Anomalistic Self-Assembled Phase Behavior of Block Copolymer Blended with Organic Derivative Depending on Temperature

Amphiphilic Pluronic block copolymers have attracted great attention in a broad spectrum of potential applications due to the excellent phase behaviors in an aqueous solution, and many efforts have been made to investigate their phase behaviors under various external conditions. With a variety of external conditions, however, the closed looplike phase behaviors of a Pluronic block copolymer in an aqueous solution have not been reported yet. Herein, we report the closed looplike (CLL) phase behavior of a Pluronic P65 triblock copolymer blended with an organic derivative, 5-methylsalicylic acid (5mS), in aqueous solution, which is very unique for block copolymers. As the 5mS concentration increases, the isotropic to ordered phase or back to isotropic phase transition temperature is decreased while the number of closed loops is increased to two. To the best of our knowledge, this is the first demonstration of a CLL phase transition of a Pluronic block copolymer in an aqueous solution, which is readily applicable to optical devices such as optical sensors or optoelectronics, and nanotemplates for a highly ordered superlattice. Furthermore, this provides new insight into the understanding on the phase behavior of a Pluronic block copolymer blended with additives

SANS Study of Ring Topology Effects on the Miscibility of Polymer Blends

Highly purified hydrogenous ring poly­(4-trimethylsilylstyrene) (<i>h</i>-PT) and deuterated ring polyisoprene (<i>d</i>-PI) samples as well as their linear counterparts were prepared, and the miscibility of three kinds of polymer blends, i.e., linear–linear, ring–linear, and ring–ring, denoted as L–L, R–L, and R–R, respectively, with all 50/50 vol % was evaluated by small angle neutron scattering (SANS) measurements. PT and PI are known as a miscible polymer pair with lower critical solution temperature (LCST) type phase diagram. At low-<i>q</i> regime of the scattering profiles, R–R blend exhibits much higher scattering intensity than L–L and R–L, while the latter two show similar profiles. Moreover, from Zimm’s analysis, the spinodal temperature of R–R was estimated to be about 100 °C lower than the other two blends, L–L and R–L. These results suggest that the miscibility of R–R is considerably lower than the other two blends, which is a clear manifestation of the topological effect on the phase behavior of the present blend

Rapid and Simultaneous Analysis of 360 Pesticides in Brown Rice, Spinach, Orange, and Potato Using Microbore GC-MS/MS

A multiresidue method for the simultaneous and rapid analysis of 360 pesticides in representative agricultural produce (brown rice, orange, spinach, and potato) was developed using a modified QuEChERS procedure combined with gas chromatography–tandem mass spectrometry (GC-MS/MS). Selected reaction monitoring transition parameters (e.g., collision energy, precursor and product ions) in MS/MS were optimized to achieve the best selectivity and sensitivity for a wide range of GC-amenable pesticides. A short (20 m) microbore (0.18 mm i.d.) column resulted in better signal-to-noise ratio with reduced analysis time than a conventional narrowbore column (30 m × 0.25 mm i.d.). The priming injection dramatically increased peak areas by masking effect on a new GC liner. The limit of quantitation was <0.01 mg/kg, and the correlation coefficients (<i>r</i>²) of matrix-matched standards were >0.99 within the range of 0.0025–0.1 mg/kg. Acetonitrile with 0.1% formic acid without additional buffer salts was used for pesticide extraction, whereas only primary–secondary amine (PSA) was used for dispersive solid phase extraction (dSPE) cleanup, to achieve good recoveries for most of the target analytes. The recoveries ranged from 70 to 120% with relative standard deviations of ≤20% at 0.01 and 0.05 mg/kg spiking levels (<i>n</i> = 6) in all samples, indicating acceptable accuracy and precision of the method. Seventeen real samples from local markets were analyzed by using the optimized method, and 14 pesticides in 11 incurred samples were found at below the maximum residue limits

An Improved System for Generation of Diploid Cloned Porcine Embryos Using Induced Pluripotent Stem Cells Synchronized to Metaphase

<div><p>Pigs provide outstanding models of human genetic diseases due to their striking similarities with human anatomy, physiology and genetics. Although transgenic pigs have been produced using genetically modified somatic cells and nuclear transfer (SCNT), the cloning efficiency was extremely low. Here, we report an improved method to produce diploid cloned embryos from porcine induced pluripotent stem cells (piPSCs), which were synchronized to the G2/M stage using a double blocking method with aphidicolin and nocodazole. The efficiency of this synchronization method on our piPSC lines was first tested. Then, we modified our traditional SCNT protocol to find a workable protocol. In particular, the removal of a 6DMAP treatment post-activation enhanced the extrusion rate of pseudo-second-polar bodies (p2PB) (81.3% vs. 15.8%, based on peak time, 4hpa). Moreover, an immediate activation method yielded significantly more blastocysts than delayed activation (31.3% vs. 16.0%, based on fused embryos). The immunofluorescent results confirmed the effect of the 6DMAP treatment removal, showing remarkable p2PB extrusion during a series of nuclear transfer procedures. The reconstructed embryos from metaphase piPSCs with our modified protocol demonstrated normal morphology at 2-cell, 4-cell and blastocyst stages and a high rate of normal karyotype. This study demonstrated a new and efficient way to produce viable cloned embryos from piPSCs when synchronized to the G2/M phase of the cell cycle, which may lead to opportunities to produce cloned pigs from piPSCs more efficiently.</p></div

Differential Self-Assembly Behaviors of Cyclic and Linear Peptides

Here we ask the fundamental questions about the effect of peptide topology on self-assembly. The study revealed that the self-assembling behaviors of cyclic and linear peptides are significantly different in several respects, in addition to sharing several similarities. Their clear differences included the morphological dissimilarities of the self-assembled nanostructures and their thermal stability. The similarities include their analogous critical aggregation concentration values and cytotoxicity profiles, which are in fact closely related. We believe that understanding topology-dependent self-assembly behavior of peptides is important for developing tailor-made self-assembled peptide nanostructures

Preimplantation development and characterization of piPSNT embryos.

<p>Cloned embryos derived from metaphase piPSCs started to cleave on day 2 (A), developed to 4-cell stage on day 4 (B) and started to form blastocysts on day 6 (C) with good morphology and high total cell numbers (D). The karyotyping results demonstrated that 59.7% of blastocysts possessed normal diploid karyotypes (E, G), while most of the rest were aneuploid (F).</p

Effect of 6DMAP treatment post pPB extrusion on piPSNT embryos pre-implantation development.

<p>Effect of 6DMAP treatment post pPB extrusion on piPSNT embryos pre-implantation development.</p

Synchronization of porcine induced pluripotent cells (piPSCs) to metaphase.

<p>Control piPSCs showed a typical mouse embryonic stem cell (ESC)-like colony morphology (A). After digestion into single cells by trypsin, small round piPSCs (11–13 μm in diameter) showed high nucleus-to-cytoplasm ratio, with typical G0/G1 nuclei and several nucleoli inside the nuclei (B, C). After the cells were synchronized by a double-blocking method using aphidicolin and nocodazole, round cells emerged on the surface of the piPSCs colony (D) with much bigger cell diameters (17–21 μm) and typical metaphase chromosomal morphology. Some cells also demonstrated linear structures in the middle, which were thought to be the metaphase plate (E, F). The karyotyping analysis was performed using piPSCs at passage 35 (G). 65.7% of cells showed normal karyotype (38 chromosomes) whereas 20.7% of cells had 36 chromosomes. The piPSCs were cultured for 2 or 3 days after subculture and then subjected to synchronization treatment. After harvest, the cell cycle distribution profiles (2d-Sync. and 3d-Sync.) were analyzed by flow cytometry based on PI staining signal and compared with unsynchronized cells (H). After synchronization, most of the piPSCs were arrested at G2/M phase. Moreover, synchronization conducted 2 days after sub-culturing yielded significantly a higher G2/M percentage than 3 days (77.6 ± 1.8% vs. 72.2 ± 2.1%). The details of asterisk marked cells are shown in the upper left corner.</p

Effect of activation method on piPSNT embryos pre-implantation development.

<p>Effect of activation method on piPSNT embryos pre-implantation development.</p

Directed Assembly of High Molecular Weight Block Copolymers: Highly Ordered Line Patterns of Perpendicularly Oriented Lamellae with Large Periods

The directed assembly of block copolymer nanostructures with large periods exceeding 100 nm remains challenging because the translational ordering of long-chained block copolymer is hindered by its very low chain mobility. Using a solvent-vapor annealing process with a neutral solvent, which was sequentially combined with a thermal annealing process, we demonstrate the rapid evolution of a perpendicularly oriented lamellar morphology in high molecular weight block copolymer films on neutral substrate. The synergy with the topographically patterned substrate facilitated unidirectionally structural development of ultrahigh molecular weight block copolymer thin filmseven for the structures with a large period of 200 nmleading to perfectly guided, parallel, and highly ordered line-arrays of perpendicularly oriented lamellae in the trenched confinement. This breakthrough strategy, which is applicable to nanolithographic pattern transfer to target substrates, can be a simple and efficient route to satisfy the demand for block copolymer assemblies with larger feature sizes on hundreds of nanometers scale