Self-Assembled Tetraphenylethene-Based Nanoaggregates with Tunable Electrochemiluminescence for the Ultrasensitive Detection of E. coli.

As an effective ECL emitter, tetraphenylethene (TPE)-based molecules have recently been reported with aggregation-induced electrochemiluminescence (AIECL) property, while it is still a big challenge to control its aggregation states and obtain uniform aggregates with intense ECL emission. In this study, we develop three TPE derivatives carrying a pyridinium group, an alkyl chain, and a quaternary ammonium group via the Menschutkin reaction. The resulting molecules exhibit significantly red-shifted FL and enhanced ECL emissions due to the tunable reduction of the energy gap between the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs). More importantly, the amphiphilicity of the as-developed molecules enables their spontaneous self-assembly into well-controlled spherical nanoaggregates, and the ECL intensity of nanoaggregates with 3 -CH2- (named as C3) is 17.0-fold higher compared to that of the original 4-(4-(1,2,2-triphenylvinyl)phenyl)pyridine (TPP) molecule. These cationic nanoaggregates demonstrate a high affinity toward bacteria, and an ECL sensor for the profiling of Escherichia coli (E. coli) was developed with a broad linear range and good selectivity in the presence of an E. coli-specific aptamer. This study provides an effective way to enhance the ECL emission of TPE molecules through their derivatization and a simple way to prepare well-controlled AIECL nanoaggregates for ECL application.

Influence of temperature on bend, twist and twist-bend coupling of dsDNA.

The temperature-dependent bend and twist elasticities of dsDNA, as well as their couplings, were explored through all-atom molecular dynamics simulations. Three rotational parameters, tilt, roll, and twist, were employed to assess the bend and twist elasticities through their stiffness matrix. Our analysis indicates that the bend and twist stiffnesses decrease as the temperature rises, primarily owing to entropic influences stemming from thermodynamic fluctuations. Furthermore, the couplings between these rotational parameters also exhibit a decline with increasing temperature, although the roll-twist coupling displays greater strength than the tilt-roll and tilt-twist couplings, attributed to its more robust correction component. We elucidated the influence of temperature on bend and twist elasticities based on the comparisons between various models and existing data.

Temperature dependence of DNA elasticity: An all-atom molecular dynamics simulation study.

We used all-atom molecular dynamics simulation to investigate the elastic properties of double-stranded DNA (dsDNA). We focused on the influences of temperature on the stretch, bend, and twist elasticities, as well as the twist-stretch coupling, of the dsDNA over a wide range of temperature. The results showed that the bending and twist persistence lengths, together with the stretch and twist moduli, decrease linearly with temperature. However, the twist-stretch coupling behaves in a positive correction and enhances as the temperature increases. The potential mechanisms of how temperature affects dsDNA elasticity and coupling were investigated by using the trajectories from atomistic simulation, in which thermal fluctuations in structural parameters were analyzed in detail. We analyzed the simulation results by comparing them with previous simulation and experimental data, which are in good agreement. The prediction about the temperature dependence of dsDNA elastic properties provides a deeper understanding of DNA elasticities in biological environments and potentially helps in the further development of DNA nanotechnology.

Asymmetric Lipid Membranes under Shear Flows: A Dissipative Particle Dynamics Study.

We investigate the phase behavior of the asymmetric lipid membranes under shear flows, using the dissipative particle dynamics simulation. Two cases, the weak and strong shear flows, are considered for the asymmetric lipid microstructures. Three typical asymmetric structures, the membranes, tubes, and vesicle, are included in the phase diagrams, where the effect of two different types of lipid chain length on the formation of asymmetric membranes is evaluated. The dynamic processes are demonstrated for the asymmetric membranes by calculating the average radius of gyration and shape factor. The result indicates that different shear flows will affect the shape of the second type of lipid molecules; the shape of the first type of lipid molecules is more stable than that of the second type of lipid molecules. The mechanical properties are investigated for the asymmetric membranes by analyzing the interface tension. The results reveal an absolute pressure at the junctions of different types of particles under the weak shear flow; the other positions are almost in a state of no pressure; there is almost no pressure inside the asymmetric lipid membrane structure under the strong shear flow. The findings will help us to understand the potential applications of asymmetric lipid microstructures in the biological and medical fields.

Sliding dynamics of multi-rings on a semiflexible polymer in poly[n]catenanes.

The sliding dynamics of one- or multi-ring structures along a semiflexible cyclic polymer in radial poly[n]catenanes is investigated using molecular dynamics simulations. The fixed and fluctuating (non-fixed) semiflexible central cyclic polymers are considered, respectively. With increasing bending energy of the central cyclic polymer, for the fixed case, the diffusion coefficient increases monotonically due to the reduction of the tortuous sliding path, while for the fluctuating case, the diffusion coefficient decreases. This indicates that the contribution of the polymer fluctuation is suppressed by a further increase in the stiffness of the central cyclic chain. Compared with the one ring case, the mean-square displacement of the multiple rings exhibits a unique sub-diffusive behavior at intermediate time scales due to the repulsion between two neighboring rings. In addition, for the multi-ring system, the whole set of rings exhibit relatively slower diffusion, but faster local dynamics of threading rings and rotational diffusion of the central cyclic polymer arise. These results may help us to understand the diffusion motion of rings in radial poly[n]catenanes from a fundamental point of view and control the sliding dynamics in molecular designs.

Interaction between Bottlebrush Polymers and Phospholipid Membranes in Solutions.

In this work, the interactions between bottlebrush polymers and phospholipid membranes were investigated using dissipative particle dynamics simulations. The weak and strong adsorption phenomena between the polymers and membranes were examined by calculating the system parameters. A spring model was introduced to explain the variances in the shape factors and the radius of gyration of the bottlebrush polymers, as well as the order parameters of the phospholipid membrane in the pulling processes. This work provides further understanding for the application of bottlebrush polymers in biological processes.

Effects of Topological Constraints on Penetration Structures of Semi-Flexible Ring Polymers.

The effects of topological constraints on penetration structures of semi-flexible ring polymers in a melt are investigated using molecular dynamics simulations, considering simultaneously the effects of the chain stiffness. Three topology types of rings are considered: 01-knot (the unknotted), 31-knot and 61-knot ring polymers, respectively. With the improved algorithm to detect and quantify the inter-ring penetration (or inter-ring threading), the degree of ring threading does not increase monotonously with the chain stiffness, existing a peak value at the intermediate stiffness. It indicates that rings interpenetrate most at intermediate stiffness where there is a balance between coil expansion (favoring penetrations) and stiffness (inhibiting penetrations). Meanwhile, the inter-ring penetration would be suppressed with the knot complexity of the rings. The analysis of effective potential between the rings provides a better understanding for this non-monotonous behavior in inter-ring penetration.

An attraction-repulsion transition of force on two asymmetric wedges induced by active particles.

Effective interaction between two asymmetric wedges immersed in a two-dimensional active bath is investigated by computer simulations. The attraction-repulsion transition of effective force between two asymmetric wedges is subjected to the relative position of two wedges, the wedge-to-wedge distance, the active particle density, as well as the apex angle of two wedges. By exchanging the position of the two asymmetric wedges in an active bath, firstly a simple attraction-repulsion transition of effective force occurs, completely different from passive Brownian particles. Secondly the transition of effective force is symmetric for the long-range distance between two asymmetric wedges, while it is asymmetric for the short-range case. Our investigations may provide new possibilities to govern the motion and assembly of microscopic objects by taking advantage of the self-driven behaviour of active particles.

Predicting asymmetric phospholipid microstructures in solutions.

Asymmetric phospholipid microstructures, such as asymmetric phospholipid membranes, have potential applications in biological and medicinal processes. Here, we used the dissipative particle dynamics simulation method to predict the asymmetric phospholipid microstructures in aqueous solutions. The asymmetric phospholipid membranes, tubes and vesicles are determined and characterized by the chain density distributions and order parameters. The phase diagrams are constructed to evaluate the effects of the chain length on the asymmetric structure formations at equilibrium states, while the average radius of gyration and shape factors are calculated to analyze the asymmetric structure formations in the non-equilibrium processes. Meanwhile, we predicted the mechanical properties of the asymmetric membranes by analyzing the spatial distributions of the interface tensions and osmotic pressures in solutions.

Entropy-induced Separation of Binary Semiflexible Ring Polymer Mixtures in Spherical Confinement.

Coarse-grained molecular dynamics simulations are used to investigate the conformations of binary semiflexible ring polymers (SRPs) of two different lengths confined in a hard sphere. Segregated structures of SRPs in binary mixtures are strongly dependent upon the number density of system (ρ), the bending energy of long SRPs (Kb, long), and the chain length ratio of long to short SRPs (α). With a low ρ or a weak Kb, long at a small ratio α, long SRPs are immersed randomly in the matrix of short SRPs. As ρ and bending energy of long SRPs (Kb, long) are increased up to a certain value for a large ratio α, a nearly complete segregation between long and short SRPs is observed, which can be further characterized by the ratio of tangential and radial components of long SRPs velocity. These explicit segregated structures of the two components in spherical confinement are induced by a delicate competition between the entropic excluded volume (depletion) effects and bending contributions.

Shear-induced microstructures and dynamics processes of phospholipid cylinders in solutions.

Shear-induced microstructures and their corresponding dynamic processes are investigated for phospholipid cylinders in aqueous solution by dissipative particle dynamic simulation. Various phospholipid cylinders with cross-sections, which are formed under shear-free flow, are selected to examine the effects of shear flow on their structures and dynamic processes. Shear flow induces the transition from cylinders into vesicles at weak rate and the transition into vesicle-lamella mixtures with increased shear rate and lamella structures at the strong shear rate. Then, the average radius of gyration and shape factors of the polymer chains in the dynamic processes are discussed in detail. Results show that shear flow causes the structure of the polymer chains to be elongated along the shear direction, and the configuration of the polymer chain can be rapidly transformed into an ellipsoid structure under strong shear.

An attraction-repulsion transition of force on wedges induced by active particles.

Effective forces between two micro-wedges immersed in an active bath are investigated using Brownian dynamics simulations. Two anti-parallel and parallel wedge-like obstacles are considered respectively, and the effective forces between two wedges rely on the wedge-to-wedge distance, the apex angle of the wedge, as well as the particle density and aspect ratio. For two anti-parallel wedges, a transition from repulsion to attraction occurs by varying the apex angle, which is also sensitive to the particle density and aspect ratio. The optimal apex angle θr* (or θa*) and particle density ρ* are characterized by the saturated trapping of active particles inside a wedge. For two parallel wedges, the effective force also experiences a transition from repulsion to attraction as the wedge-to-wedge distance increases. These results originate from the collective trapping effect which is driven by the many-body dynamics of self-propelled particles in the confinement (near the boundary) of obstacles. Our results can provide insight into controlling the motion and assembly of microscopic objects through the suspension of active particles.

Self-assembly of phospholipid molecules in solutions under shear flows: Microstructures and phase diagrams.

Shear-induced microstructures and their phase diagrams were investigated for phospholipid molecules in aqueous solution by dissipative particle dynamic simulation. Self-assembled microstructures, including spherical and cylindrical micelles, spherical vesicles, lamellae, undulated lamellae, perforated lamellae, and continuous networks, were observed under various shear flows and phospholipid concentrations, where the spatial inhomogeneity and symmetry were analysed. A series of phase diagrams were constructed based on the chain lengths under various phospholipid concentrations. The phase distributions showed that the structures with spherical symmetry could be shear-induced to structures with cylindrical symmetry in the dilute solutions. In the semi-concentrated solutions, the lamellae were located in most spaces under zero shear flows, which could be shear-induced into undulated lamellae and then into cylindrical micelles. For the concentrated solutions, the strong shear flows oriented the directions of multilayer lamellae and phase transitions appeared between several cylindrical network structures. These observations on shear-induced microstructures and their distributions revealed a promising approach that could be used to design bio-microstructures based on phospholipid molecules under shear flows.

Adsorption Behavior of Polymer Chain with Different Topology Structure at the Polymer-Nanoparticle Interface.

The effect of the polymer chain topology structure on the adsorption behavior in the polymer-nanoparticle (NP) interface is investigated by employing coarse-grained molecular dynamics simulations in various polymer-NP interaction and chain stiffness. At a weak polymer-NP interaction, ring chain with a closed topology structure has a slight priority to occupy the interfacial region than linear chain. At a strong polymer-NP interaction, the "middle" adsorption mechanism dominates the polymer local packing in the interface. As the increase of chain stiffness, an interesting transition from ring to linear chain preferential adsorption behavior occurs. The semiflexible linear chain squeezes ring chain out of the interfacial region by forming a helical structure and wrapping tightly the surface of NP. In particular, this selective adsorption behavior becomes more dramatic for the case of rigid-like chain, in which 3D tangent conformation of linear chain is absolutely prior to the 2D plane orbital structure of ring chain. The local packing and competitive adsorption behavior of bidisperse matrix in polymer-NP interface can be explained based on the adsorption mechanism of monodisperse (pure ring or linear) case. These investigations may provide some insights into polymer-NP interfacial adsorption behavior and guide the design of high-performance nanocomposites.

[Monitoring of HBsAg and Risk of HBV Infection in Patients with Multiple Myeloma].

OBJECTIVE: To explore the incidence of HBsAg and the risk of HBV infection in patients with multiple myeloma (MM). METHODS: A total of 114 newly diagnosed MM patients admitted in our hospital from May 2014 to July 2016 were enrolled in MM group, 110 healthy persons were enrolled in control group. The HBsAg positive rate and HBV infection rate were compared between 2 groups; the HBV infection rate of MM patients was compared before and after chemotherapy. According to detected results, all patients were divided into HBsAg+ group and HBsAg- group, and the lever damage in 2 groups was compared before and after treatment. For HBsAg+ and HBV-DNA+ patients, the preventive antiviral treatment was performed, while for other patients the preventive antiviral treatment was not performed, then the HBV reactivation was tested in each group. RESULTS: The incidence of HBsAg+ in MM patients seem a litter higher than that in control group without statistical significance (P>0.05); the incidence and severity of HBsAg+ group were higher than those of control group before treatment, moreover the difference between 2 groups was more significant after treatment (P< 0.05). The HBsAg reactivation was not found in 4 pases with HBsAg+ who received the proventive antiviral treatment, while the HBsAg reactivation was observed in 2 cases out of 6 cases without proventive antiviral treatment; the HBsAg reactivation happened only in 1 case of HBsAg- group after treatment. The HBV infection rate in MM patients after chemotherapy was significantly enhenced as compared with infection rate before chemotherapy(P< 0.05). CONCLUSION: The HBV infection rate in MM patients is higher than that in normal persons, moreover tha HBV-reactivation may happen in patients with ocult HBV infection in process of treatment; the HBV infection correlates with MM to a certain degree. The monitoring HBsAg for MM patients contributes to evaluation of liver danage.

Aggregation-Dispersion Transition for Nanoparticles in Semiflexible Ring Polymer Nanocomposite Melts.

By employing molecular dynamics simulations, we explored the conformation transition of nanoparticles (NPs) in semiflexible ring polymer nanocomposite melts. A novel aggregation-dispersion transition for NPs in ring polymer nanocomposites occurs when the bending energy of ring chains increases. The conformations of flexible ring chains near NPs are radial distribution, and the entropic depletion interactions between a pair of NPs in flexible ring polymer nanocomposite melts are attractive, however, the rod-like ring chains wrap around the NPs and the entropic depletion interactions between NPs in rod-like ring polymer melts are repulsive. The aggregation-dispersion transition for NPs induced by chain topology in polymer nanocomposites can provide a new access to achieve miscibility in producing high-performance polymer-nanoparticle composites by simply varying the topological structure of polymers.

Phase diagrams of diblock copolymers in electric fields: a self-consistent field theory study.

We investigated the phase diagrams of diblock copolymers in external electrostatic fields by using real-space self-consistent field theory. The lamella, cylinder, sphere, and ellipsoid structures were observed and analyzed by their segment distributions, which were arranged to two types of phase diagrams to examine the phase behavior in weak and strong electric fields. One type was constructed on the basis of Flory-Huggins interaction parameter and volume fraction. We identified an ellipsoid structure with a body-centered cuboid arrangement as a stable phase and discussed the shift of phase boundaries in the electric fields. The other type of phase diagrams was established on the basis of the dielectric constants of two blocks in the electric fields. We then determined the regions of ellipsoid phase in the phase diagrams to examine the influence of dielectric constants on the phase transition between ellipsoidal and hexagonally packed cylinder phases. A general agreement was obtained by comparing our results with those described in previous experimental and theoretical studies.

Entropic Interactions in Semiflexible Polymer Nanocomposite Melts.

By employing molecular dynamics simulations, we explored the effective depletion zone for nanoparticles (NP) immersed in semiflexible polymer melts and calculated the entropic depletion interactions between a pair of NPs in semiflexible polymer nanocomposite melts. The average depletion zone volumes rely mainly on polymer chain stiffness and increase with chain stiffness increasing. In the semiflexible polymer nanocomposite melts, the entropic depletion interactions are attractive and anisotropic, and increase with chain stiffness increasing. Meanwhile, the attractive interactions between NPs and polymers can also affect strongly the entropic depletion interactions. For the semiflexible polymer nanocomposite melts in the athermal system, the entropic depletion interactions change from anisotropic to isotropic when the NP/polymer interactions increase. For NPs in the rodlike polymer melts, a mixture structure of contact/"bridging" aggregations for NPs is formed at a strong attractive NP/polymer interaction. Our calculations can provide an effective framework to predict the morphology of NPs immersed in semiflexible polymer melts.

[Neuroendocrine carcinoma of the sphennoid sinuse: a case report].

Neuroendoerine carcinoma of paranasal sinuses are rare malignant tumors, neuroendocrine carcinomas cases with the lesions at different sites differ in the prognosis, The key to improving the survival rate of the disease is early accurate diagnosis and complete surgical removal of the lesions.

Liquid crystalline assembly of rod-coil diblock copolymer and homopolymer blends by dissipative particle dynamics simulation.

Liquid crystalline assembly of rod-coil diblock copolymers blended with coil or rod homopolymers is investigated by dissipative particle dynamics simulation, considering systematically the effect of the interactions between rods and coils, the volume fraction and length of the added coil or rod homopolymers. The addition of coil or rod homopolymers induces disorder-order or order-liquid crystalline transition. In rod-coil/coil blends, the solubilization of homopolymers will saturate at a certain amount of homopolymers and then the excess homopolymers will be segregated into the central regions of coil block domains, forming "wet-dry mixture" lamellae. The solubility capacity decreases with increasing homopolymer length, determined by the competition between the mixing entropy and the elastic entropy. In rod-coil/rod blends, due to the orientational interactions between rods, the length matched rod homopolymers directly interdigitate with rod blocks with less entropy loss, thus prompting the formation of a bilayer liquid crystalline phase. The rod domain spacing Dr remains unchanged and conversely the coil domain spacing Dc becomes thin, to occupy more interfacial area. With the addition of shorter rod homopolymers, the overall lamellar spacing D of blends monotonically increases with the volume fraction of homopolymers, similar to the case of rod-coil/coil blends. Generally, rod homopolymers have a more significant impact on the liquid crystalline assembly of the blends, compared with the coil homopolymers. Our results indicate that blending with coil or rod homopolymers into a rod-coil system is an effective method to induce liquid crystal phase transition and control the phase spacing of the ordered structure.