A class of sulforhodamine labeling reagents capable of binding with a biomolecular species to produce a conjugate with fluorescent properties. The sulforhodamine labeling reagents have the structure: ##STR1## The group X is selected from an alkyl, an olefin, a monocyclic aliphatic saturated hydrocarbon, an aryl, or nothing at all. The group Y is selected from an amide, a substituted amide, or nothing at all. The group Z is selected from a monocyclic aliphatic hydrocarbon, an aryl, or an alkyl, as defined with respect to group X, a polyethylene glycol chain of the general form (CH.sub.2 CH.sub.2 O).sub.n, or nothing at all. The alkyl or polyethylene glycol chain may further have inert intermediate amide, ether, or disulfide functionalities. The group X, group Y, and group Z cannot all be nothing at all or non-existent. The group R is an electrophilic moiety suitable for conjugation of the fluorescent labeling reagent with a biomolecular species. Also disclosed is a method of making the reagents.
The invention describes reactive dyes having an alkyl spacer attached via a sulfonamide bond to a sulforhodamine 101 fluorophore, and a variety of useful conjugates prepared therefrom. The increased length of the covalent linkage due to the alkyl spacer results in dye-conjugates having a number of surprisingly advantageous properties relative to previous sulforhodamine 101-labeled conjugates, including enhanced solubility and increased fluorescence. The reactive dyes of the present invention are more stable than the known compound sulforhodamine 101 sulfonyl chloride. Novel reactive dyes are described for selective modification of groups other than amines, including thiols and photoreactive derivatives.
