THE INFLUENCE OF LABELING MECHANISMS ON THE FLUORESCENCE BEHAVIOR OF POLYMERS BEARING FLUORESCEIN LABELS

The labelling of macromolecules by fluorescent labels is a well establ ished method for studying their motion, location and environment. Ther e are a wide range of labels and methods for attaching these to polyme rs, and the resulting fluorescence behaviour can depend on both the la bel and labelling method. Fluorescein is a commonly used label because of its relative ecological safety and its pH dependence. Various meth ods for attaching fluorescein (via its amine derivative) and eosin to water soluble polymers were investigated, together with the effect on fluorescence behaviour. For fluoresceinamine, it was necessary to prev ent the lone pair on the nitrogen from quenching the fluorescence by u sing an amide (via Woodwards reagent) or isothiocyanate as the linking group between the label and macromolecule. This also largely preserve d the well known pH dependence of the fluorescence of fluorescein. Eos in (tetra bromo fluorescein) provides a constant fluorescent intensity over a wider pH range than fluorescein and can be linked to macromole cules via the carboxyl group without significantly influencing this pH stability. (C) 1997 Elsevier Science Ltd.