RESUMO
A putative class III endochitinase (ChiIII) was reported previously to be expressed dominantly in fruiting bodies of Coprinopsis cinerea, and its expression levels increased with the maturation of the fruiting bodies. This paper further reports that ChiIII is a novel chitinase with exo- and endoactivities. When the substrate was (GlcNAc)3-5, ChiIII exhibited exoactivity, releasing GlcNAc processively from the reducing end of (GlcNAc)3-5; when the substrate was (GlcNAc)6-7, the activity of ChiIII shifted to an endoacting enzyme, randomly splitting chitin oligosaccharides to various shorter oligosaccharides. This shift in the mode of action of ChiIII may be related to its stronger hydrolytic capacity to degrade chitin in fungal cell walls. The predicted structure of ChiIII shows that it lacks the α+ß domain insertion; however, its substrate binding cleft seems to be deeper than that of common endochitinases but shallower and more open than that of common exochitinases, which may be related to its exo- and endohydrolytic activities.
Assuntos
Acetilglucosamina/metabolismo , Agaricales/enzimologia , Quitinases/química , Proteínas Fúngicas/química , Oligossacarídeos/química , Oligossacarídeos/metabolismo , Agaricales/química , Agaricales/genética , Sequência de Aminoácidos , Quitina/química , Quitina/metabolismo , Quitinases/genética , Quitinases/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Dados de Sequência Molecular , Especificidade por SubstratoRESUMO
Three microporous Ln-Co-pyta heterometallic compounds [Ln4Co3(pyta)6(H2O)9].5H2O (Ln = Sm (1), Eu (2), Gd (3); H3pyta = 2,4,6-pyridinetricarboxylic acid) have interesting selective adsorption abilities towards H2/N2 and CO2/N2 because of size-selective effects; magnetic analysis reveals that has a ferromagnetic behavior.
Assuntos
Gases/química , Magnetismo , Adsorção , Modelos Moleculares , Conformação Molecular , PorosidadeRESUMO
Density functional theory calculations have been employed to study the effects of alloy on energetics and preferential adsorption sites of atomic (H, C, N, O, S), molecular (N(2), NO, CO), and radical (CH(3), OH) adsorption on RhMn(111) alloy surface, and underlying electronic and structural reasons have been mapped out. We find that though Mn is energetically favorable to stay in the subsurface region, the RhMn surface alloy may be developed via the segregation induced by strong interaction between oxygen-containing species and Mn. Independent of adsorbates (not including O and OH), the interactions between these species and Rh atoms are preferential, and enhanced in general due to the ligand effects induced by Mn nearby. In contrast, oxygen-containing species (atomic oxygen and hydroxyl) prefer to coordinate with Mn atom due to the significant hybridization between oxygen and Mn, a manifestation of the ensemble effects. The order of the binding energies on RhMn alloy surface from the least to the most strongly bound is N(2)
RESUMO
CH(x) (x=1-3) adsorptions on clean and CO precovered Rh(111) surfaces were studied by density functional theory calculations. It is found that CH(x) (x=1-3) radicals prefer threefold hollow sites on Rh(111) surfaces, and the bond strength between CH(x) and Rh(111) follows the order of CH(3)
