New derivatives of α-phenyl-N-tert-butyl nitrone (PBN) bearing a hydroxyl, an acetate, or an acetamide substituent on the N-tert-butyl moiety and para-substituted phenyl or naphthlyl moieties were synthesized. Their ability to trap hydroxymethyl radical was evaluated by electron paramagnetic resonance spectroscopy. The presence of two electron-withdrawing substituents on both sides of the nitronyl function improves the spin-trapping properties, with 4-HOOC–PBN–CH2OAc and 4-HOOC–PBN–CH2NHAc being ∼4× more reactive than PBN. The electrochemical properties of the derivatives were further investigated by cyclic voltammetry and showed that the redox potentials of the nitrones are largely influenced by the nature of the substituents both on the aromatic ring and on the N-tert-butyl function. The acetamide derivatives PBN–CH2NHAc, 4-AcNHCH2–PBN–CH2NHAc, and 4-MeO–PBN–CH2NHAc were the easiest to oxidize. A computational approach was used to rationalize the effect of functionalization on the free energies of nitrone reactivity with hydroxymethyl radical as well as on the electron affinity and ionization potential. Finally, the neuroprotection of the derivatives was evaluated in an in vitro model of cellular injury on cortical neurons. Five derivatives showed good protection at very low concentrations (0.1–10 μM), with PBN–CH2NHAc and 4-HOOC–PBN being the two most promising agents.
Two new surfactants, F 5 OM and F 5 DM, were designed as partially fluorinated analogs of ndodecyl-β-D-maltoside (DDM). The micellization properties and the morphologies of the aggregates formed by the two surfactants in water and phosphate buffer were evaluated by NMR spectroscopy, surface tension measurement (SFT), isothermal titration calorimetry (ITC), dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and analytical ultracentrifugation (AUC). As expected, the critical micellar concentration (CMC) was found to decrease with chain length of the fluorinated tail from 2.1-2.5 mM for F 5 OM to 0.3-0.5 mM for F 5 DM, and micellization was mainly entropy-driven at 25°C. Close to their respective CMC, the micelle sizes were similar for both surfactants i.e. 7 and 13 nm for F 5 OM and F 5 DM, respectively and both increased with concentration forming 4 nm diameter rods with maximum dimensions of 50 and 70 nm, respectively, at a surfactant concentration of ~30 mM. The surfactants were found to readily solubilize lipid vesicles and extract membrane proteins (MPs) directly from Escherichia coli membranes. They were found more efficient than the commercial fluorinated detergent F 6 H 2 OM over a broad range of concentrations (1-10 mM) and even better than DDM at low concentrations (1-5 mM). When transferred into the two new surfactants, the thermal stability of the proteins bacteriorhodopsin (bR) and FhuA were higher than in the presence of their solubilization detergents and similar to that in DDM; furthermore, bR was stable over several months. The membrane enzymes SpNOX and BmrA were not as active as in DDM micelles but similarly active as in F 6 OM. Together, these findings indicate both extracting and stabilizing properties of the new maltose-based fluorinated surfactants, making them promising tools in MPs applications.
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