Have recently completed a lot of MAR work. When using labeled Oleic acid as substrate I first checked the pH of sample (pH=8). The pKa for Oleic acid is 5 leading to a 99.9% presence of carboxylate anion in the solution (enviro sample) I guessed that this would instantly lead to the formation of anionic surfactant. When the sample was aerated a foam instantly formed. What I am questioning is whether this would affect uptake of oleic acid. For example the critical micelle concentration for SDS is 8.2mM for Oleic acid it is 50uM. We run MAR at a substrate concentration of 2mM. WHAT would the surfactant created during this reaction do to the cell walls (G-ve) in the sample - artificially enhanced uptake - false positives?
NB. I have noticed in a lot of others MAR work that they get good uptake of oleic or palmitic but poor to no uptake of other types of substrates. What does anyone think?
