A minicomputer-based system for process control, data acquisition, and data analysis in a diverse fast kinetics facility

Abstract— Laser flash photolysis studies of DNA‐complexed ethidium bromide were undertaken. We have observed a singlet‐singlet (S1‐Sn) absorption process for DNA‐complexed ethidium bromide. The observed lowest singlet excited state lifetime was 21 ± 2 ns. The molar difference extinction coefficient was measured to be 2.4 ± 0.4 × 103M‐1 cm‐1 at 370 nm. The assignment of this transition was confirmed by time resolved fluorescence measurements.

“…0.2. the pathlength being I cm in the analysing direction. The computer system and analysis software have been described more fully elsewhere (Foyt, 1981).…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laser Flash Photolysis Studies of Dna‐complexed Ethidium Bromide

Atherton

Beaumont²

1986

“…Laser flash photolysis experiments with HSA-bound Hp were carried out with a Quantel YG 481 Q-switched Nd:YAG laser using 532 nm as excitation wavelength. The transient species generated by 10 ns light pulses were monitored by a computer controlled kinetic spectrophotometer and analyzed by computerized procedures (Foyt, 1981). The transient decays were observed at 460 nm for Hp, 600 nm for free RB and 620 nm for HSA-bound RB, in N,-, air-and 0,-saturated solutions.…”

Section: Chemicalsmentioning

confidence: 99%

“…x 10' by using a computer-assisted iterative non-linear least squares analysis (Foyt, 1981) to independently determine the first order growth and decay rate constants. At the lower H S A concentrations the decay rate became longer and the growth rate stayed constant being a function of the O2 concentration only.…”

Section: Photokinetic Studiesmentioning

confidence: 99%

Photokinetic and Photophysical Measurements of the Sensitized Photooxidation of the Tryptophyl Residue in N‐acetyl Tryptophanamide and in Human Serum Albumin

Reddi

Lambert

Jori

et al. 1987

Abstract— The photosensitized oxidation of 10–100 μM N‐acetyl‐L‐tryptophanamide (NATA) in neutral aqueous solution and in the presence of various dyes proceeds by a pure O2(1Δg)‐involving mechanism. Incorporation of the tryptophyl (Trp) residue into the polypeptide chain of human serum albumin (HSA) has no influence on the mechanism and efficiency of Trp photooxidation when sensitized either by methylene blue, a non‐binding dye, or by rose bengal, a dye that gives non‐covalent 1: 1 complexes with HSA. This is due to the location of the Trp residue in close proximity of the protein surface and, in the case of rose bengal, to the coincidence of the photophysical properties (including the quantum yield of O2(1Δg) generation) for the free and HSA‐bound dye. Hematoporphyrin also binds to HSA with 1: 1 stoichiometry, although at a different site from rose bengal. Bound Hp again displays photophysical properties very similar with those of free Hp; however, the efficiency of Trp photo‐oxidation in HSA is about 5‐fold higher than in NATA owing to a limited rearrangement of the protein structure, induced by Hp binding, which enhances the probability of chemical quenching of O2(1Δg) by the indole ring.

“…5a, as a consequence of the quenching of 0 2 ( l A g ) by ES. Analysis to determine the ZA value corresponding to the 0 2 ( I A g ) produced by oxygen quenching of 'ES* was therefore performed with a programme for two competing first-order processes (Foyt, 1981). In Fig.…”

Section: K' K D I \ + K [Es]mentioning

confidence: 99%

ERGOSTEROL (PROVITAMIN D2) TRIPLET STATE: AN EFFICIENT SENSITISER OF SINGLET OXYGEN, O₂(1Δ_g), FORMATION

Gorman

Hamblett

Rodgers

1987

The triplet state of ergosterol (provitamin D2) has been produced in benzene by pulse radiolysis and characterised in terms of absorption spectrum, lifetime, self‐quenching properties and relaxed triplet energy. The amount of singlet oxygen, O2(1Δg), produced as a consequence of the oxygen quenching of this species has been determined by kinetic infrared emission spectroscopy. Ergosterol is significantly more efficient as a singlet oxygen sensitiser in benzene than is naphthalene, the absolute standard employed in this work.