LED array spectrophotometer for measurement of time resolved difference spectra in the 530?600 nm wavelength region

1990 ◽  
Vol 25 (3) ◽  
pp. 317-327 ◽  
Author(s):  
Christof Klughammer ◽  
J�rg Kolbowski ◽  
Ulrich Schreiber
Keyword(s):  
Wavelength Region ◽  
Difference Spectra ◽  
Time Resolved ◽  
Led Array

Time‐resolved spectra in the 80–330‐Å wavelength region from PLT tokamak plasmas

1986 ◽  
Vol 57 (8) ◽  
pp. 2058-2058 ◽  
Author(s):  
J. H. Dave ◽  
U. Feldman ◽  
J. F. Seely ◽  
A. Wouters ◽  
E. Hinnov ◽  
...  
Keyword(s):  
Wavelength Region ◽  
Tokamak Plasmas ◽  
Time Resolved

scholarly journals Time-Resolved Infrared Spectroscopy of Binuclear Rhenium (I) Polypyridyl Complexes in Solution

1999 ◽  
Vol 19 (1-4) ◽  
pp. 279-282 ◽  
Author(s):  
L. C. Abbott ◽  
C. J. Arnold ◽  
K. C. Gordon ◽  
R. E. Hester ◽  
J. N. Moore ◽  
...  
Keyword(s):  
Mixed Valence ◽  
Difference Spectra ◽  
Kinetic Measurements ◽  
Time Resolved ◽  
Bridging Ligand ◽  
Ligand Charge Transfer ◽  
Complex Forms ◽  
Time Resolved Infrared Spectroscopy ◽  
State Kinetic ◽  
Mlct State

A series of four binuclear rhenium (I) complexes of the general form [Re(CO)3Cl]2BL, where BL is a polypyridyl bridging ligand, have been studied using ultrafast time-resolved UV/visible (TRVIS) and infrared (TRIR) spectroscopies. Visible excitation produces a metal-to-ligand charge-transfer (MLCT) excited state. Kinetic measurements show that the lifetime of this MLCT state varies between 100 and 1900 ps, depending on the structure of the bridging ligand. TRIR difference spectra show that each complex forms a similar MLCT state which has mixed valence character.

Luminescence Lifetime Imaging of Oxygen, pH, and Carbon Dioxide Distribution Using Optical Sensors

2000 ◽  
Vol 54 (4) ◽  
pp. 548-559 ◽  
Author(s):  
Gregor Liebsch ◽  
Ingo Klimant ◽  
Bernhard Frank ◽  
Gerhard Holst ◽  
Otto S. Wolfbeis
Keyword(s):  
Optical Sensors ◽  
Optical Sensor ◽  
Luminescence Lifetime ◽  
Modular System ◽  
Background Suppression ◽  
Time Resolved ◽  
Typical Application ◽  
Lifetime Imaging ◽  
Led Array ◽  
Decay Times

We present a modular system for time-resolved two-dimensional luminescence lifetime imaging of planar optical chemical sensors. It is based on a fast, gateable charge-coupled device (CCD) camera without image intensifier and a pulsable light-emitting diode (LED) array as a light source. Software was developed for data acquisition with a maximum of parameter variability and for background suppression. This approach allows the operation of the system even under daylight. Optical sensors showing analyte-specific changes of their luminescence decay time were tested and used for sensing pO2, pCO2, pH, and temperature. The luminophores employed are either platinum(II)-porphyrins or ruthenium(II)-polypyridyl complexes, contained in polymer films, and can be efficiently excited by blue LEDs. The decay times of the sensor films vary from 70 μs for the Pt(II)-porphyrins to several 100 ns for the Ru(II) complexes. In a typical application, 7 mm-diameter spots of the respective optical sensor films were placed at the bottom of the wells of microtiterplates. Thus, every well represents a separate calibration chamber with an integrated sensor element. Both luminescence intensity-based and time-resolved images of the sensor spots were evaluated and compared. The combination of optical sensor technology with time-resolved imaging allows a determination of the distribution of chemical or physical parameters in heterogeneous systems and is therefore a powerful tool for screening and mapping applications.

scholarly journals Ras and GTPase-activating protein (GAP) drive GTP into a precatalytic state as revealed by combining FTIR and biomolecular simulations

2012 ◽  
Vol 109 (38) ◽  
pp. 15295-15300 ◽  
Author(s):  
Till Rudack ◽  
Fei Xia ◽  
Jürgen Schlitter ◽  
Carsten Kötting ◽  
Klaus Gerwert
Keyword(s):  
Nucleophilic Attack ◽  
Nonbridging Oxygen ◽  
Difference Spectra ◽  
Gtp Hydrolysis ◽  
Time Resolved ◽  
X Ray ◽  
Cellular Processes ◽  
Gtpase Activating Proteins ◽  
Biomolecular Simulations ◽  
Oxygen Atoms

Members of the Ras superfamily regulate many cellular processes. They are down-regulated by a GTPase reaction in which GTP is cleaved into GDP and Pi by nucleophilic attack of a water molecule. Ras proteins accelerate GTP hydrolysis by a factor of 105 compared to GTP in water. GTPase-activating proteins (GAPs) accelerate hydrolysis by another factor of 105 compared to Ras alone. Oncogenic mutations in Ras and GAPs slow GTP hydrolysis and are a factor in many cancers. Here, we elucidate in detail how this remarkable catalysis is brought about. We refined the protein-bound GTP structure and protein-induced charge shifts within GTP beyond the current resolution of X-ray structural models by combining quantum mechanics and molecular mechanics simulations with time-resolved Fourier-transform infrared spectroscopy. The simulations were validated by comparing experimental and theoretical IR difference spectra. The reactant structure of GTP is destabilized by Ras via a conformational change from a staggered to an eclipsed position of the nonbridging oxygen atoms of the γ- relative to the β-phosphates and the further rotation of the nonbridging oxygen atoms of α- relative to the β- and γ-phosphates by GAP. Further, the γ-phosphate becomes more positive although two of its oxygen atoms remain negative. This facilitates the nucleophilic attack by the water oxygen at the phosphate and proton transfer to the oxygen. Detailed changes in geometry and charge distribution in the ligand below the resolution of X-ray structure analysis are important for catalysis. Such high resolution appears crucial for the understanding of enzyme catalysis.

Atr/Ft-Ir Difference Spectroscopy of Biological Matter with Microsecond Time Resolution

1996 ◽  
Vol 50 (5) ◽  
pp. 588-596 ◽  
Author(s):  
Joachim Heberle ◽  
Christian Zscherp
Keyword(s):  
Attenuated Total Reflection ◽  
High Temporal Resolution ◽  
Difference Spectroscopy ◽  
Difference Spectra ◽  
Time Resolved ◽  
Precise Control ◽  
Biological Matter ◽  
Vis Spectroscopy ◽  
Ft Ir ◽  
Atr Spectroscopy

Attenuated total reflection (ATR) spectroscopy allows precise control of external parameters vital for proper functioning of biological matter. For the first time in biospectroscopy, ATR difference spectroscopy has been combined with the step-scan technique. The current setup integrates a broad frequency range (800–25,000 cm−1) with high temporal resolution (5 μs). Vibrations are detected that arise from single amino acids (<10−3 absorbance units) of the chromoprotein bacteriorhodopsin. Time-resolved ATR/FT-IR difference spectra are compared with conventional transmission spectra. The high mirror stability enables time-resolved FT-vis spectroscopy of the same sample with the same instrument. Potential applications even to non-light-absorbing biomaterial are discussed.

Nonlinear Optical Response of Excitons Confined to one Dimension

1987 ◽  
Vol 109 ◽  
Author(s):  
B. I. Greene ◽  
J. Orenstein ◽  
M. Thakur ◽  
D. H. Rapkine
Keyword(s):  
Single Crystals ◽  
Nonlinear Optical ◽  
Transient Absorption ◽  
Wavelength Region ◽  
Nonlinear Optical Response ◽  
One Dimension ◽  
Optical Nonlinearities ◽  
Exciton Resonance ◽  
Absorption Data ◽  
Time Resolved

ABSTRACTWe present femtosecond time-resolved transient absorption data taken on polydiacetylene-pTS single crystals over the entire wavelength region of exciton resonance. Observed optical changes are accounted for by a model which predicts quantitatively the large resonant and nonresonant optical nonlinearities.

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