Production of chemicals directly from carbon dioxide using light energy is an attractive option for a sustainable future. The 1,3-propanediol (1,3-PDO) production directly from carbon dioxide was achieved by engineered Synechococcus elongatus PCC 7942 with a synthetic metabolic pathway. Glycerol dehydratase catalyzing the conversion of glycerol to 3-hydroxypropionaldehyde in a coenzyme B12-dependent manner worked in S. elongatus PCC 7942 without addition of vitamin B12, suggesting that the intrinsic pseudovitamin B12 served as a substitute of coenzyme B12. The highest titers of 1,3-PDO (3.79±0.23 mM; 288±17.7 mg/L) and glycerol (12.62±1.55 mM; 1.16±0.14 g/L), precursor of 1,3-PDO, were reached after 14 days of culture under optimized conditions in this study.

This paper describes the synthesis, structural characterization and cellular uptake of a supramolecular 1 : 2 inclusion complex of meso-tetraphenylporphyrin having an octaarginine peptide chain (R8-TPP) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMe-β-CD). R8-TPP was synthesized by 2 approaches: (1) on-resin conjugation of the N-terminal of octaarginine with 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin, followed by cleavage from the resin, and (2) Michael addition reaction between 5-[4-(3-maleimidopropylamido)phenyl]-10,15,20-triphenylporphyrin and cysteine-octaarginine peptide (Cys-Arg8). The R8-TPP obtained from both the approaches formed stable inclusion complexes with TMe-β-CD by which non-substituted phenyl groups at the 10- and 20-positions were included to form trans-type 1 : 2 inclusion complexes. The complexation prevented the self-aggregation of R8-TPP, which resulted in the solubilisation of R8-TPP in aqueous media. A cellular uptake study using HeLa cells showed that R8-TPP complexed with TMe-β-CD in a serum-free medium was efficiently taken up by the cells and uniformly dispersed in the cytosol. In the serum-containing medium, the R8-TPP-TMe-β-CD complex dissociated, and the serum protein bound R8-TPP. The R8-TPP-protein complex was localized in the endosomes of the cells. The cytosol-dispersed R8-TPP showed a higher photo-induced cytotoxicity than its endosome-trapped counterpart.

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