Thiolysis of an O-dinitrophenyl-tyrosyl peptide results in an increased solubility in the stationary phase of a n-butanol – acetic acid – water – pyridine (15:3:12:10) (BAWP) paper chromatographic system. It is shown that this property can be used to form the basis of a diagonal paper chromatographic purification of tyrosyl peptides from enzymatic digests of proteins. The amino groups of the protein are first reacted with citraconic anhydride and then the citraconyl protein is reacted with 1-fluoro-2,4-dinitrobenzene. The dinitrophenyl-citraconyl protein is subjected to enzymatic digestion, applied to a strip of Whatman 3 MM paper, thiolyzed with 5% 2-mercaptoethanol in acetone, and subjected to chromatography using BAWP as solvent. A guide strip is removed, thiolyzed with 5% 2-mercaptoethanol in 25% pyridine, and resubjected to chromatography in BAWP at right angles to the original direction of chromatography. The tyrosyl peptides are displaced off the diagonal towards the origin. The off-diagonal peptides are isolated from the original chromatogram by thiolysis and chromatography using the diagonal chromatogram to locate the positions of the dinitrophenyl-tyrosyl peptides.
A phase study of the system: Oxalic acid/acetic acid/water; its significance in oxalic acid crystal growth
