Preparation of cationic polyacrylamides by a modified Hofmann reaction: Fluorescent labeling of cationic polyacrylamides |
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Authors: | Hiroo Tanaka Lars
dberg |
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Institution: | Hiroo Tanaka,Lars Ödberg |
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Abstract: | Cationic polyacrylamides (C-PAM) which contain both primary and quaternary amines were prepared according to the Hofmann reaction by adding choline chloride to a solution of polyacrylamide in water. The reaction was 90% complete after 60 min at 20°C. The degree of amination was over 70% and the proportion of primary and quaternary amines could be altered widely by controlling the relative concentrations of NaOH, NaOCl, and choline chloride. C-PAM was dansylated (fluorescently labeled) in a homogeneous system using aqueous dimethylformamide as solvent. The optimum excitation wavelength for dansylated C-PAM in water at room temperature (22 ± 1°C) was 333 nm and the corresponding emission wavelength 538 nm. The fluorescence intensity was almost constant at pH levels above 5, but decreased rapidly below pH 4 and was almost zero at pH 2. |
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