Sarasanandarajah Sivananthan, Kunnil Joseph, Bronk Burt V, Reinisch Lou
Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
Appl Opt. 2005 Mar 1;44(7):1182-7. doi: 10.1364/ao.44.001182.
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. We report in some detail on the room-temperature fluorescence excitation and emission spectra of DPA and its calcium ion complex and provide a comparison of the excitation-emission spectrum in a dry, wet paste and aqueous form. DPA solutions have weak, if any, fluorescence, with increased fluorescence when the DPA is dry. After 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 nm for excitation light with a wavelength of around 360 nm. There is a slight blueshift in the absorption spectra of UV-exposed DPA from the unexposed DPA solution. CaDPA in solution shows a slight fluorescence with increased fluorescence in the dry form, and a substantial increase of fluorescence was observed after UV exposure with an emission peak of around 410 nm for excitation around 305 nm. The detailed excitation-emission spectra are necessary for better interpretation of the fluorescence spectra of bacterial spores where DPA is a major chemical component.
吡啶二羧酸（DPA）及其与钙离子的复合物（CaDPA）是细菌芽孢的主要化学成分。鉴于荧光被用于芽孢的检测和鉴定，了解芽孢主要成分的光学性质很重要。我们详细报道了DPA及其钙离子复合物在室温下的荧光激发和发射光谱，并对其在干燥、湿糊和水溶液形式下的激发 - 发射光谱进行了比较。DPA溶液即使有荧光也很微弱，当DPA干燥时荧光增强。将干燥或湿润的DPA暴露于宽谱紫外光后，我们观察到荧光大幅增强，对于波长约为360 nm的激发光，最大强度发射峰在约440 nm处。与未暴露的DPA溶液相比，紫外暴露的DPA的吸收光谱有轻微蓝移。溶液中的CaDPA有轻微荧光，干燥形式下荧光增强，紫外暴露后荧光大幅增加，对于约305 nm的激发光，发射峰在约410 nm处。对于以DPA为主要化学成分的细菌芽孢荧光光谱的更好解释，详细的激发 - 发射光谱是必要的。
