Fluorescence properties of biochemicals in dry NaCl composite aerosol particles and in solutions |
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Authors: | M Putkiranta A Manninen A Rostedt J Saarela T Sorvaj?rvi M Marjam?ki R Hernberg J Keskinen |
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Institution: | 1. Department of Physics, Aerosol Physics Laboratory, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland 2. Department of Physics, Optics Laboratory, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland
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Abstract: | Several fluorophores, such as tryptophan, NADH, NADPH, and riboflavin are found in airborne micro-organisms. In this work,
the fluorescence properties of these biochemicals were studied both in dry NaCl composite aerosol particles and in saline
solutions by means of laser-induced fluorescence. Fluorescence spectra were measured from individual, airborne aerosol particles
and from solutions in cuvette. The excitation wavelength was varied in steps from 210 nm to 419 nm and the fluorescence was
detected within a wavelength band of 310–670 nm. For each sample, the measured fluorescence emission spectra were combined
into fluorescence maps. The fluorescence maximum of riboflavin in a dry NaCl composite particle is 20 nm red-shifted compared
with the solution, whereas the maxima are blue-shifted by about 25 nm for tryptophan and 15 nm for NADH and NADPH. The molecular
fluorescence cross sections have significant differences between the aerosol particles and the solutions, except for tryptophan.
For NADH and NADPH the cross sections are over 20 times larger in the aerosol particles than in the solutions probably as
a result of partial quenching of fluorescence in solution caused by the collision or stacking with the adenine moiety. The
fluorescence cross section of riboflavin is almost 60 times larger in the solution than in the dry NaCl composite aerosol.
This is probably caused by the different microenvironment around the fluorophore molecule and by the concentration quenching
in the particles where the fluorescing molecules are relatively close to each other. |
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