In a lysis buffer what is the purpose of the tris-acetate and sodium acetate?

Question

I need to know for a class the purpose of every content in a lysis buffer and the purpose of NaCl in a DNA extraction.

Answer 1

Tris hydroxy amino methane is a cation used to buffer the pH of the solution, as is acetate. Sodium is there as the cation in the sodium acetate, it is the acetate you really want. I'm puzzled by having both Tris and acetate, since they'd maintain constant pH in different pH ranges. Tris is a good mildly basic pH buffer, while acetate is a good buffer in the mildly acidic range. For DNA extraction, I'd expect the acidic range to be better; maybe your directions will give the pH. If pH 5, the acetate is there as a pH buffer. The NaCl is to maintain the proper ionic strength to keep the DNA in solution. It has a high negative charge from all the phosphate groups, so it needs to 'borrow' the Na+ from that salt to keep itself neutralized and not self-repell. The sodium and chloride ions separate in the solution, so it all works fine.

Answer 2

Tris Lysis Buffer

Answer 3

tris acetate/sodium acetate provides the buffering capacity of the solution. NaCl helps disrupt cell membranes by increasing the osmotic potential of the solution.

Answer 4

I would expect the acetate to be used to stabilize the pH at some desired level, and the NaCl to disrupt the nuclear wall (by osmotic pressure) to access the DNA. Don't take this to the bank.