A multicomponent molecular approach to artificial photosynthesis - the role of fullerenes and endohedral metallofullerenes.

In this review article, we highlight recent advances in the field of solar energy conversion at a molecular level. We focus mainly on investigations regarding fullerenes as well as endohedral metallofullerenes in energy and/or electron donor-acceptor conjugates, hybrids, and arrays, but will also discuss several more advanced systems. Hereby, the mimicry of the fundamental processes occurring in natural photosynthesis, namely light harvesting (LH), energy transfer (EnT), reductive/oxidative electron transfer (ET), and catalysis (CAT), which serve as a blue print for the rational design of artificial photosynthetic systems, stand at the focalpoint. Importantly, the key processes in photosynthesis, that is, LH, EnT, ET, and CAT, define the structure of this review with the only further differentiation in terms of covalent and non-covalent systems. Fullerenes as well as endohedral metallofullerenes are chosen by virtue of their small reorganization energies in electron transfer processes, on the one hand, and their exceptional redox behaviour, on the other hand.

Functions encoded by pyrrolnitrin biosynthetic genes from Pseudomonas fluorescens.

Pyrrolnitrin is a secondary metabolite derived from tryptophan and has strong antifungal activity. Recently we described four genes, prnABCD, from Pseudomonas fluorescens that encode the biosynthesis of pyrrolnitrin. In the work presented here, we describe the function of each prn gene product. The four genes encode proteins identical in size and serology to proteins present in wild-type Pseudomonas fluorescens, but absent from a mutant from which the entire prn gene region had been deleted. The prnA gene product catalyzes the chlorination of L-tryptophan to form 7-chloro-L-tryptophan. The prnB gene product catalyzes a ring rearrangement and decarboxylation to convert 7-chloro-L-tryptophan to monodechloroaminopyrrolnitrin. The prnC gene product chlorinates monodechloroaminopyrrolnitrin at the 3 position to form aminopyrrolnitrin. The prnD gene product catalyzes the oxidation of the amino group of aminopyrrolnitrin to a nitro group to form pyrrolnitrin. The organization of the prn genes in the operon is identical to the order of the reactions in the biosynthetic pathway.

The non-haem chloroperoxidase from Pseudomonas fluorescens and its relationship to pyrrolnitrin biosynthesis.

The non-haem chloroperoxidase gene (cpoF) from the pyrrolnitrin producer Pseudomonas fluorescens BL914 was cloned using an oligonucleotide derived from part of the N-terminal amino acid sequence of chloroperoxidase (CPO-P) from Pseudomonas pyrrocina as a probe. Based on the overexpression of cpoF in Escherichia coli and the stability of CPO-F against higher temperatures and proteases, the enzyme was purified to homogeneity. Partial characterization of the enzyme showed that it belongs to the class of bacterial non-haem CPOs. To investigate the role of CPO-F in pyrrolnitrin biosynthesis, the cpoF gene was inactivated by insertion of a kanamycin cassette. Exchange of the chromosomal cpoF gene against the disrupted copy had no influence on pyrrolnitrin production demonstrating that CPO-F was not involved in pyrrolnitrin biosynthesis.