Search

Heterochain polymers such as DNA and proteins are abundant in nature, but they are not ubiquitous in man-made polymers due to the synthetic difficulties. Traditional polymerization methodologies including chain polymerization, step-growth polymerization, and coordination polymerization all show obvious drawbacks in synthesizing heterochain polymers. The alkyne multicomponent polymerizations (MCPs) developed in the early 2000s open a new door for the synthesis of conjugated heterochain polymers with diverse structures and unique properties. This review presents the progress in novel heterochain polymers constructed by alkyne-based MCPs in the last three years. The unique properties and high-tech applications brought by heteroatoms and MCPs are summarized and perspectives on future directions are also discussed., (© 2020 Wiley-VCH GmbH.)

We investigate the translocation of a semiflexible polymer through extended patterned pores using Langevin dynamics simulations, specifically focusing on the influence of a time-dependent driving force. Our findings reveal that, akin to its flexible counterpart, a rigid chain-like molecule translocates faster when subjected to an oscillating force than a constant force of equivalent average magnitude. The enhanced translocation is strongly correlated with the stiffness of the polymer and the stickiness of the pores. The arrangement of the pores plays a pivotal role in translocation dynamics, deeply influenced by the interplay between polymer stiffness and pore-polymer interactions. For heterogeneous polymers with periodically varying stiffness, the oscillating force introduces significant variations in the translocation time distributions based on segment sizes and orientations. On the basis of these insights, we propose a sequencing approach that harnesses distinct pore surface properties that are capable of accurately predicting sequences in heteropolymers with diverse bending rigidities. [ABSTRACT FROM AUTHOR]

The human polysialyltransferases ST8Sia II and ST8Sia IV catalyze the transfer of several Neu5Ac residues onto glycoproteins forming homopolymers with essential roles during different physiological processes. In salmonids, heterogeneous set of sialic acids polymers have been described in ovary and on eggs cell surface and three genes st8sia4, st8sia2-r1 and st8sia2-r2 were identified that could be implicated in these heteropolymers. The three polysialyltransferases from the salmonid Coregonus maraena were cloned, recombinantly expressed in HEK293 cells and the ST8Sia IV was biochemically characterized. The MicroPlate Sialyltransferase Assay and the non-natural donor substrate CMP-SiaNAl were used to demonstrate enzyme activity and optimize polysialylation reactions. Polysialylation was also carried out with natural donor substrates CMP-Neu5Ac, CMP-Neu5Gc and CMP-Kdn in cell-free and cell-based assays and structural analyses of polysialylated products using the anti-polySia monoclonal antibody 735 and endoneuraminidase N and HPLC approaches. Our data highlighted distinct specificities of human and salmonid polysialyltransferases with notable differences in donor substrates use and the capacity of fish enzymes to generate heteropolymers. This study further suggested an evolution of the biological functions of polySia. C. maraena ST8Sia IV of particular interest to modify glycoproteins with a variety of polySia chains. [ABSTRACT FROM AUTHOR]

Four model polymers, representing (i) amorphous homopolymers (Kollidon K30, K30), (ii) amorphous heteropolymers (Kollidon VA64, KVA), (iii) semi-crystalline homopolymers (Parteck MXP, PXP), and (iv) semi-crystalline heteropolymers (Kollicoat IR, KIR), were examined for their effectiveness in creating posaconazole-based amorphous solid dispersions (ASDs). Posaconazole (POS) is a triazole antifungal drug that has activity against Candida and Aspergillus species, belonging to class II of the biopharmaceutics classification system (BCS). This means that this active pharmaceutical ingredient (API) is characterized by solubility-limited bioavailability. Thus, one of the aims of its formulation as an ASD was to improve its aqueous solubility. Investigations were performed into how polymers affected the following characteristics: melting point depression of the API, miscibility and homogeneity with POS, improvement of the amorphous API's physical stability, melt viscosity (and associated with it, drug loading), extrudability, API content in the extrudate, long term physical stability of the amorphous POS in the binary drug–polymer system (in the form of the extrudate), solubility, and dissolution rate of hot melt extrusion (HME) systems. The obtained results led us to conclude that the physical stability of the POS-based system increases with the increasing amorphousness of the employed excipient. Copolymers, compared to homopolymers, display greater homogeneity of the investigated composition. However, the enhancement in aqueous solubility was significantly higher after utilizing the homopolymeric, compared to the copolymeric, excipients. Considering all of the investigated parameters, the most effective additive in the formation of a POS-based ASD is an amorphous homopolymer—K30. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were carried out to investigate the evolvement of charge transport properties of a set of new discotic systems as a function of ring and heteroatom (B, Si, S, and Se) substitution on the basic structure of perylene. The replacement of six-membered rings by five-membered rings in the reference compound has shown a prominent effect on the electron reorganization energy that decreases ∼0.2 eV from perylene to the new carbon five-membered ring derivative. Heteroatom substitution with boron also revealed to lower the LUMO energy level and increase the electron affinity, therefore lowering the electron injection barrier compared to perylene. Since the rate of the charge transfer between two molecules in columnar discotic systems is strongly dependent on the orientation of the stacked cores, the total energy and transfer integral of a dimer as a disc is rotated with respect to the other along the stacking axis have been predicted. Aimed at obtaining a more realistic approach to the bulk structure, the molecular geometry of clusters made up of five discs was fully optimized, and charge transfer rate and mobilities were estimated for charge transport along a one dimensional pathway. Heteroatom substitution with selenium yields electron transfer integral values ∼0.3 eV with a relative disc orientation of 25°, which is the preferred angle according to the dimer energy profile. All the results indicate that the tetraselenium-substituted derivative, not synthetized so far, could be a promising candidate among those studied in this work for the fabrication of n-type semiconductors based on columnar discotic liquid crystals materials. [ABSTRACT FROM AUTHOR]

The rapid development of science and technology has brought urgent demand for diversity in polymer structures and functionalities, and the pursuit of new polymerizations and new polymer structures is the constant goal in polymer chemistry. Multicomponent polymerizations and multicomponent reaction involving polymer synthesis have been demonstrated to be a very powerful tool for the construction of functional polymers with diversified structures and advanced functionalities, which have become a prosperous branch of polymer chemistry. Calvo, Wagener, Sumerlin, and co-workers have prepared hyperbranched aminobisphosphonic acid polymers via reversible addition-fragmentation chain transfer self-condensing vinyl polymerization of an acrylamide-functional chain transfer monomer, followed by the introduction of the aminobisphosphonate functional group through a three-component Kabachnick-Fields reaction (2000578). [Extracted from the article]

By using a recently developed Monte Carlo algorithm and an exact numerical method, we calculate the translocation probability and the average translocation time for charged heterogeneous polymers driven through a nanopore by an external electric field. The heteropolymer chains are composed of two types of monomers (A and B) which differ only in terms of their electric charge. We present an exhaustive study of chains composed of eight monomers by calculating the average translocation time associated with the 256 possible arrangements for various ratios of the monomer charges (λA/λB) and electric field intensities E. We find that each sequence leads to a unique value of the translocation probability and time. We also show that the distribution of translocation times is strongly dependent on the two forces felt by the monomers (∼λAE and ∼λBE). Finally, we present results that highlight the effect of having repetitive patterns by studying the translocation times of various block copolymer structures for a very long chain composed of N=218 monomers (all with the same number of A and B monomers). [ABSTRACT FROM AUTHOR]

We use a replica approach to investigate the thermodynamic properties of the random heteropolymers with persistent power-law correlations in monomer sequence. We show that this type of sequences possess proteinlike properties. In particular, we show that they can fold into stable unique three-dimensional structure (the “native” structure, in protein terminology) through two different types of pathways. One is a fast folding pathway and leads directly to the native structure. Another one, a more slower pathway, passes through the microphase separated (MPS) state and includes a number of intermediate glassy states. The scale and the magnitude of the MPS are calculated. The frozen state can be reached only by sequences with weak long-range correlations. The critical value for the correlation exponent is found, above which (strong correlations) freezing is impossible. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Presence of heteroatom in dyes impacts on red shift absorption. • Absorption spectra on films favors light harvesting ability. • Dyes have proper electronic energy levels as a promising sensitizer. Abstract Two imidazole – triphenylamine based organic dyes (SD1 and SD2) configured with donor -donor-π-acceptor (D 2 -π-A) structures with reported dye material namely TPA B5 were synthesized using different acceptor units and characterized by various spectroscopic techniques. The optical and electrochemical behavior of the dyes was systematically analyzed. The obtained results were compared with TPA B5 and found that, these dyes are considered to have proper electronic energy levels as promising sensitizers in dye sensitized solar cells (DSC's). This work could facilitate the development of new way to improve the performance of anchoring units. [ABSTRACT FROM AUTHOR]

We investigate spatiotemporal dynamics of human interphase chromosomes by employing a heteropolymer model that incorporates the information of human chromosomes inferred from Hi-C data. Despite considerable heterogeneities in the chromosome structures generated from our model, chromatins are organized into crumpled globules with space-filling (SF) statistics characterized by a single universal scaling exponent (ν = 1/3), and this exponent alone can offer a quantitative account of experimentally observed, many different features of chromosome dynamics. The local chromosome structures, whose scale corresponds to that of topologically associated domains (∼ 0.1 − 1 Mb), display dynamics with a fast relaxation time (≲ 1 − 10 sec); in contrast, the long-range spatial reorganization of the entire chromatin ( Mb) occurs on a much slower time scale (≳ hour), providing the dynamic basis of cell-to-cell variability and glass-like behavior of chromosomes. Biological activities, modeled using stronger isotropic white noises added to active loci, accelerate the relaxation dynamics of chromatin domains associated with the low frequency modes and induce phase segregation between the active and inactive loci. Surprisingly, however, they do not significantly change the dynamics at local scales from those obtained under passive conditions. Our study underscores the role of chain organization of chromosome in determining the spatiotemporal dynamics of chromatin loci. [ABSTRACT FROM AUTHOR]

A number of observations have been reported on chemical capture and catalysis of anchoring materials for lithium-sulfur batteries. Here, we propose the design principles for the chemical functioned graphene as an anchor material to realize both strong chemical trapping and catalysis. Through the first principle, the periodic law is calculated from the theory. Seven different co-doping series were investigated, e.g. MN 4 @graphene (M = V, Cr, Mn, Fe, Co, Ni, and Cu). From binding energy, partial density of state, and charge density difference analysis, the FeN 4 and CrN 4 co-doped graphene show good performance for the lithium–sulfur battery from both strong anchoring and catalytic effects. For the most kinds of Li 2 S x ( x  = 1, 2, 4, 6, 8) absorption, two combinations can be achieved, including S-bonding and Li-bonding. The competition between the M S and the N Li shows the main difference of the co-doped configurations. Moreover, the S-bonding systems have better performance for both moderate chemical trapping and strong catalysis. The binding energies of Li 2 S x and Li decomposed properties considered as the key descriptors for the rational design of lithium–sulfur battery. Lastly, we offer design rules for high performance lithium–sulfur batteries based on the chemical functional graphene materials. [ABSTRACT FROM AUTHOR]

Hyper-crosslinked polymers (HCPs) are promising materials for gas capture and storage because of their low cost and easy preparation. In this work, we report the massive preparation of coumarone-indene resin-based hyper-crosslinked polymers via one-step Friedel-Crafts alkylation. Low-cost coumarone-indene resin serves as the new building block and chloroform is employed as both solvent and external crosslinker. A maximum surface area of 966 m2·g−1 is achieved, which is comparable with that of previously-reported coal tar-based porous organic polymers. Most importantly, a large number of heteroatoms including inherent oxygen atoms and introduced chlorine atoms in obtianed HCPs further enhance the interaction between specific sorbate molecule and adsorbent. Therefore, optimal structural and chemical property endow the new coumarone-indene resin-based HCPs with decent gas storage capacity (14.60 wt% at 273 K and 0.1 MPa for CO2; 1.18 wt% at 77.3 K and 0.1 MPa for H2). These results demonstrate that new HCPs are potential candidates for applications in CO2 and H2 capture. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of a new type of porous organic polymers linked by benzoxazine. The polymers were readily synthesized by condensation reaction of diamines, triphenol and paraformaldehyde. The formation of the linkage and porous structures were studied by infrared spectroscopy, solid-state 13 C-CP MAS NMR and nitrogen sorption measurements. The porosity study revealed the resultant polymers are porous materials with surface area as high as 231 m 2 g −1 . Benzoxazine backbone endows the polymers with abundant heteroatoms (N and O), which makes these polymers promising candidates for carbon dioxide adsorption and storage. We found that the best polymer showing the highest carbon dioxide adsorption up to 6.81 wt% at 273 K and 1 bar, which is due to the most microporous structure and largest adsorption affinity. These results demonstrate a convenient approach to synthesize heteroatom-rich porous organic polymers for gas adsorption and storage. [ABSTRACT FROM AUTHOR]

A novel biomorphic heteroatom-doped porous carbon with 2.86% of nitrogen and 12.36% of oxygen is synthesized by using a mold ( Rhizoctonia Solani Kuhn) as the precursor. The biomorphic porous carbon electrode material exhibits an ultra-high volumetric capacitance of up to 655 F cm −3 at current density of 0.5 A g −1 and superior cycle stability of 100% after 10,000 cycles at a current density of 10 A g −1 . This work provides a new approach to obtain biomass with low cost, no pollution, short production cycle and high yield. Furthermore, the genetic stability is more beneficial for the formation of the uniform architecture and composition. [ABSTRACT FROM AUTHOR]

In this study, we present a new application of the transmission electron microscopy dark field mode for cell imaging. We have applied this imaging mode to two types of cellular systems: human HeLa cells to analyze molecular membrane systems and HC11 mouse mammary cells containing lipid molecule droplets. We have also studied a third macromolecular system, copolymer nanoparticles for the characterization of core-shell structures. We want to show the effective use of diffraction contrast, even on amorphous systems for increasing the image contrast and the signal/noise ratio. We discuss the TEM dark field advantages for the analysis of polymers and other macromolecular systems, including biological, systems compared to the bright field mode. [ABSTRACT FROM AUTHOR]

Heteroatom-doped mesoporous carbon nanofibers (HMCNFs) were prepared by direct carbonization of highly cross-linked organic–inorganic hybrid polymeric nanofibers (PNFs) under an inert atmosphere. The HMCNFs were of large Brunauer–Emmett–Teller (BET) surface area, uniform mesopore (with diameter 4 nm), and high content of heteroatoms. Electrodes prepared by using HMCNFs showed a high specific capacitance of 214.9 F/g in 6 M KOH electrolyte, because of the large BET surface area and high content of heteroatoms. This work involved preparation of carbon nanofibers from a novel precursor and used the nanofibers in the fabrication of high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Naphthalenediimide (NDI)-based polymers co-polymerized with thienyl units are an interesting class of polymer semiconductors because of their good electron mobilities and unique film microstructure. Despite these properties, understanding how the extension of the thienyl co-monomer affects charge transport properties remains unclear. With this goal in mind, we have synthesized a series of NDI derivatives of the parent poly{[ N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene) (P(NDI2OD-T2)), which exhibited excellent electron mobility. The strategy comprises both the extension of the donor o-conjugation length and the heteroatomic fusion of the thiophene rings. These newly synthesized compounds are characterized experimentally and theoretically vis-à-vis with P(NDI2OD-T2) as the reference. UV-vis data and cyclic-voltammetry are adopted to assess the effect of the donor modification on the frontier energy levels and on the bandgap. Intra-molecular polaronic effects are accounted for by computing the internal reorganization energy with density functional theory (DFT) calculations. Finally electrons and holes transport is experimentally investigated in field-effect transistors (FETs), by measuring current-voltage characteristics at variable temperatures. Overall we have identified a regime where inter-molecular effects, such as the wavefunction overlap and the degree of energetic disorder, induced by the different donor group prevail over polaronic effects and are the leading factors in determining electrons mobility. [ABSTRACT FROM AUTHOR]

Melanins, the ubiquitous hetero-polymer pigments found widely dispersed among various life forms, are usually dark brown/black in colour. Although melanins have variety of biological functions, including protection against ultraviolet radiation of sunlight and are used in medicine, cosmetics, extraction of melanin from the animal and plant kingdoms is not an easy task. Using complementary physicochemical techniques (i.e. MALDI-TOF, FTIR absorption and cross-polarization magic angle spinning solid-state 13C NMR), we report here the characterization of melanins extracted from the nitrogen-fixing non-virulent bacterium Azotobacter chroococcum, a safe viable source. Moreover, considering dihydroxyindole moiety as the main constituent, an effort is made to propose the putative molecular structure of the melanin hetero-polymer extracted from the bacterium. Characterization of the melanin obtained from Azotobacter chroococcum would provide an inspiration in extending research activities on these hetero-polymers and their use as protective agent against UV radiation. [ABSTRACT FROM AUTHOR]

We study the conformational properties of charged polymers in a solvent in the presence of structural obstacles correlated according to a power law ~ x-a . We work within the continuous representation of a model of linear chain considered as a random sequence of charges qi = ±q0. Such a model captures the properties of polyampholytes - heteropolymers comprising both positively and negatively charged monomers. We apply the direct polymer renormalization scheme and analyze the scaling behavior of charged polymers up to the first order of an ε= 6-d, δ= 4-a-expansion. [ABSTRACT FROM AUTHOR]

The formulation of salicylate-based poly(anhydride-ester) (PAE) microspheres was optimized by altering polymer concentration and homogenization speed to improve the overall morphology. The microspheres were prepared using three salicylate-based PAEs with different chemical compositions comprised of either a heteroatomic, linear aliphatic, or branched aliphatic moiety. These PAEs broadened the range of complete salicylic acid release to now include days, weeks, and months. The molecular weight ( M), polydispersity index (PDI) and glass transition temperature ( T) of the formulated polymers were compared to the unformulated polymers. In general, the M and PDI exhibited decreased and increased values, respectively, after formulation, whereas the T changes did not follow a specific trend. Microsphere size and morphology were determined using scanning electron microscopy. These microspheres exhibited smooth surfaces, no aggregation, and size distributions ranging from 2 to 34 μm in diameter. In vitro release studies of the chemically incorporated salicylic acid displayed widely tunable release profiles. [ABSTRACT FROM AUTHOR]

The possibility of the synthesis of polymetallophenylsiloxanes with the predicted metal content in the synthesized polymers is demonstrated. Variation of the spectral luminescent properties of polyterbium- and polyeuropiumphenylsiloxanes as a function of the metal content is studied. [ABSTRACT FROM AUTHOR]

A new Tröger's base-containing aromatic dihydrazide, 2,8-bis(carboxylic)-6H, 12H-5,11-methanodibenzo-[b,f] [1,5]-diazocine dihydrazide, was prepared by the condensation of ethyl p-aminobenzoate with hexamethylenetetramine in the presence of trifluoroacetic acid, followed by converting to the dihydrazide with a high yield and high purity. A series of novel aromatic polyhydrazides were prepared from the Tröger's unit containing dihydrazide and various aromatic diacyl chlorides via low-temperature solution polycondensation in quantitative yields. All the polyhydrazides were amorphous and readily soluble at room temperature in polar organic solvents such as N, N-dimethylacetamide and N-methyl-2-pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with good glass transition temperatures (163-172°C), 10% weight-loss temperatures in excess of 460°C, and char yields at 800°C in nitrogen higher than 39%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

We have performed Parallel Tempering simulations of hydrophobic-hydrophilic heteropolymers with a simple effective, coarse-grained off-lattice model with the selected monomers and compare the global energy minimums found with Parallel Tempering algorithm with the lowest energy states identified within the multicanonical algorithm. [ABSTRACT FROM AUTHOR]

The reactivity of Co1.5PW12O40 in the direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH was investigated. The synthesized catalyst has been characterized by means of FTIR, XRD, TG, and DTA and tested in gas phase under atmospheric pressure. The effects of the reaction temperature, time on stream, and methanol weight hourly space velocity (MWHSV) on the conversion and DMC selectivity were investigated. The highest conversion (7.6%) and highest DMC selectivity (86.5%) were obtained at the lowest temperature used (200 °C). Increasing the space velocity MWHSV increased the selectivity of DMC, but decreased the conversion. A gain of 18.4% of DMC selectivity was obtained when the MWHSV was increased from 0.65 h-1 to 3.2 h-1. [ABSTRACT FROM AUTHOR]

The reaction of benzyl alcohol with 3,4,6-tri-O-acetyl-d-glucal has been investigated with several heteropoly compounds, and the optimal catalyst is 12-tungstophosphoric acid supported on carbon. In the presence of this catalyst, various alcohols gave the corresponding alkyl and aryl 2,3-unsaturated glycopyranosides in excellent yields and good anomeric selectivity under solvent-free condition. 4,6-Di-O-acetyl-2,3-dideoxy-α-d-erythro-hex-2-enopyranosyl cyanide and ethyl 4,6-di-O-acetyl-2,3-dideoxy-1-thio-α-d-erythro-hex-2-enopyranoside have also been prepared with trimethylsilyl cyanide and ethanthiol as nucleophiles, respectively. The catalyst could be easily recovered and reused several times with slight loss of activity. The selectivity to give α-anomers predominantly did not show any change in all runs. [ABSTRACT FROM AUTHOR]

Heteroatom effects were investigated on singlet-triplet energy gaps of divalent five-membered ring XC3H3C, 1X and 2X (X = CH, N, P, and As) at B3LYP/6-311++G** level. All triplet states of 1X and 2X are more stable than the related singlet state. Δ Gs - t between singlet and triplet states of 1X and 2X were changed in the order (in kcal/mol): 1As (14.43) > 1P (10.07) > 1CH (9.60) > 1N (8.50) and 2N (11.56) > 2CH (9.60) > 2P (3.07) > 2As (2.13). [ABSTRACT FROM AUTHOR]

[Display omitted] • Different folding types such as two-state folding, folding through intermediates, as well as metastability, are presented with an effective order parameter for polymers. • Gyration tensor-based analysis does not need any reference state before the simulation as that is the need for the other order parameters which are chosen in other studies in the same content. • Our paper presents the use of very useful parameters to detect conformational phase transitions in polymer chains. In the earlier works related to this aspect presents another order parameter that needs a reference conformation. Multicanonical simulations of hydrophobic-polar heteropolymers were performed with a simple and effective coarse-grained off-lattice model to identify the folding pathways and the topology of the energy landscape with gyration tensor-based parameters. We examined six exemplified sequences of heteropolymers and illustrated three of them which present definitely different folding types such as two-state folding, folding through intermediates, as well as metastability. The major advantage of this study is our chosen "order" parameter, namely gyration tensor-based analysis, does not require any reference state before the simulation as that is the need for the other order parameters which are chosen in other studies in the same context. Our paper presents the use of very useful parameters to detect conformational phase transitions in polymer chains. Another order parameter that requires a reference conformation is presented in earlier works related to this aspect. This extends the simulation into two steps. With our analysis, there is no need for a global minimum conformation so-called reference state and our simulation will be completed in one step. Furthermore, there is no relative evaluation according to the reference state. [ABSTRACT FROM AUTHOR]

Michael addition of heteroatom- and carbon-centered nucleophiles on 7-oxanorborna-2,5-diene-2-carboxaldehyde derivatives followed by a retro-Diels-Alder reaction allowed liquid- and solid-phase synthesis of a small library of α,β-unsaturated aldehydes. Emphasis should be put on the purity of the enals prepared on solid support, a purification step was not necessary. [ABSTRACT FROM AUTHOR]

The small heat-shock protein α-crystallin isolated from the eye lens exists as a large (700 kDa) heteropolymer composed of two subunits, αA and αB, of 20 kDa each. Although trace amounts of αA-crystallin are found in other tissues, non-lenticular distribution of α-crystallin is dominated by the αB homopolymer. In most vertebrate lens, the molar ratio of αA to αB is generally 3:1. However, the importance of this ratio in the eye lens is not known. In the present study, we have investigated the physiological significance of the 3:1 ratio by determining the secondary/tertiary structure, hydrophobicity and chaperone-like activity of αA- and αB-homopolymers and heteropolymers with different ratios of αA to αB subunits. Although, under physiologically relevant conditions, the αB-homopolymer (37–40 °C) has shown relatively higher activity, the αA-homopolymer or the heteropolymer with a higher αA proportion (3:1 ratio) has shown greater chaperone-like activity at elevated temperatures (>50 °C) and also upon structural perturbation. Furthermore, higher chaperone activity at elevated temperatures as well as upon structural perturbation is mainly mediated through increased hydrophobicity of αA. Although homopolymers and heteropolymers of α-crystallin did not differ in their secondary structure, changes in tertiary structure due to structural perturbations upon pre-heating are mediated predominantly by αA. Interestingly, the heteropolymer with higher αA proportion (3:1) or the αA-homopolymer seems to be better chaperones in protecting lens β- and γ-crystallins at both normal and elevated temperatures. Thus lens might have favoured a combination of these qualities to achieve optimal protection under both native and stress (perturbed) conditions for which the heteropolymer with αA to αB in the 3:1 ratio appears to be better suited. [ABSTRACT FROM AUTHOR]

Abstract: This letter details the attenuation of hERG in a class of Akt inhibitors through heteroatom insertions into aromatic rings. The development of a cell-active dual Akt 1 and 2 inhibitors devoid of hERG activity is discussed using structure–activity relationships. [Copyright &y& Elsevier]

The article presents a study on the control of structure formation of polycarbosilane (PCS) taken from polydimethylsilane (PDMS) through Kumada rearrangement. For the study, researchers used evolved gas analysis (EGA) mode of pyrolysis-gas chromotography-mass spectrometry (Py-GC-MS) in order to examine the thermal property of PDMS. They found that the molecular structure of PCS was heavily dependent on the reaction time and reaction temperature.

Abstract: Multinuclear dynamic NMR spectroscopy of 5-trifluoromethylsulfonyl-1,3,5-dioxaazinane (4) revealed the existence of two close in energy chair conformers with differently oriented CF3 groups with respect to the ring. Of the two alternative routes for their interconversion, the ring inversion path with intermediate formation of the corresponding 2,5-twist-conformer is preferred, with the energy barrier of 11.2kcal/mol in excellent agreement with the experimental value (11.7kcal/mol). The Perlin effect is studied experimentally and calculated theoretically for all CH2 groups and found to be subject to the nature of the adjacent heteroatoms O and N, respectively. [Copyright &y& Elsevier]

Abstract: Adsorption of short linear heteropolymers in slitlike pores is studied using the density functional theory and Monte Carlo simulations. The molecules are assumed to be freely jointed tangent hard spheres. The segments have different affinity with regard to the walls. Each molecule contains one surface-binding segment that interacts with the walls via Lennard–Jones () potential and a number of segments interacting with surfaces via the hard-wall potentials. A position of the surface-binding segment in the chain can be arbitrarily chosen. We have studied the influence of the pore width, the chain length and the chemical structure of molecules on adsorption and the microscopic structure of the confined fluid. The theoretical predictions are compared with Monte Carlo simulations carried out for different ‘isomeric’ pentamers. [Copyright &y& Elsevier]

We studied a simplified model of a polymer brush. It consisted of linear chains, which were restricted to a simple cubic lattice. Chain macromolecules consisted of a sequence of two different kinds of segments were arranged in a specific sequence. The chains were grafted to an impenetrable surface, i.e., they were terminally attached to the surface with one end. The number of chains was varied from low to high grafting density. The model system was studied at different solvent qualities from good to poor solvent. The properties of this model system were studied by means of Monte Carlo simulation. The sampling Metropolis-type algorithm was based on local changes of chain's conformations. The structure of the brush film was analyzed and the roughness of the surface was determined. The distribution of both types of segments was given for different grafting densities. [ABSTRACT FROM AUTHOR]

Background: Engineered living materials (ELMs) are an exciting new frontier, where living organisms create highly functional materials. In particular, protein ELMs have the advantage that their properties can be manipulated via simple molecular biology. Caf1 is a protein ELM that is especially attractive as a biomaterial on account of its unique combination of properties: bacterial cells export it as a massive, modular, non-covalent polymer which is resistant to thermal and chemical degradation and free from animal material. Moreover, it is biologically inert, allowing the bioactivity of each 15 kDa monomeric Caf1 subunit to be specifically engineered by mutagenesis and co-expressed in the same Escherichia coli cell to produce a mixture of bioactive Caf1 subunits. Results: Here, we show by gel electrophoresis and transmission electron microscopy that the bacterial cells combine these subunits into true mosaic heteropolymers. By combining two separate bioactive motifs in a single mosaic polymer we demonstrate its utility by stimulating the early stages of bone formation by primary human bone marrow stromal cells. Finally, using a synthetic biology approach, we engineer a mosaic of three components, demonstrating that Caf1 complexity depends solely upon the variety of monomers available. Conclusions: These results demonstrate the utility of engineered Caf1 mosaic polymers as a simple route towards the production of multifunctional biomaterials that will be useful in biomedical applications such as 3D tissue culture and wound healing. Additionally, in situ Caf1 producing cells could create complex bacterial communities for biotechnology. [ABSTRACT FROM AUTHOR]

Side chains of photovoltaic materials play an important role in determining charge transport property, film morphology, and the corresponding device performance. In this work, two new acceptor materials, ATT‐6 and ATT‐7 with different side chains, m‐hexylphenyl and m‐hexyloxyphenyl on the indacenodithiophene, are designed and synthesized for applications in non‐fullerene polymer solar cells. ATT‐7 shows a higher absorption coefficient, increased crystallinity, and improved electron mobility in comparison with ATT‐6. Using wide‐bandgap polymer poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione)] (PBDB‐T) as donor, optimized devices based on PBDB‐T:ATT‐7 and PBDB‐T:ATT‐6 delivers power conversion efficiencies of 10.30% and 8.39%, respectively. The higher performance of ATT‐7‐based device can be attributed to efficient exciton dissociation, reduced bimolecular recombination, and enhanced and balanced charge carrier mobilities. These results indicate that side‐chain modification is an easy but efficient way in the design of high‐performance non‐fullerene acceptors. Two new acceptor materials, ATT‐6 and ATT‐7 with different side chains of m‐hexylphenyl and m‐hexyloxyphenyl on indacenodithiophene core, are designed and synthesized. PBDB‐T: ATT‐7‐based polymer solar cells show higher power conversion efficiencies of 10.30% than a PBDB‐T:ATT‐6‐based one, 8.39%, indicating that side‐chain heteroatom effect can be effectively applied to design high‐performance organic photovoltaic materials. [ABSTRACT FROM AUTHOR]

The Cover Feature illustrates film fabrication via electropolymerization of dithieno[3,2‐b:2′,3′‐d]arsole with the assistance of Lewis acid, BF3. Dithienoheterole is an important backbone to incorporate heteroatoms into conjugated systems. This is the first example of the electropolymerization of dithienoheteroles. More information can be found in the Communication by H. Imoto et al. on page 3357 in Issue 22, 2018 (DOI: 10.1002/celc.201801069). [ABSTRACT FROM AUTHOR]

The article focuses on lanthanide discrete cage-like assemblies. Based on bent five-membered heteroatom-ring-bridged ligands, researchers have reported a series of coordination polymers and supramolecular complexes. It has been wondered whether the five-membered heteroatom ring-bridged 3 ,3'-biphenylcarboxylate type ligands could be used as an organic clip to bind lanthanide ions into discrete molecular cages.

The biological function of a protein often depends on the formation of an ordered structure in order to support a smaller, chemically active configuration of amino acids against thermal fluctuations. Here we explore the development of proteins evolving to satisfy this requirement using an off-lattice polymer model in which monomers interact as low resolution amino acids. To evolve the model, we construct a Markov process in which sequences are subjected to random replacements, insertions, and deletions and are selected to recover a predefined minimum number of solid-ordered monomers using the Lindemann melting criterion. We show that polymers generated by this process consistently fold into soluble, ordered globules of similar length and complexity to small protein motifs. To compare the evolution of the globules with proteins, we analyze the statistics of amino acid replacements, the dependence of site mutation rates on solvent exposure, and the dependence of structural distance on sequence distance for homologous alignments. Despite the simplicity of the model, the results display a surprisingly close correspondence with protein data. [ABSTRACT FROM AUTHOR]

Review: 89 refs. [ABSTRACT FROM AUTHOR]