Nucleophile-Triggered π-Topological Transformation: A New Synthetic Approach to Near-Infrared-Emissive Rhodamines.

We describe a π-topological transformation-based synthetic method for the preparation of a new type of near-infrared (NIR)-emissive rhodamine dye called Polymethine-embedded Rhodamine Fluorophore (PeR Fluor). In contrast to conventional NIR-emissive dyes that require tedious synthetic steps and/or a high cost, linear fully π-conjugated PeR Fluor can be regioselectively prepared in one step by mixing different nucleophiles with ABPXs, a family of rhodamines with a cross-conjugated structure. PeR Fluor exhibits bright NIR fluorescence emission and high photostability owing to the cooperative π-electron system of rhodamines and polymethine scaffolds.

The modular arabinanolytic enzyme Abf43A-Abf43B-Abf43C from Ruminiclostridium josui consists of three GH43 modules classified in different subfamilies.

The abnA gene from Ruminiclostridium josui encodes the large modular arabinanolytic enzyme, Abf43A-Abf43B-Abf43C, consisting of an N-terminal signal peptide, a Laminin_G_3 module, a GH43_22 module, a Laminin_G_3 module, a Big_4 module, a GH43_26 module, a GH43_34 module and a dockerin module in order with a calculated molecular weight of 204,108. Three truncated enzymes were recombinantly produced in Escherichia coli and biochemically characterized, RjAbf43A consisting of the first Laminin_G_3 module and GH43_22 module, RjAbf43B consisting of the second Laminin_G_3 module, Big_4 module and GH43_26 module, and RjAbf43C consisting of the GH43_34 module. RjAbf43A showed a strong α-l-arabinofuranosidase activity toward sugar beet arabinan, highly branched arabinan but not linear arabinan, thus it acted in the removal of arabinose side chains from sugar beet arabinan.