Intermolecular complex by electrostatic interaction and specifically coupled conjugates between polyacrylic acid (PAA) and a synthetic peptide representing 170-188 sequence from the GH loop of VP1 protein of foot-and-mouth disease virus (FMDV) were investigated as an intermolecular model system due to their importance in biotechnology and immunology. In this study, polyacrylic acid (PM) with a synthetic peptide representing 170-188 sequence from the GH loop of VP1 protein of foot-and-mouth disease virus at a wide range of mixing ratios of components (C-Peptide/C-PAA 0.1, 0.25, 0.5, 0.75 and 1.0, respectively) were characterized by size-exclusion high performance liquid chromatography with on-line refractive index, UV, light scattering and viscometer detectors. The results revealed that two molecules are both negatively charged as a result of repulsive forces preventing complex formation at neutral pH. Therefore, these molecules bound covalently to each other by using water-soluble carbodiimide when pH levels are higher than the pl of the peptide. High performance liquid chromatography analysis showed that the amount of protein-polymer complex increased and free peptide amount decreased with the increase in molar ratio of the peptide. Also, this paper presents that number of the bound peptide molecules with one PAA molecule was expressed by a Langmuir-type equation as a function of the amount of excess synthetic peptide existing free in the solution. (C) 2011 Elsevier B.V. All rights reserved.