The role of amino groups in hemoglobin function and the effects of chemical modification of these on the function of the protein have recently been reviewed (1). Amino groups are contributed by either the N-terminal residues of the globin chains or the lysine residues of the polypeptides. Depending on the reagents used and the conditions chosen, a variable degree of specificity towards amino groups can be achieved. Such studies can be of value in determining the role of individual functional groups in biological function and may be of use in the preparation of derivatives that have modified functional properties desirable in material to be used in a hemoglobin based oxygen carrier. We have recently developed a new method for hemoglobin amino group modification which has a much greater rate of reaction with a amino groups than with the 8 amino groups of lysines at physiological pH (2). This method utilizes the activation of exogenous carboxyl containing compounds with water soluble carbodiimides and subsequent reaction with the amino groups of proteins such as hemoglobin. We report here the effects on oxygen binding observed as a function of the extent and conditions of hemoglobin modification with citrate used as the exogenous carboxyl containing compound.KeywordsHill CoefficientOrder Rate ConstantOxygen AffinityOxygen BindingHill PlotThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.