SSC+NaPO4 buffers - (Mar/30/2006 )

A very basic question:

What is the special property of SSC that makes us want to wash our membrane in it? I have also seen protocol where they use Na phosphate wash buffers instead of SDS. What exactly is the priviledge of using either and the concept behind it?

Thank you

um...it's all about what type of membrane you are using, what protocol you are following (are you referring to Southerns? Northerns? Westerns? colony or plaque hybridization?)

then it's all about the appropriate buffering system for your protocol

The two important properties of a wash are the ionic strength (amount of salt) and the pH. The salt need not be NaCl. SSC and phosphate buffers would perform almost identically. If you are trying to detect with alkaline phosphatase, you need to avoid phosphate buffers. SDS is an entirely different matter, and is a detergent, improving the wetting ability. You sometimes see Tween 20 used in a similar role as a surfactant.