Photoinduced Hydrogen-Evolution System with an Antibody–Porphyrin Complex as a Photosensitizer

Abstract

A complex between a monoclonal antibody for porphyrin and zincporphyrin was utilized to construct an energy conversion system. Monoclonal antibody 2B6 bound meso-tetrakis(4-carboxyphenyl)porphyrin zinc complex (ZnTCPP) with a dissociation constant of 2.1 © 10 ¹8 M. Upon binding the antibody, the lifetime of the excited triplet state of ZnTCPP increased from 0.5 to 1.2 ms. A stable cationic radical of viologen was obtained by irradiating the solution containing the complex of 2B6 with ZnTCPP, methyl viologen (MV 2+ ), and ethylenediaminetetraacetic acid tetrasodium salt (EDTA-4Na) with light. When colloidal platinum was added as a catalyst, photoinduced hydrogen production was observed upon continuous irradiation of visible light. The estimated turnover number of photoinduced hydrogen evolution was 5.0 © 10 ¹3 s ¹1. The catalytic activity of the 2B6ZnTCPP complex on the hydrogen evolution was compared with that of ZnTCPP alone and the complexes of ZnTCPP with fragments of antibody 2B6 (2B6-H and 2B6-L). The heavy chain of antibody 2B6 mainly contributed to the complex formation with ZnTCPP and the resultant hydrogen production, and the whole antibodyZnTCPP complex led to the efficient hydrogen production.Recently, the design of new energy sources has received much attention because the exhaustion of fossil fuels has become a pressing issue. Furthermore, combustion of fossil fuels causes emission of CO 2 , which has resulted in global warming. Hence, solar energy has become popular due to its limitlessness. Moreover energy derived from hydrogen has received a lot of attention as a clean energy source. Currently, there are many attempts to create energy conversion systems, which convert solar energy into chemical energy.1 On the other hand plants and light harvesting bacteria convert solar energy into chemical energy with high efficiency. 2In the field of artificial energy conversion, hydrogen production systems by photoelectrolysis of water constructed using TiO 2 electrodes have been developed. 3 However, TiO 2 absorbs only UV light, and it cannot use the major part of sunlight. To overcome this problem, dye-sensitized hydrogen-evolution systems have been developed. 4 It is advisable to mimic the energy conversion systems in nature, and the chromophores of in vivo photosynthetic reaction centers are fixed by the protein environment. 5 The distances between electron donors and electron acceptors are noncovalently held under optimum conditions. Recently, non-covalently assembled donoracceptor arrays have been constructed utilizing hydrogen bonding, 6 metal coordination, 7 apoproteins, 8 electrostatic interactions, 9 and supramolecular formations. 10To construct a photoinduced hydrogen production system, a suitable catalyst is necessary to reduce a proton by an electron, which can be obtained by charge separation. In many cases, colloidal platinum has been used as a catalyst for proton reduction.11 To construct an artificial charge-separation system with non-covalently linked electron donors and acceptors, it is fa...

Atroposelective antibodies as a designed protein scaffold for artificial metalloenzymes

“…The microenvironment formed by mAb S1E11 is suggested to regulate the accessibility of substrates to the reaction center to give the same enantiomer of product 3 that produced by R44E1 ⊃ BIQ-Cu. Although anti-porphyrin mAb 2B6 46,47 has an unexpected affinity for BIQ-Cu (Fig. S7, K d = 7.1 × 10 −5 M), presumably due to hydrophobic interactions, catalytic reaction in the presence of BIQ-Cu and 2B6 gives racemic 3 (Table 2, Entry 4).…”

Direct Chiral Separation of Binaphthyl Derivatives Using Atroposelective Antibodies

“…As a control experiment, mAb 2B6 elicited against a water‐soluble porphyrin was used . In this case, e.e .…”

Control of Photoinduced Electron Transfer Using Complex Formation of Water-Soluble Porphyrin and Polyvinylpyrrolidone

“…Extensive effort has been devoted to mimicking the natural photosynthetic systems to study the initial process of photosynthesis and to realize highly efficient electron transfer in artificial photosynthetic systems [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Numerous studies of electron transfer systems using covalently linked electron donor and acceptor molecules have been reported [ 10 , 11 , 12 , 13 ].…”

“…Recent covalently linked donor-acceptor systems are reported and used as polymerization photoinitiators [ 14 , 15 ]. Systems with noncovalently assembled electron donor and acceptor molecules have also been constructed via hydrogen bonding [ 16 , 17 , 18 ], metal coordination [ 18 , 19 , 20 ], electrostatic interaction [ 21 , 22 , 23 ], and host–guest interaction [ 24 , 25 , 26 , 27 ]. Among these studies, those using polymer matrix have attracted widespread interest because the polymer matrix can fix the electron donors, which is similar to a natural photosynthetic system.…”