We have developed a DNA-based hybrid catalyst containing an intrastrand bipyridine ligand through direct ligand incorporation and successfully performed asymmetric intramolecular Friedel−Crafts alkylations. This is the first report on the DNA hybrid catalyst system where an intrastrand ligand is covalently introduced into the phosphate backbone. We have generated a series of active site to investigate the structural details of DNA hybrid catalysts and demonstrated that catalytic properties of DNA hybrid catalysts are governed by the disposition of the metal-binding site in the DNA duplex, the size of catalytic cavity, and the composition of nucleobases in the catalytic pocket.
Previously, two mutations (G91D and A93T)in rplV, which encodes the ribosomal large subunit protein 22 (L22), were isolated as arrest-defective mutations for SecM (7), the first identified intrinsic arrest polypeptide (7-9). These mutations are located at a constriction site in the ribosome exit tunnel. The former mutation dramatically decreased the VemP arrest efficiency, whereas the latter mutation did not; thus, specific interactions exist between the VemP nascent chain and the interior of the exit tunnel of the ribosome, and the interaction mode of VemP is different from that of SecM (6). However, the mechanism via which the conserved segment inactivates the peptidyl transfer center (PTC) 2 of the ribosome remains unclear.In this study, we constructed and evaluated an E. coli reporter system to easily and precisely Bands corresponding to the arrested polypeptide with the unprocessed signal sequence (156 residues), the arrested and signal sequence-processed polypeptide (130 residues), and the mature (signal sequenceprocessed) full-length product (174 residues) were clearly separated by large differences in mobility on SDS-PAGE (Fig. 1B, compare lanes 1-3 and 10-12).In a sec-deficient condition obtained by overexpression of the Syd protein in a secY24background (11,12), the unprocessed/arrested
We report here DNA metalloenzymes that catalyze the asymmetric Diels-Alder reaction with high conversion, excellent endo/exo selectivities, and enantioselectivities up to-97% ee. Their catalytic-pocket architectures were organized using a rational design strategy based on the Cu(II) ion, the composition of nucleobases, and the incorporation of flexible linkers. Without using the mirror image of B-DNA, DNA metalloenzymes afforded the opposite enantiomer of the Diels-Alder product compared with those obtained using a supramolecular Cu(II)-dmbpy/st-DNA catalyst system. Furthermore, we devised DNA metalloenzymes without the incorporation of an artificial binding ligand and successfully performed a Diels-Alder reaction. This study provides a new perspective on the catalytic repertoire of nucleic acids and will expand the application scope of metalloenzymes.
Materials Deoxynucleic Acid from salmon testes (st-DNA) was purchased from Aldrich and used as received. N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) and tetraethyl orthosilicate (TEOS) were purchased from TCI and used as received. All other chemicals and solvents were purchased from Sigma-Aldrich Chemicals Co., Wako Pure Chemical Ind. Ltd., TCI, and Nacalai Chemical Co. Water was deionized (specific resistance of > 18.0 MW cm at 25 °C) by a Milli-Q system (Millipore Corp.). Aza-chalcone 1a was synthesized as reported procedure. 1 Cyclopentadiene was prepared by cracking dicyclopentadiene. Substrate 4 for intramolecular Friedel-Crafts alkylations was synthesized as previously reported. 4 Methods For the synthesis of substrates and the preparative-scale reactions, NMR spectra were obtained on a JEOL JNM ECA-600 spectrometer operating at 600 MHz for 1 H NMR and in CDCl 3 unless otherwise noted. Flash Column chromatography was performed employing WakoGel
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