Photosensitized Reduction of Water to Hydrogen Using Human Serum Albumin Complexed with Zinc−Protoporphyrin IX

Abstract

We present the photophysical properties of complexes of recombinant human serum albumin (rHSA) with Zn(II)-protoporphyrin IX (ZnPP) and their activities in the photosensitized reduction of water to hydrogen (H2) using methyl viologen (MV2+) as an electron relay. The ZnPP is bound in subdomain IB of wild-type rHSA [rHSA(wt] by an axial coordination of Tyr-161 and, in the rHSA(I142H/Y161L) mutant [rHSA(His], by a His-142 coordination. Both the rHSA(wt)-ZnPP and rHSA(His)-ZnPP complexes showed a long-lived photoexcited triplet state with lifetimes (tauT) of 11 and 2.5 ms, respectively. The accommodation of ZnPP into the protein matrix efficiently eliminated the collisional triplet self-quenching process. The addition of a water-soluble electron acceptor, MV2+, resulted in a significant decrease in the triplet lifetime. The transition absorption spectrum revealed the oxidative quenching of rHSA-3ZnPP* by MV2+. The quenching rate constant (kq) and backward electron transfer rate constant (kb) were determined to be 1.4 x 10(7) and 4.7 x 10(8) M(-1) s(-1) for rHSA(wt)-ZnPP. In the presence of the colloidal PVA-Pt as a catalyst and triethanolamine (TEOA) as a sacrificial electron donor, the photosensitized reduction of water to H2 takes place. The efficiency of the photoproduction of H2 was greater than that of the system using the well-known organic chromophore, tetrakis(1-methylpyridinium-4-yl)porphinatozinc(II) (ZnTMPyP4+), under the same conditions.

Preparation and antioxidant activity of albumin binding Salen Schiff-base metal complexes

“…The scavenging effect reached 53% when the VC was added to 0.0058 mmol/L, which was similar to that of BSA/HOSalenCo (20) (Figure 9). …”

“…Since the serum albumin was considered to be nonantigenic and biodegradable, and was readily available [16], the albumin has been used as a bio-material, such as drug delivery and novel hydrophilic carriers [17][18][19][20]. However, the bovine serum albumin (BSA) has not been used for ROS-scavenging materials because the ROS-scavenging activity of the BSA is very weak [21].…”

Combined Use of Optical Spectroscopy and Computational Methods to Study the Binding and the Photoinduced Conformational Modification of Proteins When NMR and X-Ray Structural Determinations Are Not an Option

“…Photophysical and photochemical properties of dye ligands have been used in many different applications, including medical (Dolmans, Fukumura, & Jain, 2003;Dougherty et al, 1998;Henderson & Dougherty, 1992;Marcus et al, 1996;Rodriguez, Baas, & Friedberg, 2004;Sternberg, Dolphin, & Brickner, 1998), energy conversion (Komatsu, Wang, Zunszain, Curry, & Tsuchida, 2006;McConnell, Li, & Brudvig, 2010), biochemical (Harkins & Grissom, 1994), structural (Lee, Smith, & Hatton, 2005;Lee, Wang, & Hamill, 2007;Loweneck et al, 2006;Schrader et al, 2007), etc. Different dyes with individual photophysical properties can be used depending on the application.…”

“…In the case of PCT or PET in particular, the reversibility must be ensured typically by using a third molecule (e.g., triethanolamine) that can donate an electron back to the system in order to "close" the cycle as well as a catalyst (typically colloidal Pt or nanoparticles) (Komatsu et al, 2006).…”

Photoinduced conformational changes of human serum albumin bound to protoporphyrin IX and hemin

“…Within this class of photoactive molecules, protoporphyrin IX (PPIX) has long been a subject of research spanning basic photophysical and photochemical characterizations 2,3 , selfassembly 4 , and biomedical applications including its use as a photosensitizer in phototherapy and photodetection of cancer and other abnormal tissues 5,6 .…”