A study of cellular transport with the fluorescent amino acid, aminonaphthylalanine

Fluorescent positional isomers of aminonaphthylalanine were shown to be actively transported by Sarcoma 37 mouse ascites cells. After concentrative uptake by the cells, the fluorescence of the amino acid inside the cells showed the same excitation and emission spectra, the same quantum yield, the same temperature coefficient, and essentially the same degree of polarization as did the fluorescence of the amino acids in aqueous solution. Comparison of these results with data obtained from fluorescent compounds known to bind to macromolecules and whose parameters of fluorescence did change inside the cells suggests that the concentrative aspects of amino acid uptake are not due to binding onto macromolecules within the cell.