Chain Molecules Research Articles

Conformational and static properties of tagged chains in solvents: effect of chain connectivity in solvent molecules.

Polymer chains immersed in different solvent molecules exhibit diverse properties due to multiple spatiotemporal scales and complex interactions. Using molecular dynamics simulations, we study the conformational and static properties of tagged chains in different solvent molecules. Two types of solvent molecules were examined: one type consisted of chain molecules connected by bonds, while the other type consisted of individual bead molecules without any bonds. The only difference between the two solvent molecules lies in the chain connectivity. Our results show a compression of the tagged chains with the addition of bead or chain molecules. Chain molecule confinement induces a stronger compression compared to bead molecule confinement. In chain solvent molecules, the tagged chain's radius of gyration reached a minimum at a monomer volume fraction of ∼0.3. Notably, the probability distributions of chain size remain unchanged at different solvent densities, irrespective of whether the solvent consists of beads or polymers. Furthermore, as solvent density increases, a crossover from a unimodal to a bimodal distribution of bond angles is observed, indicating the presence of both compressed and expanded regions within the chain. The effective monomer-solvent interaction is obtained by calculating the partial radial distribution function and the potential of the mean force. In chain solvents, the correlation hole effect results in a reduced number of nearest neighbors around tagged monomers compared to bead solvents. The calculation of pore size distribution reveals that the solvent nonhomogeneity induced by chain connectivity leads to a broader distribution of pore sizes and larger pore dimensions at low volume fractions. These findings provide a deeper understanding of the conformational behavior of polymer chains in different solvent environments.

Preparation of two-dimensional perovskite layer by solution method for improving stability of FAPbI<sub>3</sub> perovskite solar cells

Organic-inorganic metal halide perovskite solar cells (PSCs) have been widely studied due to their excellent photoelectric conversion performance, but the inherent chemical instability of CH(NH<sub>2</sub>)<sub>2</sub>PbI<sub>3</sub> (FAPbI<sub>3</sub>) hinders its sustainable development. In particular, the surface interface of the membrane has prominent humidity sensitivity due to lower activation energy, the defect of the surface interface has a strong correlation with the film stability, and the treatment result of the defect is one of the key factors to improve the long-term stability. The FAPbI<sub>3</sub> suffers phase transition from black perovskite phase to yellow non-perovskite phase at room temperature, and the moisture will accelerate this phase transition. Interface engineering is one of the common methods to improve the stability of perovskite solar cells. In addition to interface engineering, there is a strategy of stacking a two-dimensional (2D) perovskite layer on the surface for interface passivation. However, most of the preparation methods of 2D perovskite layer have limitations. In this work, the full solution method and post-treatment mode of annealing are adopted, the hybrid perovskite solar cells of vitamin perovskite are successfully fabricated. The FAPbI<sub>3</sub> perovskite surface is uniformly spin-coated with butylamine iodide (BAI) solution, and the formation of 2D perovskite is driven on the surface of FAPbI<sub>3</sub> perovskite. Due to the passivation of surface interface defects by the 2D perovskite layer, the non-radiative recombination of charge carriers is reduced, greatly improving the carrier lifetime. Because of the hydrophobicity of long chain molecules in 2D perovskite, the long-term stability of the device is significantly improved. Consequently, the unencapsulated device containing 2D perovskite layer remains above 80% after operating at room temperature in ambient air with a relative humidity (RH) of 60% for nearly 1000 hours. The 2D perovskite layer can significantly improve the long-term stability of the film without affecting the charge carrier transport performance. This method of improving the stability of the device by constructing 2D perovskite layer is in line with the requirements and development trend of high-quality perovskite solar cells, and is a strategy with great development potential.

Generation and reactivity of the fragment ion [B12I8S(CN)]- in the gas phase and on surfaces.

Gaseous fragment ions generated in mass spectrometers may be employed as "building blocks" for the synthesis of novel molecules on surfaces using ion soft-landing. A fundamental understanding of the reactivity of the fragment ions is required to control bond formation of deposited fragments in surface layers. The fragment ion [B12X11]- (X = halogen) is formed by collision-induced dissociation (CID) from the precursor [B12X12]2- dianion. [B12X11]- is highly reactive and ion soft-landing experiments have shown that this ion binds to the alkyl chains of organic molecules on surfaces. In this work we investigate whether specific modifications of the precursor ion affect the chemical properties of the fragment ions to such an extent that attachment to functional groups of organic molecules on surfaces occurs and binding of alkyl chains is prevented. Therefore, a halogen substituent was replaced by a thiocyanate substituent. CID of the precursor [B12I11(SCN)]2- ion preferentially yields the fragment ion [B12I8S(CN)]-, which shows significantly altered reactivity compared to the fragment ions of [B12I12]2-. [B12I8S(CN)]- has a previously unknown structural element, wherein a sulfur atom bridges three boron atoms. Gas-phase reactions with different neutral reactants (cyclohexane, dimethyl sulfide, and dimethyl amine) accompanied by theoretical studies indicate that [B12I8S(CN)]- binds with higher selectivity to functional groups of organic molecules than fragment ions of [B12I12]2- (e.g., [B12I11]- and [B12I9]-). These findings were further confirmed by ion soft-landing experiments, which showed that [B12I8S(CN)]- ions attacked ester groups of adipates and phthalates, whereas [B12I11]- ions only bound to alkyl chains of the same reagents.

Controlling nano- and microfilament morphology by strategically placing chiral centers in the side chains of bent-core molecules.

Self-assembled lamellar nano- and microfilaments formed by select types of bent-core molecules are prime examples of the interplay between molecular conformation and morphological chirality. Here, we demonstrate how the strategic placement of chiral centers at C-1 and/or C-3 in the terminal alkyloxy side chains, largely based on a priori calculations of molecular conformation, leads to the predictable formation of increasingly complex nano- and microfilament morphologies. Adding to the previously described diversity of twisted and writhed filament types, we here demonstrate and explain the formation and coexistence of flat nanoribbons, nanocylinders, or nano- as well as microfilaments where the morphology spontaneously changes along the filament long axis. For some these more exotic types of filament morphology, helical multilayer filaments suddenly unwind to form flat nanoribbons that also twist again under preservation (not perversion) of the helical twist sense. Moreover, the morphologies formed by this series of molecules now allows us to demonstrate the complete transformation from flat multilayer ribbons over microfilaments and helical-wrapped nanocylinders to helical nanofilaments depending on the number and position of chiral centers in the aliphatic side chains.

What triggers the coupling of proton transfer and electron transfer at the active site of nitrogenase?

In converting N2 to NH3 the enzyme nitrogenase utilises 8 electrons and 8 protons in the complete catalytic cycle. The source of the electrons is an Fe4S4 reductase protein (Fe-protein) which temporarily docks with the MoFe-protein that contains the catalytic active cofactor, FeMo-co, and an electron transfer cluster called the P cluster. The overall mechanism involves 8 repetitions of a cycle in which reduced Fe-protein docks with the MoFe-protein, one electron transfers to the P-cluster, and then to FeMo-co, followed by dissociation of the two proteins and re-reduction of the Fe-protein. Protons are supplied serially to FeMo-co by a Grotthuss proton translocation mechanism from the protein surface along a conserved chain of water molecules (a proton wire) that terminates near S atoms of the FeMo-co cluster [CFe7S9Mo(homocitrate)] where the multiple steps of the chemical conversions are effected. It is assumed that the chemical mechanisms use proton-coupled electron-transfer (PCET) and that H atoms (e- + H+) are involved in each of the hydrogenation steps. However there is neither evidence for, or mechanism proposed, for this coupling. Here I report calculations of cluster charge distribution upon electron addition, revealing that the added negative charge is on the S atoms of FeMo-co, which thereby become more basic, and able to trigger proton transfer from H3O+ waiting at the near end of the proton wire. This mechanism is supported by calculations of the dynamics of the proton transfer step, in which the barrier is reduced by ca. 3.5 kcal mol-1 and the product stabilised by ca. 7 kcal mol-1 upon electron addition. H tunneling is probable in this step. In nitrogenase it is electron transfer that triggers proton transfer.

Crystal structures of sixteen phosphane chalcogenide complexes of gold(I) chloride, bromide and iodide.

The structures of 16 phosphane chalcogenide complexes of gold(I) halides, with the general formula R 1 3- nR 2 nPEAuX (R 1 = t-butyl; R 2 = isopropyl; n = 0 to 3; E = S or Se; X = Cl, Br or I), are presented. The eight possible chlorido derivatives are: 1a, n = 3, E = S; 2a, n = 2, E = S; 3a, n = 1, E = S; 4a, n = 0, E = S; 5a, n = 3, E = Se; 6a, n = 2, E = Se; 7a, n = 1, E = Se; and 8a, n = 0, E = Se, and the corresponding bromido derivatives are 1b-8b in the same order. However, 2a and 2b were badly disordered and 8a was not obtained. The iodido derivatives are 2c, 6c and 7c (numbered as for the series a and b). All structures are solvent-free and all have Z' = 1 except for 6b and 6c (Z' = 2). All mol-ecules show the expected linear geometry at gold and approximately tetra-hedral angles P-E-Au. The presence of bulky ligands forces some short intra-molecular contacts, in particular H⋯Au and H⋯E. The Au-E bond lengths have a slight but consistent tendency to be longer when trans to a softer X ligand, and vice versa. The five compounds 1a, 5a, 6a, 1b and 5b form an isotypic set, despite the different alkyl groups in 6a. Compounds 3a/3b, 4b/8b and 6b/6c form isotypic pairs. The crystal packing can be analysed in terms of various types of secondary inter-actions, of which the most frequent are 'weak' hydrogen bonds from methine hydrogen atoms to the halogenido ligands. For the structure type 1a, H⋯X and H⋯E contacts combine to form a layer structure. For 3a/3b, the packing is almost featureless, but can be described in terms of a double-layer structure involving borderline H⋯Cl/Br and H⋯S contacts. In 4a and 4b/8b, which lack methine groups, Cmeth-yl-H⋯X contacts combine to form layer structures. In 7a/7b, short C-H⋯X inter-actions form chains of mol-ecules that are further linked by association of short Au⋯Se contacts to form a layer structure. The packing of compound 6b/6c can conveniently be analysed for each independent mol-ecule separately, because they occupy different regions of the cell. Mol-ecule 1 forms chains in which the mol-ecules are linked by a Cmethine⋯Au contact. The mol-ecules 2 associate via a short Se⋯Se contact and a short H⋯X contact to form a layer structure. The packing of compound 2c can be described in terms of two short Cmethine-H⋯I contacts, which combine to form a corrugated ribbon structure. Compound 7c is the only compound in this paper to feature Au⋯Au contacts, which lead to twofold-symmetric dimers. Apart from this, the packing is almost featureless, consisting of layers with only translation symmetry except for two very borderline Au⋯H contacts.

Preparation and characterization of fluorine-containing benzimidazole polyimide films with a micro-branched crosslink structure

In order to solve the problem of high-water absorption and low transparency of benzimidazole polyimide (PBII) films, this study introduced fluorine-containing groups into the benzimidazole polyimide molecule chains, and a series of benzimidazole polyimide films with different fluorine-containing ratios were prepared. In addition, a micro-branched crosslinking structure was established by adding triamino compounds to the system, and the effect of the micro-branched crosslinking structure on the film properties was investigated. The research showed that adding a certain amount of fluorine-containing groups could effectively improve the optical properties and decrease water absorption of polyimide films while having a small effect on the heat resistance and thermal dimensional stability. The incorporation of a small amount of triamino compounds effectively compensated for the adverse effects on the mechanical properties, heat resistance, and thermal dimensional stability caused by the addition of fluorine-containing groups and lowering the imidization temperature. In addition, the water absorption could be further reduced by establishing a cross-linked structure. In this study, a new design idea was provided to achieve the balance of heat resistance, thermal dimensional stability, water absorption, transparency, and mechanical properties of benzimidazole polyimide films.

Effective Ion Charges in Ion Exchangers and Electrolyte Solutions

Structures, effective numbers of charges and molecular orbitals of ion pairs and representative fragments of a sulfocation exchanger in various ionic forms were calculated by the non-empirical quantum chemical method of LCAO MO. The effective charges of ions in accordance with the principles of the molecular orbital method were fractional values. For contact ion pairs, where the effective ion charges were experimentally measured by X-ray absorption spectroscopy, we obtained full agreement with the calculated values. The charge numbers of cations and anions differed in both hydrate-separated and ion-exchange systems due to the fact that the oxygen atoms of hydrated water molecules influenced the formation of molecular orbitals. According to the obtained values of the numbers of charges and interionic distances, the energies of the electrostatic interaction of ions were calculated using the integral form of Coulomb's law. Experimental values of the energies of chemical bonds of counterions and fixed ions were obtained using the conductometric contact-difference method when measuring the specific electrical conductivity of MK-40 cation exchange membranes in the range of 20-50oC and according to the Arrhenius equation. The coordination of experimental and calculated chemical bond energies in the ion exchanger was achieved after the addition of hydrogen bond energy to the electrostatic interaction energy. In order to be able to completely nonempirically calculate the energies of chemical bonds in an ion exchanger, we took the value of the hydrogen bond energy as the excitation energy of the first energy level of deformation vibrations of water molecules having a value of 19.4 kJ/mol. A comparison of the contribution of the electrostatic interaction to the total binding energy of alkali metal cations with a fixed ion showed its small role in ion exchange and membrane transport, so that in the first approximation we can say that the transfer of alkali metal cations is determined by the breaking of the hydrogen bond. For cations of a larger charge (calcium), the electrostatic energy already makes a significant contribution, and for trivalent ions, the energies of the Coulomb interaction and hydrogen bonding are close to each other. The soliton mechanism of translation of the energy of deformation vibrations along a chain of water molecules is considered, which allows explaining the decrease in energy when several hydrogen bonds are broken.

Effect of doping of organo-soluble carbon dots on ionic relaxation and conductivity of planar anchored cyanobiphenyl based nematic liquid crystal

We demonstrate here the striking effect of organo-soluble carbon dots (CDs, diameter ∼7- 8 nm) on the tunability of ionic relaxation and conductivity of the host, planar anchored thermotropic nematic liquid crystal (5CB, 4-Cyano-4′-pentylbiphenyl). The optical texture, frequency, temperature, and concentration dependent dielectric studies of pristine 5CB and CDs-5CB composites have been performed using the polarising optical microscope and high-resolution dielectric spectroscopy, respectively. The doping of 0.5 wt% CDs into planar anchored 5CB is resulted into the vertical alignment confirmed through the cross-polarised optical microscope. The doping of CDs in 5CB liquid crystal is resulted into an unprecedented faster ionic relaxation with an abatement of the ionic amplitude at room temperature. The shift in the relaxation frequency for 0.5 wt% CDs-5CB composite (induced vertical alignment) as compared to pristine 5CB (planar aligned) at 28 °C (nematic) is found to be ∼13 folds which is further increased to ∼18 folds at 38 °C (isotropic). A similar trend in the conductivity curve is also observed which further confirms the significant enhancement in conductivity value with increase in temperature and concentration of dopant CDs. The observation of enhanced ionic conductivity and faster ionic relaxation in CDs-5CB composites as compared to pristine 5CB are attributed to the complete change of planar to vertical alignment by doping of CDs on planar anchored liquid crystal sample cells. It appears that the plausible strong interaction between hydrocarbon chains of CDs and 5CB molecules through anchored substrate surfaces with increasing concentration of CDs and decrease in rotational viscosity of host 5CB with increasing temperature certainly plays a pivotal role in the tuning of ionic relaxation and conductivity in the liquid crystal sample cells. We certainly believe that our results would catalyze the cognizance of the ionic relaxation and conductivity in CDs-5CB composites and other related systems. Moreover, such composites with tunable ionic relaxation/conductivity would be certainly helpful in the fabrication of various tuneable devices such as wave front corrector, low frequency oscillation generators, dynamic light scattering, and so on.

(Invited) Electrosynthesis of Long-Chain Hydrocarbons and Oxygenates

The electroreduction of CO(2), driven by renewable electricity, can be used to sustainably generate synthetic fuels and chemical feedstocks. Long carbon chain molecules are of particular interest due to their high energy densities and utilities. However, to date, most of the CO(2) reduction products formed are limited to C2 and C3. Herein, we discuss the development of electrocatalysts for the reduction of CO(2) to long-chain oxygenates and hydrocarbons, and their underlying reaction mechanisms.CO(2) electroreduction has been previously reported to yield a range of carbonaceous products including alcohols, hydrocarbons and carboxylic acids. Interestingly, esters, an important family of organic compounds, have not been formed. We show how C3–C6 acetate esters could be produced from CO reduction in a membrane electrode assembly (MEA) cell. The near water-free reaction environment and the high local pH in the MEA played key roles in forming the esters with a Faradaic efficiency of 22 % and a current density up to −55 mA cm−2. We also disclose that inorganic nickel oxygenate (INO)-derived electrocatalysts can reduce CO2 to linear and branched C3-C6 hydrocarbons with Faradaic efficiencies up to 6.5%. We identified Niδ+ active sites which bind CO moderately. Our results show that Ni atom polarization to be important in hindering CO poisoning of nickel and thus facilitating CO2 reduction to a wider pool of valuable products.Finally, we show how MgAl layered double hydroxide (LDH) nanosheets ‘House-of-cards’ structures help to disperse CuO-derived Cu (OD-Cu) catalysts. The porous structures formed enhanced CO gas percolation through the catalyst layer. OD-Cu dispersed by the ‘House-of-cards’ structures catalysed CO electroreduction to C2+ products with a partial current density that is an order of magnitude higher than that shown by the unsupported OD-Cu.

Structural, physicochemical properties and noodle-making potential of quinoa starch and type 3, type 4, and type 5 quinoa resistant starch

This study prepared type 3, type 4, and type 5 quinoa resistant starch (QRS3, QRS4, and QRS5) from quinoa starch (QS), compared their structural and physicochemical properties and evaluated their noodle-making potential. The results showed that the molecular weight of QRS3 decreased, the number of short-chain molecules increased, and its crystal type changed to B-type after gelatinization, enzymatic hydrolysis, and retrogradation. QRS4 is a phosphorylated cross-linked starch, with a surface morphology, particle size range, and crystal type similar to QS, but displaying modified thermodynamic properties. QRS5 is a complex of amylose and palmitic acid. It displays typical V-type crystals, mainly composed of long chain molecules and primarily exhibits a block morphology. The noodles prepared by replacing 20 % wheat flour with QS, QRS3 and QRS5 have higher hardness and are suitable for people who like elasticity and chewiness. QRS4 noodles are softer and suitable for people like elderly and infants who prefer soft foods. In conclusion, significant differences were evident between the fine structures, crystal types, physicochemical properties and potential applications of QS and the three QRSs. The results may expand the application of QS and QRS in the food and pharmaceutical industries.

Effect of α-methyl on the performance of photocurable 3D printing polyurethane materials

For photosensitive polyurethane systems, reactive diluents are indispensable components whose main role is to reduce the viscosity of the polyurethane prepolymer to meet the requirements of the photocurable 3D printing technology for high fluidity of the precursor solution. Generally, the reactive diluent would be involved in the photocuring reaction, which in turn has a remarkable impact on the mechanical, reaction kinetics, and thermodynamic characteristics of the photosensitive polyurethane system. However, this feature is usually neglected in the study of photosensitive urethane acrylate (PUA) systems, so there is a considerable necessity to investigate the mechanism of active diluents in the photocured reaction of PUA systems. In this work, the effects of α-methyl groups along the chains of diluent molecules on the photoreaction kinetics, photocurable 3D printing, mechanical and mechanical properties, and thermodynamic characteristics of PUAs were investigated employing hydroxyethyl methacrylate and hydroxyethyl acrylate as active diluents, respectively. The relationship between chemical structure and kinetics of PUA systems was also elucidated by using dynamic mechanical analysis tests. The results demonstrated that the α-methyl group blocks the migration of reactive radicals, reduces the efficiency of the photoreaction, and causes an increase in the rigidity and strength of the molecular chain. This study not only revealed the effect of α-methyl on the kinetic mechanical and thermal performance of PUA systems but also paves the way for the development of a new class of photosensitive PUA materials used for the photocurable 3D printing technology.

Deep contrastive learning of molecular conformation for efficient property prediction.

Data-driven deep learning algorithms provide accurate prediction of high-level quantum-chemical molecular properties. However, their inputs must be constrained to the same quantum-chemical level of geometric relaxation as the training dataset, limiting their flexibility. Adopting alternative cost-effective conformation generative methods introduces domain-shift problems, deteriorating prediction accuracy. Here we propose a deep contrastive learning-based domain-adaptation method called Local Atomic environment Contrastive Learning (LACL). LACL learns to alleviate the disparities in distribution between the two geometric conformations by comparing different conformation-generation methods. We found that LACL forms a domain-agnostic latent space that encapsulates the semantics of an atom's local atomic environment. LACL achieves quantum-chemical accuracy while circumventing the geometric relaxation bottleneck and could enable future application scenarios such as inverse molecular engineering and large-scale screening. Our approach is also generalizable from small organic molecules to long chains of biological and pharmacological molecules.

Highly sensitive electrochemical peptide-based biosensor for marine biotoxin detection using a bimetallic platinum and ruthenium nanoparticle-tethered metal-organic framework modified electrode.

Saxitoxin (STX) is a highly toxic small-molecule cyanotoxin that is water-soluble, stable in acidic media, and thermostable. STX is hazardous to human health and the environment in ocean, thus it is an important to detect it at very low concentrations. Herein, we developed an electrochemical peptide-based biosensor for the trace detection of STX in different sample matrix utilizing differential pulse voltammetry (DPV) signal. We synthesized the nanocomposite of zeolitic imidazolate framework-67 (ZIF-67) decorated bimetallic platinum (Pt) and ruthenium (Ru) nanoparticles (Pt-Ru@C/ZIF-67) using impregnation method. The nanocomposite modified with screen-printed electrode (SPE) was subsequently used to detect STX in the range of 1-1,000ngmL-1, with a detection limit (LOD) of 26.7pgmL-1. The developed peptide-based biosensor is highly selective and sensitive towards STX detection, thus it represents a promising strategy for the development of novel portable bioassay for monitoring various hazardous molecules in aquatic food chains.

Preparation of composite coagulant for the removal of microplastics in water.

In this work, a composite flocculant (polyferric titanium sulfate-polydimethyldiallylammonium chloride [PFTS-PDMDAAC]) with a rich spatial network structure was prepared for the treatment of simulated wastewater containing polystyrene (PS) micro-nanoparticles. Characterization results showed that the surface of the PFTS-PDMDAAC was a three-dimensional network polymer of chain molecules that exhibited good thermal stability and formed an amorphous polymer containing multiply hydroxyl-bridged titanium and iron. When n(OH- ):n(Fe) = 1:2, n(PO4 3- ):n(Fe) = 0.35, n(Ti):n(Fe) = 1:8, n(DMDAAC):n(Fe) = 5:100, and the polymerization temperature is 60°C, the prepared composite flocculant has the best effect. The effects of dosage, pH, and agitation intensity on the flocculation properties of PFTS-PDMDAAC were also studied. The optimal removal rates of PS-μm and haze by PFTS-PDMDAAC were 85.60% and 90.10%, respectively, at a stirring intensity of 200 rpm, a pH of 9.0, and a PFTS-PDMDAAC dosage of 20 mg/L. The flocs produced by the PFTS-PDMDAAC flocculation were large and compact in structure, and the flocculation mechanism was mainly based on adsorption bridging. Kaolin played a promoting role in the process of PS-μm removal by PFTS-PDMDAAC floc and accelerated the formation of large and dense flocs. This study provided a reference for the coagulation method to remove micro-nanopollutants in the actual water treatment process. PRACTITIONER POINTS: A composite flocculant with rich spatial network structure (PFTS-PDMDAAC) was prepared. PFTS-PDMDAAC can effectively remove micro-nano polystyrene (PS) in wastewater. The floc produced by PFTS-PDMDAAC is large and compact in structure. The flocculation mechanism of PFTS-PDMDAAC is mainly adsorption bridging.

Effects of Counterion on the Formation and Hydration Behavior of α-Form Hydrated Crystals (α-Gels).

α-Form hydrated crystals form a lamellar gel in which the alkyl chains of the amphiphilic molecules are hexagonally arranged within bilayers below the gel-liquid crystal phase transition temperature. In practice, the lamellar gel network with excess water is called an "α-gel", particularly in the cosmetics industry. In this study, the hydration or water sorption of amphiphilic materials in water vapor was assessed using a humidity-controlled quartz crystal microbalance with dissipation monitoring (QCM-D) technique. The amphiphilic materials used in this study were hexadecyl phosphate salts neutralized with L-arginine (C16P-Arg), CsOH (C16P-Cs), KOH (C16P-K), and NaOH (C16P-Na). Small- and wide-angle X-ray scattering measurements revealed that C16P-Arg and C16P-Cs yielded α-form hydrated crystals. Humidity-controlled QCM-D measurements demonstrated that C16P-Arg and C16P-Cs more readily underwent hydration or water sorption than C16P-K and C16P-Na. The key conclusion is that the significant hydration ability of C16P-Arg and C16P-Cs promotes the formation of the corresponding α-form hydrated crystals.

Synthesis, structure and Hirshfeld surface analysis of 1,3-bis-[(1-octyl-1H-1,2,3-triazol-4-yl)meth-yl]-1H-benzo[d]imidazol-2(3H)-one.

The title mol-ecule, C29H44N8O, adopts a conformation resembling a two-bladed fan with the octyl chains largely in fully extended conformations. In the crystal, C-H⋯O hydrogen bonds form chains of mol-ecules extending along the b-axis direction, which are linked by weak C-H⋯N hydrogen bonds and C-H⋯π inter-actions to generate a three-dimensional network. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (68.3%), H⋯N/N⋯H (15.7%) and H⋯C/C⋯H (10.4%) inter-actions.

Elaboration of Nanostructured Levan-Based Colloid System as a Biological Alternative with Antimicrobial Activity for Applications in the Management of Pathogenic Microorganisms.

Considering the documented health benefits of bacterial exopolysaccharides (EPSs), specifically of bacterial levan (BL), including its intrinsic antimicrobial activity against certain pathogenic species, the current study concentrated on the development of active pharmaceutical ingredients (APIs) in the form of colloid systems (CoSs) containing silver nanoparticles (AgNPs) employing in-house biosynthesized BL as a reducing and capping agent. The established protocol of fermentation conditions implicating two species of lactic acid bacteria (LAB), i.e., Streptococcus salivarius K12 and Leuconostoc mesenteroides DSM 20343, ensured a yield of up to 25.7 and 13.7 g L-1 of BL within 72 h, respectively. An analytical approach accomplished by Fourier-transform infrared (FT-IR) spectroscopy allowed for the verification of structural features attributed to biosynthesized BL. Furthermore, scanning electron microscopy (SEM) revealed the crystalline morphology of biosynthesized BL with a smooth and glossy surface and highly porous structure. Molecular weight (Mw) estimated by multi-detector size-exclusion chromatography (SEC) indicated that BL biosynthesized using S. salivarius K12 has an impressively high Mw, corresponding to 15.435 × 104 kilodaltons (kDa). In turn, BL isolated from L. mesenteroides DSM 20343 was found to have an Mw of only 26.6 kDa. Polydispersity index estimation (PD = Mw/Mn) of produced BL displayed a monodispersed molecule isolated from S. salivarius K12, corresponding to 1.08, while this was 2.17 for L. mesenteroides DSM 20343 isolate. The presence of fructose as the main backbone and, to a lesser extent, glucose and galactose as side chain molecules in EPS hydrolysates was supported by HPLC-RID detection. In producing CoS-BL@AgNPs within green biosynthesis, the presence of nanostructured objects with a size distribution from 12.67 ± 5.56 nm to 46.97 ± 20.23 was confirmed by SEM and energy-dispersive X-ray spectroscopy (EDX). The prominent inhibitory potency of elaborated CoS-BL@AgNPs against both reference test cultures, i.e., Pseudomonas aeruginosa, Escherichia coli, Enterobacter aerogenes, and Staphylococcus aureus and those of clinical origin with multi-drug resistance (MDR), was confirmed by disc and well diffusion tests and supported by the values of the minimum inhibitory and bactericidal concentrations. CoS-BL@AgNPs can be treated as APIs suitable for designing new antimicrobial agents and modifying therapies in controlling MDR pathogens.

Design of surface with integrated properties of sterilization and desorption

As might be one of the hottest topics in public health research, the war against bacteria has been going on some thousands of years. Unfortunately, we too are threatened by bacterial adhesion and contamination as the ancients even though the health and well-being of populations has been dramatically improved owing to the advances in human medicine and environmental sanitation. In this study, we designed a double-layer coating that consisted of polymethyl methacrylate (PMMA) and carbon nanotube (CNT)-loaded polydimethylsiloxane (PDMS) and introduced antibacterial molecule chains (AMCs), which can repeatedly release and replenish reactive oxygen species (ROS), on the coating surface. Benefiting from the characteristics of releasing ROS after the AMCs were irradiated by NIR and wrinkle structure originated from the difference in thermal expansion coefficients between PMMA and PDMS, as revealed by Uv-visible absorption spectrum and morphological characterization, the performance of sterilization and desorption would be integrated into the coating surface by irradiating the coating surface with near-infrared (NIR) repeatedly. The results of antimicrobial experiments confirmed that all of the bacteria on the coating surface were terminated and deported after the coating was irradiated six times by NIR. Additionally, after bacteria were killed and desorbed, the coating would return to its original form and AMC could be re-endowed with the ability to release ROS through treatment, showing potential of being applied in the modification of biomaterials.

Hydrophobic Interaction-Induced Topology-Independent Destabilization of G-Quadruplex.

Since the inception of the G-quadruplex (G4), enormous attention has been devoted to designing small molecules which can stabilize the G-quadruplex. In contrast, the knowledge about the molecules and mechanisms involved in the destabilization of G4 is sparse, although it is well recognized that destabilization of G4 is important in neurobiology and age-related genetic issues. In this study, it has been shown that amphiphilic molecules having a long hydrocarbon chain can destabilize G4, regardless of its topology, using various biophysical and molecular dynamics simulation methods. It has been observed that the hydrophobic interaction induced by the long hydrocarbon chain of amphiphilic molecules is the main contributor in triggering the destabilization of G4, although hydrogen bonding by the polar part of the molecules also cooperates in the destabilization process. The experiment and simulation studies suggest that a long hydrocarbon chain containing amphiphilic molecules gets aggregated, and their hydrocarbon chain as well as the polar group intrude in the quartet region from the 5' side and interact with guanine bases as well as nearby loops through hydrophobic and electrostatic interactions, which trigger the destabilization of G4.