The binding of oxygen to hemoglobin is thought to be a multistep process with different rate constants for each step. With an all tantalum stopped-flow calorimeter developed earlier, we can easily measure the heat of binding of oxygen to hemoglobin. The all-tantalum system will prevent the diffusion of oxygen into the system and will allow us to measure these heats over the entire saturation range, 0-100%; preliminary measurements of.the binding heat at 50% saturation are in good agreement with published values. An in-line spectroscopic flow cell is used to measure the oxygen saturation of the mixed hemoglobin and oxygen to verify the final saturation value. The measurements at lower saturation values, less than 35%, have been made. In order to achieve high saturation values, we needed a solute which could carry more oxygen than an aqueous based solution we used at the lower saturation values. We found a fluorocarbon liquid which can hold 25 times more oxygen than water. It will be used to carry the oxygen for the measurement at higher saturation values.
