Diastereoselective Self-aggregation of Synthetic 3-(1-Hydroxyethyl)-bacteriopyrochlophyll-a as a Novel Photosynthetic Antenna Model Absorbing Near the Infrared Region¶

Abstract

3-Deacetyl-3-(1-hydroxyethyl)bacteriopyrochlorophyll-a (1), 7,8-dihydrobacteriochlorophyll-d possessing 8-ethyl, 12-methyl and 17(4)-phytyl groups, was prepared by modifying naturally occurring bacteriochlorophyll-a. The synthetic 3(1)-epimers were separated by high-performance liquid chromotagraphy, and the absolute configuration at the 3(1)-position was determined by derivatization of 1 to a structurally determined chlorin. A dichloromethane solution of 3(1)R-1 or 3(1)S-1 was diluted with a 1000-fold volume of cyclohexane to give self-aggregation species absorbing light at a near-infrared (NIR) region (<910 nm). The resulting Qy maximum in 3(1)R-1 was 860 nm and redshifted by 2170 cm(-1) from the monomeric one, whereas epimeric 3(1)S-1 showed a less redshifted peak at ca 800 nm, with a small dimeric band around 740 nm. Such visible spectra indicated that 3(1)R/S-1 formed different supramolecular structures in the self-aggregates. In contrast, self-aggregation of the 7,8-dehydro-compound 2, bacteriochlorophyll-dP, found in natural antennas of photosynthetic green bacteria showed much smaller diastereomeric control. The self-aggregates of 3(1)R-1 absorbing light in the NIR region would be models of intrinsic membraneous light-harvesting complexes 1 in photosynthetic purple bacteria as well as extramembranous antennas in green bacteria.

Time-dependent Self-assembly of 31-epimerically Pure and Mixed Zinc Methyl Bacteriopheophorbides-d in an Aqueous THF Solution

“…Additionally, naturally occurring BChls take both R and S configurations as the 3 1 -stereochemistry. In vitro aggregates of BChls and their zinc analogues showed that their supramolecular structures were dependent on the homologues and epimers (Balaban et al , 1997Chiefari et al 1995;Ishii et al 2000;Kunieda et al 2004;Miyatake et al 2001;Mizoguchi et al 2000Mizoguchi et al , 2002Saga et al 2001;Steensgaard et al 2000;Tamiaki et al 1998Tamiaki et al , 2000Tamiaki et al , 2004. A similar observation was obtained by molecular modeling studies on self-aggregates of zinc analogues (Yagai et al 2001).…”

Stereochemical conversion of C3‐vinyl group to 1‐hydroxyethyl group in bacteriochlorophyll c by the hydratases BchF and BchV: adaptation of green sulfur bacteria to limited‐light environments

“…Substrate Chlide a was prepared according to previously reported methods (Tsukatani et al, 2013b). and the substrate 3V-BChlide d was synthesized from Chlide a as described previously (Kunieda et al, 2004). Activities of BchF and BchV enzymes were assayed in a mixture containing 20 μM substrate and supernatant proteins at 2.5 mg ml −1 in a buffer containing 25 mM Tris-HCl (pH 7.8), 7.5 mM NaCl, and 10% dimethylsulfoxide after incubation at 35°C for 60 min in the dark.…”

Self-aggregation of Synthetic Protobacteriochlorophyll-d Derivatives¶

“…1) in nonpolar organic solvents as chlorosomal models (1 2-16), indicating that linear location of hydroxy, keto-carbonyl groups and a central coordinative metal including Mg, Zn and Cd in a molecule is necessary for such a self-aggregation. Natural self-aggregative BChl-c/d/e have chlorin (= 17,18-dihydroporphyrin) n-systems, and we have found that a bacteriochlorin (= 7,8,17,18-tetrahydroporphyrin) moiety was also useful for its self-aggregation (17). In this study, we report on the synthesis of zinc 3'-hydroxy-13'-0x0-porphyrins Zn-112 ( Fig.…”