Effect of side-chain length in lignin model compound on MnO2 oxidation: comparison of oxidations between C6-C2- and C6-C1-type compounds

Monomeric C6-C2-type lignin model compounds with a p-hydroxyphenyl (H), guaiacyl (G), syringyl (S), or p-ethylphenyl (E) nucleus (1-phenylethanol derivatives) were individually oxidized by MnO2 at a pH of 1.5 and room temperature. The results were compared with those of the corresponding C6-C1-type benzyl alcohol derivatives obtained in our recent report to examine the effect of the presence of the β-methyl group on the oxidation. The presence decelerated the oxidation regardless of the type of aromatic nucleus, although it did not change the order of the oxidation rates: G > S >> H > E. This deceleration results from the steric factor of the β-methyl group in the C6-C2-type compounds. The MnO2 oxidations of the corresponding C6-C2-type compounds deuterated at their α-(benzyl)positions showed that the magnitudes of the kinetic isotope effects are smaller than those observed in the oxidations of the corresponding C6-C1-type compounds, regardless of the type of aromatic nucleus. These smaller magnitudes suggest that the presence of the β-methyl group shifts the initial oxidation mode of MnO2 from direct oxidation of the benzyl position to one-electron oxidation of the aromatic nucleus. Only the S-type compounds afforded products via degradation of the aromatic nuclei.

Low-toxicity amphiphilic molecules linked by an aromatic nucleus show broad-spectrum antibacterial activity and low drug resistance

Amphiphilic molecules linked by an aromatic nucleus, possessing strong bactericidal activity, high selectivity, less drug resistance, and high in vivo efficacy against MRSA, were developed.

Expansion of the substrate range of the gentisate 1,2-dioxygenase from Corynebacterium glutamicum for the conversion of monohydroxylated benzoates

The gentisate 1,2-dioxygenases (GDOs) from Corynebacterium glutamicum and various other organisms oxidatively cleave the aromatic nucleus of gentisate (2,5-dihydroxybenzoate), but are not able to convert salicylate (2-hydroxybenzoate). In contrast, the α-proteobacterium Pseudaminobacter salicylatoxidans synthesises an enzyme (‘salicylate dioxygenase’, SDO) which cleaves gentisate, but also (substituted) salicylate(s). Sequence comparisons showed that the SDO belongs to a group of GDOs mainly originating from Gram-positive bacteria which also include the GDO from C. glutamicum ATCC 13032. The combination of sequence comparisons with previously performed structural and mutational analyses of the SDO allowed to identify an amino acid residue (Ala112) which might prevent the oxidation of (substituted) salicylate(s) by the GDO from C. glutamicum. Therefore, the relevant mutation (Ala→Gly) was introduced into the GDO from C. glutamicum. The GDO variant obtained gained the ability to oxidise salicylate and several other monohydroxylated substrates. In order to screen a broader range of enzyme variants a chromogenic assay was developed which allowed the detection of bacterial colonies converting salicylate. The applicability of this test system was proven by screening a set of GDO variants obtained by saturation mutagenesis at different positions. This demonstrated that also GDO variants carrying the mutations Ala112→Ser, Ala112→Ile and Ala112→Asp converted salicylate.

Palladium-catalyzed Br/D exchange of arenes: selective deuterium incorporation with versatile functional group tolerance and high efficiency

A facile method for introducing deuterium atoms onto an aromatic nucleus via Br/D exchange with high efficiency is disclosed.

Study on Hydrophobic Microorganism as Coal Bio-Desulfurizing Agent

Mycobacterium phlei belongs to protozoa,it is innocuous and it doesnt have any pathogenicity to all animals.Base on research of the biologic character of the hydrophobic microorganism and analysis of the FTIR spectrum and so on.Experiment results indicated that the surface of Mycobacterium phlei contains cyclanes,alicyclic hydrocarbon,aromatic nucleus and many kinds of organic function group and ionizing group so it was highly hydrophobic and highly charge.Because of this special biology surface character,Mycobacterium phlei may selective adsorption on the surface of coal and make coal form flock,and meanwhile effectually get rid of pyritic sulfur in coal.The Experimental effect of the Mycobacterium phlei on the getting rid of pyretic in the coal was obvious.The maximum pyrite desulphurization rate was reach to 72.63%,but the desulphurization percentage of organic sulfur was lower.The desulphurization rate was only 18.91%.