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Conformational and chirooptical properties of bis- ferrocene peptides

We have recently demonstrated that simple conjugates of aminoferocene and peptides I (Boc- Pro-Ala-NH-Fc) are able to form ordered secondary structural elements, while homo- or heterocirality of the amino acid sequence determines the formation of beta- or gamma-turns. Furthermore, the perturbation of inherently achiral ferrocene chromophore, caused by chiral dipeptide sequence, causes the modification of its chiroptical properties and gives rise to CD-activity in the spectral region of the absorbing chromophore. As a continuation of this study, we have synthesized dinuclear derivatives II (Fc-CO-Pro-Ala-NH-Fc) to get a deeper insight into structural preferences and fine-tuning properties of ferrocene-based peptidomimetics. Thorough spectroscopic analysis in combination with DFT calculations revealed the presence of beta-turns in the most stable conformations of II. Moreover, different shapes and intensities of bands around the UV/Vis absorption maximum of the ferrocene chromophore in circular dichroism spectra of I and II open up an opportunity to use ferrocene as a receptor for sensing secondary structures of small peptides.

ferrocene, conformational analysis, peptides, CD-spectroscopy

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