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Replicative complexes from control cells that had entered the cell cycle S phase after differentiation induction and from cells depleted of poly(ADP-ribose) polymerase (PARP) by expression of PARP antisense RNA are purified/characterized. The purpose was to clarify the roles of PARP within the DNA synthesome during DNA replication in the early stages of 3T3-L1 cell differentiation. Among other results, the DNA polymerase activities of the DNA synthesome from the S-phase control cells markedly increased relative to un-induced control cells.

Polymer nanocomposites containing carbon nanomaterials such as carbon black, carbon nanotubes, and graphene exhibit exceptional mechanical, thermal, electrical, and gas-barrier properties. Although the materials property benefits are well established, controlling the dispersion of carbon nanomaterials in polymer matrixes during processing is still a difficult task using current methods. Here, we report a simple, yet versatile method to simultaneously achieve the reduction of graphene oxide (GO) and polymerization of styrene to create reduced graphene oxide/poly-(styrene) (RGO/PS) nanocomposite materials via microwave heating. The RGO/PS mixture is then processed into films of desired thicknesses by first removing unreacted styrene and then pressing the powder at elevated temperatures. X-ray photoelectron spectroscopy proved that microwave processing was able to reduce GO, which resulted in a change in the carbon-to-oxygen ratio from 2.0 for GO to 4.5 for RGO. Furthermore, the addition of GO to the RGO/PS nanocomposites leads to an increase in the static dielectric constant (εs) relative to that of pure PS, with a minimal change in tan δ (∼0.06% at room temperature). The simultaneous microwave reduction/polymerization method described here will potentially lead to the production of polymer-based dielectric nanocomposite materials with tunable dielectric constants for energy-storage applications. [ABSTRACT FROM AUTHOR]

We have established the existence of a line of congruent first-order lamellar-to-disorder (LAM-DIS) transitions when appropriate amounts of poly(cyclohexylethylene) (C) and poly(ethylene) (E) homopolymers are mixed with a corresponding compositionally symmetric CE diblock copolymer. The line of congruent transitions, or the congruent isopleth, terminates at the bicontinuous microemulsion (BμE) channel, and its trajectory appears to be influenced by the critical composition of the C/E binary homopolymer blend. Blends satisfying congruency undergo a direct LAM-DIS transition without passing through a two-phase region. We present complementary optical transmission, small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical spectroscopy (DMS) results that establish the phase behavior at constant copolymer volume fraction and varying C/E homopolymer volume ratios. Adjacent to the congruent composition at constant copolymer volume fraction, the lamellar and disordered phases are separated by two-phase coexistence windows, which converge, along with the line of congruent transitions, at an overall composition in the phase prism coincident with the BμE channel. Hexagonal and cubic (double gyroid) phases occur at higher diblock copolymer concentrations for asymmetric amounts of C and E homopolymers. These results establish a quantitative method for identifying the detailed phase behavior of ternary diblock copolymer-homopolymer blends, especially in the vicinity of the BμE. [ABSTRACT FROM AUTHOR]

We examine the relationship between structure and ionic conductivity in salt-containing ternary polymer blends that exhibit various microstructured morphologies, including lamellae, a hexagonal phase, and a bicontinuous microemulsion, as well as the disordered phase. These blends consist of polystyrene (PS, Mn ≈ 600 g/mol) and poly(ethylene oxide) (PEO, Mn ≈ 400 g/mol) homopolymers, a nearly symmetric PS-PEO block copolymer (Mn ≈ 4700 g/mol), and lithium bis(trifluoromethane)sulfonamide (LiTFSI). These pseudoternary blends exhibit phase behavior that parallels that of well-studied ternary polymer blends consisting of A and B homopolymers compatibilized by an AB diblock copolymer. The utility of this framework is that all blends have nominally the same number of ethylene oxide, styrene, Li+, and TFSI- units, yet can exhibit a variety of microstructures depending on the relative ratio of the homopolymers to the block copolymer. For the systems studied, the ratio r = [Li+]/[EO] is maintained at 0.06, and the volume fraction of PS homopolymer is kept equal to that of PEO homopolymer plus salt. The total volume fraction of homopolymer is varied from 0 to 0.70. When heated through the order-disorder transition, all blends exhibit an abrupt increase in conductivity. However, analysis of small-angle X-ray scattering data indicates significant structure even in the disordered state for several blend compositions. By comparing the nature and structure of the disordered states with their corresponding ordered states, we find that this increase in conductivity through the order-disorder transition is most likely due to the elimination of grain boundaries. In either disordered or ordered states, the conductivity decreases as the total amount of homopolymer is increased, an unanticipated observation. This trend with increasing homopolymer loading is hypothesized to result from an increased density of "dead ends" in the conducting channel due to poor continuity across grain boundaries in the ordered state and the formation of concave interfaces in the disordered state. The results demonstrate that disordered, microphase-separated morphologies provide better transport properties than compositionally equivalent polycrystalline systems with long-range order, an important criterion when optimizing the design of polymer electrolytes. [ABSTRACT FROM AUTHOR]

This work details the phase behavior of a pseudoternary polymer blend system containing poly(ethylene oxide) (PEO) and polystyrene (PS) homopolymers, a PS-PEO block copolymer, and lithium bis(trifluoromethane)sulfonamide (LiTFSI). The phase behavior of the system is described along the volumetrically symmetric isopleth at a fixed LiTFSI concentration relative to the PEO component. The addition of LiTFSI dramatically increases the segregation strength of the blend, causing the otherwise globally disordered blends to exhibit a variety of microstructured morphologies typically found in salt-free ternary polymer blends, such as lamellae, a hexagonal phase, and a bicontinuous microemulsion. The breadth of morphologies and segregation strengths that can be accessed in this system by simply tuning blend composition establishes a new framework for the design of future ternary blend systems and, more broadly, polymeric materials where microstructured, well-segregated domains with tunable ion transport properties are desirable. [ABSTRACT FROM AUTHOR]

We report how to control the self-assembly of magnetic nanoparticles and a prototypical amphiphilic block-copolymer composed of poly(acrylic acid) and poly- styrene (PAA-b-PS). Three distinct structures were obtained by controlling the solvent- nanoparticle and polymer-nanoparticle interactions: (1) polyrnersomes densely packed with nanoparticles (magneto-polymersomes), (2) core-shell type polymer assemblies where nanoparticles are radially arranged at the interface between the polymer core and the shell (magneto-core shell), and (3) polymer micelles where nanoparticles arehomogeneously incorporated (magneto-micelles). Importantly, we show that the incorporation of nanoparticles drastically affects the self-assembly structure of block-copolymers by modifying the relative volume ratio between the hydrophobic block and the hydrophilic block. As a consequence, the self-assembly of micelle-forming block-copolymers typically produces magneto-polymersomes instead ofmagneto-micelles. On the other hand, vesicle-forming polymers tend to form magneto-micelles due to the solubilization of nanoparticles in polymer assemblies. The nanoparticle-polymer interaction also controls the nanoparticle arrangement in the polymer matrix. In N,N-dimethylformamide (DMF) where PS is not well-solvated, nanoparticles segregate from PS and form unique radial assemblies. In tetrahydrofuran (THF), which is a good solvent for both nanoparticles and PS, nanoparticles are homogeneously distributed in the polymer matrix. Furthermore, we demonstrated that the morphology of nanoparticle-encapsulating polymer assemblies significantly affects their magnetic relaxation properties, emphasizing the importance of the self-assembly structure and nanoparticle arrangement as well as the size of the assemblies. [ABSTRACT FROM AUTHOR]

Functionalization-induced phase transitions in polymer systems in which a postpolymerization reaction drives polymers to organize into colloidal aggregates are a versatile method to create nanoscale structures with applications related to biomedicine and nanoreactors. Current functionalization methods to stimulate polymer self-assembly are based on covalent bond formation. Therefore, there is a need to explore alternative reactions that result in noncovalent bond formation. Here, we demonstrate that when the Lewis acid, tris(pentafluorophenyl) borane (BCF), is added to a solution containing poly(4-diphenylphosphino styrene) (PDPPS), the system will either macrophase-separate or form micelles if PDPPS is a homopolymer or a block in a copolymer, respectively. The Lewis adduct-induced phase transition is hypothesized to result from the favorable interaction between the PDPPS and BCF, which results in a negative interaction parameter (χ). A modified Flory-Huggins model was used to determine the predicted phase behavior for a ternary system composed of a polymer, a solvent, and a small molecule. The model indicates that there is a demixing region (i.e., macrophase separation) when the polymer and small molecule have favorable interactions (e.g., χ < 0) and that the phase separation region coincides well with the experimentally determined two-phase region for mixtures containing PDPPS, BCF, and toluene. The work presented here highlights that Lewis adduct-induced phase separation is a new approach to functionalization-induced self-assembly (FISA) and that ternary mixtures will undergo phase separation if two of the components exhibit a sufficiently negative χ., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Cell membranes control mass, energy, and information flow to and from the cell. In the cell membrane a lipid bilayer serves as the barrier layer, with highly efficient molecular machines, membrane proteins, serving as the transport elements. In this way, highly specialized transport properties are achieved by these composite materials by segregating the matrix function from the transport function using different components. For example, cell membranes containing aquaporin proteins can transport ∼4 billion water molecules per second per aquaporin while rejecting all other molecules including salts, a feat unmatched by any synthetic system, while the impermeable lipid bilayer provides the barrier and matrix properties. True separation of functions between the matrix and the transport elements has been difficult to achieve in conventional solute separation synthetic membranes. In this study, we created membranes with distinct matrix and transport elements through designed coassembly of solvent-stable artificial (peptide-appended pillar[5]arene, PAP5) or natural (gramicidin A) model channels with block copolymers into lamellar multilayered membranes. Self-assembly of a lamellar structure from cross-linkable triblock copolymers was used as a scalable replacement for lipid bilayers, offering better stability and mechanical properties. By coassembly of channel molecules with block copolymers, we were able to synthesize nanofiltration membranes with sharp selectivity profiles as well as uncharged ion exchange membranes exhibiting ion selectivity. The developed method can be used for incorporation of different artificial and biological ion and water channels into synthetic polymer membranes. The strategy reported here could promote the construction of a range of channel-based membranes and sensors with desired properties, such as ion separations, stimuli responsiveness, and high sensitivity.

Polymerization-induced structural transitions have gained attention recently due to the ease of creating and modifying nanostructured materials with controlled morphologies and length scales. Here, we show that order-order and disorder-order nanostructural transitions are possible using in situ polymer grafting from the diblock polymer, poly(styrene)- block -poly(butadiene). In our approach, we are able to control the resulting nanostructure (lamellar, hexagonally packed cylinders, and disordered spheres) by changing the initial block polymer/monomer ratio. The nanostructural transition occurs by a grafting from mechanism in which poly(styrene) chains are initiated from the poly(butadiene) block via the creation of an allylic radical, which increases the overall molecular weight and the poly(styrene) volume fraction. The work presented here highlights how the chemical process of converting standard linear diblock copolymers to grafted block polymers drives interesting and controllable polymerization-induced morphology transitions.

Proliferating cell nuclear antigen (PCNA) is a member of the family of sliding clamp proteins that serves as a clamp during DNA repair, DNA replication, cell cycle control, and multiple forms of chromatin modification. PCNA functions as a homotrimer and complexes with multiple proteins in order to carry out each of these varied functions. PCNA binds to different partner proteins in the same region of its structure, called the " interdomain connecting loop", but with different affinities. This interdomain connecting loop is an intrinsically disordered region that takes different conformations when binding to different partner proteins. In this work, we performed all-atom molecular dynamics simulations on PCNA trimer unbound to any partner protein, PCNA bound to peptides from different partner proteins, and PCNA bound to the full Fen 1 protein in two different conformations. Using this massive amount of simulation results, we analyzed whether PCNA in its free trimeric form samples conformations that are similar to those when it is bound to different partner proteins. We observed that PCNA samples many of these peptide-bound conformations even when not bound to the peptides and selects specific conformations when binding to partner proteins. We also identified PCNA-peptide interactions formed in the peptide bound simulation that play a crucial role in complex formation. The calculated binding energies correlate well with the measured binding affinities of various peptides to PCNA. Lastly, we studied the internal dynamics of PCNA and propose a mechanism through which PCNA recruits binding partners. This work highlights the functional role of intrinsically disordered regions in multifunctional proteins such as PCNA.

Here we report a novel approach to prepare all-nanoparticle vesicles using ligand-stabilized gold particles as a building block. Hydroxyalkyl-terminated gold nanoparticles were spontaneously organized into well-defined hollow vesicle-like assemblies in water without any template. The unusual anisotropic self-assembly was attributed to the ligand rearrangement on nanoparticles, which leads to increased hydroxyl group density at the nanoparticle/water interface. One-dimensional strings were formed instead of vesicles with increasing surface ligand density, which supports the hypothesis. The size and the wall thickness of vesicles were controlled by adjusting the concentration of nanoparticles or by adding extra surfactants. The work presented here highlights the dynamic nature of surface ligands on gold particles and demonstrates that the combination of ligand rearrangement and the hydrophobic effect can be used as a versatile tool for anisotropic self-assembly of nanoparticles.

Rheological evidence of composition fluctuations in disordered diblock copolymers near the order-disorder transition (ODT) has been documented in the literature over the past three decades, characterized by a failure of time-temperature superposition (tTS) to reduce linear dynamic mechanical spectroscopy (DMS) data in the terminal viscoelastic regime to a temperature-independent form. However, for some materials, most notably poly(styrene- b -isoprene) (PS-PI), no signature of these rheological features has been found. We present small-angle X-ray scattering (SAXS) results on symmetric poly(cyclohexylethylene- b -ethylene) (PCHE-PE) diblock copolymers that confirm the presence of fluctuations in the disordered state and DMS measurements that also show no sign of the features ascribed to composition fluctuations. Assessment of DMS results published on five different diblock copolymer systems leads us to conclude that the effects of composition fluctuations can be masked by highly asymmetric block dynamics, thereby resolving a long-standing disagreement in the literature and reinforcing the importance of mechanical contrast in understanding the dynamics of ordered and disordered block polymers.

We have systematically mapped the phase behavior of a series of symmetric CE/C/E ternary copolymer/homopolymer mixtures, where C is poly(cyclohexylethylene) and E is poly(ethylene), identifying the location in composition of the technologically important bicontinuous microemulsion (BμE) channel as a function of diblock molecular weight. The lamellar-to-disorder transition, characterized by dynamic mechanical spectroscopy, small-angle X-ray scattering, and optical transmission measurements, exhibits increasingly second-order behavior as the BμE state is approached with increasing homopolymer content. Real-space transmission electron microscopy images obtained from rapidly frozen specimens evidence the development of large-scale fluctuating smectic correlations in the disordered state as the order-disorder transition is approached. This discovery provides fresh insights into the unexplained role of fluctuations in the formation of the BμE in ternary mixtures formed from binary blends of homopolymers that display an Ising-like critical point and a symmetric diblock copolymer governed by a weak, fluctuation-induced, first-order phase transition.

We report the size-controlled self-assembly of polymersomes through the cooperative self-assembly of nanoparticles and amphiphilic polymers. Polymersomes densely packed with magnetic nanoparticles in the polymersome membrane (magneto-polymersome) were fabricated with a series of different sized iron oxide nanoparticles. The distribution of nanoparticles in a polymersome membrane was size-dependent; while small nanoparticles were dispersed in a polymer bilayer, large particles formed a well-ordered superstructure at the interface between the inner and outer layer of a bilayer membrane. The yield of magneto-polymersomes increased with increasing the diameter of incorporated nanoparticles. Moreover, the size of the polymersomes was effectively controlled by varying the size of incorporated nanoparticles. This size-dependent self-assembly was attributed to the polymer chain entropy effect and the size-dependent localization of nanoparticles in polymersome bilayers. The transverse relaxation rates (r2) of magneto-polymersomes increased with increasing the nanoparticle diameter and decreasing the size of polymersomes, reaching 555 ± 24 s(-1) mM(-1) for 241 ± 16 nm polymersomes, which is the highest value reported to date for superparamagnetic iron oxide nanoparticles.

Here, we report the formation of polymer vesicles (polymersomes) uniformly decorated with gold nanoparticles (AuNPs) through the interfacial self-assembly of 11-mercapto-1-undecanol (MUL)-stabilized AuNPs and two prototypical amphiphilic polymers (i.e., polystyrene- block -poly(acrylic acid) (PS- b -PAA), poly(ethylene oxide)- block -polylactide (PEO- b -PLA)). The addition of MUL-capped nanoparticles during the self-assembly process was found to stabilize colloidal polymer assemblies that otherwise tend to form macroscopic aggregates in water. Multicompartment polymersomes with complex internal membrane structures were formed at high nanoparticle volume percent, demonstrating that the interfacial assembly of nanoparticles can be used to create interesting new types of polymer assemblies while providing additional functionalities. This strategy offers a simple method for the formation of nanoparticle-loaded polymersomes that is applicable to various types of amphiphilic polymers.

One- or two-dimensional arrays of iron oxide nanoparticles were formed in colloidal assemblies of amphiphilic polymers. Electron tomography imaging revealed that nanoparticles are arranged into one-dimensional strings in magneto-micelles or two-dimensional sheets in magneto-core/shell assemblies. The distinct directional assembly behavior was attributed to the interparticle interaction relative to the nanoparticle-polymer interaction, which was modulated by varying the cosolvent used for the solution phase self-assembly. Magneto-core/shell assemblies with varying structural parameters were formed with a range of different sized as-synthesized nanoparticles. The transverse magnetic relaxivity rates (r2) of a series of different assemblies were determined to examine the effect of nanoparticle arrangement on the magnetic relaxivity for their potential applications in MRI. The results indicated that the assembly structure of nanoparticles in polymer micelles significantly affects the r2 of surrounding water, providing a way to control magnetic relaxivity.

Here, we report a simple method to control the location of nanoparticles in colloidal block-copolymer assemblies by using nanoparticles modified with mixed surface ligands. The binary self-assembly of amphiphilic polymers of polystyrene- b -poly(acrylic acid) (PS- b -PAA) and gold nanoparticles (AuNPs) modified with a hydrophobic ligand, dodecanethiol (DT), led to polymer micelles with nanoparticles segregated in the core of polymer micelles. On the other hand, AuNPs modified with mixed ligands of mercaptoundecanol (MUL) and DT were distributed at the PS-PAA interface, reducing the interfacial energy between the two polymers. This result was in good agreement with the prediction by the surface energy calculations. We also showed that the AuNPs with mixed ligands can decorate preformed polymer assemblies by the interfacial self-assembly. Furthermore, we demonstrated the compartmentalization of two different types of nanoparticles in colloidal polymer assemblies based on the strategy.

Nanoparticles can form unique cavity-like structures in core-shell type assemblies of block copolymers through the cooperative self-assembly of nanoparticles and block copolymers. We show that the self-assembly behavior is general for common as-synthesized alkyl-terminated nanoparticles for a range of nanoparticle sizes. We examined various self-assembly conditions such as solvent compositions, nanoparticle coordinating ligands, volume fraction of nanoparticles, and nanoparticle sizes in order to elucidate the mechanism of the radial assembly formation. These experiments along with strong segregation theory calculations indicated that both the enthalpic interaction and the polymer stretching energy are important factors in the coassembly formation. The slightly unfavorable interaction between the hydrophobic segment of polymers and alkyl-terminated nanoparticles causes the accumulation of nanoparticles at the interface between the polymer core and the shell, forming the unique cavity-like structure. The coassemblies were stabilized for a limited range of nanoparticle volume fractions within which the inclusion of nanoparticle layers reduces the polymer stretching. The volume fraction range yielding the well-defined radial coassembly structure was mapped out with varying nanoparticle sizes. The experimental and theoretical phase map provides the guideline for the coassembly formation of as-synthesized alkyl-terminated nanoparticles and amphiphilic block copolymers.

Conjugated polymers have excellent light-emitting properties that are useful for biological imaging and sensing applications. Here, we report a new way to form stable, water-soluble suspensions of conjugated polymers by encapsulating them in amphiphilic block copolymers. It was found that the folding property of conjugated polymers is a critical factor for solubilizing them into typical coil-coil block copolymer micelles. By introducing saturated bonds into conjugated polymers, they were readily encapsulated in block copolymer micelles, resulting in highly fluorescent polymer nanoparticles. The emission wavelength of fluorescent micelles can be tuned by controlling the number of encapsulated light-emitting polymers per micelle as well as changing the exciton delocalization length in conjugated polymers. This strategy has been extended to make multifunctional (i.e., fluorescent and magnetic) nanoparticles by encapsulating iron oxide nanoparticles in light-emitting polymers.

Aberrant glycosylation has been implicated in various types of cancers and changes in glycosylation may be associated with signaling pathways during malignant transformation. Glycomic profiling of blood serum, in which cancer cell proteins or their fragments with altered glycosylation patterns are shed, could reveal the altered glycosylation. We performed glycomic profiling of serum from patients with no known disease (N = 18), patients with high grade dysplasia (HGD, N = 11) and Barrett's esophagus (N = 5), and patients with esophageal adenocarcinoma (EAC, N = 50) in an attempt to delineate distinct differences in glycosylation between these groups. The relative intensities of 98 features were significantly different among the disease onsets; 26 of these correspond to known glycan structures. The changes in the relative intensities of three of the known glycan structures predicted esophageal adenocarcinoma with 94% sensitivity and better than 60% specificity as determined by receiver operating characteristic (ROC) analysis. We have demonstrated that comparative glycomic profiling of EAC reveals a subset of glycans that can be selected as candidate biomarkers. These markers can differentiate disease-free from HGD, disease-free from EAC, and HGD from EAC. The clinical utility of these glycan biomarkers requires further validation.

Glycomic profiles derived from human blood sera of 10 healthy males were compared to those from 24 prostate cancer patients. The profiles were acquired using MALDI-MS of permethylated N-glycans released from 10-microL sample aliquots. Quantitative permethylation was attained using solid-phase permethylation. Principal component analysis of the glycomic profiles revealed significant differences among the two sets, allowing their distinct clustering. The first principal component distinguished the 24 prostate cancer patients from the healthy individuals. It was determined that fucosylation of glycan structures is generally higher in cancer samples (ANOVA test p-value of 0.0006). Although more than 50 N-glycan structures were determined, 12 glycan structures, of which six were fucosylated, were significantly different between the two sample sets. Significant differences were confirmed through two independent statistical tests (ANOVA and ROC analyses). Ten of these structures had significantly higher relative intensities in the case of the cancer samples, while the other two were less abundant in the cancer samples. All 12 structures were statistically significant, as suggested by their very low ANOVA scores (<0.001) and ROC analysis, with area under the curve values close to 1 or 0. Accordingly, these structures can be considered as cancer-specific glycans and potential prostate cancer biomarkers. Therefore, serum glycomic profiling appears worthy of further investigation to define its role in cancer early detection and prognostication.