Autofluorescence of atmospheric bioaerosols – fluorescent biomolecules and potential interferences

Abstract

Primary biological aerosol particles (PBAP) are an important subset of air particulate matter with a substantial contribution to the organic aerosol fraction and potentially strong effects on public health and climate. Recent progress has been made in PBAP quantification by utilizing real-time bioaerosol detectors based on the principle that specific organic molecules of biological origin such as proteins, coenzymes, cell wall compounds and pigments exhibit intrinsic fluorescence. The properties of many fluorophores have been well documented, but it is unclear which are most relevant for detection of atmospheric PBAP. The present study provides a systematic synthesis of literature data on potentially relevant biological fluorophores. We analyze and discuss their relative importance for the detection of fluorescent biological aerosol particles (FBAP) by online instrumentation for atmospheric measurements such as the ultraviolet aerodynamic particle sizer (UV-APS) or the wide issue bioaerosol sensor (WIBS). <br><br> In addition, we provide new laboratory measurement data for selected compounds using bench-top fluorescence spectroscopy. Relevant biological materials were chosen for comparison with existing literature data and to fill in gaps of understanding. The excitation-emission matrices (EEM) exhibit pronounced peaks at excitation wavelengths of ~280 nm and ~360 nm, confirming the suitability of light sources used for online detection of FBAP. They also show, however, that valuable information is missed by instruments that do not record full emission spectra at multiple wavelengths of excitation, and co-occurrence of multiple fluorophores within a detected sample will likely confound detailed molecular analysis. Selected non-biological materials were also analyzed to assess their possible influence on FBAP detection and generally exhibit only low levels of background-corrected fluorescent emission. This study strengthens the hypothesis that ambient supermicron particle fluorescence in wavelength ranges used for most FBAP instruments is likely to be dominated by biological material and that such instrumentation is able to discriminate between FBAP and non-biological material in many situations. More detailed follow-up studies on single particle fluorescence are still required to reduce these uncertainties further, however

Protein Cross-Linking and Oligomerization through Dityrosine Formation upon Exposure to Ozone

“…Fluorescence spectra were recorded on a LS 45 luminescence spectrometer (PerkinElmer, Inc., Waltham, MA, USA). A detailed instrument description is given in Poḧlker et al 31 Samples were analyzed in a 10 × 10 × 40 mm UV quartz cuvette (Hellma Analytics, Mullheim, Germany). The photomultiplier tube detector voltage was 600 V. Excitation wavelengths were 240−400 nm (10 nm increments), whereas emission was recorded from 280 to 560 nm (0.5 nm increments).…”

Photophoretic trapping-Raman spectroscopy for single pollens and fungal spores trapped in air

“…Light at 488 nm is known to excite relatively strong fluorescence in bacteria and tree leaves [8]. Sporopollenin in pollens and fungal spores is reported to fluoresce in the 400-650 nm range with high fluorescence intensity when excited at 300-550 nm [56,57]. Flavins are likely to be a main contributor to the fluorescence in the 500-580 nm range in bacteria, but probably contribute a much smaller fraction of the fluorescence in this range in pollens and fungal spores because they have many other fluorescent molecules [56,57].…”

Identification of single microbial particles using electro-dynamic balance assisted laser-induced breakdown and fluorescence spectroscopy

“…Fluorescence spectra or fluorescence band (single or multiple) intensity measurement can be utilized to discriminate bioaerosols from other aerosols (P€ ohlker et al 2012;Pan 2015). Fluorescence-based online bioaerosol instruments, such as BioScout, WIBS, and UV-APS, have been used in various environments, but it is really challenging to classify different types of bioaerosols with these instruments (Gabey et al 2010;Huffman et al 2010;Saari et al 2014).…”

“…It is an effective method for detecting biological molecules such as tryptophan, NAD(P)H, and flavins that are typically present in microbial cells (Lakowicz 2009). LIF enables the differentiation of bioaerosols from other airborne particles through their fluorescence ability (P€ ohlker et al 2012;Hill et al 2013). Saari et al (2013) demonstrated that bacterial and fungal spores may be distinguished from each other through their dissimilar fluorescence spectra.…”

“…Furthermore, these methods have relatively low time resolution (Reponen et al 2011). Laser-induced fluorescence (LIF) is a modern technique for real-time bioaerosol detection (Hill et al 1995;Kaye et al 2005;P€ ohlker et al 2012). It is an effective method for detecting biological molecules such as tryptophan, NAD(P)H, and flavins that are typically present in microbial cells (Lakowicz 2009).…”