Nanodisc, amphipol or detergent belts in cryoEM reconstructions of membrane proteins are similar and correspond to a common ordered solvent layer

SummaryTo maintain membrane proteins soluble in aqueous solution, amphipathic compounds are used to shield the hydrophobic patch of their membrane insertion, which forms a belt around the protein. This hydrophobic belt is seldom looked at due to the difficulty to visualize it. Cryo-EM is now offering this possibility, where belts are visible in 3D reconstructions. We investigated membrane proteins solved in nanodiscs, amphipols or detergents to analyze whether the nature of the amphipathic compound influences the belt size in 3D reconstructions. We identified belt boundaries in map-density distributions and measured distances for every reconstruction. We showed that all the belts create on average similar reconstructions, whether they originate from the same protein, or from protein from different shapes and structures. There is no difference among detergents or types of nanodisc used. These observations illustrate that the belt observed in 3D reconstructions corresponds to the minimum ordered layer around membrane proteins.

Varying the Dimensionality of Cu(II)-Based Coordination Polymers Through Solvent Influence

This work reports the synthesis and structure of a large porous zeotype network observed within compound (1) using {Cu2(piv)4} as the linking unit (piv = pivalate). The slow in situ formation of the hmt ligand (hexamethylenetetramine) appears to be key in generating a µ4-bridging mode of the hmt-node. Attempts to improve the low yield of compound (1) using different solvent layer diffusion methods resulted in the µ3-hmt complexes (2) and (3). Both compounds exhibit a 3D network of two intertwined chiral networks. Strong hydrogen bonding present in (3) leads to the formation of intertwined, DNA-like double-helix structures. The use of bulky solvents in the synthesis of compound (4) leads to the structure crystallizing solvent-free. The packing of (4) is dominated by energy minimization, which is achieved when the 1D-“cylinders” pack into the closest possible arrangement. This work highlights the potential for solvent controlled synthesis of extended copper-hmt systems.

Controlling the Internal Structures of Polymeric Microspheres via the Introduction of a Water-Soluble Organic Solvent

Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in the foam phase preparation of porous polymeric microspheres. The introduction of a water-soluble organic solvent enables the control of polymeric microspheres’ internal structures, from porous to hollow. Because a water-soluble organic solvent is introduced, the organic solvent may be diffused toward the interface because of the affinity between the organic solvent and the oil droplets, resulting an accumulation of organic solvent molecules at the interface to form an organic solvent layer. The presence of this layer may decrease the evaporation rate of the internal organic solvent in an oil droplet, which extends the time for the mingling of porogen droplets to form a few large pores or even an extremely large single pore inside. This method is also capable of altering the thickness of hollow microspheres’ shells in a desired way, with improved efficiency, yield and the capacity for continuous use on an industrial scale.

Shear induced formation of lubrication layers of negative normal stress gels

Many biopolymer gels generate negative normal stress, with which their polymer networks shrink in the normal of applied shear. Shearing such a gel produces a solvent layer, which greatly reduces the contact friction between the gel and the solid surface.

An exceptional 5:4 enantiomeric structure

The only crystals that could be grown from racemic solutions of the PF6−salt of the resolvable cation [Ru(2,9-dimethyl-1,10-phenanthroline)2(dipyrido[3,2-d:2′,3′-f]quinoxaline)]2+have translational symmetry only (space groupP1), contain nine independent sets of ions, and include numerous independent solvent molecules (11 acetone, one diethyl ether and possibly several water molecules). Layers of hydrophobic cations alternate with layers containing most of the anions and solvent molecules. All nine cations have the same basic conformation, which is distorted by the presence of the methyl substituents on the two 1,10-phenanthroline ligands. Four pairs of enantiomeric cations within a layer are related by approximate inversion centers; the ninth cation, which shows no sign of disorder, makes the layer chiral. Within the cation layers stripes parallel to [110] of six cations alternate with stripes of three; the local symmetry and the cation orientations are different in the two stripes. These stripes are reflected in the organization of the anion/solvent layer. Theca80:20 inversion twinning found indicates that enantiomeric preference is transmitted less perfectly across the anion/solvent layer than within the cation layer. The structure is exceptional in having nine independent formula units and an unbalanced set (ratio 4:5) of resolvable enantiomers. The difficulty in growing crystals of this material is consistent with its structural complexity.

Inverse solvent effects in the heterogeneous and homogeneous epoxidation of cis-2-heptene with [2-percarboxyethyl]-functionalized silica and meta-chloroperbenzoic acid

The organized solvent layer on the solid surface determines the reaction rate in the heterogeneous epoxidation of cis-2-heptene.