Two Dimensional Multiwavelength Fluorescence Spectra of Dipicolinic Acid and Calcium Dipicolinate

摘要

Dipicolinic acid (DPA) and the Ca2+ complex of DPA (CaDPA) are major chemical components of bacterial spores. With fluorescence being considered for the detection and identification of spores, it is important to understand the optical properties of the major components of the spores. In this paper we report in some detail on the room temperature fluorescence excitation and emission spectra of DPA and its calcium ion complex and comparison of the excitation-emission spectrum in a dry, wet paste and aqueous form. DPA solutions have very weak, if any, fluorescence and it is only slightly greater in the dry state. After the exposure to a broad source UV light of the DPA, wet or dry, we observe a large increase in fluorescence with a maximum intensity emission peak at around 440 mn for excitation light with wavelength around 360 nm. There is a slight blue shift in the absorption spectra of UV exposed DPA from the unexposed DPA solution. CaDPA in solution and dried show very slight fluorescence and a substantial increase of fluorescence was observed after UV exposure with emission peak around 410 nm. for excitation around 305 nm. The detailed excitation-emission spectra presented here are necessary for better interpretation of the fluorescence spectra of bacterial spores where DPA is a major chemical component.