Abstract. The Copernicus Atmosphere Monitoring Service (CAMS) reanalysis is the latest global reanalysis dataset of atmospheric composition produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), consisting of three-dimensional time-consistent atmospheric composition fields, including aerosols and chemical species. The dataset currently covers the period 2003–2016 and will be extended in the future by adding 1 year each year. A reanalysis for greenhouse gases is being produced separately. The CAMS reanalysis builds on the experience gained during the production of the earlier Monitoring Atmospheric Composition and Climate (MACC) reanalysis and CAMS interim reanalysis. Satellite retrievals of total column CO; tropospheric column NO2; aerosol optical depth (AOD); and total column, partial column and profile ozone retrievals were assimilated for the CAMS reanalysis with ECMWF's Integrated Forecasting System. The new reanalysis has an increased horizontal resolution of about 80 km and provides more chemical species at a better temporal resolution (3-hourly analysis fields, 3-hourly forecast fields and hourly surface forecast fields) than the previously produced CAMS interim reanalysis. The CAMS reanalysis has smaller biases compared with most of the independent ozone, carbon monoxide, nitrogen dioxide and aerosol optical depth observations used for validation in this paper than the previous two reanalyses and is much improved and more consistent in time, especially compared to the MACC reanalysis. The CAMS reanalysis is a dataset that can be used to compute climatologies, study trends, evaluate models, benchmark other reanalyses or serve as boundary conditions for regional models for past periods.

A new and promising tool in membrane research is the detergent-free solubilization of membrane proteins by styrene–maleic acid copolymers (SMAs). These amphipathic molecules are able to solubilize lipid bilayers in the form of nanodiscs that are bounded by the polymer. Thus, membrane proteins can be directly extracted from cells in a water-soluble form while conserving a patch of native membrane around them. In this review article, we briefly discuss current methods of membrane protein solubilization and stabilization. We then zoom in on SMAs, describe their physico-chemical properties, and discuss their membrane-solubilizing effect. This is followed by an overview of studies in which SMA has been used to isolate and investigate membrane proteins. Finally, potential future applications of the methodology are discussed for structural and functional studies on membrane proteins in a near-native environment and for characterizing protein–lipid and protein–protein interactions.

The styrene-maleic acid (SMA) copolymer is rapidly gaining attention as a tool in membrane research, due to its ability to directly solubilize lipid membranes into nanodisk particles without the requirement of conventional detergents. Although many variants of SMA are commercially available, so far only SMA variants with a 2:1 and 3:1 styreneto-maleic acid ratio have been used in lipid membrane studies. It is not known how SMA composition affects the solubilization behavior of SMA. Here, we systematically investigated the effect of varying the styrene/maleic acid on the properties of SMA in solution and on its interaction with membranes. Also the effect of pH was studied, because the proton concentration in the solution will affect the charge density and thereby may modulate the properties of the polymers. Using model membranes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine lipids at pH > pH agg , we found that membrane solubilization is promoted by a low charge density and by a relatively high fraction of maleic acid units in the polymer. Furthermore, it was found that a collapsed conformation of the polymer is required to ensure efficient insertion into the lipid membrane and that efficient solubilization may be improved by a more homogenous distribution of the maleic acid monomer units along the polymer chain. Altogether, the results show large differences in behavior between the SMA variants tested in the various steps of solubilization. The main conclusion is that the variant with a 2:1 styrene-to-maleic acid ratio is the most efficient membrane solubilizer in a wide pH range.

<p><strong>Abstract.</strong> The Copernicus Atmosphere Monitoring Service (CAMS) reanalysis is the latest global reanalysis data set of atmospheric composition produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), consisting of 3-dimensional time-consistent atmospheric composition fields, including aerosols and chemical species. The dataset currently covers the period 2003–2016 and will be extended in the future by adding one year each year. A reanalysis for greenhouse gases is being produced separately. The CAMS reanalysis builds on the experience gained during the production of the earlier Monitoring Atmospheric Composition and Climate (MACC) reanalysis and CAMS interim reanalysis. Satellite retrievals of total column CO, tropospheric column NO<sub>2</sub>, aerosol optical depth and total column, partial column and profile ozone retrievals were assimilated for the CAMS reanalysis with ECMWF’s Integrated Forecasting System. The new reanalysis has an increased horizontal resolution of about 80 km and provides more chemical species at a better temporal resolution (3-hourly analysis fields, 3-hourly forecast fields and hourly surface forecast fields) than the previously produced CAMS interim reanalysis. The CAMS reanalysis has smaller biases compared to independent ozone, carbon monoxide, nitrogen dioxide and aerosol optical depth observations than the previous two reanalyses and is much improved and more consistent in time, especially compared to the MACC reanalysis. The CAMS reanalysis is a dataset that can be used to compute climatologies, study trends, evaluate models, benchmark other reanalyses or serve as boundary conditions for regional models for past periods.</p>

Membrane fusion plays a central role in biological processes such as neurotransmission and exocytosis. An important class of proteins that induce membrane fusion are called SNARE (soluble N-ethyl malemeide sensitive factor attachment protein receptors) proteins. To induce membrane fusion, two SNARE proteins embedded in opposing membranes form a four-helix coiled-coil motif together with a third, cytoplasmic, SNARE protein. Coiled-coil formation brings the two membranes into close proximity allowing fusion to occur. Importantly, structural investigations have demonstrated that native membrane fusion only occurs when the orientation of the coiled-coil motif resembles that of a zipper. The zipper orientation arises when parallel coiled-coil formation takes place between peptides that are anchored into apposing membranes at identical termini, thereby forcing the membranes into close contact. Recently, we have designed a synthetic model for membrane fusion, which is based on a set of lipidated coiled-coil forming peptide pairs which are denoted E-K. When incorporated into liposomal membranes, coiled-coil formation between these lipidated peptides induces targeted and efficient membrane fusion of liposomes. Our model system mimics SNARE-driven membrane fusion, as it contains a coiled-coil motif which has a zipper-like orientation, similar to that of the SNARE proteins. Here we investigate whether the zipper-like orientation of the coiled-coil motifs is a prerequisite for membrane fusion in our model system. Our strategy is based on conjugation of the transmembrane anchor to either the N- or the C-terminus of peptides E and K. Whereas the use of a set of complementary peptides with the membrane anchor on identical peptide termini yields the zipper-like orientation of the coiled-coil complex, membrane anchors on opposite peptide termini results in a non-zipper-like coiled-coil orientation. Surprisingly, it was observed that efficient and targeted membrane fusion was induced even when the coiled-coil motif did not form the zipper-like orientation. This demonstrates that for our model system, the zipper model for membrane fusion does not apply.