Derivatives of 2,5-anhydroallitol and 2,5-anhydroaltritol

Two routes to protected derivatives of 2,5-anhydroallitol were investigated. The first route, involving a two-step reduction of 2,5-anhydro-6-O-benzoyl-3,4-O-isopropylidene-D-allonitrile (4), gave a mixture of 2,5-anhydro-6-O-benzoyl-3,4-O-isopropylidene-D-altritol (7) and a lesser amount of the desired 2,5-anhydro-6-O-benzoyl-3,4-O-isopropylidene-D-allitol (6). Isomerization was shown to occur in the first reduction step—treatment of the nitrile 4 with Raney nickel, sodium hypophosphite, and acetic acid. The second route gave isomerically pure 2,5-anhydro-3,4,6-tri-O-benzyl-D-allitol (21) via reduction of the corresponding ethyl allonate (18).     

CpcF-dependent regulation of pigmentation and development in Fremyella diplosiphon

Cyanobacteria harvest light for photosynthesis using photosynthetic light-harvesting complexes called phycobilisomes (PBSs). Lyases are enzymes responsible for covalent attachment of light-absorbing chromophores to the phycobiliproteins (PBPs) contained in PBSs. We isolated a pigmentation mutant in the filamentous cyanobacterium Fremyella diplosiphon and determined that it possesses an insertional mutation in cpcF, which encodes one component of a heterodimeric phycocyanin lyase. Here, we discuss the implications of the mutation in cpcF on light-dependent pigmentation and morphology responses characteristic of complementary chromatic adaptation in F. diplosiphon. Although cpcF encodes a phycocyanin lyase, significant decreases in the levels of all classes of PBPs are associated with CpcF deficiency in F. diplosiphon. Notably, CpcF deficiency has a limited effect on the shape of F. diplosiphon cells, but significantly impacts filament length. Possible mechanisms for the broad impact of CpcF deficiency on pigmentation and filament morphology are discussed.