Switching Supramolecular Polymeric Materials with Multiple Length Scales

It was demonstrated that polymeric supramolecular nanostructures with several length scales allow straightforward tailoring of hierarchical order-disorder and order-order transitions and the concurrent switching of functional properties. Poly(4-vinyl pyridine) (P4VP) was stoichiometrically protonated with methane sulfonic acid (MSA) to form P4VP(MSA)1.0, which was then hydrogen-bonded to pentadecylphenol. Microphase separation, re-entrant closed-loop macrophase separation, and high-temperature macrophase separation were observed. When MSA and pentadecylphenol were complexed to the P4VP block of a microphase-separated diblock copolymer poly[styrene-block-(4-vinyl pyridine)], self-organized structures-in-structures were obtained whose hierarchical phase transitions can be controlled systematically. This microstructural control on two different length scales (in the present case, at 48 and 350 angstroms) was then used to introduce temperature-dependent transitions in electrical conductivity.

Orientation of Supramolecular Self-Organized Polymeric Nanostructures by Oscillatory Shear Flow

Macroscopic orientation of self-organized supramolecular polymeric materials has been demonstrated by oscillatory shear flow using in-situ small-angle X-ray scattering (SAXS). In the case when a homopolymer poly(4-vinylpyridine) and pentadecylphenol molecules are stoichiometrically complexed to form comb copolymer-like supermolecules, the self-organized lamellar local structures align parallel when sheared below the order-disorder transition temperature at 56 °C using 0.5 Hz frequency and 100% strain amplitude. Therefore, the hydrogen bonds between the phenolic and pyridine groups are strong enough to withstand the applied flow. In the case of a diblock copolymer of polystyrene and poly(4-vinylpyridine) stoichiometrically complexed with pentadecylphenol molecules to form the supermolecules, the self-organization yields lamellar-within-lamellar local structure near room temperature. The larger lamellar diblock copolymer structure showed a parallel orientation relative to the shearing plates upon shearing at 125 °C (i.e., above the order-disorder transition of the short length scale comb copolymer-like structure) with initially 0.5 Hz and finally 1 Hz, both at 50% strain amplitude. On cooling, the short length scale lamellar structure, consisting of poly(4-vinylpyridine) block and pentadecylphenol, is formed inside the layers of the comb copolymer-like material in perpendicular orientation.

Integrative Genomics Reveals Novel Molecular Pathways and Gene Networks for Coronary Artery Disease

10.1371/journal.pgen.1004502PLoS Genetics107e100450

Exceptional conservation of horse–human gene order on X chromosome revealed by high-resolution radiation hybrid mapping

Development of a dense map of the horse genome is key to efforts aimed at identifying genes controlling health, reproduction, and performance. We herein report a high-resolution gene map of the horse (Equus caballus) X chromosome (ECAX) generated by developing and typing 116 gene-specific and 12 short tandem repeat markers on the 5,000-rad horse × hamster whole-genome radiation hybrid panel and mapping 29 gene loci by fluorescence in situ hybridization. The human X chromosome sequence was used as a template to select genes at 1-Mb intervals to develop equine orthologs. Coupled with our previous data, the new map comprises a total of 175 markers (139 genes and 36 short tandem repeats, of which 53 are fluorescence in situ hybridization mapped) distributed on average at ≈880-kb intervals along the chromosome. This is the densest and most uniformly distributed chromosomal map presently available in any mammalian species other than humans and rodents. Comparison of the horse and human X chromosome maps shows remarkable conservation of gene order along the entire span of the chromosomes, including the location of the centromere. An overview of the status of the horse map in relation to mouse, livestock, and companion animal species is also provided. The map will be instrumental for analysis of X linked health and fertility traits in horses by facilitating identification of targeted chromosomal regions for isolation of polymorphic markers, building bacterial artificial chromosome contigs, or sequencing