Ultrafast photoelectron spectroscopy near liquid water interfaces: The solvated electron

Solvatisierte Elektronen in flüssigem Wasser - auch hydratisierte Elektronen genannt - spielen eine wichtige Rolle in vielen physikalischen, chemischen und biologischen Prozessen. Die vertikale Bindungsenergie hydratisierter Elektronen ist eine entscheidende Größe um ihre Stabilität und Reaktivität zu verstehen. Mit einem einzigartigen experimentellen Aufbau, der eine High-Harmonic-Lichtquelle und Mikro-Flüssigstrahltechnologien verknüpft wurden in dieser Arbeit erstmals Photoelektronenspektren von hydratisierten Elektronen aufgezeichnet. Mit einem ersten ultrakurzen Laserpuls (Pump-Puls) im ultravioletten Spektralbereich (267 nm) werden solvatisierte Elektronen im Mikro-Flüssigstrahl erzeugt. Nach einer Zeitverzögerung von bis zu 100 ps nach der Erzeugung werden mit der High-Harmonic Strahlung (38.6 eV, Probe Puls) Photoelektronen freigesetzt. Mit verschiedenen experimentellen Ansätzen erhalten wir Photoelektronenspektren mit Signalen bei (3.3 ± 0.1) eV und (1.6 ± 0.1) eV, welche wir den vertikalen Bindungsenergien von vollständig solvatisierten und oberflächengebundenen Elektronen zuordnen. Unsere Experimente beweisen die Existenz oberflächengebundener Elektronen an der Wasser/Gas Grenzfläche mit einer Lebensdauer von mindestens 100 ps. Diese Ergebnisse legen eine Energieskala für hydratisierte Elektronen fest, die neue Einblicke in viele Elektronentransfer-Prozesse ermöglicht. In dieser Arbeit wird das Konzept der "Resonanten Dissoziativen Elektronenanlagerung" (RDEA) vorgestellt. Es beruht auf dem Vergleich von Resonanzen für Elektronenanlagerung an molekulare Systeme mit der Energieskala hydratisierter Elektronen. Dieses Konzept eröffnet nicht nur einen neuen Blickwinkel auf strahlungsinduzierte DNA Schäden und atmosphärische Prozesse, die zur Bildung des Ozonlochs führen könnten, es könnte sogar unser gesamtes Verständnis elektroneninduzierter Prozesse in wässriger Umgebung grundlegend bereichern

REACTIVITY OF CHLOROPHYLL a/b-PROTEINS AND MICELLAR TRITON X-100 COMPLEXES OF CHLOROPHYLLS a OR b WITH BOROHYDRIDE

The reaction of several plant chlorophyll-protein complexes with NaBH4 has been studied by absorption spectroscopy. In all the complexes studied, chlorophyll b is more reactive than Chi a, due to preferential reaction of its formyl substituent at C-7. The complexes also show large variations in reactivity towards NaBH4 and the order of reactivity is: LHCI > PSII complex > LHCII > PSI > P700 (investigated as a component of PSI). Differential pools of the same type of chlorophyll have been observed in several complexes. Parallel work was undertaken on the reactivity of micellar complexes of chlorophyll a and of chlorophyll b with NaBH4 to study the effect of aggregation state on this reactivity. In these complexes, both chlorophyll a and b show large variations in reactivity in the order monomer > oligomer > polymer with chlorophyll b generally being more reactive than chlorophyll a. It is concluded that aggregation decreases the reactivity of chlorophylls towards NaBH4 in vitro, and may similarly decrease reactivity in naturally-occurring chlorophyll-protein complexes

Light-induced relaxation dynamics of the ferricyanide ion revisited by ultrafast XUV photoelectron spectroscopy

Photoinduced charge transfer in transition-metal coordination complexes plays a prominent role in photosynthesis and is fundamental for light-harvesting processes in catalytic materials. However, revealing the relaxation pathways of charge separation remains a very challenging task because of the complexity of relaxation channels and ultrashort time scales. Here, we employ ultrafast XUV photoemission spectroscopy to monitor fine mechanistic details of the electron dynamics following optical ligand-to-metal charge-transfer excitation of ferricyanide in aqueous solution. XUV probe light with a time resolution of 100 fs, in combination with density functional theory employing the Dyson orbital formalism, enabled us to decipher the primary and subsequently populated electronic states involved in the relaxation, as well as their energetics on sub-picosecond timescales. We find strong evidence for the spin crossover followed by geometrical distortions due to vibronic interactions (Jahn–Teller effect) in the excited electronic states, rather than localization/delocalization dynamics, as suggested previously

Photophysics of the electronic states S0 and S1 for the coplanar molecular structures of the α,ω-diphenylpolyenes DPH and DPO

Spectroscopy of the monoclinic and orthorhombic crystalline forms of all-trans-diphenylhexatriene (DPH) and all-trans-diphenyloctatetraene (DPO) show absorption and emission bands that do not generate the widely known Stokes shift of the polyene compounds, discovered by Hausser et al. in 1953 and repeatedly studied over the last 60 years. It can be concluded from our study that the crystallization system, whether in a monoclinic or orthorhombic system, does not significantly influence the photophysics of DPH and DPO in the crystal phas

A common supersolid low-density skin sliperizing ice and toughening water surface

Skins of water and ice share the same attribute of supersolidity characterized by the identical H-O vibration frequency of 3450 cm-1. Molecular undercoordination and inter-electron-pair repulsion shortens the H-O bond and lengthen the O:H nonbond, leading to a dual process of nonbonding electron polarization. This relaxation-polarization process enhances the dipole moment, elasticity,viscosity, thermal stability of these skins with 25% density loss, which is responsible for the hydrophobicity and toughness of water skin and for the slippery of ice.Comment: arXiv admin note: text overlap with arXiv:1401.804

De Novo Transcriptomic Analysis of an Oleaginous Microalga: Pathway Description and Gene Discovery for Production of Next-Generation Biofuels

Background: Eustigmatos cf. polyphem is a yellow-green unicellular soil microalga belonging to the eustimatophyte with high biomass and considerable production of triacylglycerols (TAGs) for biofuels, which is thus referred to as an oleaginous microalga. The paucity of microalgae genome sequences, however, limits development of gene-based biofuel feedstock optimization studies. Here we describe the sequencing and de novo transcriptome assembly for a non-model microalgae species, E. cf. polyphem, and identify pathways and genes of importance related to biofuel production. Results: We performed the de novo assembly of E. cf. polyphem transcriptome using Illumina paired-end sequencing technology. In a single run, we produced 29,199,432 sequencing reads corresponding to 2.33 Gb total nucleotides. These reads were assembled into 75,632 unigenes with a mean size of 503 bp and an N50 of 663 bp, ranging from 100 bp to.3,000 bp. Assembled unigenes were subjected to BLAST similarity searches and annotated with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) orthology identifiers. These analyses identified the majority of carbohydrate, fatty acids, TAG and carotenoids biosynthesis and catabolism pathways in E. cf. polyphem. Conclusions: Our data provides the construction of metabolic pathways involved in the biosynthesis and catabolism of carbohydrate, fatty acids, TAG and carotenoids in E. cf. polyphem and provides a foundation for the molecular genetics and functional genomics required to direct metabolic engineering efforts that seek to enhance the quantity and character o