More allergies due to moist fine dust?

Protein-containing suspended particles change chemically in moist air

From glass to gel: In the light microscope, it is easy to see how a particle of the protein bovine serum albumin (BSA) alters its structure when it absorbs moisture. Its contours soften as the glassy particle swells. This also makes it easier to access for chemical changes. © Manabu Shiraiwa / MPII for Chemistry
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How strong pollen and other organic suspended particles in the air cause allergies, among other things, depends on the humidity: For as a research team has now found, change protein-containing particles at high humidity of a glassy to a gelatinous consistency. The resulting chemical changes make the particles more potent allergens. The formation of precipitation is also promoted, as the scientists report in the journal "Proceedings of the National Academy of Sciences" (PNAS).

It is well known from the local kitchen that protein-based foods remain dried for longer. Moist, they are rapidly decomposed by microorganisms and chemically oxidized faster. Researchers led by Ulrich Pöschl and Manabu Shiraiwa at the Max Planck Institute for Chemistry have now discovered that moisture also accelerates the chemical changes that atmospheric proteins experience in air pollutants. High humidity and oxidizing gases such as ozone cause the proteins in organic particulate matter such as flower pollen to age chemically faster.

From the glass to the gel

When dry, proteins are glassy and can only be oxidized and decomposed at their surface by reactive gases such as ozone. However, when the humidity is high, the proteins absorb water and change from a glassy state to a kind of gel. "The protein gel has water-filled pores and channels that allow ozone and other reactive gases to penetrate the entire protein and chemically alter it. This not only changes the molecular structure, but also the biological function, "explains Shiraiwa. "We calculated that the protein conversion half-life can be reduced from days to a few seconds, depending on humidity, temperature, and ozone levels."

Allergenic potential of pollen increases

The results are important, for example, to better assess the harmful effects of organic particulate matter. For example, ozone and nitrogen oxides increase the allergenic effects of proteins in pollen or pollen grains. This is also referred to as summer smog air pollution with high concentrations of ozone and nitrogen oxides, it is especially in the summer months in high traffic density and strong sunlight.

"These air pollutants are therefore suspected to be involved in the increase of allergic diseases in industrialized countries. Similar reactions are also involved in the influence of air pollution on airway inflammation and biological aging processes, "explains P schl, head of the study. display

More precipitation due to organic fine dust

The moisture-dependent phase transformation from the glassy to the gelatinous protein also influences how organic particulate matter behaves in the atmosphere. Moist, gel-like aerosol particles react with atmospheric trace gases and can form liquid cloud droplets. By contrast, glassy particles are largely inert, meaning that they are not involved in chemical reactions. However, they can serve as crystallization nuclei for ice crystals, which are involved in the formation of precipitate.

In further experiments and model calculations, the researchers now want to further determine the influence of moisture content and phase state on the reactivity of organic particles in order to quantify and predict the effects of particulate matter on health and climate. (Proceedings of the National Academy of Sciences online, 2011; doi: 10.1073 / pnas.1103045108)

(Max Planck Society, 27.06.2011 - NPO)