Chirally-modified metal surfaces: energetics of interaction with chiral molecules

Imparting chirality to non-chiral metal surfaces by adsorption of chiral modifiers is a highly promising route to create effective heterogeneously catalyzed processes for the production of enantiopure pharmaceuticals. One of the major current challenges in heterogeneous chiral catalysis is the fundamental-level understanding of how such chirally-modified surfaces interact with chiral and prochiral molecules to induce their enantioselective transformations. Herein we report the first direct calorimetric measurement of the adsorption energy of chiral molecules onto well-defined chirally-modified surfaces. Two model modifiers 1-(1-naphthyl)ethylamine and 2-methylbutanoic acid were used to impart chirality to Pt(111) and their interaction with propylene oxide was investigated by means of single-crystal adsorption calorimetry. Differential adsorption energies and absolute surface uptakes were obtained for the R- and S-enantiomers of propylene oxide under clean ultrahigh vacuum conditions. Two types of adsorption behavior were observed for different chiral modifiers, pointing to different mechanisms of imparting chirality to metal surfaces. The results are analyzed and discussed in view of previously reported stereoselectivity of adsorption processe

Real-time monitoring of cellular dynamics using a microfluidic cell culture system with integrated electrode array and potentiostat

A versatile microfluidic, multichamber cell culture and analysis system with an integrated electrode array and potentiostat suitable for electrochemical detection and microscopic imaging is presented in this paper. The system, which allows on-line electrode cleaning and modification, was developed for real-time monitoring of cellular dynamics, exemplified in this work by monitoring of redox metabolism inside living yeast cells and dopamine release from PC12 cell

Energetics of Elementary Reaction Steps Relevant for CO Oxidation: CO and O₂ Adsorption on Model Pd Nanoparticles and Pd(111)

The energetics of elementary surface processes relevant for CO oxidation, particularly CO and O2 adsorption, were investigated by a direct calorimetric method on model Pd nanoparticles and on the extended Pd(111) single crystal surface. The focus of this study lies on a detailed understanding of how a nanometer scale confinement of matter affects the binding strength of gaseous adsorbates. We report adsorption energies and sticking coefficients of CO and O2 measured as a function of the adsorbate surface coverage both on pristine and O-covered Pd surfaces. The reduced dimensions of the Pd substrate were found to affect the binding strength of the adsorbates in two principle ways: (i) via the change of the local adsorption environment that can result e.g. in stronger adsorbate bonding at the particle's low coordinated surface sites and (ii) via the contraction of the Pd lattice in small clusters and a concomitant weakening of chemisorptive interaction. Particularly for O2 adsorption, the change of the adsorption site from a three-fold hollow on Pd(111) to the edge site on Pd nanoparticles ([similar]4 nm sized on average) was found to result in a strong increase of the Pd–O bond strength. In contrast, CO adsorbs weaker on Pd nanoparticles as compared to the extended Pd(111) surface. In total, the binding energies of adsorbates on Pd and with this their surface coverages turn out to depend in a non-monotonic way on the particular structure of Pd surfaces, including the local structure of the adsorption site as well as the global properties of the small clusters arising e.g. from the lattice contraction

Trends in the Binding Strength of Surface Species on Nanoparticles: How Does the Adsorption Energy Scale with the Particle Size?

Thumbnail image of graphical abstract The binding energy of oxygen on Pd nanoparticles was measured by a direct calorimetric method as a function of the particle size. The reduced dimensionality of the Pd substrate results in two counteracting trends: an increase of the Pd[BOND]O binding strength due to a change of the local configuration of the adsorption site and a strong decrease of the Pd[BOND]O bonding due to the reduction of the cluster size

Telomere length increase after weight loss induced by bariatric surgery: results from a 10 year prospective study

BACKGROUND/OBJECTIVES Obesity contributes to telomere attrition. Studies focusing on short-term effects of weight loss have been unable to identify protection of telomere length. This study investigates long-term effects of pronounced weight loss induced by bariatric surgery on telomere length. SUBJECTS/METHODS One hundred forty-two patients were recruited in a prospective, controlled intervention study, follow-up investigations were done after 10.46±1.48 years. A control group of normal weight participants was recruited and followed from 1995 to 2005 in the Bruneck Study. A total of 110 participants from each study was matched by age and sex to compare changes in telomere length. Quantitative PCR was used to determine telomere length. RESULTS Telomere length increased significantly by 0.024±0.14 (P=0.047) in 142 bariatric patients within 10 years after surgery. The increase was different from telomere attrition in an age- and sex-matched cohort population of the Bruneck Study (-0.057±0.18; β=0.08; P=0.003). Significant changes in telomere length disappeared after adjusting for baseline body mass index (BMI) because of general differences in BMI and telomere length between the two study populations (β=0.07; P=0.06). Age was proportional to telomere length in matched bariatric patients (r=0.188; P=0.049) but inversely correlated with telomere length in participants of the Bruneck Study (r=-0.197; P=0.039). There was no association between percent BMI/excess weight loss and telomere attrition in bariatric patients. Baseline telomere length in bariatric patients was inversely associated with baseline plasma cholesterol and triglyceride concentrations. Telomere shortening was associated with lower high-density lipoprotein cholesterol and higher fasting glucose concentration at baseline in bariatric patients. CONCLUSIONS Increases in relative telomere length were found after bariatric surgery in the long term, presumably due to amelioration of metabolic traits. This may overrule the influence of age and baseline telomere length and facilitate telomere protection in patients experiencing pronounced weight loss

IMproving Preclinical Assessment of Cardioprotective Therapies (IMPACT) criteria: guidelines of the EU-CARDIOPROTECTION COST Action

10.1007/s00395-021-00893-5Basic Research in Cardiology11615