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Direct amide synthesis from equimolar amounts of carboxylic acid and amine using mesoporous silica as a versatile heterogeneous catalyst is reported. [ABSTRACT FROM AUTHOR]

The basidiomycete Coprinopsis cinerea produces five cellobiohydrolases belonging to glycoside hydrolase family 6 (GH6). Among these enzymes, C. cinerea cellulase 6C (CcCel6C), but not C. cinerea cellulase 6A (CcCel6A), can efficiently hydrolyze carboxymethyl cellulose and is constitutively expressed in C. cinerea. In contrast, CcCel6A possesses a cellulose-binding domain, and is strongly induced by cellobiose. Here, we determined the crystal structures of the CcCel6A catalytic domain complexed with a Hepes buffer molecule, with cellobiose, and with p-nitrophenyl β- d-cellotrioside ( pNPG3). A notable feature of the GH6 cellobiohydrolases is that the active site is enclosed by two loops to form a tunnel, and the loops have been demonstrated to open and close in response to ligand binding. The enclosed tunnel of CcCel6A-Hepes is seen as the open form, whereas the tunnels of CcCel6A-cellobiose and CcCel6A- pNPG3 adopt the closed form. pNPG3 was not hydrolyzed by CcCel6A, and bound in subsites +1 to +4. On the basis of this observation, we constructed two mutants, CcCel6A D164A and CcCel6C D102A. Neither CcCel6A D164A nor CcCel6C D102A hydrolyze phosphoric acid-swollen cellulose. We have previously determined the crystal structures of CcCel6C unbound and in complex with ligand, both of which adopt the open form. In the present study, both CcCel6A and CcCel6C mutants were identified as the closed form. However, the motion angle of CcCel6C was more than 10-fold greater than that of CcCel6A. The width of the active site cleft of CcCel6C was narrowed, owing to a tweezer-like motion. Database The coordinates and structure factors described in this article have been deposited in the Protein Data Bank under the accession codes , , , , and [ABSTRACT FROM AUTHOR]

The heterogeneous amidation reaction proves successful for the transformation of aryl and alkyl carboxylic acids as well as N-Boc-protected amino acids with primary aliphatic amines and secondary amines such as morpholine while delivering the desired amides in high to excellent yields. [ABSTRACT FROM AUTHOR]

Highlights: [•] The structure of the N-terminal domain of a GH131 protein was determined. [•] The structure is composed of a β-jelly roll fold. [•] The possible active site is wide and shallow. [•] Arg96, Glu98, Glu138, and His218 are likely to be catalytically critical. [•] The catalytic mechanism could be different from that of typical glycosidases. [ABSTRACT FROM AUTHOR]

Flash lamp annealing (FLA) technology is proposed as a new method of activating implanted impurities. By optimizing FLA and implantation conditions, junction depth (Xj) at the concentration of 1 × 10[sup 18] cm[sup -3] and the sheet resistance of 13 nm and 700 Ω/s. for As and 14 nm and 770 Ω/sq for BF[sub 2] with junction leakage lower than 1 × 10[sup -16] A/µm² at 1.5 V were successfully obtained without wafer slip and warpage problems. [ABSTRACT FROM AUTHOR]