Thermo-FTIR spectroscopic study of the siderophore ferrioxamine B: Spectral analysis and stereochemical implications of iron chelation, pH, and temperature

Hagar Siebner-Freibach, Shmuel Yariv, Yitzhak Lapides, Yitzhak Hadar, Yona Chen

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

FTIR spectra of the microbial siderophore, ferrioxamine B, and its nonchelated form (iron free; desferrioxamine B) were studied to facilitate in-depth investigation on the undisrupted structure of the siderophore and its interactions with the environment. Effects of iron chelation as well as those of various levels of pH and temperature on the stereochemical structure of the free ligand and the ferric complex were examined. The presence of a number of functional groups in these compounds and the mutual interaction between them resulted in significant shifts and overlapping of their characteristic absorption bands. Thermal and pH treatments combined with a comprehensive use of curve-fitting analysis facilitated bands resolution. Absorption bands of all functional groups were identified. The results imply that the compact and rigid structure of the ferric complex (ferrioxamine B) is sustained by intense and specific intramolecular hydrogen bonds. Dehydration was the main process observed at low temperature (25-60°C). At 105°C the free ligand form (desferrioxamine B) had already begun to decompose, whereas ferrioxamine B exhibited stability. The thermal destruction became acute at the 170°C treatment for both molecules. The secondary amide groups and the hydroxamate groups, which comprise the binding site for the Fe atom in the complex, were found to be the most sensitive to the thermal degradation. Significant pH effects were observed only for desferrioxamine B samples at pH 9, accompanied by partial decomposition, similar to that observed at 105°C. Deprotonation of desferrioxamine B was found to begin with the deprotonation of the NH 3+ group. Characteristics of the rigid conformational structure of the ferric complex and the state of the NH3+ group, both assumed to play an important role in the recognition and uptake of the siderophore by membranal receptors, were elaborated by means of FTIR and are discussed in detail.

Original languageEnglish
Pages (from-to)3434-3443
Number of pages10
JournalJournal of Agricultural and Food Chemistry
Volume53
Issue number9
DOIs
StatePublished - 4 May 2005
Externally publishedYes

Keywords

  • Desferrioxamine B
  • Ferrioxamine B
  • IR spectroscopy
  • Siderophore

ASJC Scopus subject areas

  • Chemistry (all)
  • Agricultural and Biological Sciences (all)

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