keyword
MENU ▼
Read by QxMD icon Read
search

Femtosecond

keyword
https://www.readbyqxmd.com/read/28230868/tuning-calcium-biosensors-with-a-single-site-mutation-structural-dynamics-insights-from-femtosecond-raman-spectroscopy
#1
Sean R Tachibana, Longteng Tang, Yanli Wang, Liangdong Zhu, Weimin Liu, Chong Fang
Fluorescent protein biosensors are popular reporters for biological processes and life sciences, but their fundamental working mechanisms remain unclear. To characterize the functional fluorescence events on their native timescales, we implemented wavelength-tunable femtosecond stimulated Raman spectroscopy (FSRS) to shed light on a blue-green emission-ratiometric fluorescent protein based Ca(2+) biosensor with a single Pro377Arg mutation. The transient Raman modes of the embedded chromophore from ca. 1000-1650 cm(-1) exhibit characteristic intensity and frequency dynamics which infer the underlying atomic motions and photochemical reaction stages...
February 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28230358/membrane-independence-of-ultrafast-photochemistry-in-pharaonis-halorhodopsin-testing-the-role-of-bacterioruberin
#2
Itay Gdor, Maya Mani-Hazan, Noga Friedman, Mordechai Sheves, Sanford Ruhman
Ultrafast photochemistry of p-HR in the intact Natronomonas pharaonic membrane has been studied by photoselective femtosecond pump-hyperspectral probe spectroscopy with high time resolution. Two variants of this sample, one with wild type retinal prosthetic groups, and another after shifting retinal absorption deep into the blue by reducing the Schiff base linkage were studied, and compared with previous results on detergent solubilized p-HR. This comparison shows that retinal photo-isomerization dynamics are identical in the membrane and in the solubilized sample...
February 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28225007/full-3d-modelling-of-pulse-propagation-enables-efficient-nonlinear-frequency-conversion-with-low-energy-laser-pulses-in-a-single-element-tripler
#3
Tomasz M Kardaś, Michał Nejbauer, Paweł Wnuk, Bojan Resan, Czesław Radzewicz, Piotr Wasylczyk
Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus...
February 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28224790/ph-dependent-photodeprotection-of-formaldehyde-homolytic-c-c-scission-in-acidic-aqueous-solution-versus-heterolytic-c-c-scission-in-basic-aqueous-solution
#4
Mingyue Liu, Wenjian Tang, Ming-De Li, David Lee Phillips
The photodeprotection of formaldehyde was investigated for 3-(1-hydroxypropan-2-yl)benzophenone (3-HPBP) with ultrafast time-resolved spectroscopy. The femtosecond transient absorption results indicated the singlet excited state of 3-HPBP transformed efficiently into its triplet state by a fast intersystem crossing. In acidic (pH=0) and basic (pH=12.5) aqueous solutions, the triplet intermediate was a key precursor for the deprotection of formaldehyde via two different pathways. However little photodeprotection was observed in neutral (pH=7) aqueous solution where the triplet intermediate appeared to undergo a proton coupled electron transfer process to form a ketyl radical transient...
February 22, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28219079/light-induced-structural-changes-and-the-site-of-o-o-bond-formation-in-psii-caught-by-xfel
#5
Michihiro Suga, Fusamichi Akita, Michihiro Sugahara, Minoru Kubo, Yoshiki Nakajima, Takanori Nakane, Keitaro Yamashita, Yasufumi Umena, Makoto Nakabayashi, Takahiro Yamane, Takamitsu Nakano, Mamoru Suzuki, Tetsuya Masuda, Shigeyuki Inoue, Tetsunari Kimura, Takashi Nomura, Shinichiro Yonekura, Long-Jiang Yu, Tomohiro Sakamoto, Taiki Motomura, Jing-Hua Chen, Yuki Kato, Takumi Noguchi, Kensuke Tono, Yasumasa Joti, Takashi Kameshima, Takaki Hatsui, Eriko Nango, Rie Tanaka, Hisashi Naitow, Yoshinori Matsuura, Ayumi Yamashita, Masaki Yamamoto, Osamu Nureki, Makina Yabashi, Tetsuya Ishikawa, So Iwata, Jian-Ren Shen
Photosystem II (PSII) is a huge membrane-protein complex consisting of 20 different subunits with a total molecular mass of 350 kDa for a monomer. It catalyses light-driven water oxidation at its catalytic centre, the oxygen-evolving complex (OEC). The structure of PSII has been analysed at 1.9 Å resolution by synchrotron radiation X-rays, which revealed that the OEC is a Mn4CaO5 cluster organized in an asymmetric, 'distorted-chair' form. This structure was further analysed with femtosecond X-ray free electron lasers (XFEL), providing the 'radiation damage-free' structure...
February 20, 2017: Nature
https://www.readbyqxmd.com/read/28217747/insights-into-photosystem-ii-from-isomorphous-difference-fourier-maps-of-femtosecond-x-ray-diffraction-data-and-quantum-mechanics-molecular-mechanics-structural-models
#6
REVIEW
Jimin Wang, Mikhail Askerka, Gary W Brudvig, Victor S Batista
Understanding structure-function relations in photosystem II (PSII) is important for the development of biomimetic photocatalytic systems. X-ray crystallography, computational modeling, and spectroscopy have played central roles in elucidating the structure and function of PSII. Recent breakthroughs in femtosecond X-ray crystallography offer the possibility of collecting diffraction data from the X-ray free electron laser (XFEL) before radiation damage of the sample, thereby overcoming the main challenge of conventional X-ray diffraction methods...
February 10, 2017: ACS Energy Lett
https://www.readbyqxmd.com/read/28215341/dissection-and-characterization-of-microtubule-bundles-in-the-mitotic-spindle-using-femtosecond-laser-ablation
#7
R Buđa, K Vukušić, I M Tolić
The mitotic spindle is a highly organized and dynamic structure required for segregation of the genetic material into two daughter cells. Although most of the individual players involved in building the spindle have been characterized in vitro, a general understanding of how all of the spindle players act together in vivo is still missing. Hence, in recent years, experiments have focused on introducing mechanical perturbations of the spindle on a micron scale, thereby providing insight into its function and organization, as well as into forces acting in the spindle...
2017: Methods in Cell Biology
https://www.readbyqxmd.com/read/28212034/observation-of-the-global-dynamic-collectivity-of-a-hydration-shell-around-apomyoglobin
#8
Yangzhong Qin, Luyuan Zhang, Lijuan Wang, Dongping Zhong
Protein surface hydration is critical to its structural properties and biological activities. However, it is still unknown whether the hydration shell is intrinsically connected and how its fluctuations dynamically interact with protein motions. Here, by selecting five site-specific locations with distinctly different environments around apomyoglobin surface, we used a tryptophan scan with femtosecond fluorescence spectroscopy and simultaneously detected hydration-water dynamics and tryptophan sidechain relaxations with temperature dependence...
February 17, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28211728/electron-vortices-in-femtosecond-multiphoton-ionization
#9
D Pengel, S Kerbstadt, D Johannmeyer, L Englert, T Bayer, M Wollenhaupt
Multiphoton ionization of potassium atoms with a sequence of two counter-rotating circularly polarized femtosecond laser pulses produces vortex-shaped photoelectron momentum distributions in the polarization plane describing Archimedean spirals. The pulse sequences are produced by polarization shaping and the three-dimensional photoelectron distributions are tomographically reconstructed from velocity map imaging measurements. We show that perturbative ionization leads to electron vortices with c_{6} rotational symmetry...
February 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28210504/comparison-of-maximum-stretch-forces-between-femtosecond-laser-assisted-capsulotomy-and-continuous-curvilinear-capsulorhexis
#10
Mari Takagi, Takashi Kojima, Kei Ichikawa, Yoshiki Tanaka, Yukihito Kato, Rie Horai, Akeno Tamaoki, Kazuo Ichikawa
The current study reports comparing the postoperative mechanical properties of the anterior capsule between femtosecond laser capsulotomy (FLC) and continuous curvilinear capsulorhexis (CCC) of variable size and shape in porcine eyes. All CCCs were created using capsule forceps. Irregular or eccentric CCCs were also created to simulate real cataract surgery. For FLC, capsulotomies 5.3 mm in diameter were created using the LenSx® (Alcon) platform. Fresh porcine eyes were used in all experiments. The edges of the capsule openings were pulled at a constant speed using two L-shaped jigs...
2017: Journal of Ophthalmology
https://www.readbyqxmd.com/read/28210176/femtosecond-astigmatic-keratotomy-for-postkeratoplasty-astigmatism
#11
Nasser Al Sabaani, Salem Al Malki, Mohanna Al Jindan, Abdullah Al Assiri, Samar Al Swailem
PURPOSE: To evaluate the initial outcomes of femtosecond laser arcuate keratotomies (AK) to correct high astigmatism after keratoplasty. METHODS: This retrospective non-comparative interventional study included 52 consecutive patients (52 eyes) who underwent Intralase-enabled arcuate keratotomies. Changes in uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BCVA), mean refractive and keratometric astigmatism, preoperative and postoperative manifest refraction and complications were the main outcome measures...
July 2016: Saudi Journal of Ophthalmology: Official Journal of the Saudi Ophthalmological Society
https://www.readbyqxmd.com/read/28207256/can-excited-state-electronic-coherence-be-tuned-via-molecular-structural-modification-a-first-principles-quantum-electronic-dynamics-study-of-pyrazolate-bridged-pt-ii-dimers
#12
David B Lingerfelt, Patrick J Lestrange, Joseph J Radler, Samantha E Brown-Xu, Pyosang Kim, Felix N Castellano, Lin X Chen, Xiaosong Li
Materials and molecular systems exhibiting long-lived electronic coherence can facilitate coherent transport, opening the door to efficient charge and energy transport beyond traditional methods. Recently, signatures of a possible coherent, recurrent electronic motion were identified in femtosecond pump-probe spectroscopy experiments on a bi-nuclear platinum complex, where a persistent periodic beating in the transient absorption signal's anisotropy was observed. In this study, we investigate the excitonic dynamics that underlie the suspected electronic coherence for a series of bi-nuclear platinum complexes exhibiting a range of inter-platinum distances...
February 16, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28206747/ultrafast-dynamics-of-manganese-iii-manganese-ii-and-free-base-bacteriochlorin-is-there-time-for-photochemistry
#13
Fabio A Schaberle, Artur R Abreu, Nuno P F Gonçalves, Gonçalo F F Sá, Mariette M Pereira, Luís G Arnaut
Manganese(III) and manganese(II) complexes of halogenated sulfonamide tetraphenylbacteriochlorins were prepared for the first time via a transmetalation reaction and shown to be stable at room temperature. The behavior of the electronic states of the paramagnetic complexes is remarkably different from those of the metal-free bacteriochlorins or diamagnetic metallobacteriochlorins. The Mn(3+) complex exhibits eight electronic transitions between different states from 300 to 1100 nm, with a very prominent band (molar absorption coefficient of ca...
February 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28205063/excitation-energy-transfer-from-the-bacteriochlorophyll-soret-band-to-carotenoids-in-the-lh2-light-harvesting-complex-from-ectothiorhodospira-haloalkaliphila-is-negligible
#14
A P Razjivin, E P Lukashev, V O Kompanets, V S Kozlovsky, A A Ashikhmin, S V Chekalin, A A Moskalenko, V Z Paschenko
Pathways of intramolecular conversion and intermolecular electronic excitation energy transfer (EET) in the photosynthetic apparatus of purple bacteria remain subject to debate. Here we experimentally tested the possibility of EET from the bacteriochlorophyll (BChl) Soret band to the singlet S2 level of carotenoids using femtosecond pump-probe measurements and steady-state fluorescence excitation and absorption measurements in the near-ultraviolet and visible spectral ranges. The efficiency of EET from the Soret band of BChl to S2 of the carotenoids in light-harvesting complex LH2 from the purple bacterium Ectothiorhodospira haloalkaliphila appeared not to exceed a few percent...
February 16, 2017: Photosynthesis Research
https://www.readbyqxmd.com/read/28203055/resident-surgeon-efficiency-in-femtosecond-laser-assisted-cataract-surgery
#15
Andrew C Pittner, Brian R Sullivan
PURPOSE: Comparison of resident surgeon performance efficiencies in femtosecond laser-assisted cataract surgery (FLACS) versus conventional phacoemulsification. PATIENTS AND METHODS: A retrospective cohort study was conducted on consecutive patients undergoing phacoemulsification cataract surgery performed by senior ophthalmology residents under the supervision of 1 attending physician during a 9-month period in a large Veterans Affairs medical center. Medical records were reviewed for demographic information, preoperative nucleus grade, femtosecond laser pretreatment, operative procedure times, total operating room times, and surgical complications...
2017: Clinical Ophthalmology
https://www.readbyqxmd.com/read/28202732/atomic-structure-of-granulin-determined-from-native-nanocrystalline-granulovirus-using-an-x-ray-free-electron-laser
#16
Cornelius Gati, Dominik Oberthuer, Oleksandr Yefanov, Richard D Bunker, Francesco Stellato, Elaine Chiu, Shin-Mei Yeh, Andrew Aquila, Shibom Basu, Richard Bean, Kenneth R Beyerlein, Sabine Botha, Sébastien Boutet, Daniel P DePonte, R Bruce Doak, Raimund Fromme, Lorenzo Galli, Ingo Grotjohann, Daniel R James, Christopher Kupitz, Lukas Lomb, Marc Messerschmidt, Karol Nass, Kimberly Rendek, Robert L Shoeman, Dingjie Wang, Uwe Weierstall, Thomas A White, Garth J Williams, Nadia A Zatsepin, Petra Fromme, John C H Spence, Kenneth N Goldie, Johannes A Jehle, Peter Metcalf, Anton Barty, Henry N Chapman
To understand how molecules function in biological systems, new methods are required to obtain atomic resolution structures from biological material under physiological conditions. Intense femtosecond-duration pulses from X-ray free-electron lasers (XFELs) can outrun most damage processes, vastly increasing the tolerable dose before the specimen is destroyed. This in turn allows structure determination from crystals much smaller and more radiation sensitive than previously considered possible, allowing data collection from room temperature structures and avoiding structural changes due to cooling...
February 15, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28201910/mode-specific-excited-state-dynamics-study-of-bis-phenylethynyl-benzene-from-ultrafast-raman-loss-spectroscopy
#17
Khokan Roy, Surajit Kayal, Freek Ariese, Andrew Beeby, Siva Umapathy
Femtosecond transient absorption (fs-TA) and Ultrafast Raman Loss Spectroscopy (URLS) have been applied to reveal the excited state dynamics of bis(phenylethynyl)benzene (BPEB), a model system for one-dimensional molecular wires that have numerous applications in opto-electronics. It is known from the literature that in the ground state BPEB has a low torsional barrier, resulting in a mixed population of rotamers in solution at room temperature. For the excited state this torsional barrier had been calculated to be much higher...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28198887/femtosecond-two-photon-planar-laser-induced-fluorescence-of-carbon-monoxide-in-flames
#18
Daniel R Richardson, Sukesh Roy, James R Gord
Two-photon, planar laser-induced fluorescence (TP-PLIF) of carbon monoxide was performed in steady and driven flames using femtosecond (fs) laser pulses at 1 kHz. Excitation radiation at 230.1 nm (full-width at half-maximum bandwidth of 270  cm<sup>-1</sup>) was used to pump many rovibrational two-photon transitions in the B<sup>1</sup>∑<sup>+</sup>←X<sup>1</sup>∑<sup>+</sup> system. Visible fluorescence in the range 362-516 nm was captured using an image intensifier and high-speed camera...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198871/generating-high-contrast-near-single-cycle-waveforms-with-third-order-dispersion-compensation
#19
Henry Timmers, Yuki Kobayashi, Kristina F Chang, Maurizio Reduzzi, Daniel M Neumark, Stephen R Leone
Femtosecond laser pulses lasting only a few optical periods hold the potential for probing and manipulating the electronic degrees of freedom within matter. However, the generation of high-contrast, few-cycle pulses in the high power limit still remains nontrivial. In this Letter, we present the application of ammonium dihydrogen phosphate (ADP) as an optical medium for compensating for the higher-order dispersion of a carrier-envelope stable few-cycle waveform centered at 735 nm. The ADP crystal is capable of removing the residual third-order dispersion present in the spectral phase of an input pulse, resulting in near-transform-limited 2...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198846/femtosecond-two-photon-laser-induced-fluorescence-of-krypton-for-high-speed-flow-imaging
#20
Yejun Wang, Cade Capps, Waruna D Kulatilaka
Ultrashort-pulse (femtosecond-duration) two-photon laser-induced fluorescence (fs-TPLIF) of an inert gas tracer krypton (Kr) is investigated. A detailed spectroscopic study of fluorescence channels followed by the 5p<sup>'</sup>←←4p excitation of Kr at 204.1 nm is reported. The experimental line positions in the 750-840 nm emission region agree well with the NIST Atomic Spectra Database. The present work provides an accurate listing of relative line strengths in this spectral region. In the range of laser pulse energies investigated, a quadratic dependence was observed between the Kr-TPLIF signal and the laser pulse energy...
February 15, 2017: Optics Letters
keyword
keyword
16590
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"