Chasing charge localization and chemical reactivity following photoionization in liquid water

The ultrafast dynamics of the cationic hole formed in bulk liquid water following ionization is investigated by ab initio molecular dynamics simulations and an experimentally accessible signature is suggested that might be tracked by femtosecond pump-probe spectroscopy. This is one of the fastest fundamental processes occurring in radiation-induced chemistry in aqueous systems and biological tissue. However, unlike the excess electron formed in the same process, the nature and time evolution of the cationic hole has been hitherto little studied. Simulations show that an initially partially delocalized cationic hole localizes within ~30 fs after which proton transfer to a neighboring water molecule proceeds practically immediately, leading to the formation of the OH radical and the hydronium cation in a reaction which can be formally written as H(2)O(+) + H(2)O → OH + H(3)O(+). The exact amount of initial spin delocalization is, however, somewhat method dependent, being realistically described by approximate density functional theory methods corrected for the self-interaction error. Localization, and then the evolving separation of spin and charge, changes the electronic structure of the radical center. This is manifested in the spectrum of electronic excitations which is calculated for the ensemble of ab initio molecular dynamics trajectories using a quantum mechanics/molecular mechanics (QM∕MM) formalism applying the equation of motion coupled-clusters method to the radical core. A clear spectroscopic signature is predicted by the theoretical model: as the hole transforms into a hydroxyl radical, a transient electronic absorption in the visible shifts to the blue, growing toward the near ultraviolet. Experimental evidence for this primary radiation-induced process is sought using femtosecond photoionization of liquid water excited with two photons at 11 eV. Transient absorption measurements carried out with ~40 fs time resolution and broadband spectral probing across the near-UV and visible are presented and direct comparisons with the theoretical simulations are made. Within the sensitivity and time resolution of the current measurement, a matching spectral signature is not detected. This result is used to place an upper limit on the absorption strength and/or lifetime of the localized H(2)O(+) ((aq)) species.     

Multireference state-specific Mukherjee's coupled cluster method with noniterative triexcitations using uncoupled approximation

A new version of the multireference Mukherjee's coupled cluster method with perturbative triexcitations has been formulated, which is based on the uncoupled approximation applied to the triples equation. In contrast to the method developed by Evangelista et al. [J. Chem. Phys. 132, 074107 (2010)], the proposed approach does not require to solve the equation for T(3) amplitudes iteratively, yet yields results of essentially the same quality. The method, abbreviated as MR MkCCSD(Tu), has been implemented in the ACES II program package and its assessment has been performed on the BeH(2) model and on the tetramethyleneethane molecule.     

Wavelets from Laguerre Polynomials and Toeplitz-Type Operators

We study a parameterized family of Toeplitz-type operators with respect to specific wavelets whose Fourier transforms are related to Laguerre polynomials. On the one hand, this choice of wavelets underlines the fact that these operators acting on wavelet subspaces share many properties with the classical Toeplitz operators acting on the Bergman spaces. On the other hand, it enables to study poly-Bergman spaces and Toeplitz operators acting on them from a different perspective. Restricting to symbols depending only on vertical variable in the upper half-plane of the complex plane these operators are unitarily equivalent to a multiplication operator with a certain function. Since this function is responsible for many interesting features of these Toeplitz-type operators and their algebras, we investigate its behavior in more detail. As a by-product we obtain an interesting observation about the asymptotic behavior of true poly-analytic Bergman spaces. Isomorphisms between the Calderón-Toeplitz operator algebras and functional algebras are described and their consequences in time-frequency analysis and applications are discussed.     

A New Approach how to Define the Coefficient of Electroactivity of Adenine and Its Twelve Derivatives Using Flow Injection Analysis with Amperometric Detection

We studied the electrochemical behaviour of adenine derivates (adenosine, 2‐aminopurine, 2,6‐diaminopurine, 6‐benzyl‐aminopurine, adenosine monophosphate, cyclic adenosine monophosphate, nicotinamide adenine dinucleotide, adenosine triphosphate, S‐adenosyl‐L ‐methionine, and synthetic derivatives AD‐3, AD‐6 and AD‐9) using flow injection analysis with electrochemical detection using a glassy carbon electrode. The influences of pH, flow rate and potential on the signal height of the studied derivates were tested. The optimal pH was 3, the flow rate of the mobile phase 0.75 mL min^?1 and the potential 1100 mV. Further, we attempted to characterize each of the studied derivatives by mathematical equations and classic analytical parameters. The lowest detection limit was estimated for adenine as 0.9 nM and 2‐aminopurine as 0.5 nM.     

Synthesis of both enantiomers of the docosahexaenoic acid ester of 13-hydroxyoctadecadienoic acid (13-DHAHLA)

Recently, several different classes of endogenous lipids have been reported that display antidiabetic and anti-inflammatory effects. Due to their minute presence in human samples, access to synthetic material of each enantiomer becomes necessary for exact structural elucidation and extensive biological evaluation. Herein we report the multi-milligram synthesis of both enantiomers of the docosahexaenoic acid ester of 13-hydroxyoctadecadienoic acid (13-DHAHLA) from commercially available starting materials.     

Targeting a Large Active Site: Structure-Based Design of Nanomolar Inhibitors of Trypanosoma brucei Trypanothione Reductase

Trypanothione reductase (TR) plays a key role in the unique redox metabolism of trypanosomatids, the causative agents of human African trypanosomiasis (HAT), Chagas’ disease, and leishmaniases. Introduction of a new, lean propargylic vector to a known class of TR inhibitors resulted in the strongest reported competitive inhibitor of Trypanosoma (T.) brucei TR, with an inhibition constant K_i of 73 nm , which is fully selective against human glutathione reductase (hGR). The best ligands exhibited in vitro IC₅₀ values (half-maximal inhibitory concentration) against the HAT pathogen, T. brucei rhodesiense, in the mid-nanomolar range, reaching down to 50 nm. X-Ray co-crystal structures confirmed the binding mode of the ligands and revealed the presence of a HEPES buffer molecule in the large active site. Extension of the propargylic vector, guided by structure-based design, to replace the HEPES buffer molecule should give inhibitors with low nanomolar K_i and IC₅₀ values for in vivo studies.     

Cooperation of customers in traveling salesman problems with profits

Optimization Letters - In the profitable tour problem, the carrier decides whether to visit a particular customer with respect to the prize the customer offers for being visited and traveling cost...     

Study of water in Ca-montmorillonite by thermal analysis and positron annihilation lifetime spectroscopy

Journal of Thermal Analysis and Calorimetry - The aim of this study is to characterize adsorbed liquid in montmorillonite structure for different levels of adsorption by both thermoanalytical and...     

Use of green fluorescent proteins for in vitro biosensing

Due to the considerable stability of green fluorescent proteins and their capacity to be readily permutated or mutated, they may be exploited in multiple ways to enhance the functionality of in vitro biosensors. Many possibilities, such as the formation of chimeras with other proteins or antibodies, as well as Förster resonance emission transfer performance, may be used for the highly sensitive and specific detection of the target molecules. This review considers the great potential of green fluorescent proteins as the fluorescent probing or recognition biomolecule in various in vitro biosensors applications, as well as obstacles associated with their use.     

Preparation and biodistribution of <Superscript>59</Superscript>Fe-radiolabelled iron oxide nanoparticles

We report on the ⁵⁹Fe radiolabelling of iron oxide nanoparticle cores through post-synthetic isotope exchange (⁵⁹Fe-IONP_ex) and precursor labelling (⁵⁹Fe-IONP_pre). Scanning electron microscopy and dynamic light scattering measurements showed no impact of radiolabelling on nanoparticle size or morphology. While incorporation efficiencies of these methods are comparable—83 and 90% for precursor labelling and post-synthetic isotope exchange, respectively—⁵⁹Fe-IONP_pre exhibited much higher radiochemical stability in citrated human plasma. Quantitative ex vivo biodistribution study of ⁵⁹Fe-IONP_pre coated with triethylene glycol was performed in Wistar rats. Following the intravenous administration, high ⁵⁹Fe concentration was observed in the lung and the organs of the reticuloendothelial system such as the liver, the spleen and the femur.