1. Iron(III) sequestration by synthetic hydroxypyridinone siderophores and exchange with desferrioxamine B J. M. Harrington, 1 S. Dhungana, 1 S. Chittamuru, 2 H. K. Jacobs, 2 A. S. Gopalan, 2 and A.L. Crumbliss 1 1 Department of Chemistry, Duke University, Durham, NC 27708- 0346 and 2 Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003-8001

2. The Iron Paradox Precipitation of Fe(OH) 3 (Fe 2 O 3, etc.) Redox chemistry Able to Participate in Haber-Weiss Cycle

3. Synthetic Siderophores

4. N 2 (LH) 2 synthesis

5. N 2 (LH) 2 Thermodynamics pK a1 = 3.8 ±.1 pK a2 = 5.91 ±.09 pK a3 = 7.94 ±.05 pK a4 = 9.21 ±.02

6. Fe-N 2 (LH) 2 Competition + 2 EDTA  2 [Fe(EDTA)] + 3 [Fe 3+ ] = 2.47 x 10 -4 M, [N 2 (LH) 2 ] = 3.70 x 10 -4 M, T = 25 °C, μ = 0.10.

7. Fe-N 2 (LH) 2 spectrophotometric titration [Fe 3+ ] = 2.0 x 10 -4 M, [N 2 (LH) 2 ] = 3.0 x 10 -4 M, T = 25 °C, μ = 0.10. 2+ + 2 OH - 

8. Log β FeLH of Fe- N 2 (LH) 2 log β 230 = 60.46 ±.02 log β 110 = 20.39 ±.02 log β 111 = 21.3 ±.1 2 Fe 3+ + 3 N 2 (LH) 2  Fe 3+ + N 2 (LH) 2  Fe 3+ + N 2 (LH) 2 + H + 

9. Speciation for Fe-N 2 (LH) 2 system Fe(N 2 L 2 ) Fe 2 (N 2 L 2 ) 3 Fe(N 2 L 2 ) Fe 3+ Fe(OH) 4 - [Fe 3+ ] = 2 x 10 -4 M, [N 2 (LH) 2 ] = 3 x 10 -4 M, T = 25 °C, μ = 0.10. Fe(OH) 2+

10. N 3 (LH) 3 synthesis

11. N 3 (LH) 3 Thermodynamics pK a1 = 3.97 ±.07 pK a2 = 5.1 ±.1 pK a3 = 7.50 ±.02 pK a4 = 8.84 ±.03 pK a5 = 10.40 ±.04

12. Fe(N 3 (LH) 3 )-EDTA Competition [Fe +3 ] = [N 3 (LH) 3 ] = 4 x 10 -4 M, [EDTA] = 0- 10:1 equivalents, T = 25 °C, μ =0.10. + EDTA  Fe(EDTA) +

13. Fe-N 3 (LH) 3 spectrophotometric titration pK a = 3.10pK a2 = 13.22 [Fe 3+ ] = [N 3 (LH) 3 ] = 4.4 x 10 -4 M, T = 25 °C, μ =0.10

14. log β FeLH of N 3 (LH) 3 log β 110 = 27.34 ±.04 log β 111 = 30.44 ±.08 log β 11-1 = 17.66 ±.09 Fe 3+ + N 3 (LH) 3 + H +  Fe 3+ + N 3 (LH) 3  Fe 3+ + N 3 (LH) 3 + OH - 

15. Speciation for Fe-N 3 L 3 system Fe(N 3 L 3 )H Fe(N 3 L 3 ) Fe(N 3 L 3 )H [Fe 3+ ] = 1 x 10 -4 M, [N 3 (LH) 3 ] = 1 x 10 -4 M, T = 25 °C, μ = 0.10. Fe(N 3 L 3 ) Fe(N 3 L 3 )OH Fe 3+ Fe(OH) 4 - Fe(OH) 2+ Fe(N 3 L 3 )OH -

16. pFe values pFe = -log[Fe 3+ ] free LigandpFe 1 Deferiprone19.4 2 Rhodotorulic Acid21.90 3 N 2 (LH) 2 22.07 4 N 3 (LH) 3 23.49 4 Deferasirox23.5 5 Deferrioxamine B26.6 3 Enterobactin35.6 3 1 – [Fe +3 ] = 10 -6, [L] = 10 -5, pH = 7.4 2 – Liu, et al, J. Med. Chem., 1999, 42, 4814 3 – Harris, et al, JACS, 1979, 101, 2722 4 - This work 5 - Steinhauser, et al, Eur. J. Inorg. Chem., 2004, 2004, 4177

17. Host-Guest complex formation Batinic-Haberle, I.; Spasojevic, I.; Crumbliss, A. L.; Inorg. Chem.; 1996, 35(8), 2352-2359. Dhungana, S.; White, P. S.; Crumbliss, A. L.; JACS; 2003, 125(48), 14760-14767.

18. Host-Guest Complex EtOH/MeOH

19. Proposed Host-Guest complex DFB: N 3 (LH) 3 = 50:1 ESI-MS peak: Observed m/z = 1121.5 Proposed H 2 O adduct

20. Exchange kinetics of [FeN 3 L 3 ] with Desferrioxamine B Fit to single exponential decay k obs = 8.8 x 10 -5 sec -1, k 2nd, app = 0.0242 M -1 sec -1. +  +

21. Proposed exchange mechanism +   + ……

22. Conclusions N 2 (LH) 2 is a stable chelator of iron, and could provide insight into development of more effective chelation therapy treatments for iron overload. We also characterized the complexation reactions of N 3 (LH) 3 with iron, showing that it can bind iron effectively. An exchange reaction can be observed between N 3 (LH) 3 and deferrioxamine B, but not N 2 (LH) 2, suggesting that host-guest interaction may be involved in exchange mechanism.

23. Acknowledgements Thanks: Dr. Al Crumbliss Esther Tristani The Crumbliss Lab Group Duke University Center for Biomolecular and Tissue Engineering NIH NSF