Characterization of the heme iron in pyridoxylated hemoglobin cross-linkedby glutaraldehyde using Mossbauer spectroscopy

The heme iron in human adult hemoglobin modified by both pyridoxal-5'-phosp hate and glutaraldehyde was characterized by Mossbauer spectroscopy and com pared with non-modified hemoglobin. Mossbauer spectra of the samples were m easured at 87 and 295 K (lyophilized form) and at 87 K (frozen solution). T he values of quadrupole splitting for the oxy-form of modified hemoglobin w ere found to be lower than those of the oxy-form of hemoglobin without modi fications in lyophilized form and frozen solution, respectively. On the oth er hand, the values of quadrupole splitting for the deoxy-form of modified and non-modified hemoglobins in frozen solution were the same. The Mossbaue r spectra of the oxy-form of modified hemoglobin were also analyzed in term s of the heme iron non-equivalence in alpha- and beta-subunits of tetramer. The differences of the tendencies of temperature dependencies of quadrupol e splitting for the oxy-form of modified and non-modified hemoglobins in ly ophilized form were shown. These results indicated that the heme iron elect ronic structure and stereochemistry were changed in the oxy-form of pyridox ylated hemoglobin cross-linked by glutaraldehyde. (C) 2000 Elsevier Science B.V. All rights reserved.