A statistical-thermodynamic view of cooperative structural changes in phospholipid bilayer membranes: their potential role in biological function

It is a great honor to receive the Huffman Memorial Award from the Calorimetry Conference. Such an honor was certainly not on my list of expectations when I first became interested in calorimetric experimentation over 20 years ago. I thank the conference for this honor and the many of you who have aided and encouraged the work which this award recognizes. In 1969, I had the opportunity to spend three months in the laboratories of the late Stig Sunner and Ingemar Wadsii at the University of Lund, Sweden. It was during that visit that I first became acquainted with state-of-the-art calorimetric equipment. That visit provided me the opportunity to explore from a practical perspective the many possibilities of applying calorimetric techniques to probe the thermodynamic details of questions of biological interest. My interest in, and motivation for, using calorimetric techniques has always been driven by specific thermodynamic questions related to biological systems. The original questions were related to understanding the thermodynamic mechanism of unfolding of globular proteins in aqueous solution. In the early sixties these thermally induced unfolding transitions were assessed by spectroscopic changes primarily and calculation of thermodynamic quantities associated with the process required that the two-state approximation (i.e. the protein existed in one of only two thermodynamic states) be valid, an assumption which had no previous means of being proven. Additionally, in 1964 Brandts(‘**) put forth a phenomenological