AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Fluorescence of Bioaerosols: Concentrations and Optical Properties of Relevant Molecules Needed for Modeling Emission from Bacteria
STEVEN HILL, Yong-Le Pan, Chatt Williamson, Joshua Santarpia, Hanna Hill, US Army Research Laboratory
Abstract Number: 69 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract Fluorescence is useful for detection and partial classification of bioaerosols, especially in flow-through single-particle systems. A problem in modeling the fluorescence of bioaerosols is in estimating/finding the concentrations and optical properties of the fluorescent and other absorbing molecules in bioaerosols. We have extracted/estimated from the microbiology and biochemistry literature the concentrations, absorption and fluorescence spectra, and fluorescence quantum yields of the main absorbing and fluorescing primary metabolites and macromolecules in bacteria. Included are amino acids and nucleic acids (and polymers of these: proteins, DNA, RNA); coenzymes (nicotinamide adenine dinucleotides, flavins, vitamers of B6); quinols; and calcium dipicolinate. Secondary metabolites are not included. The uncertainties in the numbers extracted range from less than 10% (e.g., for the molar absorptivity of DNA) to 20 fold or more (e.g., for the concentrations of several metabolites in bacteria when the growth conditions are unknown). We also describe a simple model that uses these concentrations and optical properties to simulate the emission from particles composed of bacteria, viruses or proteins. The bioparticles are modeled as homogeneous spheres. Calculated total fluorescence cross sections for particles excited at 266, 280, and 355 nm are compared with measured values from the literature for several bacteria, bacterial spores and albumins. The calculated 266-nm and 280-nm excited fluorescence is within a factor of 3.5 of the measurements for the vegetative cells and proteins. However, the measured fluorescence of spores is overestimated by a factor of 10 or more, suggesting that in spores the fluorescence of tryptophan is significantly quenched.
Acknowledgements
This research was supported by the Basic and Supporting Science--program of the Defense Threat Reduction Agency (DTRA) and US Army Research Laboratory (ARL) mission fund.