Evidence for New Enantiospecific Interaction Force in Chiral Biomolecules

Abstract

Enantiospecific biorecognition interactions are key to many biological events. Commonly, bio-affinity values, measured in these processes, are higher than those calculated by available methods. We report here the first direct measurement of the interaction force between right and left handed helical polyalanine peptides using atomic force microscope (AFM) and calculations based on a simple theoretical model. A force difference of 60pN between same and opposite enantiomer interactions is measured. Additional measurements show spin dependency and fast decay of the interaction term, consistent with spin exchange interactions. This short range enantiospecific interaction term is especially relevant in crowded biological systems. The results shed light on the importance of spin and exchange interactions in biological processes, providing explanation to the discrepancies between past calculations and experiments.

The effect of spin exchange interaction on protein structural stability

“…Owing to the magnetic nature of the nanoparticles used and the chirality of the proteins, in accordance with the CISS effect, interactions between them should also transiently influence spin distribution in the protein. 9 Theoretical work also supports the idea of charge reorganization in chiral molecules being followed by spin polarization. In that case the strength of interaction is controversial with predictions for small effects, 39 as well as for large effects that are in the ball park of experiments.…”

“…A possible missing link in our understanding of the protein folding process may relate to additional interaction forces involving chiral potentials and electron spin polarization. 9 Though standard chemical synthesis usually produces a racemic mixture of both enantiomeric forms, and synthesis of a pure enantiomer reduces entropy and requires the investment of energy, biological molecules appear predominantly in only one enantiomeric form. 10 Proteins are chiral on several levels, from the amino acid building blocks to the folded conformation of a peptide and the arrangement of separate subunits to form a functional structure.…”

“…18 A difference is therefore expected between the interactions of each enantiomer with magnetic surfaces, which possess well defined spin orientation. 19 These unequal interactions lead to various effects, such as controlled surface magnetization, 20 preferred adsorption of one enantiomer on a magnetized surface, 18 differences in interaction forces between enantiomers 9 and differences in the work function of modified surfaces. 21 In the context of protein structural stability, CISS may supply a possible mechanism by which chirality influences intrapeptide interactions.…”

“…A relationship was found between the handedness of two artificial polypeptides and the interaction force between them. 9 The underlying physical parameter to which these observations are attributed is spin exchange interaction between spatially adjacent regions of the two polypeptides. Same-handed polypeptides were found to form stronger interactions than those between opposite-handed polypeptides, generating chiral potentials of 5-10 kcals mol À1 that are comparable in strength to existing terms in molecular simulations.…”

Enzymatic polymerization of enantiomeric DOPA into films with enhanced rigidity and stability

“…[5][6][7] Over the past decade, much effort has been devoted to investigating the chirality self-assembly of various molecules such as amino acids, peptides, and polymers into supramolecular materials with different structures and functions. [8][9][10] However, the effect of monomer chirality on the simultaneous covalent and noncovalent polymerization process has not been fully explored.…”