Nuclear Magnetic Resonance Chemical Shift as a Probe for Single-Molecule Charge Transport.

Existing modelling tools, developed to aid the design of efficient molecular wires and to better understand their charge-transport behaviour and mechanism, have limitations in accuracy and computational cost. Further research is required to develop faster and more precise methods that can yield information on how charge transport properties are impacted by changes in the chemical structure of a molecular wire. In this study, we report a clear semilogarithmic correlation between charge transport efficiency and nuclear magnetic resonance chemical shifts in multiple series of molecular wires, also accounting for the presence of chemical substituents. The NMR data was used to inform a simple tight-binding model that accurately captures the experimental single-molecule conductance values, especially useful in this case as more sophisticated density functional theory calculations fail due to inherent limitations. Our study demonstrates the potential of NMR spectroscopy as a valuable tool for characterising, rationalising, and gaining additional insights on the charge transport properties of single-molecule junctions.

Enhanced charge transport across molecule-nanoparticle-molecule sandwiches.

The electrical properties of large area molecular devices consisting of gold nanoparticles (GNPs) sandwiched between a double layer of alkanedithiol linkers have been examined. These devices have been fabricated by a facile bottom-up assembly in which an alkanedithiol monolayer is first self-assembled on an underlying gold substrate followed by nanoparticle adsorption and then finally assembly of the top alkanedithiol layer. These devices are then sandwiched between the bottom gold substrates and a top eGaIn probe contact and current-voltage (I-V) curves recorded. Devices have been fabricated with 1,5-pentanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol and 1,10-decanedithiol linkers. In all cases the electrical conductance of the double SAM junctions with GNPs is higher than the corresponding and much thinner single alkanedithiol SAM. Competing models for this enhanced conductance are discussed and it is suggested to have a topological origin arising from how the devices assemble or structure during the fabrication, which gives more efficient cross device electron transport pathways without the GNPs producing short circuits.

Effects of acute and sub-acute hypobaric hypoxia on oxidative stress: a field study in the Alps.

PURPOSE: High altitude results in lower barometric pressure and hence partial pressure of O2 decrease can lead to several molecular and cellular changes, such as generation of reactive oxygen species (ROS). Electron Paramagnetic Resonance technique was adopted in the field, to evaluate the effects of acute and sub-acute hypobaric hypoxia (HH) on ROS production by micro-invasive method. Biological biomarkers, indicators of oxidative stress, renal function and inflammation were investigated too. METHODS: Fourteen lowlander subjects (mean age 27.3 ± 5.9 years) were exposed to HH at 3269 m s.l. ROS production, related oxidative damage to cellular components, systemic inflammatory response and renal function were determined through blood and urine profile performed at 1st, 2nd, 4th, 7th, and 14th days during sojourn. RESULTS: Kinetics of changes during HH exposition showed out significant (range p < 0.05-0.0001) increases that at max corresponds to 38% for ROS production rate, 140% for protein carbonyl, 44% for lipid peroxidation, 42% for DNA damage, 200% for inflammatory cytokines and modifications in renal function (assessed by neopterin concentration: 48%). Conversely, antioxidant capacity significantly (p < 0.0001) decreased - 17% at max. CONCLUSION: This 14 days in-field study describes changes of oxidative-stress biomarkers during HH exposure in lowlanders. The results show an overproduction of ROS and consequent oxidative damage to protein, lipids and DNA with a decrease in antioxidant capacity and the involvement of inflammatory status and a transient renal dysfunction. Exposure at high altitude induces a hypoxic condition during acute and sub-acute phases accompanied by molecular adaptation mechanism indicating acclimatization.

P260Right cardiac chambers remodeling in marathon and ultra-trail athletes detected by speckle-tracking echocardiography.

BACKGROUND: Strenuous and chronic exercise training can have detrimental effects on cardiac morphology and function. Our aim was to evaluate the cardiac adaptation between 2 different specialties' endurance athletes: marathon runners (M) and ultra-trailers (UT). METHODS: 47 M (age 45±7, men 32; training: 18 (9-53) years*days/week), 41 UT (age 42±9, men 38, training: 30 (15-66) years*days/week) were submitted in rest condition to conventional 2D echocardiography and Speckle-Tracking echo (STE) (Beyond Diogenes 2.0, AMID) during agonistic season and compared with 15 age matched sedentary individuals (S) (age 43±6, men 10). RESULTS: Left ventricle (LV) global longitudinal strain (GLS) and global radial strain (GRS) were increased in M and UT compared to S (see table) without differences in LV anatomy and function. Right ventricle (RV) end-diastolic area (p=0.026), fractional area changing (p=0.008) and RV GLS were increased in UT compared to M. Moreover UT showed larger right atrium (RA) volume compared to M (p=0.03) and S (p=0.003). RA GLS was reduced in UT compared to M while the RA Global Circumferential Strain was significantly increased in UT. After adjusted for age, sex and HR as covariates, UT showed a reduced RA GLS (OR 0.907; CI 0.856-0.961) and increased RV FAC (OR 1.172; CI: 1.044-1.317) compared to M; while when compared to S subjects, UT showed increased RA volume (OR 1.048; CI 1.002-1.096) and RV GLS (OR 0.667; CI 0.490-0.907). CONCLUSION: UT showed higher RV and RA morphological and functional remodeling in comparison with M. 2D-STE is a useful tool to investigate the deformation dynamic in different sport specialties. Further studies will be necessary to clarify the long-term consequences for cardiac health due to myocardial perturbations.MUTSpLV GLS-28.59±3.43*-27.64±4.18*-24.82±4.53<0.05LV GRS69.85±8.94*66.59±11.19*56.27±16.25<0.001RV GLS-25.60±10.54-30.41±4.38*-27.10±4.64<0.05RA GLS37.15±13.4931.65±9.60*35.37±9.99<0.05RA GCS17.46±6.4222.28±8.97*23.37±6.47<0.01.

1H NMR spin-spin relaxation and imaging in porous systems: an application to the morphological study of white portland cement during hydration in the presence of organics.

Proton nuclear magnetic resonance (NMR) spin-spin relaxation and imaging have been applied to investigate white Portland cement pastes during hydration in the absence and in the presence of organic solvents. The main organic solvent investigated was methanol, alone or together with the organic waste 2-chloroaniline (2-CA), an aromatic amine representative of an important class of highly toxic compounds. For all the analysed samples, prepared with a solvent-to-cement ratio of 0.4, the decay of the echo magnetization has been fitted by adopting a model that combines an exponential component with a gaussian one. The calculated independent relaxation parameters have been discussed in terms of morphological and dynamical changes that occur during the cement hardening process and pore formation. Three kinds of water molecules: "solid-like" (chemically and physically bound), "liquid-like" (porous trapped) and "free" water, endowed with anisotropic, near isotropic and isotropic motion, respectively, were identified. Spin-echo images collected on the same samples during the hydration kinetics, allowed the changes of water and solvents spatial distribution in the porous network to be monitored, showing percolation phenomena and confirming the multimodal open channels structure of the hardened cement system. Both T(2) relaxation and imaging data indicated that a pronounced delay occurs in the cement hardening when organics are present.

Magnetic resonance imaging of molecular transport in living morning glory stems.

MRI was applied to investigate the transport pathways in Morning Glory plant stems. The study was carried out on living plants without affecting their integrity. The architecture of a dicotyledonous plant was deeply characterized: the root system structure and the vascular bundle location were identified, the presence of central voids caused by cell maturation and loss were observed in the stem. Molecular transport components were recognized, by observing the concentration profile of a tracer, which changed with time after its absorption by the plant roots. MRI analysis revealed the presence of an axial transport as the progress of the tracer front through the vascular bundles and a radial molecular transport from the vascular bundles toward the surface of the stem. As a result, the tracer molecular transport formed the parabolic tracer front (PTF). A model was built up through the analysis of the PTF that consisted of an axial front at the peak position and a radial front at the width of the parabolic tail. PTF analysis revealed differences between the tracer transport velocities in the axial and the radial directions in the plant stem. The model revealed that the width of the parabolic tail reflected the magnitudes of diffusion and permeation of the tracer in the plant stem.

Quantitative analysis of anaerobic metabolism in resting anoxic muscle by 31P and 1H MRS.

31P and 1H MRS high resolution measurements at 4.7 T were carried out in isolated frog (Rana esculenta) gastrocnemius muscle during anoxia to assess, using reference compounds, the concentration of high energy phosphates (approximately P = phosphocreatine (PC) plus adenosinetriphosphate (ATP)), inorganic phosphate (P(i)), phosphomonoesters (PME) and lactate (La): Two sets of measurements were performed, with (p) and without (up) muscle IAA poisoning and the time course of the metabolite concentration changes was described. The rate of phosphocreatine hydrolysis during the first phase of anaerobiosis, when no lactate is accumulated in either case, appears to be greater in p than in up preparations. This finding can be explained with the sizeable accumulation of phosphomonoesters (PME) in the former. The efficiency of anaerobic glycolysis, i.e. the approximately P/La ratio, recalculated taking into account also PME changes, was found to be 1.48 +/- 0.28, a value higher than that obtained by previous chemical measurements and close to the maximum stoichiometric approximately P/La value. Hence, the in vivo substrate of glycolysis, in the resting anoxic frog gastrocnemius, appears to be almost exclusively glycogen.