WATER BINDING ON COLLAGEN BY INVERSE PHASE GAS-CHROMATOGRAPHY - THERMODYNAMIC CONSIDERATIONS

In a previous publication, the details of using inverse phase gas chromatography (IPGC) for determining the moisture sorption isotherms of proteins were outlined. In the present article, the moisture sorption isotherms of collagen at five temperatures in the range of 40-60 °C are described using this method. The thermodynamics of the sorption process are considered by application of the BET equation, the Clausius-Clapeyron equation, and the Zimm-Lundberg cluster theory. Almost the entire region of the isotherms studied was found to be in or below the monomolecular layer as defined by the BET equation. The calculated values of the Zimm-Lundberg cluster function were negative throughout, indicating the absence of water clustering. The isosteric heat of adsorption was found to be highest at the lowest moisture contents studied and then dropped slightly before leveling off at a constant value of 6.8 kcal/mol characteristic of hydrogen bonding. © 1979, American Chemical Society. All rights reserved.