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Your search keyword '"Larsen, Delmar S."' showing total 338 results
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338 results on '"Larsen, Delmar S."'

51. Use of ultrafast dispersed pump-dump-probe and pump-repump-probe spectroscopes to explore the light-induced dynamics of peridinin in solution

Author

Papagiannakis, Emmanouil, Vengris, Mikas, Larsen, Delmar S., van Stokkum, Ivo H.M., Hiller, Roger G., and van Grondelle, Reink

Subjects
Molecular dynamics -- Research, Carotenoids -- Research, Chemicals, plastics and rubber industries
Abstract

A study was conducted of the optical pump-induced dynamics of the highly asymmetric carotenoid peridinin in methanol by dispersed pump-probe, pump-dump-probe and pump-repump-probe transient absorption spectroscopy in the visible region. The pump-probe measurements show that the decay of the initially excited S2 state populates two excited states.

Published
2006

52. Excitation-Wavelength-Dependent Photocycle Initiation Dynamics Resolve Heterogeneity in the Photoactive Yellow Protein from Halorhodospira halophila

Author

Mix, L. Tyler, primary, Carroll, Elizabeth C., additional, Morozov, Dmitry, additional, Pan, Jie, additional, Gordon, Wendy Ryan, additional, Philip, Andrew, additional, Fuzell, Jack, additional, Kumauchi, Masato, additional, van Stokkum, Ivo, additional, Groenhof, Gerrit, additional, Hoff, Wouter D., additional, and Larsen, Delmar S., additional

Published
2018
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53. Mediation of ultrafast light-harvesting by a central dimer in phycoerythrin 545 studied by transient absorption and global analysis

Author

Doust, Alexander B., Larsen, Delmar S., Curmi, Paul M.G., Grondelle, Rienk van, Scholes, Gregory D., Stokkum, Ivo H.M.van, and Wilk, Krystyna E.

Subjects
Photosynthesis -- Research, Chromophores -- Optical properties, Chromophores -- Structure, Chromophores -- Chemical properties, Absorption of light -- Research, Chemicals, plastics and rubber industries
Abstract

Ultrafast femtosecond transient absorption measurements of energy-transfer dynamics for the antenna protein phycoerythrin 545,PE545, isolated from a unicellular cryptophyte Rhodomonas CS24 is reported. The phycoerythrobilins are excited at both 485 and 530 nm, and the spectral response is probed between 400 and 700 nm.

Published
2005

54. Ultrafast dynamics of isolated model photoactive yellow protein chromophores: 'Chemical Perturbation Theory' in the laboratory

Author

Vengris, Mikas, Grondelle, Rienk van, Larsen, Delmar S., Horst, Michael A. van der, Larsen, Olaf F.A., and Hellingwerf, Klaas J.

Subjects
Absorption spectra -- Usage, Molecular dynamics -- Research, Chromophores -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

The ultrafast dynamics of a number of model photoactive yellow protein chromophores is investigated. The observed transient absorption spectra in terms of the spectral signatures ascribed to solvation, excited-state twisting, and vibrational relaxation are also discussed.

Published
2005

55. Ultrafast excited and ground-state dynamics of the green fluorescent protein chromophore in solution

Author

Vengris, Mikas, van Stokkum, Ivo H. M., He, Xiang, Bell, Alasdair F., Tonge, Peter J., van Grondelle, Rienk, and Larsen, Delmar S.

Subjects
Photons -- Analysis, Photons -- Properties, Spectrum analysis -- Analysis, Chemicals, plastics and rubber industries
Abstract

A study was conducted, using wavelength and time-resolved pump-probe and pump-dump-probe spectroscopy, to investigate the excited and ground-state photoinduced dynamics of the green fluorescent protein (GFP) chromophore and 4'-hydroxybenzylidene-2,3-dimethylimidazolinone (HBDI). The result identifies two pathways such as a 1-photon excited-state twisting, and a 2-photon ionized process.

Published
2004

56. Three pulse photon echo studies of nondipolar solvation: Comparison with a viscoelastic model.

Author

Larsen, Delmar S., Ohta, Kaoru, and Fleming, Graham R.

Subjects
*SOLVATION, *QUADRUPOLE moments
Abstract

Discusses the use of the three pulse stimulated photo echo peak shift (3PEPS) measurements to probe the solvation of a quadrupolar solute in three room temperature nondipolar solvents. Absorption spectrum for perylenetetracarbonyl diamide (PERY) in benzene; Plotting of the integrated photon echo profiles against the coherence time at fixed population times.

Published
1999
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57. Initial steps of signal generation in photoactive yellow protein revealed with femtosecond mid-infrared spectroscopy

Author

Groot, Marie Louise, van Wilderen, Luuk J.G.W., Larsen, Delmar S., van der Horst, Michael A., van Stokkum, Ivo H.M., Hellingwerf, Klaas J., and van Grondelle, Rienk

Subjects
Cellular signal transduction -- Physiological aspects, Hydrogen bonding -- Analysis, Photodetectors -- Physiological aspects, Photochemistry -- Research, Bacterial proteins, Biological sciences, Chemistry
Abstract

Results demonstrate structural changes in the excited state of the bacterial photoactive yellow protein's chromophore, p-coumaric acid. Ligh absorption by the protein leads to the hydrogen bond disruption in the chromophore's C=O group and formation of a stable cis ground state in approximately 2 picoseconds. Further, relaxation of the coumaryl tail occurs in 0.9-1 nanoseconds.

Published
2003

58. Ultrafast protein dynamics of bacteriorhodopsin probed by photon echo and transient absorption spectroscopy

Author

Kennis, John T.M., Larsen, Delmar S., Ohta, Kaoru, Facciotti, Marc T., Glaeser, Robert M., and Fleming, Graham R.

Subjects
Transients (Dynamics) -- Analysis, Photoreceptors -- Analysis, Bacteriorhodopsin -- Spectra, Chemicals, plastics and rubber industries
Abstract

The nature, origin, and dynamical aspects of bacteriorhodopsin (bR) reorganization that exhibits a large reorganization energy lambda of 2520 cm(super -1) on optical excitation. The results of a femtosecond three-pulse echo peak shift (3PEPS), transient grating (TG) and transient absorption (TA) study, complemented with those of steady-state absorption and fluorescence spectroscopy in wild-type bR and the D85S mutant in its blue and purple, halide-pumping forms is reported.

Published
2002

61. Correlating structural and photochemical heterogeneity in cyanobacteriochrome NpR6012g4.

Author

Sunghyuk Lim, Qinhong Yu, Gottlieb, Sean M., Che-Wei Chang, Rockwell, Nathan C., Martin, Shelley S., Madsen, Dorte, Lagarias, J. Clark, Larsen, Delmar S., and Ames, James B.

Subjects
PHYTOCHROMES, PHYCOBILIPROTEINS, CYANOBACTERIA biotechnology, PLANT growth regulation, OPTOGENETICS
Abstract

Phytochrome photoreceptors control plant growth, development, and the shade avoidance response that limits crop yield in highdensity agricultural plantings. Cyanobacteriochromes (CBCRs) are distantly related photosensory proteins that control cyanobacterial metabolism and behavior in response to light. Photoreceptors in both families reversibly photoconvert between two photostates via photoisomerization of linear tetrapyrrole (bilin) chromophores. Spectroscopic and biochemical studies have demonstrated heterogeneity in both photostates, but the structural basis for such heterogeneity remains unclear. We report solution NMR structures for both photostates of the red/green CBCR NpR6012g4 from Nostoc punctiforme. In addition to identifying structural changes accompanying photoconversion, these structures reveal structural heterogeneity for residues Trp655 and Asp657 in the red-absorbing NpR6012g4 dark state, yielding two distinct environments for the phycocyanobilin chromophore. We use site-directed mutagenesis and fluorescence and absorbance spectroscopy to assign an orangeabsorbing population in the NpR6012g4 dark state to the minority configuration for Asp657. This population does not undergo full, productive photoconversion, as shown by time-resolved spectroscopy and absorption spectroscopy at cryogenic temperature. Our studies thus elucidate the spectral and photochemical consequences of structural heterogeneity in a member of the phytochrome superfamily, insights that should inform efforts to improve photochemical or fluorescence quantum yields in the phytochrome superfamily. [ABSTRACT FROM AUTHOR]

Published
2018
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62. Excitation-Wavelength-Dependent Photocycle Initiation Dynamics Resolve Heterogeneity in the Photoactive Yellow Protein from Halorhodospira halophila

Author

Mix, L. Tyler, Carroll, Elizabeth C., Morozov, Dmitry, Pan, Jie, Gordon, Wendy Ryan, Philip, Andrew, Fuzell, Jack, Kumauchi, Masato, van Stokkum, Ivo, Groenhof, Gerrit, Hoff, Wouter D., and Larsen, Delmar S.

Abstract

Photoactive yellow proteins (PYPs) make up a diverse class of blue-light-absorbing bacterial photoreceptors. Electronic excitation of the p-coumaric acid chromophore covalently bound within PYP results in triphasic quenching kinetics; however, the molecular basis of this behavior remains unresolved. Here we explore this question by examining the excitation-wavelength dependence of the photodynamics of the PYP from Halorhodospira halophilavia a combined experimental and computational approach. The fluorescence quantum yield, steady-state fluorescence emission maximum, and cryotrapping spectra are demonstrated to depend on excitation wavelength. We also compare the femtosecond photodynamics in PYP at two excitation wavelengths (435 and 475 nm) with a dual-excitation-wavelength-interleaved pump–probe technique. Multicompartment global analysis of these data demonstrates that the excited-state photochemistry of PYP depends subtly, but convincingly, on excitation wavelength with similar kinetics with distinctly different spectral features, including a shifted ground-state beach and altered stimulated emission oscillator strengths and peak positions. Three models involving multiple excited states, vibrationally enhanced barrier crossing, and inhomogeneity are proposed to interpret the observed excitation-wavelength dependence of the data. Conformational heterogeneity was identified as the most probable model, which was supported with molecular mechanics simulations that identified two levels of inhomogeneity involving the orientation of the R52 residue and different hydrogen bonding networks with the p-coumaric acid chromophore. Quantum calculations were used to confirm that these inhomogeneities track to altered spectral properties consistent with the experimental results.

Published
2024
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63. Packing Dependent Electronic Coupling in Single Poly(3-hexylthiophene) H- and J-Aggregate Nanofibers

Author

Martin, Thomas P., Wise, Adam J., Busby, Erik, Gao, Jian, Roehling, John D., Ford, Michael J., Larsen, Delmar S., Moulé, Adam J., and Grey, John K.

Abstract

Nanofibers (NFs) of the prototype conjugated polymer, poly(3-hexylthiophene) (P3HT), displaying H- and J-aggregate character are studied using temperature- and pressure-dependent photoluminescence (PL) spectroscopy. Single J-aggregate NF spectra show a decrease of the 0–0/0–1 vibronic intensity ratio from ∼2.0 at 300 K to ∼1.3 at 4 K. Temperature-dependent PL line shape parameters (i.e., 0–0 energies and 0–0/0–1 intensity ratios) undergo an abrupt change in the range of ∼110130 K suggesting a change in NF chain packing. Pressure-dependent PL lifetimes also show increased contributions from an instrument-limited decay component which is attributed to greater torsional disorder of the P3HT backbone upon decreasing NF volume. It is proposed that the P3HT alkyl side groups change their packing arrangement from a type I to type II configuration causing a decrease in J-aggregate character (lower intrachain order) in both temperature- and pressure-dependent PL spectra. Chain packing dependent exciton and polaron relaxation and recombination dynamics in NF aggregates are next studied using transient absorption spectroscopy (TAS). TAS data reveal faster polaron recombination dynamics in H-type P3HT NFs indicative of interchain delocalization whereas J-type NFs exhibit delayed recombination suggesting that polarons (in addition to excitons) are more delocalized along individual chains. Both time-resolved and steady-state spectra confirm that excitons and polarons in J-type NFs are predominantly intrachain in nature that can acquire interchain character with small structural (chain packing) perturbations.

Published
2024
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67. Biological systems: Applications and perspectives

Author

Fidder, Henk, primary, Heyne, Karsten, additional, Schenkl, Selma, additional, van Mourik, Frank, additional, van der Zwan, Gert, additional, Haacke, Stefan, additional, Chergui, Majed, additional, Vengris, Mikas, additional, Larsen, Delmar S., additional, Papagiannakis, Emmanouil, additional, Kennis, John T. M., additional, van Grondelle, Rienk, additional, Brüggemann, Ben, additional, May, Volkhard, additional, Corral, Inés, additional, González, Leticia, additional, Lauer, Alexandra, additional, Meerbach, Eike, additional, Schütte, Christof, additional, Horenko, Illia, additional, Schmidt, Burkhard, additional, and Wolf, Jean-Pierre, additional

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74. Toward an Understanding of the Retinal Chromophore in Rhodopsin Mimics

Author

Huntress, Mark M., primary, Gozem, Samer, additional, Malley, Konstantin R., additional, Jailaubekov, Askat E., additional, Vasileiou, Chrysoula, additional, Vengris, Mikas, additional, Geiger, James H., additional, Borhan, Babak, additional, Schapiro, Igor, additional, Larsen, Delmar S., additional, and Olivucci, Massimo, additional

Published
2013
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