Compressor optimization with compressor-based multiphoton intrapulse interference phase scan (MIIPS).

The multiphoton intrapulse interference phase scan (MIIPS) technique is modified to optimize the compressor settings of a chirped pulse amplification (CPA) laser system. Here, we use the compressor itself to perform the phase scan inherent in MIIPS measurement . A frequency-resolved optical gating measurement shows that the pulse duration of the compressor optimized using the modified MIIPS technique is 33.8 fs with a 2.24 rad temporal phase variation above 2% intensity. The measured time-bandwidth product is 0.60, which is close to that of transform-limited Gaussian pulse (0.44).

Fluorescence measurements of environmental relaxation at the lipid-water interface region of bilayer membranes.

Nanosecond time-resolved emission spectroscopy is used to characterize the complex fluorescence behavior of the probe 2-p-toluidinonaphthalene 6-sulfonate (2,6 p-TNS) when adsorbed to several bilayer membrane system. These include egg phosphatidylcholine vesicles with and without added cholesterol as well as erythrocyte ghost membranes. In each case a nanosecond time-dependent shift of the fluorescence emission to lower energy follows pulsed photoexcitation. The properties of the time-resolved surfaces obtained are consistent with a non-exponential decay law which describes a continuous interaction process of 2,6 p-TNS with its local environment in the membrane. This environment consists in part of polar residues (water plus polar head region) undergoing nanosecond motions. The pure phosphatidylcholine bilayer system was studied at four temperatures and electronic and spectral relaxation contributions to the total fluorescence decay were separated. Temperature coefficients for empirical rate parameters derived for the separated processes were obtained. It appears that a treatment of the fluorescence behavior of amphiphilic probes such as 2,6 p-TNS adsorbed to bilayer membranes at temperatures near ambient in which a single lifetime and radiative decay channel have been assumed is inappropriate.

Nanosecond time-resolved emission spectroscopy of a fluorescence probe adsorbed to L-alpha-egg lecithin vesicles.

Nanosecond time-resolved emission spectra (TRES) are fluorescence emission spectra obtained at discrete times during the fluorescence decay. The complete data-set obtainable is a surface representing the intensity at all wavelengths and times during the emission decay time. When 2-p-toluidinonaphthalene-6-sulfonate (2,6 p-TNS) is adsorbed to egg lecithin vesicles, an excited-state reaction associated with energetic changes of the emitting species occurs on the nanosecond time scale. Convolution of the fluorescence decay with the excitation response introduces an artifact in the time-dependent spectra. A precedure is described by which this artifact can be eliminated. The data for the generation of time-resolved emission spectra are obtained with a computer-interfaced instrument based on the single-photon counting method.