51
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Tang L, Liu W, Wang Y, Zhu L, Han F, Fang C. Ultrafast Structural Evolution and Chromophore Inhomogeneity inside a Green-Fluorescent-Protein-Based Ca(2+) Biosensor. J Phys Chem Lett 2016; 7:1225-30. [PMID: 26982256 DOI: 10.1021/acs.jpclett.6b00236] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Understanding excited-state structural dynamics of fluorescent-protein-based biosensors for Ca(2+) imaging is crucial for developing new in vivo Ca(2+) indicators and advancing bioimaging. We implemented wavelength-tunable femtosecond stimulated Raman spectroscopy (FSRS) with a 530 nm Raman pump to uncover the working mechanism of an intensiometric fluorescent-protein biosensor, G-GECO1.1, highlighting the deprotonation process of its embedded chromophore. Besides confirming the dynamic difference of excited-state proton transfer (ESPT) in the Ca(2+)-free/bound protein, we revealed a chromophore two-ring twisting process with time constants of 36/60 ps that competes with ESPT. In contrast with FSRS data collected using the 800 nm Raman pump, the bluer Raman pump enables us to access a subset of reactant population with partially deprotonated character that exhibits an additional ESPT component on the ∼5 ps time scale. These findings provide deep mechanistic insights into the inhomogeneity and subpopulation-specific conformational dynamics of biosensor chromophores, which will guide the rational design of improved biosensors for metal ion imaging.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Weimin Liu
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Yanli Wang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Fangyuan Han
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Chong Fang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
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52
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Dietze DR, Mathies RA. Femtosecond Stimulated Raman Spectroscopy. Chemphyschem 2016; 17:1224-51. [DOI: 10.1002/cphc.201600104] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Daniel R. Dietze
- Department of Chemistry; University of California in Berkeley; CA Berkeley 94720 USA
| | - Richard A. Mathies
- Department of Chemistry; University of California in Berkeley; CA Berkeley 94720 USA
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53
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Oscar BG, Liu W, Rozanov ND, Fang C. Ultrafast intermolecular proton transfer to a proton scavenger in an organic solvent. Phys Chem Chem Phys 2016; 18:26151-26160. [DOI: 10.1039/c6cp05692j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The structural dynamics basis of intermolecular proton transfer from photoacid to acetate in methanol is revealed using femtosecond stimulated Raman spectroscopy.
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Affiliation(s)
- Breland G. Oscar
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Weimin Liu
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Nikita D. Rozanov
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Chong Fang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
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54
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Sum-Frequency-Generation-Based Laser Sidebands for Tunable Femtosecond Raman Spectroscopy in the Ultraviolet. APPLIED SCIENCES-BASEL 2015. [DOI: 10.3390/app5020048] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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55
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Spies C, Shomer S, Finkler B, Pines D, Pines E, Jung G, Huppert D. Solvent dependence of excited-state proton transfer from pyranine-derived photoacids. Phys Chem Chem Phys 2015; 16:9104-14. [PMID: 24700348 DOI: 10.1039/c3cp55292f] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Steady-state and time-resolved techniques were employed to study the excited-state proton-transfer (ESPT) rate of two newly synthesized 8-hydroxy-1,3,6-pyrenetrisulfonate (pyranine, HPTS) derived photoacids in three protic solvents, water, methanol and ethanol. The ESPT rate constant k(PT) of tris(1,1,1,3,3,3-hexafluoropropan-2-yl)-8-hydroxypyrene-1,3,6-trisulfonate, 1a, whose pK(a)* ~ -4, in water, methanol and ethanol is 3 × 10(11) s(-1), 8 × 10(9) s(-1) and 5 × 10(9) s(-1) respectively. (8-Hydroxy-N1,N3,N6-tris(2-hydroxyethyl)-N1,N3,N6-trimethylpyrene-1,3,6 trisulfonamide, 1b) is a weaker acid than 1a but still a strong photoacid with pK(a)* ~ -1 and the ESPT rate in water, methanol and ethanol is 7 × 10(10) s(-1), 4 × 10(8) s(-1) and 2 × 10(8) s(-1). We qualitatively explain our kinetic results by a Marcus-like free-energy correlation which was found to have a general form suitable for describing proton transfer reactions in both the proton-adiabatic and the proton-non-adiabatic limits.
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Affiliation(s)
- Christian Spies
- Biophysical Chemistry, Saarland University, Campus, Building B2 2, D-66123 Saarbrücken, Germany.
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56
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Tang L, Liu W, Wang Y, Zhao Y, Oscar BG, Campbell RE, Fang C. Unraveling ultrafast photoinduced proton transfer dynamics in a fluorescent protein biosensor for Ca(2+) imaging. Chemistry 2015; 21:6481-90. [PMID: 25761197 DOI: 10.1002/chem.201500491] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Indexed: 11/08/2022]
Abstract
Imaging Ca(2+) dynamics in living systems holds great potential to advance neuroscience and cellular biology. G-GECO1.1 is an intensiometric fluorescent protein Ca(2+) biosensor with a Thr-Tyr-Gly chromophore. The protonated chromophore emits green upon photoexcitation via excited-state proton transfer (ESPT). Upon Ca(2+) binding, a significant population of the chromophores becomes deprotonated. It remains elusive how the chromophore structurally evolves prior to and during ESPT, and how it is affected by Ca(2+) . We use femtosecond stimulated Raman spectroscopy to dissect ESPT in both the Ca(2+) -free and bound states. The protein chromophores exhibit a sub-200 fs vibrational frequency shift due to coherent small-scale proton motions. After wavepackets move out of the Franck-Condon region, ESPT gets faster in the Ca(2+) -bound protein, indicative of the formation of a more hydrophilic environment. These results reveal the governing structure-function relationship of Ca(2+) -sensing protein biosensors.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003 (USA)
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57
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Wang L, Liu W, Fang C. Elucidating low-frequency vibrational dynamics in calcite and water with time-resolved third-harmonic generation spectroscopy. Phys Chem Chem Phys 2015; 17:17034-40. [DOI: 10.1039/c5cp01813g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Coherent low-frequency vibrational dynamics in condensed phase from crystal, water, to aqueous electrolyte are elucidated by time-resolved third-harmonic-generation (TRTHG) spectroscopy.
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Affiliation(s)
- Liang Wang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Center (lab)
- Corvallis
- USA
| | - Weimin Liu
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Center (lab)
- Corvallis
- USA
| | - Chong Fang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Center (lab)
- Corvallis
- USA
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58
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Shi H, Lercher JA, Yu XY. Sailing into uncharted waters: recent advances in the in situ monitoring of catalytic processes in aqueous environments. Catal Sci Technol 2015. [DOI: 10.1039/c4cy01720j] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review presents recent advances inin situstudies of catalytic processes in the aqueous environment with an outlook of mesoscale imaging.
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Affiliation(s)
- Hui Shi
- Fundamental and Computer Sciences Directorate
- Pacific Northwest National Laboratory (PNNL)
- Richland
- USA
| | - Johannes A. Lercher
- Fundamental and Computer Sciences Directorate
- Pacific Northwest National Laboratory (PNNL)
- Richland
- USA
- Department of Chemistry
| | - Xiao-Ying Yu
- Fundamental and Computer Sciences Directorate
- Pacific Northwest National Laboratory (PNNL)
- Richland
- USA
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59
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Houari Y, Chibani S, Jacquemin D, Laurent AD. TD-DFT Assessment of the Excited State Intramolecular Proton Transfer in Hydroxyphenylbenzimidazole (HBI) Dyes. J Phys Chem B 2014; 119:2180-92. [DOI: 10.1021/jp505036d] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ymène Houari
- Laboratoire
CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la
Houssinière, BP 92208, 44322 Nantes Cedex 3, France
| | - Siwar Chibani
- Laboratoire
CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la
Houssinière, BP 92208, 44322 Nantes Cedex 3, France
| | - Denis Jacquemin
- Laboratoire
CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la
Houssinière, BP 92208, 44322 Nantes Cedex 3, France
- Institut Universitaire
de France, 103, bd Saint-Michel, F-75005 Paris Cedex 05, France
| | - Adèle D. Laurent
- Laboratoire
CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la
Houssinière, BP 92208, 44322 Nantes Cedex 3, France
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60
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Wang Y, Tang L, Liu W, Zhao Y, Oscar BG, Campbell RE, Fang C. Excited state structural events of a dual-emission fluorescent protein biosensor for Ca²⁺ imaging studied by femtosecond stimulated Raman spectroscopy. J Phys Chem B 2014; 119:2204-18. [PMID: 25226022 DOI: 10.1021/jp505698z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Fluorescent proteins (FPs) are luminescent biomolecules that emit characteristic hues upon irradiation. A group of calmodulin (CaM)-green FP (GFP) chimeras have been previously engineered to enable the optical detection of calcium ions (Ca(2+)). We investigate one of these genetically encoded Ca(2+) biosensors for optical imaging (GECOs), GEM-GECO1, which fluoresces green without Ca(2+) but blue with Ca(2+), using femtosecond stimulated Raman spectroscopy (FSRS). The time-resolved FSRS data (<800 cm(-1)) reveal that initial structural evolution following 400 nm photoexcitation involves small-scale coherent proton motions on both ends of the chromophore two-ring system with a <250 fs time constant. Upon Ca(2+) binding, the chromophore adopts a more twisted conformation in the protein pocket with increased hydrophobicity, which inhibits excited-state proton transfer (ESPT) by effectively trapping the protonated chromophore in S1. Both the chromophore photoacidity and local environment form the ultrafast structural dynamics basis for the dual-emission properties of GEM-GECO1. Its photochemical transformations along multidimensional reaction coordinates are evinced by distinct stages of FSRS spectral evolution, particularly related to the ∼460 and 504 cm(-1) modes. The direct observation of lower frequency modes provides crucial information about the nuclear motions preceding ESPT, which enriches our understanding of photochemistry and enables the rational design of new biosensors.
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Affiliation(s)
- Yanli Wang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331-4003, United States
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61
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Excited-state structural dynamics of a dual-emission calmodulin-green fluorescent protein sensor for calcium ion imaging. Proc Natl Acad Sci U S A 2014; 111:10191-6. [PMID: 24987121 DOI: 10.1073/pnas.1403712111] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Fluorescent proteins (FPs) have played a pivotal role in bioimaging and advancing biomedicine. The versatile fluorescence from engineered, genetically encodable FP variants greatly enhances cellular imaging capabilities, which are dictated by excited-state structural dynamics of the embedded chromophore inside the protein pocket. Visualization of the molecular choreography of the photoexcited chromophore requires a spectroscopic technique capable of resolving atomic motions on the intrinsic timescale of femtosecond to picosecond. We use femtosecond stimulated Raman spectroscopy to study the excited-state conformational dynamics of a recently developed FP-calmodulin biosensor, GEM-GECO1, for calcium ion (Ca(2+)) sensing. This study reveals that, in the absence of Ca(2+), the dominant skeletal motion is a ∼ 170 cm(-1) phenol-ring in-plane rocking that facilitates excited-state proton transfer (ESPT) with a time constant of ∼ 30 ps (6 times slower than wild-type GFP) to reach the green fluorescent state. The functional relevance of the motion is corroborated by molecular dynamics simulations. Upon Ca(2+) binding, this in-plane rocking motion diminishes, and blue emission from a trapped photoexcited neutral chromophore dominates because ESPT is inhibited. Fluorescence properties of site-specific protein mutants lend further support to functional roles of key residues including proline 377 in modulating the H-bonding network and fluorescence outcome. These crucial structural dynamics insights will aid rational design in bioengineering to generate versatile, robust, and more sensitive optical sensors to detect Ca(2+) in physiologically relevant environments.
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62
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Freitas AA, Quina FH, Maçanita AAL. Femtosecond and temperature-dependent picosecond dynamics of ultrafast excited-state proton transfer in water-dioxane mixtures. J Phys Chem A 2014; 118:10448-55. [PMID: 24925753 DOI: 10.1021/jp504189m] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Synthetic flavylium salts like the 7-hydroxy-4-methylflavylium (HMF) cation have been used as prototypes to study the chemistry and photochemistry of anthocyanins, the major group of water-soluble pigments in the plant kingdom. In this work, a combination of fluorescence upconversion with femtosecond time resolution and time-correlated single photon counting (TCSPC) with picosecond time resolution have been employed to investigate in details the excited-state proton transfer (ESPT) of HMF in water and in binary water/1,4-dioxane mixtures. TCSPC measurements as a function of temperature provide activation parameters for all of the individual rate constants involved in the proton transfer, including those for dissociation and recombination of the geminate excited base-proton pair (A*···H(+)) that can be detected in the water/dioxane mixtures (but not in water). Unlike the other rate constants, the deprotonation rate constant kd shows a non-Arrhenius dependence on temperature in both water and water/dioxane mixtures. At low temperatures kd is close to the dielectric relaxation rate of the solvent with a barrier of ca. 8 kJ mol(-1), suggesting that the solvent reorganization is the rate-limiting step. At higher temperatures (>30 °C) the proton transfer process is nearly barrierless and solvent-dependent. Fluorescence upconversion results in H2O, D2O, and water/dioxane mixtures confirm the two-step model for the ESPT of HMF and provide additional details of the early events prior to the onset of proton transfer, attributed to conformational relaxation and solvent reaccommodation around the initially formed excited state. The results are consistent with DFT calculations that indicate that charge redistribution occurs after rather than prior to the onset of the ESPT process.
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Affiliation(s)
- Adilson A Freitas
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , 1649-004 Lisbon, Portugal
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63
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Simkovitch R, Akulov K, Shomer S, Roth ME, Shabat D, Schwartz T, Huppert D. Comprehensive Study of Ultrafast Excited-State Proton Transfer in Water and D2O Providing the Missing RO–···H+ Ion-Pair Fingerprint. J Phys Chem A 2014; 118:4425-43. [DOI: 10.1021/jp5002435] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ron Simkovitch
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Katherine Akulov
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shay Shomer
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Michal E. Roth
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Doron Shabat
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tal Schwartz
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dan Huppert
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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64
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Kuchlyan J, Banik D, Kundu N, Ghosh S, Banerjee C, Sarkar N. Effect of confinement on excited-state proton transfer of firefly's chromophore D-luciferin in AOT reverse micelles. J Phys Chem B 2014; 118:3401-8. [PMID: 24624892 DOI: 10.1021/jp500210n] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Excited-state intermolecular proton transfer of D-luciferin in reverse micelles has been investigated using steady-state and time-resolved fluorescence spectroscopy measurement. The different polar cores have been chosen for the study of proton transfer dynamics in aerosol-OT (AOT) reverse micelles. It is shown that aqueous reverse micelle is the suitable environment for the photoprotolytic reaction of D-luciferin. The neutral form of the chromophore is present both in ground and excited state at W0 = 0. The proton transfer in nanometer size water pool of water/AOT/n-heptane begins at W0 = 8 and increases with increasing W0 values. However, the intermolecular excited-state proton transfer (ESPT) of D-luciferin is inhibited in nonaquous reverse micelles with DMF and DMSO as a polar core. Thus, the requirement of ESPT of D-luciferin to take place in reverse micelles consists of polar protic solvent like water as a polar core.
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Affiliation(s)
- Jagannath Kuchlyan
- Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB, India
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65
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Finkler B, Spies C, Vester M, Walte F, Omlor K, Riemann I, Zimmer M, Stracke F, Gerhards M, Jung G. Highly photostable "super"-photoacids for ultrasensitive fluorescence spectroscopy. Photochem Photobiol Sci 2014; 13:548-62. [PMID: 24469857 DOI: 10.1039/c3pp50404b] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photoacid 8-hydroxypyren-1,3,6-trisulfonic acid (HPTS, pyranine) is a widely used model compound for the examination of excited state proton transfer (ESPT). We synthesized five "super"-photoacids with varying hydrophilicity and acidity on the basis of HPTS. By chemical modification of the three sulfonic acid substituents, the photoacidity is enhanced by up to more than five logarithmic units from pK*≈ 1.4 to ∼-3.9 for the most acidic compound. As a result, nearly quantitative ESPT in DMSO can be observed. The novel photoacids were characterized by steady-state and time-resolved fluorescence techniques showing distinctively red shifted spectra compared to HPTS while maintaining a high quantum yield near 90%. Photostability of the compounds was checked by fluorescence correlation spectroscopy (FCS) and was found to be adequately high for ultrasensitive fluorescence spectroscopy. The described photoacids present a valuable palette for a wide range of applications, especially when the properties of HPTS, i.e. highly charged, low photostability and only moderate excited state acidity, are limiting.
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Affiliation(s)
- Björn Finkler
- Biophysical Chemistry, Saarland University, Campus B2 2, 66123 Saarbrücken, Germany.
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66
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Electrolytic synthesis of aqueous aluminum nanoclusters and in situ characterization by femtosecond Raman spectroscopy and computations. Proc Natl Acad Sci U S A 2013; 110:18397-401. [PMID: 24167254 DOI: 10.1073/pnas.1315396110] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The selective synthesis and in situ characterization of aqueous Al-containing clusters is a long-standing challenge. We report a newly developed integrated platform that combines (i) a selective, atom-economical, step-economical, scalable synthesis of Al-containing nanoclusters in water via precision electrolysis with strict pH control and (ii) an improved femtosecond stimulated Raman spectroscopic method covering a broad spectral range of ca. 350-1,400 cm(-1) with high sensitivity, aided by ab initio computations, to elucidate Al aqueous cluster structures and formation mechanisms in real time. Using this platform, a unique view of flat [Al13(μ3-OH)6(μ2-OH)18(H2O)24](NO3)15 nanocluster formation is observed in water, in which three distinct reaction stages are identified. The initial stage involves the formation of an [Al7(μ3-OH)6(μ2-OH)6(H2O)12](9+) cluster core as an important intermediate toward the flat Al13 aqueous cluster.
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67
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Liu W, Wang L, Han F, Fang C. Distinct broadband third-harmonic generation on a thin amorphous medium-air interface. OPTICS LETTERS 2013; 38:3304-3307. [PMID: 23988941 DOI: 10.1364/ol.38.003304] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We achieve a series of distinct broadband third-harmonic generation (THG) signals at the amorphous glass-air interface attributed to third-order and cascaded third-order nonlinear processes. A novel THG laser sideband arises from cascaded interaction between fundamental pulses and the cascaded four-wave mixing signals. The spatially separated THG sidebands with distinct spectral profiles manifest femtosecond quantum beats. Using a versatile setup with two crossing near-IR pulses temporally delayed to each other, we design an incident pulse polarization control method on the THG sideband lasers and also acquire the low-frequency surface Raman spectrum of the amorphous medium.
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Affiliation(s)
- Weimin Liu
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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68
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Han F, Liu W, Fang C. Excited-state proton transfer of photoexcited pyranine in water observed by femtosecond stimulated Raman spectroscopy. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.03.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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69
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Grumstrup EM, Chen Z, Vary RP, Moran AM, Schanze KS, Papanikolas JM. Frequency Modulated Femtosecond Stimulated Raman Spectroscopy of Ultrafast Energy Transfer in a Donor–Acceptor Copolymer. J Phys Chem B 2013; 117:8245-55. [DOI: 10.1021/jp404498u] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Erik M. Grumstrup
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel
Hill, North Carolina 27514, United States
| | - Zhuo Chen
- Department of Chemistry and
Center for Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Ryan P. Vary
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel
Hill, North Carolina 27514, United States
| | - Andrew M. Moran
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel
Hill, North Carolina 27514, United States
| | - Kirk S. Schanze
- Department of Chemistry and
Center for Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - John M. Papanikolas
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel
Hill, North Carolina 27514, United States
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70
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Liu W, Zhu L, Wang L, Fang C. Cascaded four-wave mixing for broadband tunable laser sideband generation. OPTICS LETTERS 2013; 38:1772-1774. [PMID: 23722739 DOI: 10.1364/ol.38.001772] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate the versatile broadband wavelength tunability of frequency upconverted multicolor cascaded four-wave-mixing (CFWM) signals spanning the continuous wavelength range from UV to near IR in a thin type-I BBO crystal using 35 fs, 800 nm fundamental and chirped IR supercontinuum white light pulses. Two sets of spatially dispersed CFWM laser sidebands are concomitantly generated from two incident pulses as well as their second-harmonic-generation and sum-frequency-generation pulses in a crossing geometry. The tunable cascaded signals with ultrabroad bandwidth can be readily achieved via spatially rotating the BBO crystal to different phase-matching conditions and temporally varying the time delay between the two incident near-IR pulses.
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Affiliation(s)
- Weimin Liu
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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71
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Wang Y, Liu W, Tang L, Oscar B, Han F, Fang C. Early time excited-state structural evolution of pyranine in methanol revealed by femtosecond stimulated Raman spectroscopy. J Phys Chem A 2013; 117:6024-42. [PMID: 23642152 DOI: 10.1021/jp312351r] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
To understand chemical reactivity of molecules in condensed phase in real time, a structural dynamics technique capable of monitoring molecular conformational motions on their intrinsic time scales, typically on femtoseconds to picoseconds, is needed. We have studied a strong photoacid pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, HPTS, pK(a)* ≈ 0) in pure methanol and observed that excited-state proton transfer (ESPT) is absent, in sharp contrast with our previous work on HPTS in aqueous solutions wherein ESPT prevails following photoexcitation. Two transient vibrational marker bands at ~1477 (1454) and 1532 (1528) cm(-1) appear in CH3OH (CD3OD), respectively, rising within the instrument response time of ~140 fs and decaying with 390-470 (490-1400) fs and ~200 ps time constants in CH3OH (CD3OD). We attribute the mode onset to small-scale coherent proton motion along the pre-existing H-bonding chain between HPTS and methanol, and the two decay stages to the low-frequency skeletal motion-modulated Franck-Condon relaxation within ~1 ps and subsequent rotational diffusion of H-bonding partners in solution before fluorescence. The early time kinetic isotope effect (KIE) of ~3 upon methanol deuteration argues active proton motions particularly within the first few picoseconds when coherent skeletal motions are underdamped. Pronounced quantum beats are observed for high-frequency modes consisting of strong phenolic COH rocking (1532 cm(-1)) or H-out-of-plane wagging motions (952 cm(-1)) due to anharmonic coupling to coherent low-frequency modes impulsively excited at ca. 96, 120, and 168 cm(-1). The vivid illustration of atomic motions of HPTS in varying H-bonding geometry with neighboring methanol molecules unravels the multidimensional energy relaxation pathways immediately following photoexcitation, and provides compelling evidence that, in lieu of ESPT, the photoacidity of HPTS promptly activates characteristic low-frequency skeletal motions to search phase space mainly concerning the phenolic end and to efficiently dissipate vibrational energy via skeletal deformation and proton shuttling motions within the intermediate, relatively confined excited-state HPTS-methanol complex on a solvent-dependent dynamic potential energy surface.
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Affiliation(s)
- Yanli Wang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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72
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Cina JA, Kovac PA. How fissors works: observing vibrationally adiabatic conformational change through femtosecond stimulated Raman spectroscopy. J Phys Chem A 2013; 117:6084-95. [PMID: 23590752 DOI: 10.1021/jp312878t] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
With the help of a two-dimensional model system comprising a slow conformational degree of freedom and a higher-frequency vibration, we investigate the molecular-level origin and dynamical information content of femtosecond stimulated Raman spectroscopy (fissors) signals. Our treatment avails itself of the time scale separation between conformational and vibrational modes by incorporating a vibrationally adiabatic approximation to the conformational dynamics. We derive an expression for the fissors signal without resort to the macroscopic concepts of light- and phonon-wave propagation employed in prior coupled-wave analyses. Numerical calculations of fissors spectra illustrate the case of relatively small conformational mass (still large enough that conformational motion does not induce any change in the vibrational quantum number) in which conformational sidebands accompany a central peak in the Raman gain at a conformationally averaged vibrational transition frequency, and the case of a larger conformational mass in which the sidebands merge with the central peak and the frequency of the latter tracks the time-evolving conformational coordinate.
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Affiliation(s)
- Jeffrey A Cina
- Department of Chemistry and Oregon Center for Optics, University of Oregon, Eugene, Oregon 97403, USA.
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73
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Brenlla A, Veiga M, Pérez Lustres JL, Ríos Rodríguez MC, Rodríguez-Prieto F, Mosquera M. Photoinduced Proton and Charge Transfer in 2-(2′-Hydroxyphenyl)imidazo[4,5-b]pyridine. J Phys Chem B 2013; 117:884-96. [DOI: 10.1021/jp311709c] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Alfonso Brenlla
- Departamento
de Química Física and Centro
Singular de Investigación en Química Biolóxica
e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - Manoel Veiga
- Departamento
de Química Física and Centro
Singular de Investigación en Química Biolóxica
e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - J. Luis Pérez Lustres
- Departamento
de Química Física and Centro
Singular de Investigación en Química Biolóxica
e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - M. Carmen Ríos Rodríguez
- Departamento
de Química Física and Centro
Singular de Investigación en Química Biolóxica
e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - Flor Rodríguez-Prieto
- Departamento
de Química Física and Centro
Singular de Investigación en Química Biolóxica
e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - Manuel Mosquera
- Departamento
de Química Física and Centro
Singular de Investigación en Química Biolóxica
e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
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