12 research outputs found
Three-dimensional view of ultrafast dynamics in photoexcited bacteriorhodopsin in the multiphoton regime and biological relevance
How does chemistry scale in complexity to unerringly direct biological functions? Nass Kovacs et al. have shown that bacteriorhodopsin undergoes structural changes tantalizingly similar to the expected pathway even under excessive excitation. Is the protein structure so highly evolved that it directs all deposited energy into the designed function
Direct observation of nuclear reorganization driven by ultrafast spin transitions
One of the most basic molecular photophysical processes is that of spin transitions and intersystem crossing between excited states surfaces. The change in spin states affects the spatial distribution of electron density through the spin orbit coupling interaction. The subsequent nuclear reorganization reports on the full extent of the spin induced change in electron distribution, which can be treated similarly to intramolecular charge transfer with effective reaction coordinates depicting the spin transition. Here, single-crystal [FeII(bpy)3] (PF6)2, a prototypical system for spin crossover (SCO) dynamics, is studied using ultrafast electron diffraction in the single-photon excitation regime. The photoinduced SCO dynamics are resolved, revealing two distinct processes with a (450 ± 20)-fs fast component and a (2.4 ± 0.4)-ps slow component. Using principal component analysis, we uncover the key structural modes, ultrafast Fe–N bond elongations coupled with ligand motions, that define the effective reaction coordinate to fully capture the relevant molecular reorganization
The impact of oral health conditions, socioeconomic status and use of specific substances on quality of life of addicted persons
Comparação entre Ãndices de vegetação obtidos por imagens aéreas com veÃculo aéreo não tripulado (VANT) e satélite.
O sensoriamento remoto (SR), amplamente utilizado em diferentes áreas do conhecimento, também pode ser aplicado para o manejo de sistemas agropecuários. Entre as diferentes técnicas aplicadas sobre os produtos de SR, pode se destacar o uso de Ãndices de vegetação, que buscam relacionar variações do comportamento espectral medido através de imagens com diferentes parâmetros biofÃsicos das plantas. E a qualidade dos produtos resultantes depende diretamente da precisão das imagens utilizadas. Nesse sentido, este trabalho teve como objetivo comparar os Ãndices de vegetação obtidos a partir de imagens de satélite e através de veÃculo aéreo não tripulado (VANT) em uma área de pastagem irrigada. Foram utilizadas imagens do satélite Landsat-8 e fotografias obtidas com câmeras acopladas em VANT (modelo convencional RGB e adaptada NGB, com bandas no visÃvel e infravermelho próximo). Para as duas fontes de dados, foram calculados os seguintes Ãndices: NDVI, o Ãndice clássico no monitoramento da vegetação; o MPRI, que é correlato ao NDVI, porém se utiliza somente das bandas do espectro visÃvel; o NDVI adaptado à câmeras digitais RGB e; o ENDVI, um aprimoramento do NDVI proposto para otimizar o uso de câmeras RGB. Os Ãndices obtidos pelas duas fontes foram então correlacionados. A fim de tornar a comparação com imagens Landsat-8 mais adequada, os valores digitais das imagens de VANT foram convertidos para valores de reflectância. Os resultados mostraram uma correlação positiva intermediária dos Ãndices NDVI e ENDVI obtidos a partir das imagens de satélite e VANT, que pode ter sido afetada tanto pela diferença de escala das imagens quanto pela variação temporal nas datas de aquisição de ambos os produtos. Evidenciou-se também a necessidade de calibração dos dados das imagens tomadas com VANTs, para garantir que a conversão para reflectância seja mais adequada. De modo geral, os Ãndices estudados mostraram-se sensÃveis para indicar as variações na área estudada e confirmaram que podem ser ferramentas de agricultura de precisão, auxiliando no planejamento do manejo das pastagens com a aplicação da Agricultura de Precisão
Photoreversible Ultrafast Dynamics of Ring Opening and Increased Conjugation under Spatial Confinement
Isomerization through stereochemical changes and modulation in bond order conjugation are processes that occur ubiquitously in diverse chemical systems and for pho-
tochromic spirocompounds, it imparts them their functionality as phototransformable molecules. However, these transformations have been notoriously challenging to observe in crystals due to steric hindrance but are necessary ingredients for the development of reversible spiro-based crystalline devices. Here we report the detection of spectroscopic signatures of merocyanine due to photoisomerization within thin films of crystalline spiropyran following 266 nm excitation. Our femtosecond spectroscopy experiments reveal bond breaking, isomerization, and increase in bond order conjugation
to form merocyanine on a time scale of < 2 ps. They further unveil a lifetime of several picoseconds of this photoproduct, implying that the system is highly reversible in the solid state. Preliminary femtosecond electron diffraction studies suggest that lattice strain favors the return of photoproduct back to the closed spiroform. Our work thus paves the way for spiropyran-derived compounds for ultrafast studies and applications
Capturing Functionally Relevant Protein Motions at the Atomic Level: Femtosecond Time Resolved Serial Crystallography of Ligand Dissociation of Carboxy-Myoglobin
The recent advent of X-Ray free electron lasers with highest brilliance and femtosecond pulses opens new possibilities for time-resolved protein crystallography [Miller, R.J.D, Science, 2014, 343, 1108-1116]. A fundamental biophysical question becomes accessible experimentally now: The investigation of protein dynamics with all atomic resolution on the shortest biochemically relevant timescale around 100 fs. Here is where bond-breaking events occur, which in turn translate into secondary and tertiary structure changes and cause a protein to fulfill its function over a wide range of timescales
Fixed-target serial oscillation crystallography at room temperature
A fixed-target approach to high-throughput room-temperature serial synchrotron crystallography with oscillation is described. Patterned silicon chips with microwells provide high crystal-loading density with an extremely high hit rate. The microfocus, undulator-fed beamline at CHESS, which has compound refractive optics and a fast-framing detector, was built and optimized for this experiment. The high-throughput oscillation method described here collects 1–5° of data per crystal at room temperature with fast (10° s−1) oscillation rates and translation times, giving a crystal-data collection rate of 2.5 Hz. Partial datasets collected by the oscillation method at a storage-ring source provide more complete data per crystal than still images, dramatically lowering the total number of crystals needed for a complete dataset suitable for structure solution and refinement – up to two orders of magnitude fewer being required. Thus, this method is particularly well suited to instances where crystal quantities are low. It is demonstrated, through comparison of first and last oscillation images of two systems, that dose and the effects of radiation damage can be minimized through fast rotation and low angular sweeps for each crystal
Fixed target combined with spectral mapping: approaching 100% hit rates for serial crystallography
The advent of ultrafast highly brilliant coherent X-ray free-electron laser sources has driven the development of novel structure-determination approaches for proteins, and promises visualization of protein dynamics on sub-picosecond timescales with full atomic resolution. Significant efforts are being applied to the development of sample-delivery systems that allow these unique sources to be most efficiently exploited for high-throughput serial femtosecond crystallography. Here, the next iteration of a fixed-target crystallography chip designed for rapid and reliable delivery of up to 11 259 protein crystals with high spatial precision is presented. An experimental scheme for predetermining the positions of crystals in the chip by means of in situ spectroscopy using a fiducial system for rapid, precise alignment and registration of the crystal positions is presented. This delivers unprecedented performance in serial crystallography experiments at room temperature under atmospheric pressure, giving a raw hit rate approaching 100% with an effective indexing rate of approximately 50%, increasing the efficiency of beam usage and allowing the method to be applied to systems where the number of crystals is limited
Fixed target combined with spectral mapping: approaching 100% hit rates for serial crystallography
The advent of ultrafast highly brilliant coherent X-ray free-electron laser sources has driven the development of novel structure-determination approaches for proteins, and promises visualization of protein dynamics on sub-picosecond timescales with full atomic resolution. Significant efforts are being applied to the development of sample-delivery systems that allow these unique sources to be most efficiently exploited for high-throughput serial femtosecond crystallography. Here, the next iteration of a fixed-target crystallography chip designed for rapid and reliable delivery of up to 11 259 protein crystals with high spatial precision is presented. An experimental scheme for predetermining the positions of crystals in the chip by means of in situ spectroscopy using a fiducial system for rapid, precise alignment and registration of the crystal positions is presented. This delivers unprecedented performance in serial crystallography experiments at room temperature under atmospheric pressure, giving a raw hit rate approaching 100% with an effective indexing rate of approximately 50%, increasing the efficiency of beam usage and allowing the method to be applied to systems where the number of crystals is limited
Serial femtosecond and serial synchrotron crystallography yield data of equivalent quality: a systematic comparison
For the two proteins myoglobin (MB) and fluoroacetate dehalogenase (FAcD), we present a systematic comparison of crystallographic diffraction data collected by serial femtosecond (SFX) and serial synchrotron crystallography (SSX). To maximize comparability, we used the same batch of crystals, the same sample delivery device, as well as the same data analysis software. Overall figures of merit indicate that the data of both radiation sources are of equivalent quality. For both proteins reasonable data statistics can be obtained with approximately 5000 room temperature diffraction images irrespective of the radiation source. The direct comparability of SSX and SFX data indicates that diffraction quality is rather linked to the properties of the crystals than to the radiation source. Time-resolved experiments can therefore be conducted at the source that best matches the desired time-resolution