Los modelos arquitectónicos de Sir John Soane: un catálogo

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La maqueta arquitectónica: Barroco inglés

Peer Reviewe

La maqueta arquitectónica: Barroco inglés

Contributi di: Giovanni Aquilino, Alessio Cavicchi, Mara Cerquetti, Eleonora Cutrini, Stefano Della Torre, Concetta Ferrara, Barbara Fidanza, Alessandro Hinna, Massimo Montella, Roberto Pern

Los modelos arquitectónicos de Sir John Soane: un catálogo

Peer Reviewe

Los modelos arquitectónicos de Sir John Soane: un catálogo

Peer Reviewe

Using light scattering to assess how phospholipid-protein interactions affect complex I functionality in liposomes.

Acknowledgements: This study was supported by a Feodor-Lynen fellowship from the Alexander von Humboldt Foundation to JE, a Leverhulme Research Grant to MMR (RPG-2018-183), and by the Medical Research Council (MC_UU_00015/2 to JH). Francisca Figueiredo (Imperial College) is acknowledged for initial DLS and ELS measurements with varying lipid content in PLs. We thank the anonymous reviewers for their helpful comments.Complex I is an essential membrane protein in respiration, oxidising NADH and reducing ubiquinone to contribute to the proton-motive force that powers ATP synthesis. Liposomes provide an attractive platform to investigate complex I in a phospholipid membrane with the native hydrophobic ubiquinone substrate and proton transport across the membrane, but without convoluting contributions from other proteins present in the native mitochondrial inner membrane. Here, we use dynamic and electrophoretic light scattering techniques (DLS and ELS) to show how physical parameters, in particular the zeta potential (ζ-potential), correlate strongly with the biochemical functionality of complex I-containing proteoliposomes. We find that cardiolipin plays a crucial role in the reconstitution and functioning of complex I and that, as a highly charged lipid, it acts as a sensitive reporter on the biochemical competence of proteoliposomes in ELS measurements. We show that the change in ζ-potential between liposomes and proteoliposomes correlates linearly with protein retention and catalytic oxidoreduction activity of complex I. These correlations are dependent on the presence of cardiolipin, but are otherwise independent of the liposome lipid composition. Moreover, changes in the ζ-potential are sensitive to the proton motive force established upon proton pumping by complex I, thereby constituting a complementary technique to established biochemical assays. ELS measurements may thus serve as a more widely useful tool to investigate membrane proteins in lipid systems, especially those that contain charged lipids

Limonene derived phosphines in the cobalt-catalysed hydroformylation of alkenes

Cobalt complexes involved in the hydroformylation of alkenes using (4R,S)-4,8-dimethyl-2-octadecyl-2-phosphabicyclo[3.3.1]nonane (LIM-18), which consists of a mixture of two diastereomers, have been studied. Complexation to cobalt has been used to separate or enrich the enantiomers so that spectroscopic parameters can be determined for complexes of the form [CO2(CO)(8-n)(LIM-18)(n)] (n = 1 or 2) and [Co(CO)(3)(LIM-18)(2)][Co(CO)(4)] containing the different diastereomers. An X-ray structure of a complex of the form [Co(CO)(3)(LIM-18)](2) shows it to contain the (4R) isomer, but since this was isolated from a mixed solution of diastercomers, this does not definitively identify whether the (4R) or (4S) isomer is the more strongly coordinating isomer. Experimental studies backed up with molecular modelling suggest that steric and electronic effects determine which isomer reacts preferentially in coordination, protonation and methylation reactions. The (4R) isomer is the more strongly coordinating and is metallated preferentially, although the (4S) isomer is the more basic. Variable temperature and high pressure NMR studies on the acyl complex, [Co(C(O)C5H9)(CO)(3)(LIM-18)], suggest that product elimination may be accompanied by isomerisation to branched acyl species. Modified cobalt catalysed hydroformylation of reactions suggest that the two diastereomers of LIM-18 do not give greatly different rates or selectivities and that a long chain secondary alkyl substituent on the LIM gives lower linear selectivity and a faster rate than LIM-18. LIM-Bu-t gives a selectivity similar to that obtained using LIM-18.</p