Analysis of egg-based model wall paintings by use of an innovative combined dot-ELISA and UPLC-based approach

Abstract

The chemical analysis of egg-based wall paintings-the mezzo fresco technique-is an interesting topic in the characterisation of organic binders. A revised procedure for a dot-enzyme-linked immunosorbent assay (dot-ELISA) able to detect protein components of egg-based wall paintings is reported. In the new dot-ELISA procedure we succeeded in maximizing the staining colour by adjusting the temperature during the staining reaction. Quantification of the colour intensity by visible reflectance spectroscopy resulted in a straight line plot of protein concentration against reflectance in the wavelength range 380-780 nm. The modified dot-ELISA procedure is proposed as a semi-quantitative analytical method for characterisation of protein binders in egg-based paintings. To evaluate its performance, the method was first applied to standard samples (ovalbumin, whole egg, egg white), then to model specimens, and finally to real samples (Giotto's wall paintings). Moreover, amino acid analysis performed by innovative ultra-performance liquid chromatography was applied both to standards and to model samples and the results were compared with those from the dot-ELISA tests. In particular, after protein hydrolysis (24 h, 114 °C, 6 mol L(-1) HCl) of the samples, amino acid derivatization by use of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate enabled reproducible analysis of amino acids. This UPLC amino acid analysis was rapid and reproducible and was applied for the first time to egg-based paintings. Because the painting technique involved the use of egg-based tempera on fresh lime-based mortar, the study enabled investigation of the effect of the alkaline environment on egg-protein detection by both methods.

Tween 80 and respiratory growth affect metabolite production and membrane fatty acids inLactobacillus caseiN87

“…(Florence, Italy), through the AccQ•Tag Ultra Performance Liquid Chromatography, according to Potenza et al . ().…”

“…The concentrations of amino acids in the supernatants were measured by Espikem S.r.l. (Florence, Italy), through the AccQ•Tag Ultra Performance Liquid Chromatography, according to Potenza et al (2013).…”

Identification of Ancient Silk Using an Enzyme-linked Immunosorbent Assay and Immuno-fluorescence Microscopy

“…[10][11][12][13][14][15][16][17] In recent years, immunological techniques have attracted increasing attention by those working in cultural heritage. For example, milk residues, 18,19 protein-bound materials and organic bones have been detected, [20][21][22][23][24][25] and all of these studies have demonstrated that immunoassays have the potential to identify and localize the proteins in archaeological materials both rapidly and effectively. However, most of the antibodies used in these immunoassays are readily commercially available "off-theshelf", and the need for tailored antibodies for targeted cultural heritages with high sensitivity and specificity is increasingly desirable.…”

Electrochemical Immunosensor for Detection of IgY in Food and Food Supplements

“…Different analytical methods have been proposed to identify and quantify IgY from egg yolk: ELISA; HPLC [6][7][8]; a biosensor based on surface plasmon resonance [9]; a nanostructured sensor based on electrochemical detection [10]; an electrochemical immunoassay based on electrodes arrays [11]; fluorescence switch assay [12]; or resonance light scattering [13].…”