The Experts below are selected from a list of 26757 Experts worldwide ranked by ideXlab platform
Steven G Boxer - One of the best experts on this subject based on the ideXlab platform.
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mechanism and bottlenecks in strand Photodissociation of split green fluorescent proteins gfps
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Chiyun Lin, Johan H Both, Steven G BoxerAbstract:Split GFPs have been widely applied for monitoring protein-protein interactions by expressing GFPs as two or more constituent parts linked to separate proteins that only fluoresce on complementing with one another. Although this complementation is typically irreversible, it has been shown previously that light accelerates dissociation of a noncovalently attached β-strand from a circularly permuted split GFP, allowing the interaction to be reversible. Reversible complementation is desirable, but Photodissociation has too low of an efficiency (quantum yield <1%) to be useful as an optogenetic tool. Understanding the physical origins of this low efficiency can provide strategies to improve it. We elucidated the mechanism of strand Photodissociation by measuring the dependence of its rate on light intensity and point mutations. The results show that strand Photodissociation is a two-step process involving light-activated cis-trans isomerization of the chromophore followed by light-independent strand dissociation. The dependence of the rate on temperature was then used to establish a potential energy surface (PES) diagram along the Photodissociation reaction coordinate. The resulting energetics-function model reveals the rate-limiting process to be the transition from the electronic excited-state to the ground-state PES accompanying cis-trans isomerization. Comparisons between split GFPs and other photosensory proteins, like photoactive yellow protein and rhodopsin, provide potential strategies for improving the Photodissociation quantum yield.
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mechanism and bottlenecks in strand Photodissociation of split green fluorescent proteins gfps
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Johan H Both, Keunbong Do, Steven G BoxerAbstract:Split GFPs have been widely applied for monitoring protein–protein interactions by expressing GFPs as two or more constituent parts linked to separate proteins that only fluoresce on complementing with one another. Although this complementation is typically irreversible, it has been shown previously that light accelerates dissociation of a noncovalently attached β-strand from a circularly permuted split GFP, allowing the interaction to be reversible. Reversible complementation is desirable, but Photodissociation has too low of an efficiency (quantum yield cis-trans isomerization of the chromophore followed by light-independent strand dissociation. The dependence of the rate on temperature was then used to establish a potential energy surface (PES) diagram along the Photodissociation reaction coordinate. The resulting energetics–function model reveals the rate-limiting process to be the transition from the electronic excited-state to the ground-state PES accompanying cis-trans isomerization. Comparisons between split GFPs and other photosensory proteins, like photoactive yellow protein and rhodopsin, provide potential strategies for improving the Photodissociation quantum yield.
Johan H Both - One of the best experts on this subject based on the ideXlab platform.
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mechanism and bottlenecks in strand Photodissociation of split green fluorescent proteins gfps
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Chiyun Lin, Johan H Both, Steven G BoxerAbstract:Split GFPs have been widely applied for monitoring protein-protein interactions by expressing GFPs as two or more constituent parts linked to separate proteins that only fluoresce on complementing with one another. Although this complementation is typically irreversible, it has been shown previously that light accelerates dissociation of a noncovalently attached β-strand from a circularly permuted split GFP, allowing the interaction to be reversible. Reversible complementation is desirable, but Photodissociation has too low of an efficiency (quantum yield <1%) to be useful as an optogenetic tool. Understanding the physical origins of this low efficiency can provide strategies to improve it. We elucidated the mechanism of strand Photodissociation by measuring the dependence of its rate on light intensity and point mutations. The results show that strand Photodissociation is a two-step process involving light-activated cis-trans isomerization of the chromophore followed by light-independent strand dissociation. The dependence of the rate on temperature was then used to establish a potential energy surface (PES) diagram along the Photodissociation reaction coordinate. The resulting energetics-function model reveals the rate-limiting process to be the transition from the electronic excited-state to the ground-state PES accompanying cis-trans isomerization. Comparisons between split GFPs and other photosensory proteins, like photoactive yellow protein and rhodopsin, provide potential strategies for improving the Photodissociation quantum yield.
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mechanism and bottlenecks in strand Photodissociation of split green fluorescent proteins gfps
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Johan H Both, Keunbong Do, Steven G BoxerAbstract:Split GFPs have been widely applied for monitoring protein–protein interactions by expressing GFPs as two or more constituent parts linked to separate proteins that only fluoresce on complementing with one another. Although this complementation is typically irreversible, it has been shown previously that light accelerates dissociation of a noncovalently attached β-strand from a circularly permuted split GFP, allowing the interaction to be reversible. Reversible complementation is desirable, but Photodissociation has too low of an efficiency (quantum yield cis-trans isomerization of the chromophore followed by light-independent strand dissociation. The dependence of the rate on temperature was then used to establish a potential energy surface (PES) diagram along the Photodissociation reaction coordinate. The resulting energetics–function model reveals the rate-limiting process to be the transition from the electronic excited-state to the ground-state PES accompanying cis-trans isomerization. Comparisons between split GFPs and other photosensory proteins, like photoactive yellow protein and rhodopsin, provide potential strategies for improving the Photodissociation quantum yield.
Jennifer S Brodbelt - One of the best experts on this subject based on the ideXlab platform.
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Photodissociation mass spectrometry new tools for characterization of biological molecules
Chemical Society Reviews, 2014Co-Authors: Jennifer S BrodbeltAbstract:Photodissociation mass spectrometry combines the ability to activate and fragment ions using photons with the sensitive detection of the resulting product ions by mass spectrometry. This combination affords a versatile tool for characterization of biological molecules. The scope and breadth of Photodissociation mass spectrometry have increased substantially over the past decade as new research groups have entered the field and developed a number of innovative applications that illustrate the ability of Photodissociation to produce rich fragmentation patterns, to cleave bonds selectively, and to target specific molecules based on incorporation of chromophores. This review focuses on many of the key developments in Photodissociation mass spectrometry over the past decade with a particular emphasis on its applications to biological molecules.
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Ultrafast Ultraviolet Photodissociation at 193 nm and its Applicability to Proteomic Workflows
Journal of proteome research, 2010Co-Authors: James A. Madsen, Daniel R. Boutz, Jennifer S BrodbeltAbstract:Ultraviolet Photodissociation (UVPD) at 193 nm was implemented on a linear ion trap mass spectrometer for high-throughput proteomic workflows. Upon irradiation by a single 5 ns laser pulse, efficient Photodissociation of tryptic peptides was achieved with production of a, b, c, x, y, and z sequence ions, in addition to immonium ions and v and w side-chain loss ions. The factors that influence the UVPD mass spectra and subsequent in silico database searching via SEQUEST were evaluated. Peptide sequence aromaticity and the precursor charge state were found to influence Photodissociation efficiency more so than the number of amide chromophores, and the ion trap q-value and number of laser pulses significantly affected the number and abundances of diagnostic product ions (e.g., sequence and immonium ions). Also, photoionization background subtraction was shown to dramatically improve SEQUEST results, especially when peptide signals were low. A liquid chromatography−mass spectrometry (LC−MS)/UVPD strategy was ...
Simon W North - One of the best experts on this subject based on the ideXlab platform.
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two component molecular tagging velocimetry utilizing no fluorescence lifetime and no2 Photodissociation techniques in an underexpanded jet flowfield
Applied Optics, 2009Co-Authors: Andrea G Hsu, Ravi Srinivasan, Rodney D W Bowersox, Simon W NorthAbstract:We report the application of molecular tagging velocimetry (MTV) toward two-component velocimetry as demonstrated in an underexpanded free jet flowfield. Two variants of the MTV technique are presented: 1) electronic excitation of seeded nitric oxide (NO) with gated fluorescence imaging (fluorescence lifetime) and 2) Photodissociation of seeded NO2 followed by NO fluorescence imaging (NO2 Photodissociation). The seeded NO fluorescence lifetime technique is advantageous in low-quenching, high-velocity flowfields, while the Photodissociation technique is useful in high-quenching environments, and either high- or low-velocity flowfields due to long lifetime of the NO photoproduct. Both techniques are viable for single-shot measurements, with determined root mean squared results for streamwise and radial velocities of approximately 5%. This study represents the first known application of MTV utilizing either the fluorescence lifetime or the Photodissociation technique toward two-component velocity mapping in a gaseous flowfield. Methods for increasing the spatial resolution to be comparable to particle-based tracking techniques are discussed.
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two component molecular tagging velocimetry utilizing no fluorescence lifetime and no 2 Photodissociation techniques in an underexpanded jet flowfield
Applied Optics, 2009Co-Authors: Andrea G Hsu, Ravi Srinivasan, Rodney D W Bowersox, Simon W NorthAbstract:We report the application of molecular tagging velocimetry (MTV) toward two-component velocimetry as demonstrated in an underexpanded free jet flowfield. Two variants of the MTV technique are presented: 1) electronic excitation of seeded nitric oxide (NO) with gated fluorescence imaging (fluorescence lifetime) and 2) Photodissociation of seeded NO2 followed by NO fluorescence imaging (NO2 Photodissociation). The seeded NO fluorescence lifetime technique is advantageous in low-quenching, high-velocity flowfields, while the Photodissociation technique is useful in high-quenching environments, and either high- or low-velocity flowfields due to long lifetime of the NO photoproduct. Both techniques are viable for single-shot measurements, with determined root mean squared results for streamwise and radial velocities of ~5%. This study represents the first known application of MTV utilizing either the fluorescence lifetime or the Photodissociation technique toward two-component velocity mapping in a gaseous flowfield. Methods for increasing the spatial resolution to be comparable to particle-based tracking techniques are discussed.
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treatment of the k quantum number in unimolecular reaction theory insights from product correlations
Journal of the American Chemical Society, 2002Co-Authors: Sean W Mcgivern, Simon W NorthAbstract:The connection between the K-quantum number and product correlations in the barrierless unimolecular dissociation of symmetric-top molecules is explored to establish a qualitative diagnostic for the treatment of the K-rotor dynamics in unimolecular reaction theory. We find that fragment scalar and vector correlations can provide guidance in this matter, and the Photodissociation dynamics of thermal NCNO to form CN and NO at several dissociation wavelengths are presented to demonstrate the utility of this approach. The "goodness" of the K-quantum number can be related to the amount of energy in the conserved vibrational modes at the inner transition state. On the basis of measured correlated vibrational distributions, the K-quantum number is found to be approximately conserved at the inner transition state for the Photodissociation of NCNO at 514, 520, and 526 nm. The methodology, involving a comparison of product distributions from the Photodissociation of jet and thermal ensembles at identical wavelengths, is general and may be applied to previously studied systems that dissociate along barrierless potential energy surfaces, CF(3)NO and CH(2)CO. In addition, vector correlations serve as a means to probe the K-mixing at the outer transition state, and measured v-j correlations in the Photodissociation of thermal NCNO are presented.
Weihai Fang - One of the best experts on this subject based on the ideXlab platform.
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spin orbit ab initio investigation of the Photodissociation of dibromomethane in the gas and solution phases
Journal of Computational Chemistry, 2008Co-Authors: Hongyan Xiao, Weihai FangAbstract:A clear and reliable theoretical investigation on dibromomethane (CHBr,) Photodissociation is desired. The calculation must consider: (i) relativistic effects; (ii) the potential energy curves (PECs) of spin-orbit coupling states; (iii) geometry optimization by the method with both static and dynamic electron correlations; (iv) solvent effects oil the Photodissociation in the solution. All these have been considered in this study by state-of-the-art quantum chemical calculations. The experimentally observed Photodissociation in the gas phase with products of spin-orbit-coupled states, Br(P-2(3/2)) and Br*(P-2(1/2)), was assigned by multi-state second order multiconfigurational perturbation theory in conjunction with spin-orbit interaction through complete active space state interaction (MS-CASPT2/CASSI-SO) PECs. The mechanisms of the experimentally observed Photodissociation and photoisomerization in solvent were elucidated by the MS-CASPT2/CASSI-SO method combined with polarized continuum model of the solvent. (C) 2008 Wiley Periodicals, Inc. J Comput Chem 29: 2513-2519, 2008
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spin orbit ab initio investigation of the ultraviolet photolysis of diiodomethane
ChemPhysChem, 2007Co-Authors: Luca De Vico, Roland Lindh, Weihai FangAbstract:The UV Photodissociation (<5 eV) of diiodomethane (CH(2)l(2)) is investigated by spin-orbit ab inito calculations. The experimentally observed Photodissociation channels in the gas and condensed phases are clearly assigned by multi-state second-order multiconfigurational perturbation theory in conjunction with spin-orbit interaction through complete active space-state interaction potential energy curves. The calculated results indicate that the fast dissociations of the first two singlet states of CH(2)l(2) and CH(2)l-l lead to geminate-radical products, CH(2)l(+) +l(P-2(3/2)) or CH(2)l(+) + l*(P-2(1/2)). The recombination process from CH(2)l-l to CH(2)l(2) is explained by an isomerazation process and a secondary Photodissociation reaction of CH(2)l-l. Finally, the study reveals that spin-orbits effects are sifnificant in the quantitative analysis of the electronic spectrum of the CH(2)l-l species.
