MODIFICATION OF SHORT PEPTIDES USING EPSILON-AMINOCAPROIC ACID FOR IMPROVED COATING EFFICIENCY IN INDIRECT ENZYME-LINKED IMMUNOSORBENT ASSAYS (ELISA)

The hydrophobicity of short synthetic peptides of 5-10 residues was en hanced for high coating efficiency as antigens in indirect ELISA. To o btain enhanced hydrophobicity, coupling of epsilon-aminocaproic acids to the synthetic peptides was carried out during solid phase peptide s ynthesis. As a short peptide model, three analogues of a streptavidin binding peptide consisting of 5 amino acid residues were prepared with four epsilon-aminocaproic acid residues. HPLC analysis showed a drama tic increase in hydrophobicity after modification and the modified pep tides showed a better adsorption ability than the unmodified peptides in indirect ELISA. The whole process from antigen coating to color dev elopment was carried out within 2.5 to 3 h by dissolving the peptide i n methyl alcohol and evaporating the solvent in each well of the micro plate. As an application of this method, a peptide assumed to function as one of the epitopes of the human 60 kDa Ro/SSA antigen was selecte d from hydrophilicity, acrophilicity and hydropathy plots. The peptide was synthesized having an epsilon-aminocaproic acid modification at b oth N and C terminal ends and was tested with 30 sera from patients wi th systemic lupus erythematosus (SLE), 20 normal sera and a standard a nti-Ro/SSA serum. The ELISA results revealed that the method Save a hi gh signal-to-background ratio without altering the specificity of the assay. Moreover, our process was far simpler and more rapid than conve ntional methods used in indirect ELISA. Thus this method could be usef ul in the development of techniques for the diagnosis of SLE. (C) 1997 Elsevier Science B.V.