The organized molecular structure of collagen is related to its dimensional stability. The dimensional stability of collagen arises from the interplay of various intermolecular forces such as covalent, hydrogen bonding, electrostatic interactions, hydrophobic interactions, London or van der Waals forces, and weak interactions. A structure-function relationship exists in collagen. Electrostatic interactions play an important role in dimensional stabilization. The dimensional stability of rat tail tendon (RTT) collagen fiber is affected by the change in the net fixed charge on the molecule as a function of pH. Thermal and mechanical properties are dependent on molecular and lattice orders. The pH dependence of thermal shrinkage, isometric tension, differential scanning calorimetry, swelling behavior, tensile strength, and percent extension and stress relaxation behavior are studied in 0.02M Tris-maleate buffer at pH 4-8. The observed experimental results provide compelling evidence that electrostatic interactions play an important role in the dimensional stability of RTT collagen. (C) 2000 John Wiley & Sons, Inc.