Study On The Oxygenation Ability Of The Large Hindered Iron Porphyrin Complexes With Different Ligands

Blood substitutes are driven due to worldwide blood shortages and the problems of unsafe transfusion.Many artificial oxygen carriers were synthesized through the analysis of the structure and properties of natural oxygen carrier(hemoglobin).So far.the artificial blood substitutes appearing in clinical practice are perfluorocarbons(PFC)blood substitutes,hemoglobin based oxygen carriers(HBOCs)and heme and its polymer complexes.The relationship between hemoglobin(Hb)and oxygen binding is usua1lly expressed by an oxygenation curve composed of[p(O2)]and Hb oxygen saturation(Y).Moreover,it is customary to characterize the oxygen affinity of the Hb solution by using the corresponding partial pressure of oxygen[p(O2)]50 when the oxygen saturation of the Hb solution reaches half(Y=50%).In addition,the Hill coefficient characterizing the synergistic effect between the subunits of the Hb solution also requires an oxygenation curve.Therefore.the determination of oxygenation curve is an indispensable means to study the biological activity of Hb blood substitutes.In this paper.based on the structure of hemoglobin.the meso-2.6-dihydroxyphenylporphyrin was synthesized by the reaction of boron tribromide.And then acylation of the hydroxyl group on the benzene ring to obtain a bulk sterically hindered meso 2.6-dipivaloxphenlporphyrin.The experimental results show that the double-barrier porphyrin oxygen carrier can support a stable and reversible oxygen complex with 1-methylimidazole and 1.2-dimethylimidazole in a toluene solution at 25?.At this time,the P50 corresponding to the complex formed by the coordination of Fe(?)porphyrin and 1-methylinmidazole at 1:5.1:15.1:25.1:100 is 9mmHg.21mmHg.58mmHg and 93mmHg.respectively:The p50 values of the complexes formed by the coordination of Fe(?)porphyrin and imidazole at a ratio of 1:5.1:15.1:25were23mmHg,54mmHa and 125 mmHg.respectively.The equilibrium constants(KB?KBB)and oxygen binding parameters P50 were calculated by UV-Vis spectra data.Compared to those of one-face-hindered porphyrinatoiron complexes.the equilibrium constant(KB.KBB)and oxygen binding constant KBO2 is reduced.This shows that the "double-barrier" structure porphyrin with large steric hindrance can effectively protect the binding of iron ions and oxygen molecules and is expected to become an ideal blood substitute.