A new series of hydrophilic, lipophilic, and amphiphilic alpha-phenyl-N-tert-butylnitrone (PBN) derivatives were synthesized to explore the relationship between their hydrophilic-lipophilic properties and antioxidant potency. Very potent protective effects of amphiphilic lactobionamide and tris(hydroxymethyl)aminomethane PBN derivatives were observed in mitochondrial preparations, in cell cultures, and in rotifers exposed to unspecific and mitochondria targeted oxidotoxins.

Mixed protein-surfactant micelles are used for in vitro studies and 3D crystallization when solutions of pure, monodisperse integral membrane proteins are required. However, many membrane proteins undergo inactivation when transferred from the biomembrane into micelles of conventional surfactants with alkyl chains as hydrophobic moieties.Here we describe the development of surfactants with rigid, saturated or aromatic hydrocarbon groups as hydrophobic parts. Their stabilizing properties are demonstrated with three different integral membrane proteins. The temperature at which 50% of the binding sites for specific ligands are lost is used as a measure of stability and dodecyl-β-D-maltoside ("C12-b-M") as a reference for conventional surfactants. One surfactant increased the stability of two different G protein-coupled receptors by approximately 10°C compared to C12-b-M. Another surfactant yielded a stabilization of the human Patched protein receptor by 13°C.In addition, one of the surfactants was successfully used to stabilize and crystallize the cytochrome b 6 f complex from Chlamydomonas reinhardtii. The structure was solved to the same resolution as previously reported in C12-b-M. Declaration of Interest statementThe authors report no declarations of interest. Mixed protein-surfactant micelles are often used for in vitro studies when solutions of pure, monodisperse integral membrane proteins are needed (Garavito and Ferguson-Miller, 2001). Because integral membrane proteins evolved in a lipid bilayer environment, the exchange of lipid for surfactant frequently causes a destabilization of the protein. This can result in increased activity followed by increased rate of denaturation, increased susceptibility to protease attack, accelerated heat denaturation, oxidative damage, loss of activity regulation and lack of crystallization (Tanford and Reynolds, 1976;Tate, 2010). Europe PMC Funders GroupAt the beginning of membrane protein research only surfactants developed as detergents for consumer or industrial use were available many of which were inhomogenous. In-vitro studies of solubilized membrane proteins and structural work (Rosenbusch et al., 1981;Michel and Oesterhelt, 1980) led to an increasing demand in tailored surfactants. In the micellar solution the protein should be functional and stable for extended periods of time and the micellar belt attached to the protein should be small in order to leave much of the polar protein surfaces uncovered for crystal lattice contacts (Michel, 1983).Studies of the micellar mass revealed the relation between the chemical structure of a surfactant and the size of its micelle. It was found to depend upon the ratio of the polar cross-section and the length of the extended hydrophobic chain (Israelachvili et al., 1976). In case of spherical micelles the latter matches the radius of the hydrophobic core. With alkyl chains as hydrophobic moieties of surfactants proteins require a length between an extended octyl and a dodecyl chain (Iwata, 2003).Small micelles are for...

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