ULTRAVIOLET-FLUORESCENCE MICROSCOPY OF PAINT CROSS SECTIONS:
JOHN M. MESSINGER
This study was undertaken to investigate the viability of using cycloheptaamylose-dansyl chloride complex (DC-C7A) as a fluorochrome marker for detecting proteins in paint cross sections. Dansyl chloride is a common reagent used for the fluorescent labeling and microanalysis of proteins (Kinoshita et al 1974, 1975). In water it is insoluble and hydrolyzed to the sulfonic acid. Dansyl chloride can be complexed with B-cyclodextrin to yield cycloheptaamylose-dansyl chloride complex, a reagent that is both soluble in aqueous urea solution, and very slow to hydrolyze. It was felt that this reagent might selectively stain proteins so that they could be examined by fluorescence microscopy.
To ascertain the strengths and limitations of DC-C7A, it was imperative to compare the selectivity to stain protein containing materials and the color and uniformity of staining of DC-C7A to the those properties of two other fluorochromes commonly used to detect proteins in paint cross sections: lissamine rhodamine B sulfonyl chloride (LISSA) (Wolbers and Landrey 1987) and fluorescein isothiocyanate (FITC) (Wolbers and Landrey 1987; Wolbers 1988). These stains were also compared to the commonly utilized non-fluorochrome protein stain amido black (AB2) (Martin 1977), and the stains for oil: Sudan black (SB) (Johnson and Packard 1971), and the fluorochromes rhodamine B (RB) (Wolbers and Landrey 1987) and 2′,7′ dichlorofluorescein (DCF) (Wolbers and Landrey 1987).
These stains were used to stain the following types of known media: linseed oil, casein, tempera, glair, gelatin, rabbit skin glue, and a few acrylic emulsions. Some of the media were also examined while loaded with such pigments as gypsum, whiting, titanium white, zinc white, turquoise, lamp black, and ultramarine. It was also noted whether the samples exhibited autofluorescence (fluorescence in the absence of any stain).