E. Tsuchida et al., Human serum albumin incorporating tetrakis(o-pivalamido)phenylporphinatoiron(II) derivative as a totally synthetic O-2-carrying hemoprotein, BIOCONJ CHE, 10(5), 1999, pp. 797-802
2-[8-{N-(2-Methylimidazolyl)}octanoyloxymethyl]-5,10,15,20-tetrakis(o-pival
amido)phenylphorin-atoiron(II)s (FePs) were incorporated into hydrophobic c
avities of recombinant human serum albumin (rHSA), providing a totally synt
hetic O-2-carrying hemoprotein (rHSA-FeP). An rHSA host absorbs maximally e
ight FeP molecules. Solution properties of the obtained albumin hybrid [[rH
SA] = 5 wt%; FeP/HSA = 1-8 (mol/mol)] are almost identical to those of the
rHSA itself; the specific gravity is 1.013 and the viscosity is 1.1 cP. Cir
cular dichroism spectroscopy and isoelectric focusing measurement revealed
that the second-order structure and surface charge distribution of rHSA wer
e always constant independent of the binding numbers of FeP. Hydrophobic in
teraction is probably a major molecular force of the incorporation of this
synthetic heme. rHSA-FeP can bind and release dioxygen reversibly under phy
siological conditions (in aqueous media, pH 7.3, 37 degrees C) like hemoglo
bin and myoglobin. Its O-2-coordination structure was evaluated by resonanc
e Raman spectroscopy. The O-2 rebinding after the laser flash photolysis sh
owed three-phases decay, which were analyzed by triple-exponential kinetics
. The O-2-binding affinity and O-2-association and -dissociation rate const
ants of rHSA-FeP satisfy the initial clinical requirements for O-2 infusion
as a red cell substitute.