Oxygen Quenching of Pyrenebutyric Acid Fluorescence in Water.

Abstract

Solutions of pyrenebutyrate have fluorescence lifetimes of 135 nsec in deoxygenated water and 100 nsec, and a corresponding diminished yield in air-equilibrated water. The oxygen quenching of the fluorescence is shown by means of measurements of lifetime and relative yield of fluorescence to be a diffusion-controlled phenomenon in which virtually every collision is effective. Adsorbates or chemical conjugates of pyrenebutyric acid with bovine albumin are not affected by changing the concentrations of 0, in the medium, while in concentrated urea the quenching is markedly increased. Observations of a similar kind have been carried out in polylysine conjugates and apohemoglobin adsorbates. The lifetime in the absence of oxygen (T~) in the systems studied varied from 100 to 205 nsec. From observa- tions of glycerol-water mixtures it is suggested that T~ may depend upon the polarity of the environment. The observa- tions reported here show that pyrenebutyric acid may be used to determine the accessibility of O2 in microenvironments of biological interest. In principle, such a probe could have a resolution time of 1 psec. A general treatment of quenching by collisions and complex formation is developed from considerations of the rate equations involved.