PHOTOOXIDATION OF HORSE AND SPERM-WHALE MYOGLOBIN SENSITIZED BY THE HEME GROUP

Abstract —The irradiation of horse and sperm-whale Fe 3 * or Fe 2* myoglobins with visible light showed that axial ligands that render the heme diamagnetic (e.g. O₂, CO or CN^-) endow the hemoproteins with a marked photosensitivity. In contrast, high-spin myoglobins are unaffected by visible light. These findings appear to be of general validity for all hemo-proteins and are in agreement with the involvment of the triplet state of the heme as the reactive intermediate. In all cases, the overall photoprocess occurs within a very narrow spatial range, leading to specific modification of these photooxidizable side chains adjacent to the chromophore. Therefore, this technique can be used to probe the environment of the prosthetic group in hemoproteins. In particular, our data suggest that, in horse myoglobin, histidines-93 and -64 represent the heme-linked and the distal imidazole groups, respectively; moreover, the thioether function of methionine-131 must be nearer the heme in horse than in sperm-whale myoglobin. The selectivity of the photoreaction can be further enhanced by a suitable choice of the sixth ligand, and/or by controlling the pH of the irradiated solution. For example, for both proteins, irradiation of the cyanide derivative results in specific photooxidation of the proximal histidine, whereas irradiation of horse CO-ferromyoglobin at pH values below 6 causes specific photooxidation of methionine-131. Consequently, this photooxidative procedure can also be utilized to monitor conformational changes upon binding of the heme with different ligands, as well as to achieve the selective modification of amino acid residues, which are usually buried inside the protein molecule.     

Combined mass quantitation and phenotyping of intact extracellular vesicles by a microarray platform

The interest towards extracellular vesicles (EVs) has grown exponentially over the last few years; being involved in intercellular communication and serving as reservoirs for biomarkers for tumors, they have a great potential for liquid biopsy development, possibly replacing many costly and invasive tissue biopsies.     

Nano‐ice on Boron Nitride Nanomesh: Accessing Proton Disorder

Water was investigated on a h‐BN/Rh(111) nanomesh template using variable temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. Below 52 K, two distinct phases self‐assemble within the 3.2 nm unit cell of the nanomesh that consists of “holes” and “wires”. In the 2 nm holes, an ordered phase of nano‐ice crystals with about 40 molecules is found. The ice crystals arrange in a bilayer honeycomb lattice, where hydrogen atoms of the lower layer point to the substrate. The phase on the 1 nm wires is a low density gas phase. Tunneling barrier height dI/dz spectroscopy measurements reveal the dipoles of individual molecules in the nano‐ice clusters and access proton disorder.     

The Inherent Electrochemistry of Nickel/Nickel‐Oxide Nanoparticles

The direct detection of nanoparticles is at the forefront of research owing to their environmental and toxicological applications. Herein, we studied the inherent electrochemistry of Ni and NiO nanoparticles and proposed a simple and direct electrochemical method for the determination of the concentrations of both nickel (Ni) and nickel oxide (NiO) nanoparticles in alkaline solution. A highly sensitive voltammetry technique was used to measure the oxidative signal of Ni(OH)₂ that formed spontaneously on the surface of Ni and NiO nanoparticles in alkaline media. Detection limits of 220 μg mL^?1 for Ni and 13 μg mL^?1 for NiO nanoparticles were obtained. Ni and NiO nanoparticles are used as electrode modifiers or as electrochemical signal labels in various biosensing applications. Therefore, methods to rapidly quantify the amount of Ni and NiO nanoparticles are of widespread potential use.     

The Fluorophore 4′,6‐Diamidino‐2‐phenylindole (DAPI) Induces DNA Folding in Long Double‐Stranded DNA

DAPI (4′,6‐diamidino‐2‐phenylindole) is a widely used fluorescent dye, whose complicated binding features to DNAs and RNAs have been the object of debates and are still not fully understood. In this study, different approaches were employed, including binding equilibrium measurements (spectrofluorometry), melting experiments (spectrophotometry), viscometric measurements, circular dichroism, and T‐jump kinetic analyses; all data concur in shedding light on the complex mechanistic aspects of the binding mode of DAPI to natural DNA. Conditions are found that induce the mode of the DAPI/DNA interaction to change from groove binding to intercalation. Moreover, it is observed, for the first time, that DAPI is able to induce the formation of a rather compact polymer–dye adduct under particular conditions. The results suggest that this form is a folded or coiled DNA structure stabilized by DAPI dye bridges.     

Is [Co(4)(H(2)O)(2)(α-PW(9)O(34))(2)](10-) a genuine molecular catalyst in photochemical water oxidation? Answers from time-resolved hole scavenging experiments

Water oxidation catalysts: evolution of [Co(4)(H(2)O)(2)(α-PW(9)O(34))(2)](10-) to catalytically active species is assessed by laser flash photolysis in sacrificial photocatalytic cycles with Ru(bpy)(3)(2+) as a photosensitizer.     

Novel cationic carotenoid lipids as delivery vectors of antisense oligonucleotides for exon skipping in Duchenne muscular dystrophy

Duchenne Muscular Dystrophy (DMD) is a common, inherited, incurable, fatal muscle wasting disease caused by deletions that disrupt the reading frame of the DMD gene such that no functional dystrophin protein is produced. Antisense oligonucleotide (AO)-directed exon skipping restores the reading frame of the DMD gene, and truncated, yet functional dystrophin protein is expressed. The aim of this study was to assess the efficiency of two novel rigid, cationic carotenoid lipids, C30-20 and C20-20, in the delivery of a phosphorodiamidate morpholino (PMO) AO, specifically designed for the targeted skipping of exon 45 of DMD mRNA in normal human skeletal muscle primary cells (hSkMCs). The cationic carotenoid lipid/PMO-AO lipoplexes yielded significant exon 45 skipping relative to a known commercial lipid, 1,2-dimyristoyl-sn-glycero-3-ethylphosphocholine (EPC).     

Dissociation mechanism of acetic acid in water

The reaction mechanism for acetic acid dissociation in aqueous solution has been investigated by combining the metadynamics method with transition path sampling (TPS). By using collective variables that describe not only the deprotonation of the acid but also the solvation state of the hydronium ion and its distance from the acetate, a reactive trajectory in which stable separated ions were produced was obtained. More transition trajectories were sampled by using the TPS technique, taking the metadynamics trajectory as the initial trajectory. Two different dissociation reaction pathways were determined, one driven by the breaking of an H-bond formed by the water molecule in contact with the hydroxyl and involving the formation of a metastable contact ion pair and the other characterized by a direct transfer of the proton to the solution through an unstable Zundel-ion-like intermediate.