| Abstract: | Biological macromolecules are essentially homochiral. For example, proteins mostly consist of l ‐amino acids. What happens when a chiral molecule meets itself in a mirror? For expanded polyvaline, zigzag‐helix transformation occurs. In this study, expanded polyvalines containing bis(pyridine)silver(I) moieties were synthesized and isolated as single crystals. The molecular structures were determined by X‐ray analysis, which revealed that chiral expanded poly(l ‐valine) and poly(d ‐valine) form zigzag chains. However, racemic mixture of these molecules form left‐ and right‐handed 41 helices that retain the original sequences. These secondary structures can be transformed by only flipping the C‐terminal amide plane for each unit, which is reminiscent of the relationship between an α‐helix and a β‐strand. Such expanded polypeptides can be built up into expanded protein, forming a tailor‐made three‐dimensional structure, which will lead to new functions. |
