Search

Platinum(II) metalla‐N‐heterocyclic carbene complexes featuring pyridyl heterocyclic moiety demonstrate remarkable catalytic efficiency in alkyne hydrosilylation under green light irradiation. The photocatalytic properties of complexes are rationalised by the photo‐induced charge transfer occurring in extended condensed system identified with the help of various experimental (UV/vis and emission spectroscopy, cyclic voltammetry) and theoretical methods (DFT/TD‐DFT, IFCT analysis). [ABSTRACT FROM AUTHOR]

Endo‐β‐xylanases are hemicellulases involved in the conversion of xylans in plant biomass. Here, we report a novel acidophilic β‐xylanase (ScXynA) with high transglycosylation abilities that was isolated from the filamentous fungus Scytalidium candidum 3C. ScXynA was identified as a glycoside hydrolase family 10 (GH10) dimeric protein, with a molecular weight of 38 ± 5 kDa per subunit. The enzyme catalyzed the hydrolysis of different xylans under acidic conditions and was stable in the pH range 2.6–4.5. The kinetic parameters of ScXynA were determined in hydrolysis reactions with p‐nitrophenyl‐β‐d‐cellobioside (pNP‐β‐Cel) and p‐nitrophenyl‐β‐d‐xylobioside (pNP‐β‐Xyl2), and kcat/Km was found to be 0.43 ± 0.02 (s·mM)−1 and 57 ± 3 (s·mM)−1, respectively. In the catalysis of the transglycosylation o‐nitrophenyl‐β‐d‐xylobioside (oNP‐β‐Xyl2) acted both as a donor and an acceptor, resulting in the efficient production of o‐nitrophenyl xylooligosaccharides, with a degree of polymerization of 3–10 and o‐nitrophenyl‐β‐d‐xylotetraose (oNP‐β‐Xyl4) as the major product (18.5% yield). The modeled ScXynA structure showed a favorable position for ligand entry and o‐nitrophenyl group accommodation in the relatively open −3 subsite, while the cleavage site was covered with an extended loop. These structural features provide favorable conditions for transglycosylation with oNP‐β‐Xyl2. The acidophilic properties and high transglycosylation activity make ScXynA a suitable choice for various biotechnological applications, including the synthesis of valuable xylooligosaccharides. [ABSTRACT FROM AUTHOR]

The dihalomethanes CH2X2 (X=Cl, Br, I) were co‐crystallized with the isocyanide complexes trans‐[MXM2(CNC6H4‐4‐XC)2] (M=Pd, Pt; XM=Br, I; XC=F, Cl, Br) to give an extended series comprising 15 X‐ray structures of isostructural adducts featuring 1D metal‐involving hexagon‐like arrays. In these structures, CH2X2 behave as bent bifunctional XB/XB‐donating building blocks, whereas trans‐[MXM2(CNC6H4‐4‐XC)2] act as a linear XB/XB acceptors. Results of DFT calculations indicate that all XCH2–X⋅⋅⋅XM–M contacts are typical noncovalent interactions with estimated strengths in the range of 1.3–3.2 kcal mol−1. A CCDC search reveals that hexagon‐like arrays are rather common but previously overlooked structural motives for adducts of trans‐bis(halide) complexes and halomethanes. [ABSTRACT FROM AUTHOR]