A FLUORESCENCE DOUBLE-QUENCHING STUDY OF NATIVE LIPOPROTEINS IN AN ANIMAL-MODEL OF MANGANESE DEFICIENCY

Iodide and acrylamide were applied simultaneously in a double-quenchin g experiment to compare acrylamide quenching constants for internal an d external fluorophores of high-density Lipoproteins (HDL1 and HDL2) f rom manganese-adequate (MnA) and deficient (MnD) rats, free of the ele ctrostatic effects associated with iodide. In MnA HDL1 compared to MnD HDL1, the acrylamide quenching constant for external fluorophores was different (P < 0.1). In MnA HDL2, there were two populations of fluor ophores accessible to acrylamide, whereas in MnD HDL2, all fluorophore s were accessible to both quenchers. We concluded that there were stru ctural (local environmental) differences, possibly charge-related, aro und the external fluorophores, and a slightly larger population of bur ied fluorophores in the MnD HDL1 compared with MnA HDL1. In MnA HDL2, one-third of the fluorophores were accessible to iodide, and all exter nal and internal fluorophores were accessible to acrylamide, whereas i n MnD HDL2, all fluorophores were accessible to both quenchers.