Could someone please tell me the importance of 'fixing' a PAGE gel before drying it. I have been using 40%methanol and 10% glacial acetic acid but am not sure why these are used. What does 'fixation' refer to?

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MeOH and acetic acid treatment step removes SDS, faciltate dye penetration and does destaining to the gel as well. Fix here probably has several meanings. It can maintain small pore size of the gel by physical means, because if you place the gel in DW, it will expand. It may also keep protein in denatured and less diffusive status. I dont think it means chemical cross-linking here.

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fixing means denaturing proteins (by alcohol and/or acetic acid) to be trapped in the polyacrylamid, and to prevent diffusion of proteins; moreover, alcohol speeds up drying

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Thank you. So I understand that meOH removes the SDS, which is why we use it when transfering for Westerns. But why in this case (but not in Westerns) do we need to add acetic acid?

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as I said it helps to denature proteins and also prevents swelling of the gel by water

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the meoh prevents swelling (as well as remove sds and solubilize coomassie), it will actually shrink the gel, and the acetic acid denatures the protein.

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i've swithced MeOH for EtOH (far less toxic) and this works nice too. You should give a hit to this technique

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