Excited-state dynamics of 3-hydroxychromone in gas phase.

In recent years, 3-hydroxychromone (3-HC) and its derivatives have attracted much interest for their applications as molecular photoswitches and fluorescent probes. A clear understanding of their excited-state dynamics is essential for their applications and further development of new functional 3-HC derivatives. However, the deactivation mechanism of the photoexcited 3-HC family is still puzzling as their spectral properties are sensitive to the surrounding medium and substituents.

Photoswitchable luminescent lanthanide complexes controlled and interrogated by four orthogonal wavelengths of light.

Optical information storage requires careful control of excitation and emission wavelengths in a reversible and orthogonal manner to enable efficient reading, writing, and erasing of information. Photochromic systems, in which a photoswitch is typcially coupled to an emissive organic fluorophore, have much promise in this regard. However, these suffer from considerable spectral overlap between the switch and fluorophore, such that their emissive and photoswitchable properties are not orthogonal.

Theoretical Investigation on the Reversible Photoswitch Mechanism of Benzylidene-Oxazolone System.

The design and application of molecular photoswitches have attracted much attention. Herein, we performed a detailed computational study on the photoswitch benzylidene-oxazolone system based on static electronic structure calculations and on-the-fly excited-state dynamic simulations. For the Z and E isomer, we located six and four minimum energy conical intersections (MECIs) between the first excited state (S) and the ground state (S), respectively.

Excited-state dynamics of 4-hydroxyisoindoline-1,3-dione and its derivative as fluorescent probes.

Fluorescent probes have become promising tools for monitoring the concentration of peroxynitrite, which is linked to many diseases. However, despite focusing on developing numerous peroxynitrite based fluorescent probes, limited emphasis is placed on their sensing mechanism. Here, we investigated the sensing mechanism of a peroxynitrite fluorescent probe, named BHID-Bpin, with a focus on the relevant excited state dynamics.

Constitutive Endolysosomal Perforation in Neurons allows Induction of α-Synuclein Aggregation by Internalized Pre-Formed Fibrils.

The endocytic pathway is both an essential route of molecular uptake in cells and a potential entry point for pathology-inducing cargo. The cell-to-cell spread of cytotoxic aggregates, such as those of α-synuclein (α-syn) in Parkinson's Disease (PD), exemplifies this duality. Here we used a human iPSC-derived induced neuronal model (iNs) prone to death mediated by aggregation in late endosomes and lysosomes of endogenous α-syn, seeded by internalized pre-formed fibrils of α-syn (PFFs).

Deep learning assisted single particle tracking for automated correlation between diffusion and function.

Sub-cellular diffusion in living systems reflects cellular processes and interactions. Recent advances in optical microscopy allow the tracking of this nanoscale diffusion of individual objects with an unprecedented level of precision. However, the agnostic and automated extraction of functional information from the diffusion of molecules and organelles within the sub-cellular environment, is labor-intensive and poses a significant challenge.

Subphthalocyanine-triangulene dyads: Property tuning for light-harvesting device applications.

Organic photovoltaics relies on the development of stable chromophores and redox-active organic molecules with tailor-made HOMO/LUMO energies. Here, we present the synthesis and properties of novel dyads composed of boron subphthalocyanine (SubPc) and triangulene units, connected either at the peripheral position of the subphthalocyanine or at the axial boron. The connectivity has strong implications for the absorption and fluorescence properties of the dyads, as well as their redox properties.

What Atomic Positions Determines Reactivity of a Surface? Long-Range, Directional Ligand Effects in Metallic Alloys.

Ligand and strain effects can tune the adsorption energy of key reaction intermediates on a catalyst surface to speed up rate-limiting steps of the reaction. As novel fields like high-entropy alloys emerge, understanding these effects on the atomic structure level is paramount: What atoms near the binding site determine the reactivity of the alloy surface? By statistical analysis of 2000 density functional theory calculations and subsequent host/guest calculations, it is shown that three atomic positions in the third layer of an fcc(111) metallic structure fourth-nearest to the adsorption site display significantly increased influence on reactivity over any second or third nearest atomic positions. Subsequently observed in multiple facets and host metals, the effect cannot be explained simply through the d-band model or a valence configuration model but rather by favorable directions of interaction determined by lattice geometry and the valence difference between host and guest elements.

Solar Energy Storage by Molecular Norbornadiene-Quadricyclane Photoswitches: Polymer Film Devices.

Devices that can capture and convert sunlight into stored chemical energy are attractive candidates for future energy technologies. A general challenge is to combine efficient solar energy capture with high energy densities and energy storage time into a processable composite for device application. Here, norbornadiene (NBD)-quadricyclane (QC) molecular photoswitches are embedded into polymer matrices, with possible applications in energy storing coatings.

Sustainable Flow Synthesis of Encoded Beads for Combinatorial Chemistry and Chemical Biology.

Monosized beads of polar resins were synthesized for combinatorial chemistry and chemical biology by sustainable microchannel flow synthesis. Regular, biocompatible, and optically encoded beads could be efficiently prepared on large scale and in high yield. In a preparative flow polymerization instrument, taking advantage of a designed T-connector for droplet formation, quality beads were synthesized with accurate size control using a minimal amount of recirculating silicon oil as suspension medium.

C-Terminally modified peptides via cleavage of the HMBA linker by O-, N- or S-nucleophiles.

A large variety of C-terminally modified peptides was obtained by nucleophilic cleavage of the ester bond in solid phase linked peptide esters of 4-hydroxymethyl benzamide (HMBA). The developed methods provided peptides, C-terminally functionalized as esters, amides and thioesters, with high purity directly from the resin in a single reaction step. A comprehensive screening of the reaction conditions and scope for nucleophilic cleavage of peptides from the HMBA linker was performed.

Steady State and Time Resolved Fluorescence Studies of Azadioxatriangulenium (ADOTA) Fluorophore in Silica and PVA Thin Films.

A cationic azadioxatriangulenium (ADOTA) dye was entrapped in silica thin films obtained by the sol-gel process and in poly (vinyl) alcohol (PVA) thin films. Azadioxatriangulenium is a red emitting fluorophore with a long fluorescence lifetime of ~20 ns. The fluorescent properties of azadioxatriangulenium in silica thin films and PVA films were studied by means of steady-state and time resolved fluorescence techniques.

Tetrathiafulvaleno-Annelated Porphyrins.

Two efficient synthetic routes to the first tetrathiafulvaleno-annelated porphyrins are reported. These novel porphyrin systems (see picture; Pe=pentyl) have been characterized by using a variety of techniques including EPR spectroscopy, cyclic voltammetry, and mass spectrometry. Langmuir-Blodgett films obtained from the porphyrins were used to carry out structural studies by using X-ray diffraction and atomic force microscopy.

The crystal structure of the flavin containing enzyme dihydroorotate dehydrogenase A from Lactococcus lactis.

Background: . Dihydroorotate dehydrogenase (DHOD) is a flavin mononucleotide containing enzyme, which catalyzes the oxidation of (S)-dihydroorotate to orotate, the fourth step in the de novo biosynthesis of pyrimidine nucleotides. Lactococcus lactis contains two genes encoding different functional DHODs whose sequences are only 30% identical.