Dithio compounds

1. A dithio compound having a formula D-X 1 —S—S—X 2 -A, wherein D comprises a donor fluorophore; at least one of X 1 and X 2 comprises an aryl group; and A comprises an acceptor fluorophore that is different from the donor fluorophore and that is capable of at least one of:

(A) quenching the donor fluorophore;

(B) increasing or decreasing an extinction coefficient of the donor fluorophore; and

(C) exhibiting sensitized emission when excited by the donor fluorophore.

2. The compound of claim 1 , wherein the donor fluorophore has an absorbance maximum and the acceptor fluorophore has an absorbance maximum that differ by at least about 10 nm.

3. The compound of claim 1 , wherein the donor fluorophore has an emission maximum and the acceptor fluorophore has an emission maximum that differ by at least about 10 nm.

4. The compound of claim 1 , wherein the donor fluorophore has an emission spectrum and the acceptor fluorophore has an absorption spectrum, such that the emission spectrum and absorption spectrum overlap.

5. The compound of claim 4 , wherein the emission spectrum and the absorption spectrum overlap by at least about 20%.

6. The compound of claim 1 , wherein the acceptor fluorophore is capable of quenching the donor fluorophore by dynamic quenching.

7. The compound of claim 6 , wherein the dynamic quenching occurs by fluorescence resonance energy transfer.

8. The compound of claim 1 , wherein the acceptor fluorophore is capable of quenching the fluorophore by static quenching.

9. The compound of claim 1 , wherein the sensitized emission includes fluorescence.

10. The compound of claim 1 , wherein the sensitized emission occurs by fluorescence resonance energy transfer.

11. The compound of claim 1 , wherein the donor fluorophore and the acceptor fluorophore are present in the compound at a distance of about 3-50 angstroms.

12. The compound of claim 1 , wherein the donor fluorophore and the acceptor fluorophore are present in the compound at a distance of no more than about 20 angstroms.

13. The compound of claim 1 , wherein the donor fluorophore comprises a xanthene-type fluorophore.

14. The compound of claim 1 , wherein the acceptor fluorophore comprises a xanthene-type fluorophore.

15. A method for preparing the compound of claim 1 comprising reacting precursors that include:

(A) a first precursor that comprises a donor fluorophore;

(B) a second precursor that comprises an acceptor fluorophore; and

(C) a dithio reagent having the formula X 1 —S—S—X 2 , wherein X 1 and X 2 may be the same or different and each comprise reactive groups capable of reacting with the first precursor and the second precursor.

16. The compound of claim 1 , wherein both of X 1 and X 2 comprise an aryl group.

17. The compound of claim 1 , wherein the aryl group is substituted with an amide group.

18. The compound of claim 17 , wherein at least one of X 1 and X 2 comprise an aryl group substituted with an amide group and having a formula selected from:

19. The compound of claim 18 , wherein both of X 1 and X 2 comprise an aryl group substituted with an amide group and having a formula selected from:

20. The compound of claim 19 , wherein the dithio compound has a formula:

21. The compound of claim 1 , wherein the donor fluorophore is selected from a group consisting of fluorescein and Alexa488 and the acceptor fluorophore is selected from a group consisting of para-methyl red and rhodamine.

22. The compound of claim 1 , wherein the donor fluorophore is coumarin and the acceptor fluorophore is fluorescein.

23. The method of claim 15 , wherein the dithio reagent is a diaminodiphenyldisulfide reagent.

24. The method of claim 23 , wherein the diaminodiphenyldisulfide reagent is p,p′-diaminodiphenyldisulfide.

25. A dithio compound having a formula D-S—S-A, wherein D comprises coumarin and A comprises fluorescein.