MOSAIC method builds gene fragments by hybridisation; living E. coli cells run nitrene transfer; copper catalyst converts amines under blue light
The MOSAIC method allows more than 1,000 gene fragments in a one-pot reaction. Living E. coli cells run an intermolecular nitrene transfer. A copper catalyst converts tertiary amines under blue light.
Science··Evening
MOSAIC method builds gene fragments by hybridisation
The method, called Molecular Self-Assembly Induced Cloning, replaces enzymatic assembly with hybridisation: overlapping oligonucleotides synthesised on a microchip anneal into target fragments in vitro, and host-cell DNA repair completes the assembly after uptake, allowing more than 1,000 distinct gene fragments in a single one-pot reaction. The authors report near-zero misalignment across genes in the parallel reaction, with oligonucleotide synthesis errors staying at a constant and controllable level. They also built large variant libraries of the plastic-degrading enzyme PETase and recovered variants more active than the reference enzyme. The demonstration provides a synthesis and screening platform; scaling it into an industrial process would need further work.[1]
Living E. coli cells run nitrene transfer
The authors show that a chemical reaction not found in nature, intermolecular nitrene transfer, can run on metabolic intermediates made inside living cells: E. coli biosynthesises N-acetoxyanilines, and an engineered cytochrome P450 generates and transfers N-aryl nitrenes from them. The products are amino alcohols, diamines, diarylamines and aminoalkyl arenes, substructures common in pharmaceuticals and agrochemicals and awkward to make by standard organic synthesis, and the starting material is inexpensive renewable carbon feedstock. Evolving the pathway enzymes raised titres, and the products were obtained with high enantioselectivity.[2]
Copper catalyst converts amines under blue light
N-demethylation matters in drug metabolism and in late-stage modification of amines but usually needs precious metals. The authors describe a recyclable photocatalyst of atomically dispersed copper on functionalised graphitic carbon nitride that converts tertiary amines to secondary amines in high yield under 390 nanometre light and oxygen. The reaction scaled to 10 millimoles and the catalyst kept its activity through more than 10 reuse cycles. Isolated copper sites were confirmed by X-ray photoelectron spectroscopy, solid-state NMR measurements, scanning transmission electron microscopy and extended X-ray absorption fine structure. Radical trapping, isotope labelling, kinetic analysis, in situ infrared spectroscopy and density functional calculations support a route through amine oxidation, superoxide formation, hydrogen abstraction, iminium generation and hydrolysis.[3]
