TY - JOUR A1 - Reinmuth-Selzle, K. A1 - Tchipilov, Teodor A1 - Backes, A. T. A1 - Tscheuschner, Georg A1 - Tang, K. A1 - Ziegler, K. A1 - Lucas, K. A1 - Pöschl, U. A1 - Fröhlich-Nowoisky, J. A1 - Weller, Michael G. T1 - Determination of the protein content of complex samples by aromatic amino acid analysis, liquid chromatography-UV absorbance, and colorimetry N2 - Fast and accurate determination of the protein content of a sample is an important and non-trivial task of many biochemical, biomedical, food chemical, pharmaceutical, and environmental research activities. Different methods of total protein determination are used for a wide range of proteins with highly variable properties in complex matrices. These methods usually work reasonably well for proteins under controlled conditions, but the results for non-standard and complex samples are often questionable. Here, we compare new and well-established methods, including traditional amino acid analysis (AAA), aromatic amino acid analysis (AAAA) based on the amino acids phenylalanine and tyrosine, reversed-phase liquid chromatography of intact proteins with UV absorbance measurements at 220 and 280 nm (LC-220, LC-280), and colorimetric assays like Coomassie Blue G-250 dye-binding assay (Bradford) and bicinchoninic acid (BCA) assay. We investigated different samples, including proteins with challenging properties, chemical modifications, mixtures, and complex matrices like air particulate matter and pollen extracts. All methods yielded accurate and precise results for the protein and matrix used for calibration. AAA, AAAA with fluorescence detection, and the LC-220 method yielded robust results even under more challenging conditions (variable analytes and matrices). These methods turned out to be well-suited for reliable determination of the protein content in a wide range of samples, such as air particulate matter and pollen. KW - Air particulate matter KW - Aromatic amino acid analysis KW - Atmospheric aerosol KW - Chemical protein modification KW - Derivatization KW - Nitration KW - Nitrotyrosine KW - LC-UV absorbance KW - Pollen extract KW - Protein quantification KW - Protein test KW - Kjeldahl KW - Tyrosine KW - Phenylalanine KW - Hydrolysis KW - Bradford KW - BCA test KW - 280 nm KW - Air filter samples KW - Fluorescence KW - HPLC KW - Chromatography KW - Protein content KW - 150th anniversary of BAM KW - Topical collection: Analytical Methods and Applications in the Materials and Life Sciences PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-545924 UR - https://pubmed.ncbi.nlm.nih.gov/35320366/ SP - 1 EP - 14 PB - Springer Nature Limited CY - New York, Heidelberg AN - OPUS4-54592 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -