Günther Jung

Screening for small peptidic affinity tags for the detection of ubiquitin and ubiquitinated proteins yielded the dodecapeptide amide DPDELRFNAIAL-NH₂ as a specific ubiquitin-interacting ligand. A peptide collection—based on crystal structures with ubiquitin-interacting proteins—was designed and confirmed by sequence comparison of ubiquitin-interacting motifs. Four independent physical detection methods demonstrated that the peptide binds to monomeric ubiquitin with an affinity of about 10 μM and with fast on and off rates. Fluorescence correlation spectroscopy with fluorescent peptides showed specific interaction with ubiquitin. Reflectometric interference spectroscopy with surface-immobilized peptides and isothermal calorimetry measurements confirmed the specific binding of ubiquitin and fast rate constants. ¹H,¹⁵N heteronuclear NMR localised the interaction site across the β sheet of ubiquitin. The peptide aligns well with the ubiquitin-interacting motif and represents a lead structure for the rational design of high-affinity tags for targeting ubiquitinated protein in vitro and in vivo.

N‐ and C‐terminally modified with fullerene or lipopeptide alamethicin molecules were designed for the formation of template‐free, self‐assembling, voltage‐dependent ion conducting channels. The automated solid phase synthesis of the alamethicin‐F30 sequence was performed by in situ fluoride activation on 2‐chlorotritylchloride‐polystyrene resin and the conjugation with fullerenes‐C₆₀ and ‐C₇₀ was carried out in solution. Voltage‐dependent bilayer experiments revealed preferred channel sizes for C‐terminal alamethicin F30‐fullerene‐C₆₀ and ‐C₇₀ conjugates and higher activity compared with native alamethicin, whereas N‐terminally linked fullerene balls destabilize pore formation. C‐terminal alamethicin F30‐fullerene‐C70 conjugates show pore states with remarkably long lifetimes of seconds. C‐terminal lipopeptide conjugates of alamethicin were prepared by coupling via short peptide spacers with synthetic tripalmitoyl‐S‐glyceryl‐cysteine, which represents the strong membrane anchoring N‐terminus of bacterial lipoprotein. Alamethicin‐lipopeptide conjugates exhibit high channel forming activities, whereby they self‐assemble and adopt preferred pore states with extremely long lifetimes. The novel membrane modifying peptaibol constructs are valuable lead compounds for developments in sensorics related to transmembrane ion conductance. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.

A compound library consisting of 144 pyrazole carboxylic acids and six sublibraries consisting of 24 components was analysed using electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry (ESI‐FTICR‐MS). The library was synthesised by the split‐mix method and investigated by direct infusion analysis by which 134 compounds were detected. FTICR‐MS is predestined for the direct characterisation of complex compound libraries because of its outstanding mass resolution and mass accuracy. However, discrimination within the electrospray ionisation process sometimes leads to signal suppression and thus to misinterpretation of the synthetic results. Using micro‐HPLC/MS we were able to assign all 144 compounds including all pairs of isobaric pyrazoles. We also show that, due to partial separation, FTICR‐MS is indispensable for proper detection of co‐eluting compounds. Copyright © 2001 John Wiley & Sons, Ltd.

The synthesis of the new bacteriocidal compound reutericyclin, 3-acetyl-1-(2-trans-decenoyl)-2-hydroxy-5-isobutyl-Δ²-pyrrolin-4-one, is performed by coupling of N-(2-trans-decenoyl)-l-leucine to Medlrum's acid followed by cyclization. The resulting N-acylated tetramic acid is directly C-acetylated in position 3. HPLC-purification on RP-C₁₈ gave racemic reutericyclin in high purity. 2D-NMR and FT-ICR-MS data are identical with those of natural reutericyclin.

Linear biosynthesis products from balhimycin, a tricyclic glycopeptide antibiotic of the vancomycin type, were isolated from mutants of Amycolatopsismediterranei. The structures of these intermediates, determined by NMR spectroscopy, give new impulses for the understanding of the vancomycin biosynthesis.