The sequential polytripeptides and polydipeptides, (X-Tyr-Lys)(n), (X=Gly, Ala, Pro, Ser, Leu, Ile, Phe), (Y-Lys)(n), (Y=Gly, Tyr), and (Gly-Tyr)(n), which imitate a mussel adhesive protein, have been synthesized. The molecular weights of the polypeptides were estimated to be 7,200 similar to 13,400 (19 similar to 42 repeating units), and the polypeptides were found to have satisfactory amino acid sequences. The polypeptides were crosslinked by tyrosinase, and the optimal pH in the crosslinking reaction was 7.4 in the case of the polytripeptide, (Gly-Tyr-Lys)(n). The optimal tyrosinase amount for the adhesive strength of(Gly-Tyr-Lys)(n) was 0.34 unit/mg (polypeptide) at pH 7.4. The shear adhesive strength of the polytripeptide increased with an increase in the polytripeptide concentration, and was not influenced by the third amino acid, X. The shear adhesive strengths of polytripeptides (X-Tyr-Lys)(n) were equal to one of the synthetic polydecapeptides, (Ala-Lys-Pro-Ser-Tyr-Pro-Pro-Thr-Tyr-Lys)(n) and (Gly-Pro-Lys-Thr-Tyr Pro-Pro-Thr-Tyr-Lys)(n) which were the model polydecapeptides for blue mussel and Californian mussel, respectively. (C) 2000 John Wiley & Sons, Inc.