Single-molecule photoredox catalysis.

The chemistry of life is founded on light, so is it appropriate to think of light as a chemical substance? Planck's quantization offers a metric analogous to Avogadro's number to relate the number of particles to an effective reaction of single molecules and photons to form a new compound. A rhodamine dye molecule serves as a dehalogenating photocatalyst in a consecutive photoelectron transfer (conPET) process which adds the energy of two photons, with the first photon inducing radical formation and the second photon triggering PET to the substrate molecule. Rather than probing catalytic heterogeneity and dynamics on the single-molecule level, single-photon synthesis is demonstrated: the light quantum constitutes a reactant for the single substrate molecule in a dye-driven reaction. The approach illustrates that molecular diffusion and excited-state internal conversion are not limiting factors in conPET reaction kinetics because of catalyst-substrate preassociation. The effect could be common to photoredox catalysis, removing the conventional requirement of long excited-state lifetimes.

Chemical Photocatalysis with Rhodamine 6G: Investigation of Photoreduction by Simultaneous Fluorescence Correlation Spectroscopy and Fluorescence Lifetime Measurements.

Recent research has demonstrated that consecutive excitation of the radical anion state of commercially available dye molecules-generated by a photoinduced electron-transfer process-yields sufficient energy to stimulate challenging chemical reactions in photocatalysis. For this reason, an efficient transfer of dye molecules into their radical anion states upon photoexcitation is highly desirable, as is a long radical lifetime. However, the formation of these reactive states is strongly dependent on the redox agent, the local environment, for example, the solvents and additives, as well as on the properties of the excited states of the dye molecule. Finding the best conditions for radical formation is crucial, but, owing to the complexity of the underlying photochemical process, this is usually only achieved by an iterative exploratory approach. Here, we demonstrate that the formation and lifetime of the rhodamine 6G (Rh6G) radical anion can be followed in detail by single-molecule fluorescence correlation spectroscopy combined with simultaneous fluorescence lifetime measurements. We elucidate the role of the first excited singlet and triplet states of the dye molecule in the formation of the radical at different concentrations of the reducing agent, ascorbic acid (AscA); for different solvents, water and dimethyl sulfoxide; and for different reducing agents, AscA and N, N-diisopropylethylamine; as well as for varying pH values. The results provide a guideline toward generating an increased yield of radical anions of the dye under photoexcitation. As an example, we find that the lifetime of the radical anion state of Rh6G can be increased by over an order of magnitude from 7 to 110 µs in an aerated solution.

Impact of treatment delay on mortality in ST-segment elevation myocardial infarction (STEMI) patients presenting with and without haemodynamic instability: results from the German prospective, multicentre FITT-STEMI trial.

Aims: The aim of this study was to investigate the effect of contact-to-balloon time on mortality in ST-segment elevation myocardial infarction (STEMI) patients with and without haemodynamic instability. Methods and results: Using data from the prospective, multicentre Feedback Intervention and Treatment Times in ST-Elevation Myocardial Infarction (FITT-STEMI) trial, we assessed the prognostic relevance of first medical contact-to-balloon time in n = 12 675 STEMI patients who used emergency medical service transportation and were treated with primary percutaneous coronary intervention (PCI). Patients were stratified by cardiogenic shock (CS) and out-of-hospital cardiac arrest (OHCA). For patients treated within 60 to 180 min from the first medical contact, we found a nearly linear relationship between contact-to-balloon times and mortality in all four STEMI groups. In CS patients with no OHCA, every 10-min treatment delay resulted in 3.31 additional deaths in 100 PCI-treated patients. This treatment delay-related increase in mortality was significantly higher as compared to the two groups of OHCA patients with shock (2.09) and without shock (1.34), as well as to haemodynamically stable patients (0.34, P < 0.0001). Conclusions: In patients with CS, the time elapsing from the first medical contact to primary PCI is a strong predictor of an adverse outcome. This patient group benefitted most from immediate PCI treatment, hence special efforts to shorten contact-to-balloon time should be applied in particular to these high-risk STEMI patients. Clinical Trial Registration: NCT00794001.

Electrocardiographic diagnosis of left ventricular hypertrophy in aortic valve disease: evaluation of ECG criteria by cardiovascular magnetic resonance.

BACKGROUND: Left ventricular hypertrophy (LVH) is a hallmark of chronic pressure or volume overload of the left ventricle and is associated with risk of cardiovascular morbidity and mortality. The purpose was to evaluate different electrocardiographic criteria for LVH as determined by cardiovascular magnetic resonance (CMR). Additionally, the effects of concentric and eccentric LVH on depolarization and repolarization were assessed. METHODS: 120 patients with aortic valve disease and 30 healthy volunteers were analysed. As ECG criteria for LVH, we assessed the Sokolow-Lyon voltage/product, Gubner-Ungerleider voltage, Cornell voltage/product, Perugia-score and Romhilt-Estes score. RESULTS: All ECG criteria demonstrated a significant correlation with LV mass and chamber size. The highest predictive values were achieved by the Romhilt-Estes score 4 points with a sensitivity of 86% and specificity of 81%. There was no difference in all ECG criteria between concentric and eccentric LVH. However, the intrinsicoid deflection (V6 37 +/- 1.0 ms vs. 43 +/- 1.6 ms, p < 0.05) was shorter in concentric LVH than in eccentric LVH and amplitudes of ST-segment (V5 -0.06 +/- 0.01 vs. -0.02 +/- 0.01) and T-wave (V5 -0.03 +/- 0.04 vs. 0.18 +/- 0.05) in the anterolateral leads (p < 0.05) were deeper. CONCLUSION: By calibration with CMR, a wide range of predictive values was found for the various ECG criteria for LVH with the most favourable results for the Romhilt-Estes score. As electrocardiographic correlate for concentric LVH as compared with eccentric LVH, a shorter intrinsicoid deflection and a significant ST-segment and T-wave depression in the anterolateral leads was noted.