DSA: a new internal standard for NMR studies in aqueous solution.
[structure: see text] The widely used internal standard for NMR studies in aqueous solution DSS (sodium 4,4-dimethyl-4-silapentane-1-sulfonate) can interact with cationic peptides, diminishing its value for such studies. This paper introduces DSA (4,4-dimethyl-4-silapentane-1-ammonium trifluoroacetate) as a new internal standard that does not suffer from this problem.