Two-dimensional multiwavelength fluorescence spectra of dipicolinic acid and calcium dipicolinate

Abstract

Public reporting burden (or this collection of information is estimated AUTHOR(S)Sivananthan Sarasanandarajah, Joseph Kunnil, Burt V. Bronk, Lou Reinisch PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Department of Physics and Astronomy University of Canterbury Private Bag 4800 Christchurch, New Zealand SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Air AFRL-HE-WP-TR-2004-0140 SUPPLEMENTARY NOTES 12a. DISTRIBUTION AVAILABILITY STATEMENTApproved for Public Release; distribution is unlimited. 12b DISTRIBUTION CODE ABSTRACT (Max/mum 200 words)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 nm 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.

Autofluorescence of atmospheric bioaerosols – fluorescent biomolecules and potential interferences

“…The emission occurs around 440 nm, with an excitation maximum at 360 nm. The calcium salt CaDPA is also known to be fluorescent with peak emission at approximately 410 nm, when excited between 280 and 340 nm (Alimova et al, 2003;Sarasanandarajah et al, 2005). Since DPA occurs exclusively in bacterial endospores, it has been used as a spectral signature for spore detection (Bronk et al, 2000).…”

“…Note that experimental data for DPA are not available through the present study, but were added to Fig. 3 from Sarasanandarajah et al (2005) because of its importance in bacterial spores. Both emission hotspots directly correspond with the operational range of most bioaerosol detectors, as shown in Fig.…”

Modeling LIDAR Detection of Biological Aerosols to Determine Optimum Implementation Strategy

“…Riboflavin absorption peaks at 385 nm and its broadband emission peaks at 525 nm (NRC 2005). And with excitation at 360 nm, observance of 440 nm peak fluorescence from dipicolinic acid (DPA) can be used to discriminate between vegetative and sporulated bacteria (Nudelman et al 2000;Sarasanandarajah et al 2005a). Research is currently underway to determine if adding these additional excitation wavelengths will enhance the ability to determine viability at the same time as discriminating biological spores from vegetative bacteria or non-biological particles in the environment.…”

Semiquantitative model for response of biological molecules containing C, N, O and H to laser pulses, with initial application to dipicolinic acid

“…This molecule is prevalent in bacterial spores [17,18] and has been used as a marker molecule in various spectroscopic detection schemes [17,[19][20][21][22]. This molecule is an ideal test molecule for our parameters as it contains the atoms oxygen and nitrogen yet consists of a parent ring structurally similar to benzene, a molecule we have previously investigated with SERID [5,23].…”