Divergent biosynthesis yields a cytotoxic aminomalonate-containing precolibactin.

Colibactin is an as-yet-uncharacterized genotoxic secondary metabolite produced by human gut bacteria. Here we report the biosynthetic discovery of two new precolibactin molecules from Escherichia coli, including precolibactin-886, which uniquely incorporates the highly sought genotoxicity-associated aminomalonate building block into its unprecedented macrocyclic structure. This work provides new insights into the biosynthetic logic and mode of action of this colorectal-cancer-linked microbial chemical.

Chloroalkyl piperazine and nitrogen mustard porphyrins: synthesis and anticancer activity.

Fifteen new chloroalkyl piperazine and nitrogen mustard porphyrins have been synthesized by the direct condensation of chloroalkyl piperazine, nitrogen mustard benzaldehyde, and pyrrole. Each porphyrin bears 1-4 chloroalkyl piperazine or nitrogen mustard moieties, which have been used as drugs. The Lindsey method was modified to synthesize chloroalkyl piperazine and nitrogen mustard porphyrins. To successfully synthesize chloroalkyl piperazine and nitrogen mustard porphyrins, catalyst acidity was proved to be the key factor, while the ratio of pyrrole to aldehyde had great influence on product yield. The synthetic chloroalkyl piperazine and nitrogen mustard porphyrins were characterized by elementary analysis, MS, (1)H NMR, IR, and UV-vis. Their anticancer activity to bel-7404 liver cancer cells was tested by the MTT assay. Most of the synthetic porphyrins had good anticancer activity toward bel-7404 liver cancer cells in the absence of light. These compounds might be potential anticancer medicines.

An anthracene/porphyrin dimer fluorescence energy transfer sensing system for picric acid.

The fluorescence energy transfer between anthracene (donor) and 5-p-[[4-(10'15'20'-triphenyl-5'-porphinato) phenyloxyl]-1-butyloxyl] phenyl-10,15,20-triphenyl-porphyrin (DTPP as acceptor) and an optical fiber sensor for the determination of picric acid based on this theory were studied. Because the emission spectrum of anthracene was largely overlapped with the absorption spectrum of the DTPP, the phenomenon of energy transfer occurred when anthracene and DTPP were immobilized in a PVC membrane. The membrane based on anthracene and DTPP contacting with picric acid showed much stronger fluorescence quenching comparing to membranes containing only anthracene or DTPP. The use of DTPP as acceptor was compared with 5,10,15,20-tetraphenylporphyrin (TPP). Both porphyrin compounds can be used as the acceptor, with DTPP clearly preferred. Under optimum conditions, picric acid in a sample solution can be determined from 3.0x10(-7) to 2.0x10(-3)moll(-1) with a detection limit of 1.5x10(-7)moll(-1). The proposed optical fiber sensor shows satisfactory characteristics including good reproducibility, reversibility and selectivity as well as a short response time. The recovery tests of picric acid in industrial wastewaters were satisfactory.