Search for: All records

Morphological novelties, or key innovations, are instrumental to the diversification of the organisms. In plants, one such innovation is the evolution of zygomorphic flowers, which is thought to promote outcrossing and increase flower morphological diversity. We isolated three allelic mutants from twoMimulusspecies displaying altered floral symmetry and identified the causal gene as the ortholog ofArabidopsis BLADE-ON-PETIOLE. We found that MlBOP and MlCYC2A physically interact and this BOP-CYC interaction module is highly conserved across the angiosperms. Furthermore, MlBOP self-ubiquitinates and suppressesMlCYC2Aself-activation. MlCYC2A, in turn, impedes MlBOP ubiquitination. Thus, this molecular tug-of-war between MlBOP and MlCYC2A fine-tunes the expression ofMlCYC2A, contributing to the formation of bilateral symmetry in flowers, a key trait in angiosperm evolution. 

We studied the production of levoglucosenone (LGO) via levoglucosan (LGA) dehydration using Brønsted solid acid catalysts in tetrahydrofuran (THF). The use of propylsulfonic acid functionalized silica catalysts increased the production of LGO by a factor of two compared to the use of homogeneous acid catalysts. We obtained LGO selectivities of up to 59% at 100% LGA conversion using solid Brønsted acid catalysts. Water produced during the reaction promotes the solvation of the acid proton reducing the activity and the LGO production. Using solid acid catalysts functionalized with propylsulfonic acid reduces this effect. The hydrophilicity of the catalyst surface seems to have an effect on reducing the interaction of water with the acid site, improving the catalyst stability. 

Levoglucosanol (LGOL) is a critical intermediate for the bio-based production of hexane-1,2,5,6-tetrol, 1,2,6-hexanetriol, and 1,6-hexanediol. Here we report on the aqueous-phase hydrogenation of cellulose-derived dihydrolevoglucosenone (Cyrene™) to LGOL using a calcined and reduced heterogeneous copper/hydrotalcite/mixed oxide catalyst, denoted as Cu8/MgAlO x - HP . The turnover frequency for LGOL conversion over this copper-containing catalyst is equal to 0.013 s −1 at 353 K as measured in a flow reactor which is half the one obtained using 0.4 wt% Pd/Al 2 O 3 . Moreover, while Cu8/MgAlO x - HP shows a stable activity, the activity of 0.4 wt% Pd/Al 2 O 3 decreases with time-on-stream. Neither Cu- nor Al-leaching is observed (resp. <1 ppb and <1 ppm) but Mg leaching can be seen (5.5 ppm). The latter leaching relates to the acidity of the Cyrene/H 2 O mixture (pH 3.5–4.5 range), which is due to the occurrence of the geminal diol moiety of Cyrene, an acidic species. In contrast, additional and consecutive oxidation and reduction of the catalyst leads to a gradual decrease in activity over time. Applying still further oxidation/reduction cycles to this catalyst tends to decrease its activity with some overall stabilization being observed from the fourth run onwards. Mg-leaching is shown to change the relative meso-to-macro pore content, but leaves the total pore volume unchanged between the fresh and the spent catalyst. In spite of the high copper loading (8 wt%), small Cu-nanoparticles (2–3 nm) are present over the hydrotalcite/mixed oxide surface of the Cu8/MgAlO x - HP material, and these particles do not aggregate during the hydrogenation reaction.