Preparation and SO₂ Absorption/Desorption Properties of Crosslinked Poly(1,1,3,3‐Tetramethylguanidine Acrylate) Porous Particles

Abstract

We have probed Pichia stipitis CBS 6054 Old Yellow Enzyme 2.6 (OYE 2.6) by several strategies including X‐ray crystallography, ligand binding and catalytic assays using the wild‐type as well as libraries of site‐saturation mutants. The alkene reductase crystallized in space group P 63 2 2 with unit cell dimensions of 127.1×123.4 Å and its structure was solved to 1.5 Å resolution by molecular replacement. The protein environment surrounding the flavin mononucleotide (FMN) cofactor was very similar to those of other OYE superfamily members; however, differences in the putative substrate binding site were also observed. Substrate analog complexes were analyzed by both UV‐Vis titration and X‐ray crystallography to provide information on possible substrate binding interactions. In addition, four active site residues were targeted for site saturation mutagenesis (Thr 35, Ile 113, His 188, His 191) and each library was tested against three representative Baylis–Hillman adducts. Thr 35 could be replaced by Ser with no change in activity; other amino acids (Ala, Cys, Leu, Met, Gln and Val) resulted in diminished catalytic efficiency. The Ile 113 replacement library yielded a range of catalytic activities, but had very little impact on stereoselectivity. Finally, the two His residues (188 and 191) were essentially intolerant of substitutions with the exception of the His 191 Asn mutant, which did show significant catalytic ability. Structural comparisons between OYE 2.6 and Saccharomyces pastorianus OYE1 suggest that the key interactions between the substrate hydroxymethyl groups and the side‐chain of Thr 35 and/or Tyr 78 play an important role in making OYE 2.6 an (S)‐selective alkene reductase.

Preparation and SO2 Sorption/Desorption Behavior of an Ionic Liquid Supported on Porous Silica Particles

“…Similar incomplete desorption has been also observed in the ionic liquid TMGA and IL polymers such as poly(TMGA) and poly(TMGA-co-MBA). 16,17 It is also evident in Figure 6 that the SO 2 sorption rates of TMGL-SiO 2 were very high, reaching their equilibrium sorption capacities in about 15 min at 30°C. The sorption rates were also very high at 20°C and were much higher than that of pure TMGL, as shown in Figure 7.…”

Transformation of self‐assembled structures from spherical aggregates in solution to a network structure on a two‐dimensional surface

“…The lower contact angle would lead to a relatively larger wetting scale, thus results in the less material on a volumetric basis and tends to be easier to form a film with monolayer structure. Because of their long range nanoporous structures, the network‐based films observed here could have various potential applications, such as gas separation, biosensors, or catalyst supports…”

Properties of Metal-Doped Covalent Organic Frameworks and Their Interactions with Sulfur Dioxide

“…Reducing sulfur dioxide emission has become one of the most important social and environmental challenges [3][4][5]. It should be pointed out that adsorption by porous nanomaterials is recognized as an efficient and economical approach for capture of low concentration SO 2 from mixture gases [6][7][8][9][10]. Covalent organic frameworks (COFs) are ideal porous materials for gas capture due to their low density, good stability, and large surface area [11][12][13][14][15].…”