Gerhard Kunesch

Desferrioxamine-dependent iron transport in Erwinia amylovora CFBP1430: cloning of the gene encoding the ferrioxamine receptor FoxR

Iron deprivation of Erwinia amylovora CFBP1430, a species causing fire blight on Pomoïdeae, was shown to induce the production of siderophores of the desferrioxamine (dfo) family and two outer membrane polypeptides with apparent molecular weight of about 70 and 80 kDa, respectively. Cyclic dfo E was characterized as the major metabolite. Phage MudIIpR13 insertional mutagenesis and screening on CAS-agar medium yielded three dfo non-producing and one overproducing clones. These clones failed to grow in the presence of the Fe(III) chelator EDDHA and were determined further as dfo and ferrioxamine transport negative mutants, respectively. The transport mutant which appeared to lack the 70 kDa polypeptide in the outer membrane allowed the purification of dfo E. Growth under iron limitation of dfo negative mutants was stimulated with ferrioxamine E and B but not with other ferrisiderophores tested. The host DNA sequence flanking the left terminal part of the MudIIpR13 prophage responsible for the transport mutation was cloned and used to probe a parental gene library by DNA-DNA hybridization. Two recombinant cosmids restoring the transport mutation to normal were identified. Both cosmids also conferred the ability to utilize ferrioxamine B and E as iron sources on a FhuE1 mutant of Escherichia coli. This correlated with the production of an additional polypeptide of 70 kDa in the outer membrane of E. coli transconjugants, thus confirming that this protein serves the ferrioxamine receptor function (FoxR) in E. amylovora.

Investigation of cyclodextrin inclusion compounds using FT-IR and Raman spectroscopy

Abstract The investigation by FT-IR and Raman spectroscopy of several cyclodextrin inclusion complexes reveals structural features not readily accessible by other spectroscopic methods. Thus, the cis conformation of terephthalaldehyde dominates within the α-cyclodextrin cavity. The locked and unlocked acetate group of hydroquinone diacetate in β-cyclodextrin can be easily distinguished, while p-benzenedimethanol diacetate displays the features of a “solid solution”. Finally, the detection of hydrogen bonding in the α-cyclodextrin inclusion compound of butanediol diacetate brings to light even more complex supramolecular structures.

An efficient and stereoselective synthesis of insect pheromones by way of nickel-catalyzed Grignard reactions. Syntheses of gossyplure and pheromones of Eudia pavonia and Droxophila melanogaster.

Abstract Three pheromones, (6Z,11Z)-hexadeca-6,11-dien-1-yl acetate (from Eudia pavonia), (5Z,9Z)-heptacosa-5,9-diene (from Drosophila melanogaster) and gossyplure, have been synthesized each by two consecutive consequences of nickel-assisted Grignard reactions with cyclic enol ethers and preparation of Grignard reagents from the resultant alcohols.

A New Total Synthesis of Ferrioxamine E through Metal-templated Cyclic Trimerization

Abstract Ferrioxamine E was synthesized in a one step cyclic trimerization of the ferric complex of N-5-aminopentyl-N-(hydroxy)-succinamic acid. This reaction was also performed using gallium (III) as the template. N-5-aminopentyl-N-(hydroxy)-succinamic acid was prepared according to methods described in the literature. Electrospray ionization mass spectrometry (ESI/MS) allows the detection of the pseudo-molecular ion peaks of Fe(III) and Ga(III) complexes of desferrioxamine E thus prepared. HPLC and 1H and 13C NMR data of the Ga(III)/desferrioxamine E complex are also reported.

A new regioselective synthesis of N1- and N8-monoacylated spermidines

Abstract N 1 - and N 8 -ferulylspermidine are obtained in three steps from the easily accessible intermediates 4a and 4b .

Short, regio- and stereo-selective preparation of 1,5- and 1,6-dienes. Syntheses of eudia pavonia pheromone and gossyplure.

Abstract Two pheromones, (Z)-6,(Z)-11-hexadecadien-1-yl acetate (from Eudia pavonia ) and gossyplure, have been synthesized each by two consecutive sequences of nickel-assisted Grignard reactions with cyclic enol ethers and the preparation of Grignard reagents from the resultant alcohols, followed each by copper-promoted Grignard reaction with a small-ring ether and subsequent acetylation.

Investigation of Temperature Effects on Cyclodextrin Compounds Through FT-IR Spectroscopy

Abstract The infrared spectra of inclusion compounds of terephthalaldehyde and two aromatic esters with α- or β- cyclodextrin are studied. A wide range of temperatures provides significant modifications of the spectra which are explained by rotational isomerism of the guest molecule.