INFLUENCE OF THE POLYMERIZATION STEP ALONE ON OXYGEN-AFFINITY AND COOPERATIVITY DURING PRODUCTION OF HYPERPOLYMERS FROM NATIVE HEMOGLOBINS WITH CROSS-LINKERS

The aim of this study was to find out how the polymerization per se ch anges oxygen affinity (P5O) and cooperativity (n50) of various soluble huge hyperpolymers prepared from native hemoglobins by crosslinking. Increase of cooperativity would be expected considering natural hemogl obin networks. Those hyperpolymers with molecular weights of some 10(6 ) g/mol are candidates for artificial oxygen-carrying blood additives rather than volume substitutes. Human and bovine hemoglobin reacted wi th several crosslinkers (2,5-diisothiocyanatobenzenesulfonate (DIBS); 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS); 1,3-butadiene d iepoxide (BUDE); glutaraldehyde (GDA)) in concentrated (case 1) and di luted (case 2) hemoglobin solutions. With high concentration hyperpoly mer and with low concentration only monomer products were obtained. P5 0 and n50 of the products were determined at pH = 7.4, PCO2 = 40 mmHg, temp. = 37 degrees C. The difference of properties in both cases are regarded as the influence of polymerization per se. Considering this d ifference we found with almost all combinations of hemoglobin and cros slinker an increase of O-2 affinity, with DIBS and DIDS cooperativity was not changed and with BUDE and GDA it was decreased. As compared wi th native hemoglobin loss of cooperativity is considerable in any comb ination and condition, but comparing human and bovine hemoglobin the f irst seems to maintain better cooperativity. In contrast bovine hemogl obin as compared with human hemoglobin maintains better or even decrea ses its O-2 affinity upon reaction with the crosslinkers forming both, monomer and hyperpolymer products, especially in the deoxy state. DIB S and DIDS react very similarly. As a general conclusion only deoxy st ate reactions led to appropriate products regarding an artificial oxyg en carrier. A differentiated analysis of some samples clearly indicate s crosslinking with increased homotropic cooperativity on going from m onomer to hyperpolymer reaction products.