Structure-function relationship studies for novel GMDP-peptide mimic, RVPPRYHAKISPMVN (RN-peptide) were performed on array of truncated and 'Ala-scan' analogues. The shortest peptide fragment possessing detectable affinity towards anti-GMDP-antibodies was demonstrated to be PRYH. RN-peptide analogues lacking up to 8 residues at C-terminus were found to retain adjuvant activity with the minimal active peptide being RVPPRYH. Evaluation of Ala-scan analogues highlighted that adjuvant activity is most critically dependent on both arginine residues, but also is sensitive to substitution of K9, I10, S11 and M13 amino acid residues, the functional importance of which was additionally confirmed by testing peptides truncated at both termini. © 2011 Elsevier Ltd.