No abstract

The stability of porcine brain inositol monophosphatase in the presence of increasing concentrations of urea was investigated at pH 7.5. Exposure of the enzyme to 8 M urea brings about the dissociation of the dimeric species of 58 kDa into monomeric forms as revealed by gel filtration chromatography. Unfolding of the protein by 8 M urea results in a decrease of the ellipticity at 220 nm (20%) together with a perturbation of the near-UV circular dichroism spectrum. Urea-treated inositol monophosphatase binds Co2+ ions with a dissociation constant of 3.3 microM. The enzyme is catalytically competent when assayed with 4-nitrophenyl-phosphate in the presence of the activating ion Co2+ at pH 7.5 in 8 M urea. The apparent activation constant for Co2+ is 2.5 mM. It is postulated that partially folded conformations of monomeric species preserve their catalytic function because the affinity of Co2+ ions for the metal coordination center of the protein is not perturbed by exposure to 8 M urea.

A novel triazine-based covalent organic framework (TFPT-Bz COF) has been constructed by the condensation of 2,4,6-tris(5-formyl-2-pyridinoxy)-1,3,5-triazine (TFPT) and benzidine (BZ) with deep eutectic solvent (DES) as the reaction medium. After the introduction of Pd ions through strong coordination to TFPT-Bz COF matrix, the constructed TFPT-Bz COF/Pd composite exhibited excellent catalytic activity for CÀ H arylation of azoles with aryl halides in 2methyltetrahydrofuran. The protocol allows the arylation of a variety of substituted azoles with diverse aryl halides in high to excellent yield. Moreover, the TFPT-Bz COF/Pd catalyst can be recycled several times without significantly reducing its activity.