Transient Covalent Polymers through Carbodiimide-Driven Assembly.

Biochemical systems make use of out-of-equilibrium polymers generated under kinetic control. Inspired by these systems, many abiotic supramolecular polymers driven by chemical fuel reactions have been reported. Conversely, polymers based on transient covalent bonds have received little attention, even though they have the potential to complement supramolecular systems by generating transient structures based on stronger bonds and by offering a straightforward tuning of reaction kinetics. In this study, we show that simple aqueous dicarboxylic acids give poly(anhydrides) when treated with the carbodiimide EDC. Transient covalent polymers with molecular weights exceeding 15,000 are generated which then decompose over the course of hours to weeks. Disassembly kinetics can be controlled using simple substituent effects in the monomer design. The impact of solvent polarity, carbodiimide concentration, temperature, pyridine concentration, and monomer concentration on polymer properties and lifetimes has been investigated. The results reveal substantial control over polymer assembly and disassembly kinetics, highlighting the potential for fine-tuned kinetic control in nonequilibrium polymerization systems.

Impact of gene expression profiling on diagnosis and survival after metastasis in patients with uveal melanoma.

Surveillance frequency for metastasis is guided by gene expression profiling (GEP). This study evaluated the effect of GEP on time to diagnosis of metastasis, subsequent treatment and survival. A retrospective study was conducted of 110 uveal melanoma patients with GEP (DecisionDx-UM, Castle Biosciences, Friendswood, Texas, USA) and 110 American Joint Committee on Cancer-matched controls. Surveillance testing and treatment for metastasis were compared between the two groups and by GEP class. Rates of metastasis, overall survival and melanoma-related mortality were calculated using Kaplan-Meier estimates. Baseline characteristics and follow-up time were balanced in the two groups. Patients' GEP classification was 1A in 41%, 1B in 25.5% and 2 in 33.6%. Metastasis was diagnosed in 26.4% ( n  = 29) in the GEP group and 23.6% ( n  = 26) in the no GEP group ( P  = 0.75). Median time to metastasis was 30.5 and 22.3 months in the GEP and no GEP groups, respectively ( P  = 0.44). Median months to metastasis were 34.7, 75.8 and 26.1 in class 1A, 1B and 2 patients, respectively ( P  = 0.28). Disease-specific 5-year survival rates were 89.4% [95% confidence interval (CI): 81.0-94.2%] and 84.1% (95% CI: 74.9-90.1%) in the GEP and no GEP groups respectively ( P  = 0.49). Median time to death from metastasis was 10.1 months in the GEP group and 8.5 months in the no GEP group ( P  = 0.40). There were no significant differences in time to metastasis diagnosis and survival outcomes in patients with and without GEP. To realize the full benefit of GEP, more sensitive techniques for detection of metastasis and adjuvant therapies are required.

Carbodiimide-Driven Toughening of Interpenetrated Polymer Networks.

Recent work has demonstrated that temporary crosslinks in polymer networks generated by chemical "fuels" afford materials with large, transient changes in their mechanical properties. This can be accomplished in carboxylic-acid-functionalized polymer hydrogels using carbodiimides, which generate anhydride crosslinks with lifetimes on the order of minutes to hours. Here, the impact of the polymer network architecture on the mechanical properties of transiently crosslinked materials was explored. Single networks (SNs) were compared to interpenetrated networks (IPNs). Notably, semi-IPN precursors that give IPNs on treatment with carbodiimide give much higher fracture energies (i.e., resistance to fracture) and superior resistance to compressive strain compared to other network architectures. A precursor semi-IPN material featuring acrylic acid in only the free polymer chains yields, on treatment with carbodiimide, an IPN with a fracture energy of 2400 J/m2, a fourfold increase compared to an analogous semi-IPN precursor that yields a SN. This resistance to fracture enables the formation of macroscopic complex cut patterns, even at high strain, underscoring the pivotal role of polymer architecture in mechanical performance.

PET-RAFT Polymerization of Star Polymers with Folded ortho-Phenylene Cores.

ortho-Phenylenes are one of the simplest classes of aromatic foldamers, adopting helical geometries because of aromatic stacking interactions. The folding and misfolding of ortho-phenylenes are slow on the NMR timescale at or below room temperature, allowing detection of folding states using 1 H NMR spectroscopy. Herein, an ortho-phenylene hexamer is coupled with a RAFT chain transfer agent (CTA) on each repeat unit. A variety of acrylic monomers are polymerized onto the CTA-functionalized ortho-phenylene using PET-RAFT to yield functionalized star polymers with ortho-phenylene cores. The steric bulk of the acrylate monomer units as well as the chain length of each arm of the star polymer is varied. 1 H NMR spectroscopy shows that the folding of the ortho-phenylenes do not vary, providing a robust helical core for star polymer systems.

Chemically Fueled Reinforcement of Polymer Hydrogels.

Carbodiimide-fueled anhydride bond formation has been used to enhance the mechanical properties of permanently crosslinked polymer networks, giving materials that exhibit transitions from soft gels to covalently reinforced gels, eventually returning to the original soft gels. Temporary changes in mechanical properties result from a transient network of anhydride crosslinks, which eventually dissipate by hydrolysis. Over an order of magnitude increase in the storage modulus is possible through carbodiimide fueling. The time-dependent mechanical properties can be modulated by the concentration of carbodiimide, temperature, and primary chain architecture. Because the materials remain rheological solids, new material functions such as temporally controlled adhesion and rewritable spatial patterns of mechanical properties have been realized.

Engineering Chiral Induction in Centrally Functionalized o-Phenylenes.

Work on foldamers, nonbiological oligomers that mimic the hierarchical structure of biomacromolecules, continues to yield new architectures of ever increasing complexity. o-Phenylenes, a class of helical aromatic foldamers, are well-suited to this area because of their structural simplicity and the straightforward characterization of their folding in solution. However, control of structure requires, by definition, control over folding handedness. Control over o-phenylene twist sense is currently lacking. While chiral induction from groups at o-phenylene termini has been demonstrated, it would be useful to instead direct twisting from internal positions to leave the ends free. Here, we explore chiral induction in a series of o-phenylenes with chiral imides at their centers. Conformational behavior has been studied by nuclear magnetic resonance and circular dichroism spectroscopies and density functional theory calculations. Chiral induction in otherwise unfunctionalized o-phenylenes is generally poor. However, strategic functionalization of the helix surface with trifluoromethyl or methyl groups allows it to better interact with the imide groups, greatly increasing diastereomeric excesses. The sense of chiral induction is consistent with computational models that suggest that it primarily arises from a steric effect.

Conformational Control of ortho-Phenylenes by Terminal Amides.

Control over the folding of oligomers, be it broad induction of a preferred helical handedness or subtle changes in the orientations of individual functional groups, is important for applications ranging from molecular recognition to long-range conformational communication. Here, we report a series of ortho-phenylene hexamers functionalized with achiral and chiral amides at their termini. NMR spectroscopy, taking advantage of 19F labeling, allows multiple conformers to be detected for each compound. In combination with CD spectroscopy and DFT calculations, specific geometries corresponding to each conformer have been identified and quantified. General conclusions about the effect of sterics and the amide linker on conformational behavior have been drawn, revealing some similarities to and key differences from previously reported imines. A model for twist sense control has been developed that is supported by computational models.

Unintended pregnancy and childhood maltreatment: The protective effect of positive relationships.

BACKGROUND: Childhood maltreatment is associated with sexual risk-taking behaviors in adulthood but can also have generational effects on maternal/child health. METHODS: This cross-sectional study examined the relationship between childhood abuse and neglect and unintended pregnancy, and then assessed the effect of relationship attributes on this outcome. RESULTS: Findings indicate parenting women (n = 153) in long-term relationships who experienced childhood emotional abuse had higher scores of unintended pregnancies (p = .023). Yet women with moderate/high partner appraisal (perceptions of their partner's attributes used to assess interpersonal conflicts) showed no difference in unintended pregnancies between those with and without emotional abuse in childhood. Women with emotional abuse and low partner appraisal had higher unintended pregnancy scores (p = .002). DISCUSSION/CONCLUSION: This study has implications for public health nursing and life course research demonstrating that a positive adult interpersonal environment can reduce the sequelae of adverse health outcomes associated with childhood emotional abuse. The results reinforce the importance of screening adults for childhood maltreatment to establish early risk for unintended pregnancy.

Molecular detection of two new putative species of gammaherpesvirus in petaurid possums.

A molecular survey of herpesviruses in Australian native mammals was conducted, spanning 260 individuals from 27 species. Among the herpesviruses detected, a putative new gammaherpesvirus species was detected in the yellow-bellied glider (Petaurus australis), and another in the critically endangered Leadbeater's possum (Gymnobelideus leadbeateri). In addition, the known host range of the putative species macropodid gammaherpesvirus 3 (MaHV-3) is herein extended to the western grey kangaroo (Macropus fuliginosus). These findings expand our understanding of herpesviruses in Australian mammals and may inform biosecurity protocols for captive and translocated populations.

Aromatic foldamers as molecular springs in network polymers.

Polymer networks crosslinked with spring-like ortho-phenylene (oP) foldamers were developed. NMR analysis indicated the oP crosslinkers were well-folded. Polymer networks with oP-based crosslinkers showed enhanced energy dissipation and elasticity compared to divinylbenzene crosslinked networks. The energy dissipation was attributed to the strain-induced reversible unfolding of the oP units. Energy dissipation increased with the number of helical turns in the foldamer.

Population Pharmacokinetic Modelling of Acetaminophen and Ibuprofen: the Influence of Body Composition, Formulation and Feeding in Healthy Adult Volunteers.

BACKGROUND AND OBJECTIVE: Combined acetaminophen and ibuprofen are common antipyretic and analgesic drugs. Formulation and feeding affect drug absorption. Drug clearance has a nonlinear relationship with total body weight. The covariate effect of fat mass on acetaminophen and ibuprofen pharmacokinetics remains unexplored. This study sought to quantify acetaminophen and ibuprofen pharmacokinetics with intravenous, tablet, sachet and oral suspension formulations in fed and fasted states. METHODS: Pooled time-concentration data for acetaminophen and ibuprofen were available from fasting and fed healthy adults. Data from intravenous, tablet, sachet and suspension formulations were analysed using nonlinear mixed-effects models. Body composition was considered as a covariate on clearances and volumes of distribution (Vd). Size metrics investigated were total body weight, fat and fat-free mass. Theory-based allometry was used to scale pharmacokinetic parameters to a 70 kg individual. A factor on absorption half-life and lag time quantified delays due to feeding for oral formulations. Pharmacokinetic-pharmacodynamic simulations were used to explore the time courses of pain response for acetaminophen and ibuprofen for each formulation. RESULTS: Pooled data included 116 individuals (18-49 years, 49-116 kg) with 6095 acetaminophen and 6046 ibuprofen concentrations available for analysis. A two-compartment pharmacokinetic model with first-order elimination described disposition for both drugs. Normal fat mass was the best covariate to describe acetaminophen clearance (CL), with a factor for fat contribution (FFATCL) of 0.816. Acetaminophen volume of distribution was described using total body weight. Normal fat mass was the best covariate to describe ibuprofen clearance (FFATCL = 0.863) and volume of distribution: (FFATV = 0.718). Clearance and central volume of distribution were 24.0 L/h/70 kg and 43.5 L/h/70 kg for acetaminophen. Ibuprofen clearance and central volume of distribution were 3.79 L/h/70 kg and 10.5 L/h/70 kg. Bioavailability and absorption half-life were 86% and 12 min for acetaminophen and 94% and 27 min for ibuprofen. Absorption lag times were 5.3 min and 6.7 min for acetaminophen and ibuprofen, respectively. Feeding increased both absorption half-life and absorption lag time when compared to the tablet formulation under fasting conditions. Feeding had the most pronounced effect on the lag time associated with tablet formulation for both drugs. Time to a pain score reduction of 2 points (visual analogue score, 0-10) differed by only 5-10 min across all formulations for acetaminophen and ibuprofen. CONCLUSION: Fat mass was an important covariate to describe acetaminophen and ibuprofen pharmacokinetics. The absorption half-lives of acetaminophen and ibuprofen were increased in fed states. The delay in absorption, quantified by a lag time, was protracted for both drugs.

Guest-Driven Control of Folding in a Crown-Ether-Functionalized ortho-Phenylene.

A crown-ether-functionalized o-phenylene tetramer has been synthesized and coassembled with monotopic and ditopic, achiral and chiral secondary ammonium ion guests. NMR spectroscopy shows that the o-phenylene forms both 1:1 and 1:2 complexes with monotopic guests while remaining well-folded. Binding of an elongated ditopic guest, however, forces the o-phenylene to misfold by pulling the terminal rings apart. A chiral ditopic guest biases the o-phenylene twist sense.

Update on feline alphaherpesvirus-1 seroprevalence in Victorian feral and owned cats.

The seroprevalence of feline alphaherpesvirus-1 (FHV-1) in feral cats in Victoria, Australia, was last assessed in 1981 when serum-virus-neutralising antibodies (VNAb) against FHV-1 were detected in 11% of the sampled population from two Victorian locations. In this current study, VNAb were assessed in serum from feral cats located in Phillip Island, Point Cook and Hattah in the Mallee region in Northern Victoria. In feral cats, the seroprevalence of VNAb to FHV-1 was highest in Point Cook at 24.6% (17/69), followed by Phillip Island at 16.7% (11/66) and Hattah where no feral cats had detectable VNAb to FHV-1 (0/12). In contrast, virus-neutralising antibodies were observed in 84.1% (37/44) of Victorian-owned cats. This higher seroprevalence in owned cats is likely due to the use of FHV-1 vaccines; however, the vaccination history of the cats was not known and the development of neutralising antibodies after infection or vaccination can vary. The results are useful for understanding FHV-1 exposure in feral and owned cats and are important background information in the context of any potential future use of FHV-1-vectored vaccines.

Fluorine Labeling of ortho-Phenylenes to Facilitate Conformational Analysis.

1H NMR spectroscopy is a powerful tool for the conformational analysis of ortho-phenylene foldamers in solution. However, as o-phenylenes are integrated into ever more complex systems, we are reaching the limits of what can be analyzed by 1H- and 13C-based NMR techniques. Here, we explore fluorine labeling of o-phenylene oligomers for analysis by 19F NMR spectroscopy. Two series of fluorinated oligomers have been synthesized. Optimization of monomers for Suzuki coupling enables an efficient stepwise oligomer synthesis. The oligomers all adopt well-folded geometries in solution, as determined by 1H NMR spectroscopy and X-ray crystallography. 19F NMR experiments complement these methods well. The resolved singlets of one-dimensional 19F{1H} spectra are very useful for determining relative conformer populations. The additional information from two-dimensional 19F NMR spectra is also clearly valuable when making 1H assignments. The comparison of 19F isotropic shielding predictions to experimental chemical shifts is not, however, currently sufficient by itself to establish o-phenylene geometries.

Substituent Effects on Transient, Carbodiimide-Induced Geometry Changes in Diphenic Acids.

Nucleotide-induced conformational changes in motor proteins are key to many important cell functions. Inspired by this biological behavior, we report a simple chemically fueled system that exhibits carbodiimide-induced geometry changes. Bridging via transient anhydride formation leads to a significant reduction of the twist about the biaryl bond of substituted diphenic acids, giving a simple molecular clamp. The kinetics are well-described by a simple mechanism, allowing structure-property effects to be determined. The kinetic parameters can be used to derive important characteristics of the system such as the efficiencies (anhydride yields), maximum anhydride concentrations, and overall lifetimes. Transient diphenic anhydrides tolerate steric hindrance ortho to the biaryl bond but are significantly affected by electronic effects, with electron-deficient substituents giving lower yields, peak conversions, and lifetimes. The results provide useful guidelines for the design of functional systems incorporating diphenic acid units.

Folding-controlled assembly of ortho-phenylene-based macrocycles.

The self-assembly of foldamers into macrocycles is a simple approach to non-biological higher-order structure. Previous work on the co-assembly of ortho-phenylene foldamers with rod-shaped linkers has shown that folding and self-assembly affect each other; that is, the combination leads to new emergent behavior, such as access to otherwise unfavorable folding states. To this point this relationship has been passive. Here, we demonstrate control of self-assembly by manipulating the foldamers' conformational energy surfaces. A series of o-phenylene decamers and octamers have been assembled into macrocycles using imine condensation. Product distributions were analyzed by gel-permeation chromatography and molecular geometries extracted from a combination of NMR spectroscopy and computational chemistry. The assembly of o-phenylene decamers functionalized with alkoxy groups or hydrogens gives both [2 + 2] and [3 + 3] macrocycles. The mixture results from a subtle balance of entropic and enthalpic effects in these systems: the smaller [2 + 2] macrocycles are entropically favored but require the oligomer to misfold, whereas a perfectly folded decamer fits well within the larger [3 + 3] macrocycle that is entropically disfavored. Changing the substituents to fluoro groups, however, shifts assembly quantitatively to the [3 + 3] macrocycle products, even though the structural changes are well-removed from the functional groups directly participating in bond formation. The electron-withdrawing groups favor folding in these systems by strengthening arene-arene stacking interactions, increasing the enthalpic penalty to misfolding. The architectural changes are substantial even though the chemical perturbation is small: analogous o-phenylene octamers do not fit within macrocycles when perfectly folded, and quantitatively misfold to give small macrocycles regardless of substitution. Taken together, these results represent both a high level of structural control in structurally complex foldamer systems and the demonstration of large-amplitude structural changes as a consequence of a small structural effects.

Outcomes of treatments for keratomalacia in dogs and cats: a systematic review of the published literature including non-randomised controlled and non-controlled studies.

OBJECTIVES: The aim of this review was to interrogate the evidence base for treatment of keratomalacia in dogs and cats, through examination of the applicable literature. MATERIALS AND METHODS: Studies were screened for evidence to answer the following question Which of the treatment options for keratomalacia in dogs and cats offers the best chance of globe survival, the fastest time to resolution with globe survival, and the best visual outcome. The search utilised the PubMed (http://www.pubmed.gov/) and ISI Web of Science (http://wok.mimas.ac.uk/) databases. Databases were searched using the following terms: (keratomalacia OR corneal melt OR corneal malacia) AND (dog OR canine OR canid OR cat OR feline OR felid) AND (treatment OR outcome OR morbidity OR complications). Studies were assessed by one author (CH) and excluded if they related to less than three keratomalacia cases, experimental treatments, in vitro studies, or did not provide information regarding outcome. Studies were classified to a level of evidence according to the system described by the Oxford Centre for EvidenceBased Medicine. RESULTS: Eighteen (18) studies were identified as providing information to answer the proposed question, one as level 3, 10 as level 4 and seven as level 5 evidence. Only one study compared two treatments, the remaining were prospective or retrospective case series of a single treatment intervention. Study design was highly variable with respect to population size, followup and outcome assessment, making direct comparison difficult, and metaanalysis was not applied. CLINICAL SIGNIFICANCE: Overall, the evidence for improved outcome of one proposed treatment over another proposed treatment for keratomalacia in dogs and/or cats is very weak.

Genome Sequences of Two Marsupial Simplex Viruses, Macropodid Alphaherpesviruses 2 and 4.

We present the genome sequences of macropodid alphaherpesviruses 2 and 4, two closely related pathogens of macropods. Both encoded 68 nonredundant open reading frames (ORFs) and share 90.6% genome-wide nucleotide identity. These viruses are associated with fatal outbreaks of disease in multiple marsupial species. These sequences will be important for the development of new diagnostic tools.

High-impact exercise stimulated localised adaptation of microarchitecture across distal tibia in postmenopausal women.

We provided evidence that a 6-month regular hopping exercise intervention can increase trabecular number and possibly trabecular volume fraction of the distal tibia. Our novel localised analysis demonstrated region-specific changes, predominantly in the anterior region, in postmenopausal women. INTRODUCTION: The localisation of bone remodelling and microarchitectural adaptation to exercise loading has not been demonstrated previously in vivo in humans. The aim of this study is to assess the feasibility of using 3D image registration and high-resolution peripheral quantitative computed tomography (HR-pQCT) to investigate the effect of high-impact exercise on human trabecular bone variables and remodelling rate across the distal tibia. METHODS: Ten postmenopausal women were recruited for 6-month unilateral hopping exercises, with HR-pQCT scans taken of both exercise leg (EL) and control leg (CL) for each participant before and after the intervention. A 3D image registration was used to ensure measurements were taken at the same region. Short-term reproducibility tests were conducted prior to the assessment using identical setup. The results were assessed comparing CL and EL, and interaction (time × leg) using a two-way repeated measures analysis of variance (RM-ANOVA). RESULTS: Across the whole tibia, we observed significant increases in trabecular number (Tb.N) (+ 4.4%) and trabecular bone formation rate (tBFR) (3.3%), and a non-significant increase in trabecular bone volume fraction (BV/TV) (+ 1%) in the EL. Regional resorption was higher in the CL than the EL, with this difference being statistically significant at the lateral tibia. In the EL, tBFR was significantly higher in the anterior region than the medial but a trabecular bone resorption rate (tBRR) showed no significant regional variation. Conversely in the CL, both tBFR and tBRR were significantly higher in the anterior and lateral than the medial region. CONCLUSION: We demonstrated that it was possible to detect exercise-related bone adaptation with 3D registration of HR-pQCT scan data. Regular hopping exercise increased Tb.N and possibly BV/TV across the whole distal tibia. A novel finding of the study was that tBFR and tBRR responses to loading were localised: changes were achieved by formation rate exceeding resorption rate in the exercise leg, both globally and at the anterior region where turnover was greatest. TRIAL REGISTRATION: clinicaltrials.gov : NCT03225703.

The Transient Covalent Bond in Abiotic Nonequilibrium Systems.

Biochemical systems accomplish many critical functions with by operating out-of-equilibrium using the energy of chemical fuels. The formation of a transient covalent bond is a simple but very effective tool in designing analogous reaction networks. This Minireview focuses on the fuel chemistries that have been used to generate transient bonds in recent demonstrations of abiotic nonequilibrium systems (i.e., systems that do not make use of biological components). Fuel reactions are divided into two fundamental classifications depending on whether the fuel contributes structural elements to the activated state, a distinction that dictates how they can be used. Reported systems are further categorized by overall fuel reaction (e.g., hydrolysis of alkylating agents, carbodiimide hydration) and illustrate how similar chemistry can be used to effect a wide range of nonequilibrium behavior, ranging from self-assembly to the operation of molecular machines.