TY - JOUR
T1 - Spectroscopic and catalytic characterization of a functional Fe IIIFeII biomimetic for the active site of uteroferrin and protein cleavage
AU - Smith, Sarah J.
AU - Peralta, Rosely A.
AU - Jovito, Rafael
AU - Horn, Adolfo
AU - Bortoluzzi, Adailton J.
AU - Noble, Christopher J.
AU - Hanson, Graeme R.
AU - Stranger, Robert
AU - Jayaratne, Vidura
AU - Cavigliasso, Germán
AU - Gahan, Lawrence R.
AU - Schenk, Gerhard
AU - Nascimento, Otaciro R.
AU - Cavalett, Angélica
AU - Bortolotto, Tiago
AU - Razzera, Guilherme
AU - Terenzi, Hernán
AU - Neves, Ademir
AU - Riley, Mark J.
PY - 2012/2/20
Y1 - 2012/2/20
N2 - A mixed-valence complex, [FeIIIFeIIL1(μ-OAc) 2]BF4·H2O, where the ligand H2L1 = 2-{[[3-[((bis-(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzyl] (pyridin-2-ylmethyl)amino]methyl]phenol}, has been studied with a range of techniques, and, where possible, its properties have been compared to those of the corresponding enzyme system purple acid phosphatase. The Fe IIIFeII and FeIII2 oxidized species were studied spectroelectrochemically. The temperature-dependent population of the S = 3/2 spin states of the heterovalent system, observed using magnetic circular dichroism, confirmed that the dinuclear center is weakly antiferromagnetically coupled (H = -2JS1·S2, where J = -5.6 cm-1) in a frozen solution. The ligand-to-metal charge-transfer transitions are correlated with density functional theory calculations. The FeIIIFeII complex is electron paramagnetic resonance (EPR)-silent, except at very low temperatures (<2 K), because of the broadening caused by the exchange coupling and zero-field-splitting parameters being of comparable magnitude and rapid spin-lattice relaxation. However, a phosphate-bound FeIII2 complex showed an EPR spectrum due to population of the Stot = 3 state (J= -3.5 cm-1). The phosphatase activity of the Fe IIIFeII complex in hydrolysis of bis(2,4-dinitrophenyl) phosphate (kcat. = 1.88 × 10-3 s-1; Km = 4.63 × 10-3 mol L-1) is similar to that of other bimetallic heterovalent complexes with the same ligand. Analysis of the kinetic data supports a mechanism where the initiating nucleophile in the phosphatase reaction is a hydroxide, terminally bound to FeIII. It is interesting to note that aqueous solutions of [FeIIIFe IIL1(μ-OAc)2]+ are also capable of protein cleavage, at mild temperature and pH conditions, thus further expanding the scope of this complex's catalytic promiscuity.
AB - A mixed-valence complex, [FeIIIFeIIL1(μ-OAc) 2]BF4·H2O, where the ligand H2L1 = 2-{[[3-[((bis-(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzyl] (pyridin-2-ylmethyl)amino]methyl]phenol}, has been studied with a range of techniques, and, where possible, its properties have been compared to those of the corresponding enzyme system purple acid phosphatase. The Fe IIIFeII and FeIII2 oxidized species were studied spectroelectrochemically. The temperature-dependent population of the S = 3/2 spin states of the heterovalent system, observed using magnetic circular dichroism, confirmed that the dinuclear center is weakly antiferromagnetically coupled (H = -2JS1·S2, where J = -5.6 cm-1) in a frozen solution. The ligand-to-metal charge-transfer transitions are correlated with density functional theory calculations. The FeIIIFeII complex is electron paramagnetic resonance (EPR)-silent, except at very low temperatures (<2 K), because of the broadening caused by the exchange coupling and zero-field-splitting parameters being of comparable magnitude and rapid spin-lattice relaxation. However, a phosphate-bound FeIII2 complex showed an EPR spectrum due to population of the Stot = 3 state (J= -3.5 cm-1). The phosphatase activity of the Fe IIIFeII complex in hydrolysis of bis(2,4-dinitrophenyl) phosphate (kcat. = 1.88 × 10-3 s-1; Km = 4.63 × 10-3 mol L-1) is similar to that of other bimetallic heterovalent complexes with the same ligand. Analysis of the kinetic data supports a mechanism where the initiating nucleophile in the phosphatase reaction is a hydroxide, terminally bound to FeIII. It is interesting to note that aqueous solutions of [FeIIIFe IIL1(μ-OAc)2]+ are also capable of protein cleavage, at mild temperature and pH conditions, thus further expanding the scope of this complex's catalytic promiscuity.
UR - http://www.scopus.com/inward/record.url?scp=84863290794&partnerID=8YFLogxK
U2 - 10.1021/ic201711p
DO - 10.1021/ic201711p
M3 - Article
SN - 0020-1669
VL - 51
SP - 2065
EP - 2078
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 4
ER -