Single-step biofriendly synthesis of surface modifiable, near-spherical gold nanoparticles for applications in biological detection and catalysis

There is an increased interest in understanding the toxicity and rational design of gold nanoparticles (GNPs) for biomedical applications in recent years. Such efforts warrant reliable, viable, and biofriendly synthetic methodology for GNPs with homogeneous sizes and shapes, particularly sizes above 30 nm, which is currently challenging. In the present study, an environmentally benign, biofriendly, single-step/single-phase synthetic method using dextrose as a reducing and capping agent in a buffered aqueous solution at moderate temperature is introduced. The resulting GNPs are near-spherical, stable, catalytically active, place exchangeable, and water-soluble within the size range of 10-120 nm. The added advantage of the biologically friendly reaction medium employed in this new synthetic approach provides a method for the direct embedment/integration of GNPs into biological systems such as the E. coli bacterium without additional capping ligand or surface modification processes.     

Photoageing of Baltic amber – Influence of daylight radiation behind window glass on surface colour and chemistry

The aim of this study was to provide evidence about the interaction between Baltic amber and daylight behind window glass, essential to understanding the mechanisms by which the material degrades in museum environments and to propose techniques for preventive conservation based on the control of environmental parameters where amber objects are stored or displayed. To investigate the photodegradation of Baltic amber, the methodology consisted of artificial ageing, in order to initiate degradation of model amber samples, and non-destructive analytical techniques, in order to identify and quantify changes in colour and chemical properties. Prism-shaped samples, obtained from a large amber piece, were exposed to different microclimatic conditions, subjected to accelerated photoageing and analysed by spectrocolorimetry, infrared spectroscopy and Raman spectroscopy. The experiments provided results about surface discolouration, oxidation of the molecular structure and breakdown of unsaturated carbon-carbon bonds in various environmental conditions, confirming the degrading role of daylight behind window glass. The conclusions of this study can be applied to the development of techniques for preventive conservation of museum collections containing amber objects.     

Stelliferins J-N, isomalabaricane-type triterpenoids from Okinawan marine sponge Rhabdastrella cf. globostellata

Five new isomalabaricane-type triterpenoids, stelliferins J-N (1-5), were isolated from Okinawan marine sponge Rhabdastrella cf. globostellata. The structures of 1-5 were elucidated from the spectroscopic data and chemical means including application of a modified Mosher’s method and an exciton chirality method.     

Fungal cyclooligomer depsipeptides: from classical biochemistry to combinatorial biosynthesis

This review surveys the biological activities and the iterative and recursive biosynthetic mechanisms of fungal cyclooligomer depsipeptides, and their structural diversification by various combinatorial biosynthetic methods.     

Biological monitoring of 3-phenoxybenzoic acid in urine by an enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) method was employed for determination of the pyrethroid biomarker, 3-phenoxybenzoic acid (3-PBA) in human urine samples. The optimized coating antigen concentration was 0.5 ng/mL with a dilution of 1:4000 for the 3-PBA antibody and 1:6000 for the enzyme conjugate. Urine samples were hydrolyzed with concentrated hydrochloric acid; extracted with dichloromethane and solvent-exchanged into a methanol/buffer solution, prior to analysis in a 96-microwell plate immunoassay. Quantitative recoveries of 3-PBA were obtained for fortified urine samples by ELISA (92 ± 18%) as well as by gas chromatography/mass spectrometry (GC/MS) (90 ± 13%). The overall method precision of these samples was within ±20% for both the ELISA and GC/MS methods. Analytical results from over one hundred urine samples showed that the ELISA and GC/MS data were highly correlated, with a correlation coefficient of 0.95. At the 10 ng/mL comparative concentration level, the false positive rate was 0% and the false negative rate was 0.8% for ELISA when using GC/MS as the reference method. The ELISA method has a suitable low detection limit for 3-PBA to assess pyrethroid exposures in non-occupational settings.     

Asymmetrical hippocampal connectivity in mesial temporal lobe epilepsy: evidence from resting state fMRI

Background

Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform. The amplitude resolution was impoverished by reducing the number of bits to represent the signal samples. Auditory evoked magnetic fields (AEFs) were measured in the left and right hemisphere of sixteen healthy subjects.

Results

We found that the AEF amplitudes increased significantly with stimulus distortion for all stimulus types, which indicates that the right-hemispheric N1m sensitivity is not related exclusively to degradation of acoustic properties of speech. In addition, the P1m and P2m responses were amplified with increasing distortion similarly in both hemispheres. The AEF latencies were not systematically affected by the distortion.

Conclusions

We propose that the increased activity of AEFs reflects cortical processing of acoustic properties common to both speech and non-speech stimuli. More specifically, the enhancement is most likely caused by spectral changes brought about by the decrease of amplitude resolution, in particular the introduction of periodic, signal-dependent distortion to the original sound. Converging evidence suggests that the observed AEF amplification could reflect cortical sensitivity to periodic sounds.     

Non-convex dissipation potentials in multiscale non-equilibrium thermodynamics

Reformulating constitutive relation in terms of gradient dynamics (being derivative of a dissipation potential) brings additional information on stability, metastability and instability of the dynamics with respect to perturbations of the constitutive relation, called CR-stability. CR-instability is connected to the loss of convexity of the dissipation potential, which makes the Legendre-conjugate dissipation potential multivalued and causes dissipative phase transitions that are not induced by non-convexity of free energy, but by non-convexity of the dissipation potential. CR-stability of the constitutive relation with respect to perturbations is then manifested by constructing evolution equations for the perturbations in a thermodynamically sound way (CR-extension). As a result, interesting experimental observations of behavior of complex fluids under shear flow and supercritical boiling curve can be explained.     

In search of the ‘impenetrable’ volume of a molecule in a noncovalent complex

ABSTRACT

We propose to characterise the “impenetrable” volumes of molecules A and B in a complex A---B by finding that contour of its electronic density that separates the molecular surfaces of A and B but leaves them almost touching. The volume of the complex within that contour is always less than within the 0.001 au contour. The percent difference measures the interpenetration of the two molecules at equilibrium, and is found to directly correlate with the binding energy of the complex. We interpret the volume of each molecule that is enclosed by the almost-touching contour as that molecule's impenetrable volume relative to its particular partner. The percents by which the molecules' relative impenetrable volumes differ from their 0.001 au volumes in the free states also correlate with the strengths of the interactions. This allows the “absolute” impenetrable volume of any molecule to be estimated as ～25% of its 0.001 au volume in the free state. However this absolute impenetrable volume is only approached by the molecule in a relatively strong interaction.     

Serial Cross-Sectional Observations of Sun-Protective Behaviors at an Annual Outdoor Motorsport Event in Tropical Queensland,Australia

Skin cancer, the most prevalent cancer in Caucasians residing at low latitudes, can primarily be prevented by avoiding overexposure to sunlight. Serial cross-sectional observations were conducted at an outdoor motorsport event held in Townsville, Queensland each July (Southern winter) to determine whether sun-protection habits changed over time. Most (71.1%) of the 1337 attendees observed (97.6% lightly pigmented skin, 64.0% male) wore a hat (any style shading the face), while few (18.5%) wore three-quarter or full-length sleeves. While hat-wearing rates (any style) were similar in 2009 (326, 72.6%) and 2013 (625, 70.4%), the use of sun-protective styles (wide-brimmed/bucket/legionnaires) decreased from 29.2% to 18.6% over the same period, primarily because the use of sun-protective hats halved (from 28.7% to 14.0%) among females, while decreasing from 29.4% to 21.1% in males. Although relatively few individuals wore sun-protective (three-quarter-length or full-length) sleeves regardless of year (OR = 0.117, P < 0.0001), encouragingly, the use of sun-protective sleeves more than doubled between 2009 (10.5%) and 2013 (22.5%). Interestingly females, albeit the minority, at this sporting event were less likely to wear a hat (OR = 0.473, P < 0.0001) than males. These findings highlight the need for continued momentum toward skin cancer primary prevention through sun protection with a dedicated focus on outdoor sporting settings.