worked, so why not?). You made me curious myself, so I did some googlling:
https://books.google.de/books?id=NSSFjn2-SuUC&pg=PA66&lpg=PA66&dq=ammonium+ions+DNA+PCR&source=bl&ots=u9JwrFXQNL&sig=IFiwnhA04CrAgxmlay1BaT6x6_4&hl=de&sa=X&ved=0ahUKEwiG25Ohh4XNAhVBtRQKHazlDAUQ6AEINDAC#v=onepage&q=ammonium%20ions%20DNA%20PCR&f=false
http://genome.cshlp.org/content/2/3/234.long
https://www.genelink.com/Literature/ps/M40-3021-PCR_Additives_Ver5.1.pdf
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