Zn<SUP>2+</SUP>-Complexation by a β-Peptidic Helix and Hairpin Containing β<SUP>3</SUP>hCys and β<SUP>3</SUP>hHis Building Blocks: Evidence from CD Measurements. Preliminary Communication

Two new β³-homohistidine- and β³-homocysteine-containing β-peptides have been prepared by solid-phase synthesis. A β-octapeptide (2) contains seven β³-amino acids and one β²-amino acid. The β²/β³ segment has been placed in the middle of this peptide, which contains β³-amino acids of alternating configuration, to induce the formation of a hairpin secondary structure. A β-decapeptide (3) has been designed to fold to a 3<INF>14</INF>-helical secondary structure with neighboring His side chains in 6- and 9-positions. Circular-dichroism (CD) measurements show the capability of both peptides to bind Zn²⁺ ions in aqueous solution. In the case of the β-octapeptide, binding of Zn²⁺ causes a dramatic change of the CD spectrum, indicating a change or a stabilization of its secondary structure. Zn²⁺ Ions clearly stabilize the 3<INF>14</INF>-helix of the β-decapeptide, in neutral and basic solution. For the construction of the two new β-peptides, we needed to have a supply of the β-amino acid derivatives Fmoc-β³hCys(Trt)-OH and Fmoc-β³hHis(Trt)-OH, the preparation of which is described herein.