Functionalized Proline-Rich Peptides Bind the Bacterial Second Messenger c-di-GMP.

c-di-GMP is an attractive target in the fight against bacterial infections since it is a near ubiquitous second messenger that regulates important cellular processes of pathogens, including biofilm formation and virulence. Screening of a combinatorial peptide library enabled the identification of the proline-rich tetrapeptide Gup-Gup-Nap-Arg, which binds c-di-GMP selectively over other nucleotides in water. Computational and CD spectroscopic studies provided a possible binding mode of the complex and enabled the design of a pentapeptide with even higher binding strength towards c-di-GMP. Biological studies showed that the tetrapeptide inhibits biofilm growth by the opportunistic pathogen P. aeruginosa.

Novel three-color FRET tool box for advanced protein and DNA analysis.

We report on a new three-color FRET system which we were able to verify in peptides as well as in synthetic DNA. All three chromophores could be introduced by a building block approach avoiding postsynthetic labeling. Additional features are robustness, matching spectroscopic properties, high-energy transfer, and sensitivity. The system was investigated in detail on a set of peptides as well as an array of tailored oligonucleotides. The detailed analysis of the experimental data and comparison with theoretical considerations were in excellent agreement. It is shown that in the case of polypeptides specific interaction with the fluorescence probes has to be considered. In contrast with DNA, the fluorescence probes did not show any indications of such interactions. The novel three-color FRET toolbox revealed the potential for applications studying fundamental processes of three interacting molecules in life science applications.

Quenching of the long-lived Ru(II)bathophenanthroline luminescence for the detection of supramolecular interactions.

A feasibility study based on tailor-made peptide sequences for a new robust luminescence probe-system using the long-lived luminescence of a Ru(II)-bathophenanthroline complex in combination with an efficient anthraquinone-type quencher is presented. Due do their high chemical stability, both dyes can be introduced during solid-phase peptide synthesis avoiding post-synthetic labelling. Photophysical measurements revealed an intense quenching of the luminescence of the Ru-complex (65-68%) which was also confirmed by calculations resulting from decay time measurements. The long-lived luminescence allows for a time-gated detection scheme, which can reduce any luminescence contribution from matrix components.