A5029179434- Advanced Fluorescence Microscopy Techniques
- Photosynthetic Processes and Mechanisms
- Photoreceptor and optogenetics research
- Spectroscopy and Quantum Chemical Studies
- Microfluidic and Bio-sensing Technologies
- Photochemistry and Electron Transfer Studies
- Nonlinear Optical Materials Studies
- Quantum Information and Cryptography
- Laser-Matter Interactions and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Microfluidic and Capillary Electrophoresis Applications
- Laser-Plasma Interactions and Diagnostics
- Cell Image Analysis Techniques
- Advanced Biosensing Techniques and Applications
- Orbital Angular Momentum in Optics
- Advanced Fiber Laser Technologies
- Advanced biosensing and bioanalysis techniques
- Innovative Microfluidic and Catalytic Techniques Innovation
- Single-cell and spatial transcriptomics
- RNA and protein synthesis mechanisms
- Mechanical and Optical Resonators
- Analytical Chemistry and Sensors
- DNA and Nucleic Acid Chemistry
- Advanced Electron Microscopy Techniques and Applications
- Electrowetting and Microfluidic Technologies
University of Colorado Boulder
2016-2025
Joint Institute for Laboratory Astrophysics
2015-2025
National Institute of Standards and Technology
2012-2024
University of Colorado System
2007-2023
Los Alamos National Laboratory
2015
Lund University
2015
National Institute of Standards
2009
Northern Illinois University
2008
Washington State University
2008
Colorado School of Mines
2007
Ultrafast fluorescence upconversion measurements were carried out on the peripheral (LH2) light harvesting antenna complex of Rhodobacter sphaeroides isolated in detergents N-octyl-β-d-glucopyranoside and lauryl dimethylamine oxide. The B800 B850 bands excited separate experiments, emission was detected each case. We make use recently determined crystal structure a purple bacterial LH2 to simulate our data calculate exciton level aggregate. excitation transfer occurs with 650 fs time...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExcitation Transfer in the Core Light-Harvesting Complex (LH-1) of Rhodobacter sphaeroides: An Ultrafast Fluorescence Depolarization and Annihilation StudyStephen E. Bradforth, Ralph Jimenez, Frank van Mourik, Rienk Grondelle, Graham R. FlemingCite this: J. Phys. Chem. 1995, 99, 43, 16179–16191Publication Date (Print):October 1, 1995Publication History Published online1 May 2002Published inissue 1 October...
The dynamics of solvation an excited chromophore in pure water and a restricted space with limited number molecules have been studied. time-dependent Stokes shift Coumarin 480 (C480) 460 (C460) were measured using femtosecond fluorescence upconversion time-correlated single-photon-counting techniques. system was inclusion complex dyes γ-cyclodextrin (γCD). results molecular simulations are compared the observed solvent response γCD cavity. relaxation times range from <100 fs to 1.2 ns....
The JILA multidimensional optical nonlinear spectrometer (JILA-MONSTR) is a robust, ultrastable platform consisting of nested and folded Michelson interferometers that can be actively phase stabilized. This generates square identical laser pulses adjusted to have arbitrary time delay between them while maintaining stability. JILA-MONSTR provides output for excitation materials phase-stabilized reference heterodyne detection the induced signal. arrangement ideal performing coherent...
Three-pulse echo peak shift measurements were performed on the B875 and B850 bands of detergent-isolated LH1 LH2 complexes at room temperature. The shifts are much larger decay faster than typically observed for dye molecules in solution. Simulations based optical transition frequency correlation function, M(t), presented. M(t) includes contributions from rapid protein fluctuations, vibrational motion, energy transfer. model reproduces temperature absorption spectra B875, shows that coupling...
Excitation with entangled photon pairs may lead to an increase in the efficiency of two-photon absorption at low flux. The corresponding process, (E2PA), has been investigated numerous theoretical and experimental studies. However, significant ambiguity inconsistency remain literature about absolute values E2PA cross sections. Here, we use a fluorescence-based registration scheme experimentally determine upper bounds on sections for six fluorophores. These are up 4 orders magnitude lower...
The solvent-dependent ground-state conformational equilibrium and excited-state dynamics of 2-(2'-hydroxyphenyl)benzoxazole have been characterized in several solvents on the femtosecond to nanosecond time scales. only observable tautomer is enol, which exists between syn- anti-rotational isomers. In anti-enol isomer, phenyl hydroxyl group appears not interact strongly with solvent but rather forms a strong intramolecular hydrogen bond benzoxazole oxygen atom. syn-enol proton may or form an...
Ultrafast fluorescence upconversion has been used to probe electronic excitation transfer within the B800−B820 light-harvesting antenna of Rhodopseudomonas acidophila strain 7050. Emission from carotenoid S2 band decays in 54 ± 8 fs, and bacteriochlorophyll B820 Qy rises approximately 110 fs. The rise time is wavelength-dependent. Energy-transfer rates between several neighboring are calculated. Coupling strengths estimated through transition dipole−transition dipole, polarization,...
The approximately linear scaling of fluorescence quantum yield (ϕ) with lifetime (τ) in fluorescent proteins (FPs) has inspired engineering brighter fluorophores based on screening for increased lifetimes. Several recently developed FPs such as mTurquoise2, mScarlet, and FusionRed-MQV which have become useful live cell imaging are products selection strategies. However, the underlying photophysical basis improved brightness not been scrutinized. In this study, we focused understanding...
It has been proposed that entangled two-photon absorption (E2PA) can be observed with up to 1010 lower photon flux than its classical counterpart, therefore enabling ultralow-power fluorescence microscopy. However, there is a significant controversy regarding the magnitude of this quantum enhancement in excitation efficiency. We investigated signals from Rhodamine 6G and LDS798 excited CW laser or an pair source at ∼1060 nm. signal originates hot-band (HBA), which one-photon thermally...
Photon echo spectroscopy has been used to measure the response of three antibody-binding sites perturbation from electronic excitation a bound antigen, fluorescein. The antibodies show motions that range in time scale tens femtoseconds nanoseconds. Relative others, one antibody, 4-4-20, possesses rigid binding site likely results short and inflexible heavy chain complementarity-determining region 3 (HCDR3) loop critical Tyr acts as "molecular splint," rigidifying antigen across its most...
While it is accepted that protein flexibility plays a role in folding, catalysis, and molecular recognition, few techniques are capable of the rigorous measurement motions required to quantify flexibility. Three-pulse photon echo shift spectroscopy can be used measure time scale motions, we have this technique, along with steady-state binding structural data, examine immunological evolution an anti-fluorescein antibody. Two light chain somatic mutations increase affinity for fluorescein by...
We describe a laser-driven x-ray plasma source designed for ultrafast absorption spectroscopy. The is comprised of 1 kHz, 20 W, femtosecond pulsed infrared laser and water target. present the spectra as function energy pulse duration. Additionally, we investigate temperature photon flux vary energy. obtain 75 μm FWHM spot size, containing ∼10(6) photons/s, by focusing produced x-rays with polycapillary optic. Since acquisition requires averaging measurements from >10(7) pulses, also data on...
Fluorescent biosensors are important measurement tools for in vivo quantification of pH, concentrations metal ions and other analytes, physical parameters such as membrane potential. Both the development these sensors their implementation examining cellular heterogeneity requires technology measuring sorting cells based on fluorescence levels before after chemical or perturbations. We developed a droplet microfluidic platform screening separation cell populations basis response expressed...
We introduce a toluene-filled fiber platform for two-photon absorption measurements. By confining both the light and molecular sample inside 5 μm hollow core of fiber, we increase distance over which nonlinear light–matter interaction occurs. With only 7.3 nL excitation volume, measure classical (C2PA) at an average laser power as low 1.75 nW, is 45-fold improvement conventional free-space technique. use this to attempt entangled (E2PA), process with limited regime where quantum advantage...
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDirect Observation of Protein Vibrations by Selective Incorporation Spectroscopically Observable Carbon−Deuterium Bonds in Cytochrome cJodie K. Chin, Ralph Jimenez, and Floyd E. RomesbergView Author Information Department Chemistry, The Scripps Research Institute 10550 North Torrey Pines Road, La Jolla, California 92037 Cite this: J. Am. Chem. Soc. 2001, 123, 10, 2426–2427Publication Date (Web):February 16, 2001Publication History Received14...
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTTautomerization Dynamics of a Model Base Pair in DNAOsama K. Abou-Zied, Ralph Jimenez, and Floyd E. RomesbergView Author Information Department Chemistry, The Scripps Research Institute 10550 North Torrey Pines Road, La Jolla, California 92037 Cite this: J. Am. Chem. Soc. 2001, 123, 19, 4613–4614Publication Date (Web):April 18, 2001Publication History Received11 October 2000Published online18 April 2001Published inissue 1 May...