Atomistic characterization of the active-site solvation dynamics of a model photocatalyst

The interactions between the reactive excited state of molecular photocatalysts and surrounding solvent dictate reaction mechanisms and pathways, but are not readily accessible to conventional optical spectroscopic techniques. Here we report an investigation of the structural and solvation dynamics following excitation of a model photocatalytic molecular system [Ir 2 (dimen) 4 ] 2+, where dimen is para-diisocyanomenthane. The time-dependent structural changes in this model photocatalyst, as well as the changes in the solvation shell structure, have been measured with ultrafast diffuse X-ray scattering and simulated with Born-Oppenheimer Molecular Dynamics. Both methods provide direct access to the solute-solvent pair distribution function, enabling the solvation dynamics around the catalytically active iridium sites to be robustly characterized. Our results provide evidence for the coordination of the iridium atoms by the acetonitrile solvent and demonstrate the viability of using diffuse X-ray scattering at free-electron laser sources for studying the dynamics of photocatalysis. © The Author(s) 201617111sciescopu

Coherent control of photofragment distributions using laser phase modulation in the weak-field limit

6 págs.; 4 figs.© 2015 American Chemical Society. The possibility of quantum interference control of the final state distributions of photodissociation fragments by means of pure phase modulation of the pump laser pulse in the weak-field regime is demonstrated theoretically for the first time. The specific application involves realistic wave packet calculations of the transient vibrational populations of the Br2(B, vf) fragment produced upon predissociation of the Ne–Br2(B) complex, which is excited to a superposition of resonance states using pulses with different linear chirps. Transient phase effects on the fragment populations are found to persist for long times (about 200 ps) after the pulse is over due to interference between overlapping resonances in Ne–Br2(B).This work was funded by the Ministerio de Ciencia e Innovacion (Spain), Grant No. FIS2011-29596-C02-01, and the COST Action, Grant No. CM1002. The Centro de Supercomputacion de Galicia (CESGA, Spain) is acknowledged for the use of its resources.Peer Reviewe

Unravelling the role of quantum interference in the weak-field laser phase modulation control of photofragment distributions

8 págs.; 6 figs.The role played by quantum interference in the laser phase modulation coherent control of photofragment distributions in the weak-field regime is investigated in detail in this work. The specific application involves realistic wave packet calculations of the transient vibrational populations of the Br(B,v) fragment produced upon predissociation of the Ne-Br(B) complex, which is excited to a superposition of overlapping resonance states using different fixed bandwidth pulses where the linear chirps are varied. The postpulse transient phase modulation effects observed on fragment populations for a long time window are explained in terms of the mechanism of interference between overlapping resonances. A detailed description of how the interference mechanism affects the magnitude and the time window of the phase control effects is also provided. In the light of the results, the conditions to maximize phase modulation control on fragment distributions are discussed. This journal is©the Owner Societies 2016This work was funded by the Ministerio de Ciencia e Innovación (Spain), Grant No. FIS2011-29596-C02-01, and COST Action program, Grant No. CM1401 and CM1405. The Centro de Supercomputación de Galicia (CESGA, Spain) is acknowledged for the use of its resources.Peer Reviewe

Passive immunity in cattle against enterotoxigenic Escherichia coli: serologic evaluation of a bacterin containing K99 and F41 fimbriae in colostrum of vaccinated females and calf serum Imunidade passiva contra Escherichia coli enterotoxigênica: avaliação sorológica de uma bacterina contendo as fímbrias K99 e F41 no colostro de fêmeas vacinadas e no soro de bezerros

A bacterin from enterotoxigenic Escherichia coli (ETEC), containing fimbriae K99 and F41, was produced and its capacity to induce anti-K99 and anti-F41 antibodies in colostrum of vaccinated cows and in calf serum, and the persistence of these antibodies in neonates were determined. Three experiments were performed on two commercial farms. In all experiments animals were allotted randomly to the blocks, each block consisting of two pregnant females (a vaccinated one and a control one) and their respective calves. In experiment A (farm 1), comprised of 18 blocks, the animals received a vaccine dose 30 days before delivery. In experiment B (farm 1), consisted of 26 blocks, the animals received two vaccine doses (60 and 30 days before delivery). In experiment C (farm 2), consisted of 22 blocks, the animals received two vaccine doses (60 and 30 days before delivery). In experiments A and B pregnant cows and heifers were used and colostrum and serum from 24- to 36-hour-old calves were collected. In experiment C, pregnant embryo-recipient heifers were used and colostrum and sera from calves at 7, 14, 28 and 42 days of age were collected. Anti-K99 and anti-F41 antibodies were detected by ELISA using purified K99 and F41 fimbrial antigens. In experiment A no difference between treated and control groups was observed for the concentration of anti-K99 and anti-F41 antibodies in colostrum and calf serum. In experiment B a difference (P<0.001) was observed for colostrum of vaccinated females and for serum of their calves. In experiment C, difference between vaccinated and control animals was observed for colostrum and calf serum at 7, 14, 28 (P<0.001 in all cases) and 42 days of age (P= 0.003). The results showed the efficiency of the bacterin to induce detectable humoral immune response.<br>Produziu-se uma bacterina de Escherichia coli enterotoxigênica (ETEC) contendo as fímbrias K99 e F41 e avaliaram-se a capacidade de indução de anticorpos anti-K99 e anti F-41 no colostro de vacas vacinadas e no soro de bezerros e a persistência dos anticorpos nos neonatos. Três experimentos foram realizados em duas fazendas comerciais. Os animais foram aleatoriamente alocados em blocos, de duas fêmeas prenhes (uma vacinada e outra controle) e seus respectivos bezerros. No experimento A (fazenda 1), com 18 blocos, os animais receberam uma dose da vacina, 30 dias antes do parto. No experimento B (fazenda 1), com 26 blocos, os animais receberam duas doses de vacina, aos 60 e 30 dias antes do parto. No experimento C (fazenda 2), com 22 blocos, os animais receberam o mesmo esquema de vacinação do experimento B. Nos experimentos A e B foram coletados colostro das parturientes e soro dos bezerros entre 24 e 36 horas de vida. No experimento C, foram usadas novilhas receptoras de embriões e coletados colostro e soro dos bezerros aos 7, 14, 28 e 42 dias de idade. Anticorpos anti-K99 e anti-F41 foram detectados por ELISA utilizando antígenos K99 e F41 purificados. No experimento A não foi observada diferença entre o grupo vacinado e o controle quanto à detecção de anticorpos. No experimento B foi observada diferença (P<0,001) entre o colostro de fêmeas vacinadas e o soro de seus bezerros. No C houve diferença entre o grupo vacinado e o controle para o colostro e o soro dos bezerros aos 7, 14, 28 (P<0,001) e 42 dias de idade (P= 0,003). A bacterina utilizada foi eficiente para a indução de resposta imune humoral detectável