... An equal volume of buffer was added to the front compartment of the reference cuvette. ... Rapid centrifuge filtration was used to measure a K d for CH 3 -H 4 folate binding to MetH(2−649) (34 ... A stock solution of (6R,S)-[methyl - 14 C]CH 3 -H 4 folate was dissolved in 8 mM sodium ...