Transient increase of tryptophan fluorescence of enzyme caused by photoexcitation of ligand in luciferase-luciferin complex.

An experiment was proposed and accomplished that was based on the hypothesis of the dissociation of the luciferase-luciferin complex in photoexcitation. A pump-probe experiment was performed with the use of picosecond laser pulses and was based on the effect of quenching of enzyme tryptophan fluorescence caused by luciferin binding. A photoinduced increase of the tryptophan fluorescence intensity was detected. Experimental results were interpreted on the basis of the assumptions on photoinduced dissociation of the luciferin-luciferase complex and Forster energy transfer from tryptophan to luciferin. Under the assumption on the photoinduced dissociation and stationary quenching of tryptophan fluorescence the rate of propagation of the conformational changes in the protein caused by the complex dissociation was estimated to be >20 m/s.

One-dimensional coherent four-wave mixing as a way to image the spatial distribution of atoms in a laser-produced plasma.

An experimental technique based on coherent one-dimensional hyper-Raman-resonant four-wave mixing in broad cylindrically focused light beams has been developed for line-by-line imaging of spatial distribution of excited atoms in a low-temperature plasma of optical breakdown. The technique was applied to map excited lead atoms in a low-temperature laser-produced plasma.

Enhancement of second-harmonic generation with femtosecond laser pulses near the photonic band edge for different polarizations of incident light.

We present experimental evidence of enhancement of second-harmonic generation as a result of an increase of the fundamental-field energy density within a multilayer structure near the photonic band edge.

Polarization sensitive coherent anti-Stokes Raman scattering spectroscopy of the amide I band of proteins in solutions.

Polarization sensitive coherent anti-Stokes Raman scattering (PCARS) spectroscopy is a fruitful technique to study Raman vibrations of diluted molecules under off-electron resonant conditions. We apply PCARS as a direct spectroscopic method to investigate the broad amide I band of proteins in heavy water. In spontaneous Raman spectroscopy, this band is not well resolved. We fit a number of spectra taken of each protein under different polarization conditions, with a single set of parameters. It then appears that some substructure is observed in the amide I band. From this substructure, we determine the percentage of alpha-helix, beta-sheet, and random coil for the proteins lysozyme, albumin, ribonuclease A, and alpha-chymotrypsin.

Laser picosecond microspectrofluorometry of haematoporphyrin in cells and liposomes.

The results of a laser picosecond microspectrofluorometric study of the spectral and kinetic characteristics of haematoporphyrin (Hp) fluorescence at various sites in cultured SPEV cells and phosphatidylcholine liposomes are presented. The computer-controlled detection system is based on the single-photon counting method with picosecond time resolution. In aqueous medium, the Hp fluorescence spectrum is characterized by two bands at 615 and 675 nm. In living cells and liposomes, Hp fluorescence is red shifted to 630 and 690 nm. In addition a new band at 665 nm is detected. The dependence of this band on the incubation time and Hp concentration was investigated. The fluorescence decay kinetics of Hp in a culture medium, liposome and a cell nuclear membrane were measured. Possible Hp aggregate formation in the lipid bilayer and its implications are discussed.

Time-domain polarization coherent anti-Stokes Raman spectroscopy of Tl atoms: dephasing measurements of separate multipole moments.

Polarization nondegenerate nonstationary coherent anti-Stokes Raman spectroscopy was used in measurements of pulse responses for separate electronic multipole moments. The 6P(1/2)-6P(3/2) transition of Tl atoms was investigated. Doppler dephasing conditions, quantum beats of the hyperfine components of this transition are clearly seen when pure anisotropic scattering is registered, but they are small in the case of purely antisymmetric scattering. Under collisional dephasing conditions the relaxation rates of anisotropic and antisymmetric scattering agree with existing theory within +/-5%.

Two-photon Raman excitation and coherent anti-Stokes Raman spectroscopy probing of population changes in polyatomic molecules: a novel nonlinear optical technique for vibrational-relaxation studies.

Two-photon Raman excitation is used to populate selectively vibrational states in CO(2) and SF(6). The collisional population of 01(1)0, 02(2)0, 03(1)0, 11(1)0, etc. by means of 10 degrees 0 and 02 degrees 0 states in CO(2) gas is studied by coherent anti-Stokes Raman spectroscopy. No population transfer is observed between Fermi-resonant CO(2)(10 degrees 0) and CO(2)(02 degrees 0) states with the rate constant K greater, similar 7 10(4) sec(-1) Torr(-1). The lifetime of the SF(6)(100000) state is found to be taurho greater, similar 15 microsec Torr.

High-resolution cw CARS spectra of liquid nitrogen dissolved in liquefied Ar, Kr, O(2), CO, and CH(4).

The high-resolution cw CARS technique has revealed solvent-induced alterations in linewidth and position of the 2326.5-cm(-1) Raman line of liquid, nitrogen, which becomes strongly broadened when Kr or CH(4) is added and is almost unaltered in solutions with CO and O(2). The interpretation is given in terms of motional narrowing and vibrational dephasing theory.