Siderophore Transport in Mycobacteria Analyzed by Mössbauer Spectroscopy: Possible Routes to Novel Antibiotics against These Organisms?

Iron uptake of the ⁵⁷Fe-siderophores ferricrocin, rhizoferrin and citrate in M. smegmatis was analyzed by in situ Mössbauer spectroscopy. Siderophore dependent uptake and metabolic utilization patterns of ⁵⁷Fe were found. Rhizoferrin is accumulated in the organism and, therefore, represents a suitable candidate for the synthesis of novel siderophore-antibiotics conjugates.     

Synthesis of heterocyclic sulfonylureas

We examined the scope of the previously reported one-pot synthesis [1] of chromone-3-sulfonylureas. Different anilines and heterocyclic amines were thereby reacted with chlorosulfonyl isocyanate-derived chlorosulfonylureas. These were treated with different enaminones and enamines to provide the title compounds.     

Relaxation as seen by nuclei: Comparison between conventional Mössbauer spectra and nuclear resonant scattering of synchrotron radiation

The mechanism of spin‐lattice relaxation has been investigated in the “picket‐fence” porphyrin [Fe(CH₃COO)(TP_pivP)]^-, a high‐spin iron(II) complex with unusual large quadrupole splitting of 4.25 mm s^-1, by conventional Mössbauer spectroscopy as well as by nuclear resonant forward scattering (NFS). Superparamagnetism with a blocking temperature of about 8 K is observable by both methods in the spectra of bacterioferritin from S. olivaceus. From these two examples general conclusions about the merits of both methods can be drawn.     

In vivo Mössbauer spectroscopy of iron uptake and ferrometabolism inEscherichia coli

Hyperfine Interactions - Iron limited growth of microbes results in derepression of siderophore receptor and transport-systems which can be utilized for controlled and specific siderophore...     

A57Fe Mössbauer study of iron assimilation inN. crassa mediated by siderophores

The siderophore coprogen is tansported in N. crassa as an entity. Neither ligand exchange nor reduction is a rate limiting step for intracellular accumulation. Metabolized iron was found predominantly to exist as fast relaxing Fe(II) high-spin (σ=1.32 mm/s, ΔE_Q=2.95 mm/s) and Fe(III) high-spin species (δ=0.35−0.42 mm/s ΔE_Q=0.5−0.58 mm/s). Within 27 hours, no measurable amounts of iron are transferred to ferritin like storage forms. Rather, coprogen itself serves as an intermediate iron storage compound.     

Mössbauer and EXAFS studies of bacterioferritin fromStreptomyces olivaceus

Mössbauer spectra of bacterioferritin fromStreptomyces olivaceus in zero field show essentially a transition from a quadrupole doublet to a six-line pattern at a temperature around 7–8 K and a distribution of hyperfine fields from 40 to 50 T. The EXAFS data reveal 3–4 phosphorus atoms in the second coordination shell. These features are found to be typical for various bacterioferritins.     

Synthesis of a novel heterocyclic system: 8-Fluro- 1,2,3,4,4a,10a-hexahydro-5H-[1]benzopyrano[2,3-c]pyridin-5-ol

The Synthesis of the title compound is described and its structure elucidated by ¹H nmr spectroscopy.     

Siderophores as iron storage compounds in the yeastsRhodotorula minuta andUstilago sphaerogena detected by in vivo Mössbauer spectroscopy

In the yeastsRhodotorula minuta andUstilago sphaerogena siderophores represent the main intracellular iron pool. We suggest a ferritin substituting function of these siderophores in addition to their role as iron transport agents. InRhodotorula transport and storage siderophore is the same compound whereas in Ustilago the iron-storage siderophore is ferrichrome. Besides siderophores, merely two iron metabolites can be observed. Other iron-requiring compounds are at least one order of magnitude less abundant in these yeasts. The ferrous metabolite has been detected in many other microbial systems and seems to be of general occurence and importance.