Thermal desorption characterisation of molecularly imprinted polymers. Part I: a novel study using direct-probe GC-MS analysis

A novel thermal desorption technique using a direct-probe device (Chromatoprobe) attached to a gas chromatograph–mass spectrometer is presented for the thermal pretreatment, characterisation and analysis of molecularly imprinted polymers. The technique is demonstrated as effective for the removal of volatile materials, including template and unreacted monomers, from methacrylic acid–ethylene glycol dimethacrylate copolymers imprinted with 2-aminopyridine. Mass spectrometry is a powerful technique for polymer bleed characterisation. Thermal desorption studies on reloaded template and related compounds are reported as a means of assessing polymer morphology, specific binding by imprinted polymers compared with reference non-imprinted polymers and selective binding by an imprinted polymer for its template. Calibration studies on the thermal desorption technique using an internal standard are presented with R ² > 0.999. The technique provides a novel method for assessment of polymer thermal stability, composition and morphology.     

Efficient red light photo-uncaging of active molecules in water upon assembly into nanoparticles

We introduce a means of efficiently photo-uncaging active compounds from amino-1,4-benzoquinone in aqueous environments. Aqueous photochemistry of this photocage with one-photon red light is typically not efficient unless the photocaged molecules are allowed to assemble into nanoparticles. A variety of biologically active molecules were functionalized with the photocage and subsequently formulated into water-dispersible nanoparticles. Red light irradiation through various mammalian tissues achieved efficient photo-uncaging. Co-encapsulation of NIR fluorescent dyes and subsequent photomodulation provides a NIR fluorescent tool to assess both particle location and successful photorelease.     

Searching for Small Molecules with an Atomic Sort

The discovery of biologically active small molecules requires sifting through large amounts of data to identify unique or unusual arrangements of atoms. Here, we develop, test and evaluate an atom‐based sort to identify novel features of secondary metabolites and demonstrate its use to evaluate novelty in marine microbial and sponge extracts. This study outlines an important ongoing advance towards the translation of autonomous systems to identify, and ultimately elucidate, atomic novelty within a complex mixture of small molecules.     

Facile synthesis of a diverse library of mono-3-substituted β-cyclodextrin analogues

Substituted cyclodextrins (CDs) have many applications, but synthetic challenges have limited the derivatives that can routinely be accessed. In particular, although there is considerable interest in selective derivatization at the 2- and 3-hydroxyls on the secondary face, since bulky guest molecules are most likely to project through this larger aperture, syntheses of such derivatives have required arduous procedures that afford poor yields, limiting their accessibility and utility. We address this challenge via synthetic strategies that allow facile creation of diverse libraries of water-soluble mono-3-substituted-β-cyclodextrins, via the commercially available mono-3-amino-β-cyclodextrin. The power of these strategies is confirmed through synthesis of twenty water-soluble cyclodextrin analogues with amide, thioureas or urea linkers, using one-pot reactions producing ≥55% yields and purifications that do not require chromatography. This work opens new possibilities for the design of selective host molecules for use in supramolecular chemistry, chemical separations, pharmaceutical formulations, and calibration of molecular simulations.     

Positions of the sub-band minima in GaAs(AlGa)As quantum well heterostructures

We have combined measured 5K excitonic absorption peaks with calculations of the confined particle states to determine the band offsets in GaAs(AlGa)As quantum well heterostructures. Our observations are best fitted with a conduction band-valence band split of about 75:25. This contrasts with the currently accepted value of 85:15 and the recently proposed value of 60:40.     

Interface recombination in P-type GaAs-(AlGa)As quantum well heterostructures

The process of non-radiative interface recombination is considered for quantum well heterostructures. Simple model calculations indicate that, contrary to previous suggestions, the quantum effects do not cause a large reduction in the effective interface recombination velocity, S_eff. In fact, for the same interface quality, quantum effects cause an increase in S_eff.     

Nondestructive shell-stability estimation by a combined-loading technique

Accurate nondestructive procedures for cylindrical-shell-stability investigations have long been a goal of experimentalists and practicing engineers. Stability criteria based on stress and deflection have been investigated intensively by researchers, but lateral-stiffness variation has been largely ignored. It is this aspect which is the foundation of the present work. The variation of specimen lateral stiffness with compressive axial loading is studied experimentally and it is demonstrated that buckling loads can be predicted for monocoque shells from such data. A study of the initial specimen geometry is presented and an evaluation is made of its effect on the distribution of stiffness at zero axial load. When the lateral test force used to termine the stiffness is considered as a destabilizing load in combination with the axial compression, it is shown that critical values of the force can be estimated by the “Southwell plat” procedure. These critical forces can be correlated with axial load and extrapolated to yield an accurate estimate of the buckling load. The approach greatly reduces the compressive load necessary for stability predictions over that required for other techniques.     

Cardiovascular Signal Entropy Predicts All-Cause Mortality: Evidence from The Irish Longitudinal Study on Ageing (TILDA)

In this study, the relationship between cardiovascular signal entropy and the risk of seven-year all-cause mortality was explored in a large sample of community-dwelling older adults from The Irish Longitudinal Study on Ageing (TILDA). The hypothesis under investigation was that physiological dysregulation might be quantifiable by the level of sample entropy (SampEn) in continuously noninvasively measured resting-state systolic (sBP) and diastolic (dBP) blood pressure (BP) data, and that this SampEn measure might be independently predictive of mortality. Participants’ date of death up to 2017 was identified from official death registration data and linked to their TILDA baseline survey and health assessment data (2010). BP was continuously monitored during supine rest at baseline, and SampEn values were calculated for one-minute and five-minute sections of this data. In total, 4543 participants were included (mean (SD) age: 61.9 (8.4) years; 54.1% female), of whom 214 died. Cox proportional hazards regression models were used to estimate the hazard ratios (HRs) with 95% confidence intervals (CIs) for the associations between BP SampEn and all-cause mortality. Results revealed that higher SampEn in BP signals was significantly predictive of mortality risk, with an increase of one standard deviation in sBP SampEn and dBP SampEn corresponding to HRs of 1.19 and 1.17, respectively, in models comprehensively controlled for potential confounders. The quantification of SampEn in short length BP signals could provide a novel and clinically useful predictor of mortality risk in older adults.