Biochemical, Stabilization and Crystallization Studies on a Molecular Chaperone (PaoD) Involved in the Maturation of Molybdoenzymes.,
Otelo-Cardoso, AR, Schwuchow V., Rodrigues D., Cabrita E. J., Leimkühler S., Romão MJ, and Santos-Silva T.
, PLoS One, Volume 9, p.e87295 , (2014)
AbstractMolybdenum and tungsten enzymes require specific chaperones for folding and cofactor insertion. PaoD is the chaperone of the periplasmic aldehyde oxidoreductase PaoABC. It is the last gene in the paoABCD operon in Escherichia coli and its presence is crucial for obtaining mature enzyme. PaoD is an unstable, 35 kDa, protein. Our biochemical studies showed that it is a dimer in solution with a tendency to form large aggregates, especially after freezing/thawing cycles. In order to improve stability, PaoD was thawed in the presence of two ionic liquids [C4mim]Cl and [C2OHmim]PF6 and no protein precipitation was observed. This allowed protein concentration and crystallization using polyethylene glycol or ammonium sulfate as precipitating agents. Saturation transfer difference – nuclear magnetic resonance (STD-NMR) experiments have also been performed in order to investigate the effect of the ionic liquids in the stabilization process, showing a clear interaction between the acidic ring protons of the cation and, most likely, negatively charged residues at the protein surface. DLS assays also show a reduction of the overall size of the protein aggregates in presence of ionic liquids. Furthermore, cofactor binding studies on PaoD showed that the protein is able to discriminate between molybdenum and tungsten bound to the molybdenum cofactor, since only a Mo-MPT form of the cofactor remained bound to PaoD.
Inhibition of LOX by flavonoids: a structure-activity relationship study.,
Ribeiro, D., Freitas M., Tomé SM, Silva AM, Porto G., Cabrita E. J., Marques M. M., and Fernandes E.
, European Journal of Medicinal Chemistry, Volume 72, p.137-145, (2014)
AbstractThe lipoxygenase (LOX) products have been identified as mediators of a series of inflammatory diseases, namely rheumatoid arthritis, inflammatory bowel disease, psoriasis, allergic rhinitis, atherosclerosis and certain types of cancer. Hence, LOX inhibitors are of interest for the modulation of these phenomena and resolution of the inflammatory processes. During LOX activity, peroxyl radical complexes are part of the reaction and may function as sources of free radicals. Thus antioxidants, such as flavonoids, capable of inhibiting lipid peroxidation and scavenging free radicals, may act as LOX inhibitors. The aim of this work was to assess the structure–activity relationship among a series of flavonoids concerning 5-LOX inhibition, through a systematic study of the inhibition of the formation of LTB4 in human neutrophils. The type of inhibition of the flavonoids was further studied using soybean LOX, type I, and Saturation Transfer Difference 1H NMR (STD-1H NMR) was used to characterize the binding epitopes of the compounds to LOX-1. The obtained results reinforce flavonoids as effective inhibitors of LTB4 production in human neutrophils. It was also possible to establish a structure/activity relationship for the inhibitory activity and the type of inhibition.
Ion Jelly Conductive Properties Using Dicyanamide-Based Ionic Liquids,
Carvalho, T., Augusto V., Rocha A., Lourenco N. M. T., Correia N. T., Barreiros S., Vidinha P., Cabrita E. J., and Dionisio M.
, Journal of Physical Chemistry B, Volume 118, Issue 31, p.9445-59, (2014)
AbstractThe thermal behavior and transport properties of several ion jellys (IJs), a composite that results from the combination of gelatin with an ionic liquid (IL), were investigated by dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), and pulsed field gradient nuclear magnetic resonance spectroscopy (PFG NMR). Four different ILs containing the dicyanamide anion were used: 1-butyl-3-methylimidazolium dicyanamide (BMIMDCA), 1-ethyl-3-methylimidazolium dicyanamide (EMIMDCA), 1-butyl-1-methylpyrrolidinium dicyanamide (BMPyrDCA), and 1-butylpyridinium dicyanamide (BPyDCA); the bulk ILs were also investigated for comparison. A glass transition was detected by DSC for all materials, ILs and IJs, allowing them to be classified as glass formers. Additionally, an increase in the glass transition temperature upon dehydration was observed with a greater extent for IJs, attributed to a greater hindrance imposed by the gelatin matrix after water removal, rendering the IL less mobile. While crystallization is observed for some ILs with negligible water content, it was never detected for any IJ upon thermal cycling, which persist always as fully amorphous materials. From DRS measurements, conductivity and diffusion coefficients for both cations (D+) and anions (D–) were extracted. D+ values obtained by DRS reveal excellent agreement with those obtained from PFG NMR direct measurements, obeying the same VFTH equation over a large temperature range (ΔT ≈ 150 K) within which D+ varies around 10 decades. At temperatures close to room temperature, the IJs exhibit D values comparable to the most hydrated (9%) ILs. The IJ derived from EMIMDCA possesses the highest conductivity and diffusion coefficient, respectively, 10–2 S·cm–1 and 10–10 m2·s–1. For BMPyrDCA the relaxational behavior was analyzed through the complex permittivity and modulus formalism allowing the assignment of the detected secondary relaxation to a Johari–Goldstein process. Besides the relevant information on the more fundamental nature providing physicochemical details on ILs behavior, new doorways are opened for practical applications by using IJ as a strategy to produce novel and stable electrolytes for different electrochemical devices.