Fluorescence of wool grease

Abstract

Wool yolk is highly fluorescent. The amount of wool yolk and intensity of wool yolk fluorescence varies along a Merino wool fibre. The fluorescence intensity of the yolk increases on travelling from tip to the root. Two components-‘grease’ and chlorophyll-contribute to the fluorescence of wool grease. The ‘grease’ fluorescence reveals the presence of a number of chromophores/components. An attempt to separate the chemical constituents and identify them was only partly successful as each of nine fractions obtained by preparatory thin-layer chromatography exhibited similar fluorescence properties. There are two types of chlorophyll presentchlorophyll a and chlorophyll b. Chlorophyll could be detected in all the wool greases examined. Artificial UV irradiation gave rise to a number of complex photochemical reactions including the destruction of chlorophyll. After an initial decrease in fluorescence intensity (for unknown reasons), there is a change of non-fluorescing visible-absorbing species to fluorescing UV-absorbing species before a final change in the latter to the former. The relative size of the changes was different for two different wool greases examined. In-situ studies using blue light as the irradiation source suggest that it also causes a (slower) decrease in fluorescence intensity, but proportionally faster for the ‘grease’ component than for the chlorophyll component.