Engineering Advanced Morphologies for Structurally Reinforced Polyolefins

The primary objective of this research is to develop new methods to enhance the mechanical properties of isotactic polypropylene (iPP). Two complementary methods were developed to produce reinforced iPP-nanographite nanocomposites. In the first method, nanocomposites were prepared through an in-situ metallocene-catalyzed polymerization technique. In the second method, a new compounding strategy was used to prepare iPP-nanographite nanocomposites with improved spatial size distribution of nanoparticle agglomerates. Finally, a new process referred to as Melt-Mastication (MM) was developed as a means to improve the mechanical properties of pure iPP through generating unique and beneficial crystal morphologies. Reinforced iPP-nanographite nanocomposites were prepared through an in-situ polymerization technique and compared to analogous composites prepared by conventional melt processing. In-situ preparation of iPP-nanogrpahite nanocomposites was accomplished via single site metallocene catalyzed polymerization of propylene within a toluene dispersion of xGnP nanoparticles. Mechanical analysis showed iPP-nanographite nanocomposites demonstrated improved stiffness and strength relative to neat iPP. The results are discussed with regard to the thermal and morphological properties. A new polymer processing method referred to as “Melt-Mastication” (MM) was developed as a means to augment the crystal morphology of iPP and thereby enhance the thermal and physical properties. Melt-Mastication is a low temperature mixing technique that subjects an iPP melt to flow induced crystallization within a chaotic flow field. Thermal calorimetry and SAXS showed that MM substantially increases the lamellar crystal thickness and crystallinity of iPP, resulting in a 50% improvement to yield strength, 55% improvement to elastic modulus, and improved temperature stability. The property improvements were attributed to a unique hierarchical organization of lamellar crystals produced by MM, distinct from conventionally prepared iPP materials. Finally, Melt-Mastication was repurposed as a compounding method for preparation of iPP-nanographite nanocomposites with enhanced nanographite dispersion. Due to flow induced crystallization, the process viscosity increases significantly during Melt-Mastication, which produces higher mixing torque and therefore shear resulting in the fragmentation of nanoparticle agglomerates. The spatial size distribution of nanographite agglomerates was evaluated via a quantitative stereological technique, and a model for agglomeration in shear flow is proposed

Factors and Convergent Validity of the Pet Attachment and Life Impact Scale (PALS)

Human-animal interaction (HAI) provides benefits for humans. Emotional attachment to pets is a possible mechanism for benefits but there is no standard operationalization for “attachment to pets.” The study presented here (N = 651) uses a pet attachment measure based on qualitative research about benefits of pets. This measure, the Pet Attachment and Life Impact Scale (PALS), has four factors that measure Love, Regulation, Personal Growth, and Negative Impacts. We present exploratory factor analysis and confirmatory factor analysis of the instrument. We then examine convergent validity with four a priori derived measures of pet attachment (Anthropomorphism Scale, CENSHARE PAS, CABS, LAPS) and a social support scale. We provide evidence that having a current relationship with a pet is related to higher scores on the PALS than having a former pet relationship, evidencing that the PALS is a relational measure. Overall, females are more attached to pets than are males, and dog owners are most attached, followed by cat owners and owners of other pets

Inhibition of skeletal muscle CLC-1 chloride channels by low intracellular pH and ATP

Skeletal muscle acidosis during exercise has long been thought to be a cause of fatigue, but recent studies have shown that acidosis maintains muscle excitability and opposes fatigue by decreasing the sarcolemmal chloride conductance. ClC-1 is the primary sarcolemmal chloride channel and has a clear role in controlling muscle excitability, but recombinant ClC-1 has been reported to be activated by acidosis. Following our recent finding that intracellular ATP inhibits ClC-1, we investigated here the interaction between pH and ATP regulation of ClC-1. We found that, in the absence of ATP, intracellular acidosis frompH 7.2 to 6.2 inhibited ClC-1 slightly by shifting the voltage dependence of common gating to more positive potentials, similar to the effect of ATP. Importantly, the effects of ATP and acidosis were cooperative, such thatATPgreatly potentiated the effect of acidosis. Adenosine had a similar effect to ATP at pH 7.2, but acidosis did not potentiate this effect, indicating that the phosphates of ATP are important for this cooperativity, possibly due to electrostatic interactions with protonatable residues of ClC-1. A protonatable residue identified by molecular modeling, His-847, was found to be critical for both pH and ATP modulation and may be involved in such electrostatic interactions. These findings are now consistent with, and provide a molecular explanation for, acidosis opposing fatigue by decreasing the chloride conductance of skeletal muscle via inhibition of ClC-1. The modulation of ClC-1 by ATP is a key component of this molecular mechanism

CRISPR nuclease off-target activity and mitigation strategies

The discovery of CRISPR has allowed site-specific genomic modification to become a reality and this technology is now being applied in a number of human clinical trials. While this technology has demonstrated impressive efficacy in the clinic to date, there remains the potential for unintended on- and off-target effects of CRISPR nuclease activity. A variety of in silico-based prediction tools and empirically derived experimental methods have been developed to identify the most common unintended effect—small insertions and deletions at genomic sites with homology to the guide RNA. However, large-scale aberrations have recently been reported such as translocations, inversions, deletions, and even chromothripsis. These are more difficult to detect using current workflows indicating a major unmet need in the field. In this review we summarize potential sequencing-based solutions that may be able to detect these large-scale effects even at low frequencies of occurrence. In addition, many of the current clinical trials using CRISPR involve ex vivo isolation of a patient’s own stem cells, modification, and re-transplantation. However, there is growing interest in direct, in vivo delivery of genome editing tools. While this strategy has the potential to address disease in cell types that are not amenable to ex vivo manipulation, in vivo editing has only one desired outcome—on-target editing in the cell type of interest. CRISPR activity in unintended cell types (both on- and off-target) is therefore a major safety as well as ethical concern in tissues that could enable germline transmission. In this review, we have summarized the strengths and weaknesses of current editing and delivery tools and potential improvements to off-target and off-tissue CRISPR activity detection. We have also outlined potential mitigation strategies that will ensure that the safety of CRISPR keeps pace with efficacy, a necessary requirement if this technology is to realize its full translational potential

X-Ray Diffuse Scattering Study on Ionic-Pair Displacement Correlations in Relaxor Lead Magnesium Niobate

Ionic-pair equal-time displacement correlations in relaxor lead magnesium niobate, $Pb(Mg_{1/3}Nb_{2/3})O_{3}$, have been investigated at room temperature in terms of an x-ray diffuse scattering technique. Functions of the distinct correlations have been determined quantitatively. The results show the significantly strong rhombohedral-polar correlations regarding Pb-O, Mg/Nb-O, and O-O' pairs. Their spatial distribution forms an ellipse or a sphere with the radii of 30-80$\AA$. This observation of local structure in the system proves precursory presence of the polar microregions in the paraelectric state which leads to the dielectric dispersion.Comment: 11 pages, 3 figure

Molecular determinants of ginkgolide binding in the glycine receptor pore

Ginkgolides are potent blockers of the glycine receptor Cl- channel (GlyR) pore. We sought to identify their binding sites by comparing the effects of ginkgolides A, B and C and bilobalide on alpha1, alpha2, alpha1beta and alpha2beta GlyRs. Bilobalide sensitivity was drastically reduced by incorporation of the beta subunit. In contrast, the sensitivities to ginkgolides B and C were enhanced by beta subunit expression. However, ginkgolide A sensitivity was increased in the alpha2beta GlyR relative to the alpha2 GlyR but not in the alpha1beta GlyR relative to the alpha1 GlyR. We hypothesised that the subunit-specific differences were mediated by residue differences at the second transmembrane domain 2' and 6' pore-lining positions. The increased ginkgolide A sensitivity of the alpha2beta GlyR was transferred to the alpha1beta GlyR by the G2'A (alpha1 to alpha2 subunit) substitution. In addition, the alpha1 subunit T6'F mutation abolished inhibition by all ginkgolides. As the ginkgolides share closely related structures, their molecular interactions with pore-lining residues were amenable to mutant cycle analysis. This identified an interaction between the variable R2 position of the ginkgolides and the 2' residues of both alpha1 and beta subunits. These findings provide strong evidence for ginkgolides binding at the 2' pore-lining position

High-pressure behaviour of GeO2: a simulation study

In this work we study the high pressure behaviour of liquid and glassy GeO2 by means of molecular dynamics simulations. The interaction potential, which includes dipole polarization effects, was parameterized from first-principles calculations. Our simulations reproduce the most recent experimental data to a high degree of precision. The proportion of the various GeOn polyhedra is determined as a function of the pressure: a smooth transition from tetrahedral to octahedral network is observed. Finally, the study of high-pressure, liquid germania confirms that this material presents an anomalous behaviour of the diffusivity as observed in analog systems such as silica and water. The importance of penta-coordinated germanium ions for such behaviour is stressed.Comment: 16 pages, 4 figures, accepted as a Fast Track Communication on Journal of Physics: Condensed Matte

Mapping a novel positive allosteric modulator binding site in the central vestibule region of human P2X7

P2X7 receptors are important in the regulation of inflammatory responses and immune responses to intracellular pathogens such as Mycobacterium tuberculosis and Toxoplasma gondii. Enhancement of P2X7 receptor responses may be useful in pathogen clearance particularly in individuals with defective microbial killing mechanisms. Ginsenosides from Panax ginseng have been discovered to act as positive allosteric modulators of P2X7. Here we describe a novel modulator binding site identified by computational docking located in the central vestibule of P2X7 involving S60, D318, and L320 in the lower body β-sheets lining the lateral portals. Potentiation of ATP-mediated responses by ginsenosides CK and Rd caused enhanced ionic currents, Ca2+ influx and YOPRO-1 uptake in stably transfected HEK-293 cells (HEK-hP2X7) plus enhanced cell death responses. Potentiation of ATP responses by CK and Rd was markedly reduced by mutations S59A, S60A, D318L and L320A supporting the proposed allosteric modulator binding site. Furthermore, mutation of the conserved residues S60 and D318 led to alterations in P2X7 response and a higher sensitivity to ATP in the absence of modulators suggesting residues in the connecting rods play an important role in regulating P2X7 gating. Identification of this novel binding site location in the central vestibule may also be relevant for structurally similar channels