Glycosyl‐Substituted Dicarboxylates as Detergents for the Extraction,Overstabilization, and Crystallization of Membrane Proteins

To tackle the problems associated with membrane protein (MP) instability in detergent solutions, we designed a series of glycosyl‐substituted dicarboxylate detergents (DCODs) in which we optimized the polar head to clamp the membrane domain by including, on one side, two carboxyl groups that form salt bridges with basic residues abundant at the membrane–cytoplasm interface of MPs and, on the other side, a sugar to form hydrogen bonds. Upon extraction, the DCODs 8 b , 8 c , and 9 b preserved the ATPase function of BmrA, an ATP‐binding cassette pump, much more efficiently than reference or recently designed detergents. The DCODs 8 a , 8 b , 8 f , 9 a , and 9 b induced thermal shifts of 20 to 29 °C for BmrA and of 13 to 21 °C for the native version of the G‐protein‐coupled adenosine receptor A_2AR. Compounds 8 f and 8 g improved the diffraction resolution of BmrA crystals from 6 to 4 Å. DCODs are therefore considered to be promising and powerful tools for the structural biology of MPs.     

Two-Dimensional Detergent Expansion Strategy for Membrane Protein Studies

Detergents are the most frequently applied reagents in membrane protein (MP) studies. The limited diversity of one-head-one-tailed traditional detergents, however, is far from sufficient for structurally distinct MPs. Expansion of detergent repertoire has a continuous momentum. In line with the speculation that detergent pre-assembly exerts superiority, herein we report for the first time cross-conjugation of two series of monomeric detergents for constructing a two-dimensional library of dimeric detergents. Optimum detergents stood out with unique preferences in the systematic evaluation of individual MPs. Furthermore, unprecedented hybrid detergents 14M8G and 14M9G enabled high-quality EM study of transporter MsbA and NMR study of G protein-coupled receptor A_2AAR, respectively. Given the abundance of cross-coupling chemistries, comprehensive diversity could be readily covered that would facilitate the finding of new detergents for the manipulation of thorny MPs and innovation of the functional and structural study in future.     

A New Crystal Form,Polymorphism, and Multi‐Morphology in Biodegradable Poly(3‐hydroxypropionate)

Summary: A new crystal morphology (δ form) of poly(3‐hydroxypropionate) (PHP) is found in cast and melt‐crystallized PHPs with low molecular weight, in which the PHP chains possibly adopt a 2₁ helix rather than the trans conformation found in the β or γ form. The fusion temperature‐ and the crystallization temperature‐dependent polymorphism are responsible for the dual morphologies and the unique growth kinetics of spherulites in the melt‐crystallized PHPs.

a) A dual‐morphology developed at 70 °C in PHP films after melting at 117 °C and b) that formed during cooling at a rate of 1 °C · min⁻¹ from 130 °C.     

Trimethylsilylcyanid als Umpolungsreagens,VI. Anionische 1,4- O→C-Silylgruppen-Umlagerung

Trimethylsilyl Cyanide — A Reagent for Umpolung, VI. Anionic 1,4-O→C-Silyl Group Rearrangement The adducts 6 from substituted acroleins 5a – f and trimethylsilyl cyanide form the anions 6 _A on deprotonation at −78°C, which are silylated by trimethylsilyl chloride to 7 or (and) 8 in positions 3 or (and) 1. On warming up to room temperature, 6a _A and 6b _A undergo smoothly 1,4-O→C-silyl group rearrangements to form 13a _A and 13b _A which can be trapped by silylation. 6c – d _A decompose on warming up. Triethylsilyl instead of trimethylsilyl groups decelerate the rearrangement appreciably. Structure and configuration of the different products are determined.     

Synthesis,Characterization, and Directional Binding of Anisotropic Biohybrid Microparticles for Multiplexed Biosensing

Anisotropic microarchitectures with different physicochemical properties have been developed as advanced materials for challenging industrial and biomedical applications including switchable displays, multiplexed biosensors and bioassays, spatially‐controlled drug delivery systems, and tissue engineering scaffolds. In this study, anisotropic biohybrid microparticles (MPs) spatio‐selectively conjugated with two different antibodies (Abs) are first developed for fluorescence‐based, multiplexed sensing of biological molecules. Poly(acrylamide‐co‐acrylic acid) is chemically modified with maleimide‐ or acetylene groups to introduce different targeting biological moieties into each compartment of anisotropic MPs. Modified polymer solutions containing two different fluorescent dyes are separately used for electrohydrodynamic co‐jetting with side‐by‐side needle geometry. The anisotropic MPs are chemically stabilized by thermal imidization, followed by bioconjugation of two different sets of polyclonal Abs with two individual compartments via maleimide‐thiol coupling reaction and Huisgen 1,3‐dipolar cycloaddition. Finally, two compartments of the anisotropic biohybrid MPs are spatio‐selectively associated with the respective monoclonal Ab‐immobilized substrate in the presence of the antigen by sandwich‐type immunocomplex formation, resulting in their ordered orientation due to the spatio‐specific molecular interaction, as confirmed by confocal laser scanning microscopy. In conclusion, anisotropic biohybrid MPs capable of directional binding have great potential as a new fluorescence‐based multiplexing biosensing system.

     

A Novel Synthesis of 1‐Aryl‐6‐bromo‐3‐(5‐ethylthio‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐pyrazolo[4,3‐b]quinolin‐9(4H)‐ones via Thermal Cyclization of 4‐Azidopyrazoles

2‐Aryl‐hydrazononitriles 3a , 3b , 3c were prepared by coupling 3‐ethylthio‐5‐cyanomethyl‐4‐phenyl‐1,2,4‐triazole ( 1 ) with diazonium salts 2a , 2b , 2c . Reacting 3a , 3b , 3c with both ethyl bromoacetate ( 4a ) and 4‐bromobenzyl bromide ( 4b ) in DMF, in the presence of K₂CO₃, at 80 °C for 3–4 h, gave the corresponding 4‐amino‐pyrazoles 6a , 6b , 6c , 6d , 6e , 6f . Diazotization of 6a , 6b , 6c , 6d , 6e , 6f , followed by reaction with NaN₃, leads to the formation of 4‐azidopyrazoles 8a , 8b , 8c , 8d , 8e , 8f , a new heterocyclic ring system. Interestingly, fusion of 4‐azidopyrazoles 8d , 8e , 8f at temperature higher than their melting points with 5 °C for 2 min did not give the expected fused pyrazolo[4,3‐c]isoxazoles 9 but furnished instead the novel pyrazolo[4,3‐b]quinolinones 10a , 10b , 10c , in high yields.     

Thermally Stabilized Blue Luminescent Poly(p‐phenylene)s Covered with Polyhedral Oligomeric Silsesquioxanes

A novel series of poly(p‐phenylene)s (PPPs) with polyhedral oligomeric silsesquioxanes (POSSs) on their side chains was prepared. The obtained POSS‐modified PPPs are as follows: 25POSS‐PPP ( 2b , containing 25 mol‐% of POSS units in all side chains), 50POSS‐PPP ( 2c , containing 50 mol‐% of POSS units in all side chains), 100POSS‐PPP ( 2d , containing 100 mol‐% of POSS units in all side chains), and 0POSS‐PPP ( 2a , as a blank polymer). Films polymer 2d showed the same absorption and photoluminescence (PL) spectra as those in CHCl₃ solution, indicating that bulky POSS units strongly suppressed intermolecular aggregation of the PPP backbone. Polymer 2d showed the same PL spectra even after thermal annealing at 150 °C for 6 h. This enhancement of PL stability is due to the significant effect of the bulky POSS units.

     

Fluorinated Hyperbranched Polyimide for Optical Waveguides

A novel fluorinated hyperbranched polyimide (HBPI) is synthesized by using a new triamine monomer, 1,3,5‐tris(2‐trifluoromethyl‐4‐aminophenoxy)benzene (TFAPOB) (A₃), as a ‘core’ molecule, 4,4‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) as a B₂ monomer, and 3,5‐ditrifuoromethylphenyl as an endcapping reagent. The polymer shows a glass transition temperature of 232 °C and a temperature of 10% weight loss at 535 °C. The HBPI presents a birefringence as low as 0.002 at 650 nm. Near‐IR results indicate that HBPI exhibits desirable properties for low loss optical waveguide applications.

     

Helical Substituted Polyacetylene‐Derived Fluorescent Microparticles Prepared by Precipitation Polymerization

This article reports the first fluorescent microparticles (MPs, approximately 600 nm in diameter) constructed using helical substituted polyacetylene and prepared via a precipitation polymerization approach. The MPs judiciously combine this interesting helical conjugated acetylene, fluorescent material and polymeric particles in one entity. The monomer containing a dansyl group undergoes precipitation polymerization in butanone/n‐heptane mixed solvent, with (nbd)Rh⁺B⁻(C₆H₅)₄ as a catalyst. MPs with a regular morphology are formed in a high yield (>80 wt%). UV‐vis spectroscopy demonstrates that the polymer chains making up the MPs adopt helical structures. The MPs show considerable fluorescence emission (λ_max, 500 nm; excited at 340 nm). Based on SEM and fluorescence images, the formation mechanism of the MPs is proposed. This methodology opens up new ways to prepare functional microstructured materials derived from substituted polyacetylenes, and may also result in opportunities for new practical applications of polyacetylene and its derivatives.

     

Disulfide-Containing Detergents (DCDs) for the Structural Biology of Membrane Proteins

Disulfide-containing detergents (DCDs) are introduced, which contain a disulfide bond in the hydrophobic tail. DCDs form smaller micelles than corresponding detergents with linear hydrocarbon chains, while providing good solubilization and reconstitution of membrane proteins. The use of this new class of detergents in structural biology is illustrated with solution NMR spectra of the human G protein-coupled receptor A_2AAR, which is an α-helical protein, and the β-barrel protein OmpX from E. coli.     

Strukturwechselbeziehungen planarer und nichtplanarer Bis(1,2‐dithioquadratato)metallat‐Wirtsgittersysteme mit CuII‐Gastkomplexen – Struktur‐ und EPR‐Untersuchungen

Structural Interactions of Planar and Non‐planar Bis(1,2‐dithiosquarato)metalate Host Lattices with Cu^II Complexes – Structure and EPR Investigations 1,2‐Dithiosquaratometalates (M = Cu, Ni, Zn) are available by direct synthesis from metal salts with dipotassium‐1,2‐dithiosquarate. The structural influence of the planar and nonplanar host lattice systems (BzlEt₃N)₂[Cu/Ni(dtsq)₂] and (BzlEt₃N)₂[Cu/Zn(dtsq)₂] on the geometrical and electronic structure of the Cu^II guest complex [Cu(dtsq)₂]^2– is studied by EPR spectroscopy. The used host lattices (BzlEt₃N)₂[Ni(dtsq)₂] (planar) and (BzlEt₃N)₂[Zn(dtsq)₂] (tetrahedral) are characterized by X‐ray structure analysis. (BzlEt₃N)₂[Ni(dtsq)₂] crystallizes in the triclinic unit cell P1 with a = 9.1021(8) Å, b = 9.4190(8) Å, c = 11.0119(10) Å, α = 92.8560(10)°, β = 95.375(2)°, γ = 104.5180(10)° and Z = 1. (BzlEt₃N)₂[Zn(dtsq)₂] crystallizes in the monoclinic unit cell C2/c with a = 21.1299(14) Å, b = 16.6641(11) Å, c = 13.8324(9) Å, β = 123.9100(10)° and Z = 4. The g and A ^Cu tensors in the Cu/Ni system are nearly axial symmetric (g_|| = 2.122, g_⊥ = 2.028; A = –159.5 · 10^–4 cm^–1, A = –36.9 · 10^–4 cm^–1). The coordination geometry of the Cu^II guest complex in the tetrahedral Cu/Zn system is rather distorted, which is shown by the changed g and A ^Cu tensor parameters (g_|| = 2.143, g_⊥ = 2.042; A = –103.0 · 10^–4 cm^–1, A ≈ –5.0 · 10^–4 cm^–1). The spin density distribution is discussed using EHT molecular orbital calculations.     

Preparation of Biodegradable Polylactide Microparticles via a Biocompatible Procedure

PLA MPs are prepared via a novel and toxic‐chemical‐free fabrication route using ethyl lactate, a green solvent and FDA‐approved aroma. MPs are obtained by a solution jet break‐up and solvent displacement method. Adjusting flow parameters allows the tuning of MPs size between 60 and 180 µm, with reduced polydispersity. Morphological analysis shows microporous particles with Janus‐like surface. A fluorophore is successfully loaded into the MPs during their formation step. This versatile green solvent‐based procedure is proven to be suitable for drug encapsulation and delivery applications. The method may be extended to different droplet generation techniques.

     

High‐Tg Thiol‐Click Thermoset Networks via the Thiol‐Maleimide Michael Addition

Thiol‐click reactions lead to polymeric materials with a wide range of interesting mechanical, electrical, and optical properties. However, this reaction mechanism typically results in bulk materials with a low glass transition temperature (T_g) due to rotational flexibility around the thioether linkages found in networks such as thiol‐ene, thiol‐epoxy, and thiol‐acrylate systems. This report explores the thiol‐maleimide reaction utilized for the first time as a solvent‐free reaction system to synthesize high‐T_g thermosetting networks. Through thermomechanical characterization via dynamic mechanical analysis, the homogeneity and T_gs of thiol‐maleimide networks are compared to similarly structured thiol‐ene and thiol‐epoxy networks. While preliminary data show more heterogeneous networks for thiol‐maleimide systems, bulk materials exhibit T_gs 80 °C higher than other thiol‐click systems explored herein. Finally, hollow tubes are synthesized using each thiol‐click reaction mechanism and employed in low‐ and high‐temperature environments, demonstrating the ability to withstand a compressive radial 100 N deformation at 100 °C wherein other thiol‐click systems fail mechanically.

     

Halogen‐Free Polyarylphosphonates and Polyelectrolyte Membranes for PEMFC by Nickel‐Catalyzed Phosphonylation with Silylated Phosphates

Summary: The nickel‐catalyzed arylphosphonylation with tris(trimethylsilyl) phosphite (TMSP) is applied to brominated high‐performance (HP) polymers in weakly coordinating high temperature solvents. At elevated temperatures, this affords halogen‐free, soluble, phosphonic acid‐functionalized polyelectrolytes and an unprecedented control of the degree of phosphonylation (ds_P). Brominated polysulfone (PSU) of various degrees of bromination (ds_Br) has been phosphonylated with TMSP in diphenyl ether at 200 °C in the presence of 1–10 mol‐% NiCl₂. Upon methanolysis, arylphosphonic PSU with ds_P up to 223 mol‐% is obtained in near quantitative bromine conversion. Catalyst residues are readily removed during methanolysis. This very versatile two‐step process affords soluble arylphosphonic polymers for casting tough membrane films. In contrast to sulfonated PSU, the arylphosphonic PSU membranes exhibit improved thermal and chemical stabilities, combined with far lower water swelling in accordance with the demands of polyelectrolyte membrane fuel cell (PEMFC) applications.

Mass swelling (sw_M) in water of sulfonated (A–C) and phosphonylated PSU (D).     

Die Undecaarsenide A3As11 (A = Rb,Cs) — Synthesen und Kristallstrukturen

Alkaline Metal Arsenides A₃As₁₁ (A = Rb, Cs): Preparation and Crystal Structures Rb₃As₁₁ and Cs₃As₁₁ were synthesized from the elements and the crystal structures of the ordered room temperature form were characterized via single crystal x‐ray studies. In the Zintl phases the As atoms form chiral ufosan‐anions As with As‐As distances ranging from 238 to 248 pm. Like K₃As₁₁ Rb₃As₁₁ crystallizes with the Na₃P₁₁ structure type (orthorhombic, space group Pbcn, a = 1108.2(2), b = 1533.5(3), c = 1060.1(2) pm, Z = 4), whereas the Cs compound (monoclinic, space group C2/c, a = 1324.5(7), b = 1524.5(9), c = 1937.2(11) pm, β = 95.29(1)°, Z = 8) forms a new structure type. The crystallographic relationship between the two structure types and the anion packings in the plastic crystalline high temperature forms are discussed.     

Poly(9‐undecyl‐9‐methyl‐fluorene) and poly(9‐pentadecyl‐9‐methyl‐fluorene): Synthesis,solution structure,and effect of side chain asymmetry on aggregation behavior

We report on solution aggregates and backbone conformation of poly(9‐undecyl‐9‐methyl‐fluorene) (PF1‐11) and poly(9‐pentadecyl‐9‐methyl‐fluorene) (PF1‐15), having two different side chains compared with poly(9,9‐dihexylfluorene) (PF6) and poly(9,9‐dioctylfluorene) (PF8) with two identical side chains. In the poor solvent methylcyclohexane (MCH), X‐ray scattering indicates that PF1‐11 and PF1‐15 appear as three‐dimensional aggregates (5–10 nm wide and thick), forming ribbon‐like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two‐dimensional aggregates (>10 nm wide and 2–3 nm thick) involving ribbon‐like agglomerates (correlation lengths much greater than 100 nm). Upon heating, all aggregates undergo a gel–sol transition which occurs at lower temperatures for PF1‐11 and PF1‐15 (<60°C) than for PF6 and PF8 (>80°C). In the good solvent toluene, PF1‐11 and PF1‐15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1–2 nm). Nuclear magnetic resonance spectra in toluene‐d₈ together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1‐11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1‐15. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 826–837     

New straightforward route for the synthesis of some 1‐oxa‐2‐silacyclopentane derivatives

Tris(dimethylsilyl)methyl lithium, (HSiMe₂)₃CLi, reacts with allyl, phenyl, benzyl, n‐propyl and n‐butyl glycidyl ethers in THF at ‐5 °C to give 1‐oxa‐2‐silacyclopentane derivatives. It seems that ring closure is facilitated by conversion of the Si? H bond into an Si? O bond. Glycidyl methacrylate (GM) random copolymers with 4‐methyl‐ and 4‐methoxy styrene, synthesized by solution free radical polymerization at 70 (±1) °C with α,α‐azobis(isobutyronitrile) (AIBN) as initiator, contained pendant epoxide functions. Treatment of these with (HSiMe₂)₃CLi did not lead to intramolecular nucleophilic attack as found for simple epoxides.     

Metallo‐Supramolecular Diethylene Glycol: Water‐Soluble Reversible Polymers

Bis(2,2′:6′,2″‐terpyrid‐4′‐yl) diethylene glycol was synthesized as a monomer unit and further utilized for polymerization with FeCl₂ in order to form water‐soluble coordination polymers. Viscosity measurements and film‐forming properties indicate the formation of linear coordination polymers or larger ring structures. The terpyridine/iron(II) complexes are stable up to temperatures of 210 °C, but can be uncomplexed by the addition of an excess of a strong competitive ligand (HEDTA) under mild conditions.

     

Synthesis of Dendritic Oligo‐Spiro(fluorene‐9,9′‐xanthene) Derivatives with Carbazole and Fluorene Pendants and their Thermal,Optical, and Electroluminescent Properties

Two novel spiro‐configured ter(arylene‐ethynylene) derivatives, TSF‐Cz and TSF‐F , have been designed and synthesized using spiro(fluorene‐9,9′‐xanthene) (SFX) as building blocks, introducing a hole‐transporting carbazole and a fluorene chromophore as the peripheral functional group into the backbone through an oxygen atom. The two well‐defined oligomers possess good solubility, film‐forming quality, and high T_g's at 140 and 126 °C, respectively. In addition, these oligomers exhibit blue photoluminescence (PL) emission both in solution and solid states. The double‐layered devices fabricated using the two materials as the emitter show a sky‐blue emission with a brightness and a current efficiency of 7 613 cd · m⁻² and 1.11 cd · A⁻¹ for TSF‐Cz , and 1 507 cd · m⁻² and 0.36 cd · A⁻¹ for TSF‐F , respectively.

     

Azide/Alkyne‐“Click”‐Reactions of Encapsulated Reagents: Toward Self‐Healing Materials

The successful encapsulation of reactive components for the azide/alkyne‐“click”‐reaction is reported featuring for the first time the use of a liquid polymer as reactive component. A liquid, azido‐telechelic three‐arm star poly(isobutylene) ( = 3900 g · mol⁻¹) as well as trivalent alkynes were encapsulated into micron‐sized capsules and embedded into a polymer‐matrix (high‐molecular weight poly(isobutylene), = 250 000 g · mol⁻¹). Using (Cu^IBr(PPh₃)₃) as catalyst for the azide/alkyne‐“click”‐reaction, crosslinking of the two components at 40 °C is observed within 380 min and as fast as 10 min at 80 °C. Significant recovery of the tensile storage modulus was observed in a material containing 10 wt.‐% and accordingly 5 wt.‐% capsules including the reactive components within 5 d at room temperature, thus proving a new concept for materials with self‐healing properties.