title: A comparison of rates of heme exchange: site-specifically cross-linked versus polymerized human hemoglobins.
abstract: The stability of the heme-globin interaction of chemically modified human hemoglobin (Hb) was tested by measuring rates of heme loss from methemoglobin. Heme transfer from methemoglobin to human serum albumin was measured by rapid-scanning spectrophotometry, and the resulting absorption matrices were analyzed by singular value decomposition. Unmodified human HbA0, hemoglobin cross-linked between beta subunits with either 2-nor-2-formylpyridoxal 5'-phosphate or 3,5-(dibromosalicyl)fumarate (DBBF), hemoglobin cross-linked between alpha subunits with DBBF, and pyridoxalated hemoglobin polymerized with either glycolaldehyde or glutaraldehyde were tested. Initial rates were evaluated by fitting the time courses to a biexponential equation using a matrix least squares curve-fitting algorithm. Reaction rates fell into two classes: (1) HbA0 and the site-specifically cross-linked hemoglobins, with biphasic rates of heme loss of 0.02 and 0.004 min-1, and (2) polymerized hemoglobins, with 10-20-fold higher rates at 0.5 and 0.03 min-1. The total fitted amplitudes of the reaction depended upon the specific modification: beta beta-cross-linked Hbs < alpha alpha-cross-linked Hb approximately glycolaldehyde polymerized Hb < glutaraldehyde polymerized Hb < HbA0.
authors.affiliation: Division of Blood Research, Letterman Army Institute of Research, Presidio of San Francisco, CA 94129-6800.
authors.forename: K D
authors.initials: KD
authors.lastname: Vandegriff
authors.forename: Y C
authors.initials: YC
authors.lastname: Le Tellier
mesh_terms: D001802:Blood Substitutes / Q000737:chemistry / Q000378:metabolism*; D003432:Cross-Linking Reagents; D004355:Drug Stability; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006441:Hemoglobin A / Q000737:chemistry / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008706:Methemoglobin / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D011108:Polymers / Q000737:chemistry / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism; D013053:Spectrophotometry
chemical_list: D001802:Blood Substitutes; D003432:Cross-Linking Reagents; D006454:Hemoglobins; D011108:Polymers; D012709:Serum Albumin; D006418:Heme; C028881:hemoglobin A(0); D008706:Methemoglobin; D006441:Hemoglobin A; D010100:Oxygen