Spectroscopic and Catalytic Characterization of a Functional FeIIIFeII Biomimetic for the Active Site of Uteroferrin and Protein Cleavage

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• 作者：Sarah J. Smith ; Rosely A. Peralta ; Rafael Jovito ; Adolfo Horn ; Jr. ; Adailton J. Bortoluzzi ; Christopher J. Noble ; Graeme R. Hanson ; Robert Stranger ; Vidura Jayaratne ; Germ谩n Cavigliasso ; Lawrence R. Gahan ; Gerhard Schenk ; Otaciro R. Nascimento ; Ang茅lica Cavalett ; Tiago Bortolotto ; Guilherme Razzera ; Hern谩n Terenzi ; Ademir Neves ; Mark J. Riley
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：February 20, 2012
• 年：2012
• 卷：51
• 期：4
• 页码：2065-2078
• 全文大小：697K
• 年卷期：v.51,no.4(February 20, 2012)
• ISSN：1520-510X

文摘

A mixed-valence complex, [Fe^IIIFe^IIL1(渭-OAc)₂]BF₄路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^IIIFe^II and Fe^III₂ 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 = 鈭?JS₁路S₂, where J = 鈭?.6 cm^鈥?) in a frozen solution. The ligand-to-metal charge-transfer transitions are correlated with density functional theory calculations. The Fe^IIIFe^II 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鈥搇attice relaxation. However, a phosphate-bound Fe^III₂ complex showed an EPR spectrum due to population of the S_tot = 3 state (J= 鈭?.5 cm^鈥?). The phosphatase activity of the Fe^IIIFe^II complex in hydrolysis of bis(2,4-dinitrophenyl)phosphate (k_cat. = 1.88 脳 10^鈥? s^鈥?; K_m = 4.63 脳 10^鈥? mol L^鈥?) 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 Fe^III. It is interesting to note that aqueous solutions of [Fe^IIIFe^IIL1(渭-OAc)₂]⁺ are also capable of protein cleavage, at mild temperature and pH conditions, thus further expanding the scope of this complex鈥檚 catalytic promiscuity.