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Opt Express ; 26(3): 3646-3660, 2018 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-29401892


Laser-induced fluorescence (LIF) techniques to analyze atmospheric aerosols are commonly applied for research and human exposure monitoring, but are very expensive or offer poor spectral resolution. Here, we discuss how a recently proposed instrument can acquire resolved fluorescence spectra from many individual particles in a single camera image using four excitation wavelengths matched with common biological fluorophores for particle discrimination at lower cost. We discuss emission intensity calibration and demonstrate spectral differentiation among four species of pollen. These data provide context for how the instrument could be developed for pollen and mold-spore detection or for use by citizen scientists.

Fungos , Pólen , Espectrometria de Fluorescência/instrumentação , Calibragem , Humanos , Lasers
Anal Bioanal Chem ; 410(4): 1389-1396, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29214534


Lactoferrin (LF) is an important multifunctional protein that comprises a large fraction of the protein mass in certain human fluids and tissues, and its concentration is often used to assess health and disease. LF can be nitrated by multiple routes, leading to changes in protein structure, and nitrated proteins can negatively impact physiological health via nitrosative stress. Despite an awareness of the detrimental effects of nitrated proteins and the importance of LF within the body, cost-effective methods for detecting and quantifying nitrated lactoferrin (NLF) are lacking. We developed a procedure to selectively quantify NLF using sandwich enzyme-linked immunosorbent assay (ELISA), utilizing a polyclonal anti-LF capture antibody paired with a monoclonal anti-nitrotyrosine detector antibody. The assay was applied to quantify NLF in samples of pure LF nitrated via two separate reactions at molar ratios of excess nitrating agent to the total number of tyrosine residues between 10/1 and 100/1. Tetranitromethane (TNM) was used as a laboratory surrogate for an environmental pathway selective for production of 3-nitrotyrosine, and sodium peroxynitrite (ONOO-) was used as a surrogate for an endogenous nitration pathway. UV-vis spectroscopy (increased absorbance at 350 nm) and fluorescence spectroscopy (emission decreased by > 96%) for each reaction indicate the production of NLF. A lower limit of NLF detection using the ELISA method introduced here was calculated to be 0.065 µg mL-1, which will enable the detection of human-physiologically relevant concentrations of NLF. Our approach provides a relatively inexpensive and practical way to assess NLF in a variety of systems. Graphical abstract We developed a procedure to selectively quantify nitrated lactoferrin (NLF) protein using a sandwich enzyme-linked immunosorbent assay (ELISA) and verified results against several spectroscopic techniques. Our approach provides an inexpensive and practical way to assess NLF in a variety of systems.

Exposição Ambiental , Ensaio de Imunoadsorção Enzimática/métodos , Lactoferrina/análise , Nitratos/química , Doença , Humanos , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta
Nature ; 525(7568): 234-8, 2015 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-26354482


The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties. The formation of ice in clouds is facilitated by the presence of airborne ice-nucleating particles. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice. Sea-spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer. Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice-nucleating material is probably biogenic and less than approximately 0.2 micrometres in size. We find that exudates separated from cells of the marine diatom Thalassiosira pseudonana nucleate ice, and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice-nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol, in combination with our measurements, suggest that marine organic material may be an important source of ice-nucleating particles in remote marine environments such as the Southern Ocean, North Pacific Ocean and North Atlantic Ocean.

Atmosfera/química , Gelo , Aerossóis/síntese química , Aerossóis/química , Ar , Organismos Aquáticos/química , Regiões Árticas , Diatomáceas/química , Congelamento , Compostos Orgânicos/análise , Compostos Orgânicos/química , Fitoplâncton/química , Água do Mar/química
Environ Sci Technol ; 42(12): 4478-85, 2008 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-18605574


A recently developed method to rapidly quantify the elemental composition of bulk organic aerosols (OA) using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is improved and applied to ambient measurements. Atomic oxygen-to-carbon (O/C) ratios characterize the oxidation state of OA, and O/C from ambient urban OA ranges from 0.2 to 0.8 with a diurnal cycle that decreases with primary emissions and increases because of photochemical processing and secondary OA (SOA) production. Regional O/C approaches approximately 0.9. The hydrogen-to-carbon (H/C, 1.4--1.9) urban diurnal profile increases with primary OA (POA) as does the nitrogen-to-carbon (N/C, approximately 0.02). Ambient organic-mass-to-organic-carbon ratios (OM/OC) are directly quantified and correlate well with O/C (R2 = 0.997) for ambient OA because of low N/C. Ambient O/C and OM/OC have values consistent with those recently reported from other techniques. Positive matrix factorization applied to ambient OA identifies factors with distinct O/C and OM/OC trends. The highest O/C and OM/OC (1.0 and 2.5, respectively) are observed for aged ambient oxygenated OA, significantly exceeding values for traditional chamber SOA,while laboratory-produced primary biomass burning OA (BBOA) is similar to ambient BBOA, O/C of 0.3--0.4. Hydrocarbon-like OA (HOA), a surrogate for urban combustion POA, has the lowest O/C (0.06--0.10), similar to vehicle exhaust. An approximation for predicting O/C from unit mass resolution data is also presented.

Aerossóis/análise , Espectrometria de Massas/métodos , Calibragem