Spatial Variation of Acanthophlebia cruentata (Ephemeroptera), a Mayfly Endemic to Te Ika-a-Maui-North Island of Aotearoa, New Zealand.

The mayfly Acanthophlebia cruentata of Aotearoa, New Zealand, is widespread in Te Ika-a-Maui North Island streams, but has never been collected from South Island despite land connection during the last glacial maximum. Population structure of this mayfly might reflect re-colonisation after volcanic eruptions in North Island c1800 years ago, climate cycling or conceal older, cryptic diversity. We collected population samples from 33 locations to estimate levels of population genetic diversity and to document phenotypic variation. Relatively low intraspecific haplotype divergence was recorded among mitochondrial cytb sequences from 492 individuals, but these resolved three geographic-haplotype regions (north, west, east). We detected a signature of isolation by distance at low latitudes (north) but evidence of recent population growth in the west and east. We did not detect an effect of volcanic eruptions but infer range expansion into higher latitudes from a common ancestor during the last glacial period. As judged from wing length, both sexes of adult mayflies were larger at higher elevation and we found that haplotype region was also a significant predictor of Acanthophlebia cruentata size. This suggests that our mitochondrial marker is concordant with nuclear genetic differences that might be explained by founder effect during range expansion.

Substrate-selective positive allosteric modulation of PTPRD's phosphatase by flavonols.

The receptor type protein tyrosine phosphatase D (PTPRD) is expressed by neurons and implicated in interesting phenotypes that include reward from addictive substances, restless leg syndrome and neurofibrillary tangle densities in Alzheimer's disease (AD-NFTs). However, the brain phosphotyrosine phosphoprotein (PTPP) substrates for PTPRD's phosphatase have not been clearly defined. Although we have identified small molecule inhibitors of PTPRD's phosphatase that are candidates for reducing reward from addictive substances, no positive allosteric modulators of this phosphatase that might be candidates for reducing AD-NFTs have been reported. We now report identification of candidate brain substrates for PTPRD based on their increased phosphorylation in knockout vs wildtype animals, coexpression with PTPRD in neuronal subtypes and brisk dephosphorylation by recombinant human PTPRD phosphatase. We also report discovery that quercetin and other flavonols, though not closely-related flavones, enhance rates of PTPRD's dephosphorylation of a group of these candidate substrate PTPPs but not others. This substrate-selective positive allosteric modulation provides a novel pharmacological action. Flavonol-mediated increases in PTPRD's dephosphorylation of the GSK3 ß and α kinases that hyperphosphorylate tau, the major component of AD-NFTs, could help to explain recent data concerning genetic and dietary impacts on Alzheimer's disease.

Structure-activity studies of PTPRD phosphatase inhibitors identify a 7-cyclopentymethoxy illudalic acid analog candidate for development.

Interest in development of potent, selective inhibitors of the phosphatase from the receptor type protein tyrosine phosphatase PTPRD as antiaddiction agents is supported by human genetics, mouse models and studies of our lead compound PTPRD phosphatase inhibitor, 7-butoxy illudalic acid analog 1 (7-BIA). We now report structure-activity relationships for almost 70 7-BIA-related compounds and results that nominate a 7- cyclopentyl methoxy analog as a candidate for further development. While efforts to design 7-BIA analogs with substitutions for other parts failed to yield potent inhibitors of PTPRD's phosphatase, ten 7-position substituted analogs displayed greater potency at PTPRD than 7-BIA. Several were more selective for PTPRD vs the receptor type protein tyrosine phosphatases S, F and J or the nonreceptor type protein tyrosine phosphatase N1 (PTPRS, PTPRF, PTPRJ or PTPN1/PTP1B), phosphatases at which 7-BIA displays activity. In silico studies aided design of novel analogs. A 7-position cyclopentyl methoxy substituted 7-BIA analog termed NHB1109 displayed 600-700 nM potencies in inhibiting PTPRD and PTPRS, improved selectivity vs PTPRS, PTPRF, PTPRJ or PTPN1/PTP1B phosphatases, no substantial potency at other protein tyrosine phosphatases screened, no significant potency at any of the targets of clinically-useful drugs identified in EUROFINS screens and significant oral bioavailability. Oral doses up to 200 mg/kg were well tolerated by mice, though higher doses resulted in reduced weight and apparent ileus without clear organ histopathology. NHB1109 provides a good candidate to advance to in vivo studies in addiction paradigms and toward human use to reduce reward from addictive substances.

Nanostructured Amorphous Silicas Hydrophobized by Various Pathways.

Various nanostructured amorphous silicas [fumed silicas such as crude (A-300), hydro-compacted (cA-300, TS 100), and precipitated silica Syloid 244] were modified by different polydimethylsiloxanes such as PDMS5, PDMS100, PDMS200, PDMS1000, and PDMS12500 (the label numbers show the viscosity (η) values) using dimethyl carbonate (DMC) as a siloxane-bond-breaking reagent. In addition, hexamethyldisilazane was used to modify fumed silica cA-300. The nanocomposites were characterized using microscopy, infrared spectroscopy, thermodesorption, nitrogen adsorption-desorption, solid-state NMR spectroscopy, small-angle X-ray scattering, and zeta-potential methods. It was found that the morphological, textural, and structural characteristics of silicas grafted with PDMS depend strongly not only on the type and content of the polymers used but also on the organization of nonporous nanoparticles (NPNP) in secondary structures (aggregates of NPNP and agglomerated aggregates, ANPNP), as well on the reaction temperature (T r). Specifically, we determined that ANPNP with a macro/mesoporous character are favorable for the effective modification of the silicas studied with short polymers and no DMC addition but at higher temperatures or for a longer silicone polymer with the presence of DMC and at lower temperatures. In particular, the PDMS/DMC-modified silicas are of great interest from a practical point of view because they remain in a dispersed state with no strong compaction of the secondary structures after modification, and this corresponds to a better distribution of the modified nanoparticles in polymeric or other matrices.

A 29Si, 1H, and 13C Solid-State NMR Study on the Surface Species of Various Depolymerized Organosiloxanes at Silica Surface.

Three poly(organosiloxanes) (hydromethyl-, dimethyl-, and epoxymethylsiloxane) of different chain lengths and pendant groups and their mixtures of dimethyl (DMC) or diethyl carbonates (DEC) were applied in the modification of fumed silica nanoparticles (FSNs). The resulting modified silicas were studied in depth using 29Si, 1H, and 13C solid-state NMR spectroscopy, elemental analysis, and nitrogen adsorption-desorption (BET) analysis. The obtained results reveal that the type of grafting, grafting density, and structure of the grafted species at the silica surface depend strongly on the length of organosiloxane polymer and on the nature of the "green" additive, DMC or DEC. The spectral changes observed by solid-state NMR spectroscopy suggest that the major products of the reaction of various organosiloxanes and their DMC or DEC mixtures with the surface are D (RR'Si(O0.5)2) and T (RSi(O0.5)3) organosiloxane units. It was found that shorter methylhydro (PMHS) and dimethylsiloxane (PDMS) and their mixtures with DMC or DEC form a denser coverage at the silica surface since SBET diminution is larger and grafting density is higher than the longest epoxymethylsiloxane (CPDMS) used for FSNs modification. Additionally, for FSNs modified with short organosiloxane PMHS/DEC and also medium organosiloxane PDMS/DMC, the dense coverage formation is accompanied by a greater reduction of isolated silanols, as shown by solid-state 29Si NMR spectroscopy, in contrast to reactions with neat organosiloxanes. The surface coverage at FSNs with the longest siloxane (CPDMS) greatly improves with the addition of DMC or DEC. The data on grafting density suggest that molecules in the attached layers of FSNs modified with short PMHS and its mixture of DMC or DEC and medium PDMS and its mixture of DMC form a "vertical" orientation of the grafted methylhydrosiloxane and dimethylsiloxane chains, in contrast to the reaction with PDMS/DEC and epoxide methylsiloxane in the presence of DMC or DEC, which indicates a "horizontal" chain orientation of the grafted methyl and epoxysiloxane molecules. This study highlights the major role of solid-state NMR spectroscopy for comprehensive characterization of solid surfaces.

Cleavage of Organosiloxanes with Dimethyl Carbonate: A Mild Approach To Graft-to-Surface Modification.

In this work, we explore the depolymerization of poly(dimethylsiloxane) (PDMS-100) and poly(methylphenylsiloxane) (PMPS) using dimethyl carbonate (DMC) and develop a surface functionalization method by utilizing the DMC-imparted active methoxy end groups of the partially depolymerized polysiloxanes. The efficiency of dimethyl carbonate as a reagent for organosiloxane cleavage was confirmed by means of 1H NMR spectroscopy, size-exclusion chromatography, and viscosity measurements. The reaction of fumed silica with organosiloxanes (PMPS, PDMS-50) in the presence of DMC was investigated using the ζ-potential, 29Si and 13C solid-state NMR spectroscopy, IR spectroscopy, CHN analysis, contact angle goniometry, thermogravimetric analysis, scanning and transmission electron microscopy (TEM), and rheology. It was found that the interaction of PMPS/DMC with an SiO2 surface produced hydrophobic and thermally stable moieties (up to 550 °C) with a densely packed (average 2.2 groups/nm2) alkylsiloxane network for SiO2/PMPS + DMC in comparison with SiO2/PMPS (average 1.4 groups/nm2). Surface functionalization was successfully attained at a relatively moderate temperature of 200 °C. Scanning electron microscopy data show that the average size of aggregates of PMPS/DMC-modified silica nanoparticles is smaller than that of the initial silica and silica modified with neat PMPS. TEM images reveal uniform distribution of the PMPS/DMC mixture across the SiO2 surface. Rheology studies show thixotropic behavior in industrial oil (I-40A), a fully reversible nanostructure and shorter structure recovery time for fumed silica modified in the presence of DMC.

Self-assembly/disassembly of giant double-hydrophilic polymersomes at biologically-relevant pH.

Self-assembled giant polymer vesicles prepared from double-hydrophilic diblock copolymers, poly(ethylene oxide)-b-poly(acrylic acid) (PEO-PAA) show significant degradation in response to pH changes. Because of the switching behavior of the diblock copolymers at biologically-relevant pH environments (2 to 9), these polymer vesicles have potential biomedical applications as smart delivery vehicles.

The Role of Membrane Fluidization in the Gel-Assisted Formation of Giant Polymersomes.

Polymersomes are being widely explored as synthetic analogs of lipid vesicles based on their enhanced stability and potential uses in a wide variety of applications in (e.g., drug delivery, cell analogs, etc.). Controlled formation of giant polymersomes for use in membrane studies and cell mimetic systems, however, is currently limited by low-yield production methodologies. Here, we describe for the first time, how the size distribution of giant poly(ethylene glycol)-poly(butadiene) (PEO-PBD) polymersomes formed by gel-assisted rehydration may be controlled based on membrane fluidization. We first show that the average diameter and size distribution of PEO-PBD polymersomes may be readily increased by increasing the temperature of the rehydration solution. Further, we describe a correlative relationship between polymersome size and membrane fluidization through the addition of sucrose during rehydration, enabling the formation of PEO-PBD polymersomes with a range of diameters, including giant-sized vesicles (>100 µm). This correlative relationship suggests that sucrose may function as a small molecule fluidizer during rehydration, enhancing polymer diffusivity during formation and increasing polymersome size. Overall the ability to easily regulate the size of PEO-PBD polymersomes based on membrane fluidity, either through temperature or fluidizers, has broadly applicability in areas including targeted therapeutic delivery and synthetic biology.

Dynamic assembly of polymer nanotube networks via kinesin powered microtubule filaments.

We describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors. These networks displayed enhanced robustness, persisting more than 24 h post-assembly (compared to 4-5 h for corresponding lipid networks). The transport of materials in and on the polymer membranes differs substantially from the transport on analogous lipid networks. Specifically, our data suggest that polymer mobility in nanotubular structures is considerably different from planar or 3D structures, and is stunted by 1D confinement of the polymer subunits. Moreover, quantum dots adsorbed onto polymer nanotubes are completely immobile, which is related to this 1D confinement effect and is in stark contrast to the highly fluid transport observed on lipid tubules.

Salt, shake, fuse--giant hybrid polymer/lipid vesicles through mechanically activated fusion.

Large (200 nm) poly(ethylene oxide)-b-poly(butadiene) polymer vesicles fuse into giant (>1 µm) vesicles with mild agitation in dilute aqueous NaCl solutions. This unusual effect is attributed to the salt-induced contraction of the poly(ethylene oxide) corona, reducing steric resistance between vesicles and, with agitation, increasing the probability of contact between the hydrophobic cores of adjacent membranes. In addition, NaCl and agitation facilitated the creation of giant hybrid vesicles from much smaller homogeneous polymersomes and liposomes. Whereas lipid vesicles do not readily fuse with each other under the same circumstances, they did fuse with polymersomes to produce hybrid polymer/lipid vesicles.