RESUMO
For the first time the influence of the chirality of the gel fibers in protein crystallogenesis has been studied. Enantiomeric hydrogels 1 and 2 were tested with model proteins lysozyme and glucose isomerase and a formamidase extracted from B. cereus. Crystallization behaviour and crystal quality of these proteins in both hydrogels are presented and compared.
Assuntos
Aldose-Cetose Isomerases/química , Amidoidrolases/química , Hidrogéis/química , Muramidase/química , Peptídeos/química , Dicroísmo Circular , Cristalização , Microscopia Eletrônica de TransmissãoRESUMO
Titanocene carboxylate 1 is an excellent chemoselective reagent for unprecedented α-regioselective Barbier-type reactions. It constitutes the first titanocene(III) able to tolerate epoxides and readily reduced carbonyl compounds, such as aromatic and α,ß-unsaturated aldehydes.
RESUMO
9-Alkyl xanthenones with different aliphatic pendant groups have been easily prepared by means of nucleophilic addition of the corresponding Grignard derivative to a tert-butyldimethylsilyl ether (TBDMS)-protected 3,6-dihydroxy-xanthenone. The photophysical behavior of the new dyes has been explored by using absorption, steady-state-, and time-resolved fluorescence measurements. We determined the equilibrium constants, visible spectral characteristics, fluorescence quantum yield, and decay times. Remarkably, they retain similar fluorescent properties of fluorescein including the characteristic phosphate-mediated excited-state proton-transfer (ESPT) reaction. 6-Hydroxy-9-isopropyl-3H-xanthen-3-one (5) was investigated in living cells; it presented a good permeability and efficient accumulation inside the cytosol. For the first time, we reported that the requirement of an aryl group at C-9 is no longer needed and new fluorescent sensors can be therefore easily developed.
