Evidence for new enantiospecific interaction force in chiral biomolecules

Abstract

Enantiospeci c biorecognition interactions are key to many biological events. Commonly, bio-a nity values, measured in these processes, are higher than those calculated by available methods. We report here the rst 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 enantiospeci c 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. Main TextNature is based on chiral molecules, namely molecules that appear in two forms, enantiomers, that are mirror images of each other. Interestingly, chiral biomolecules, like proteins and sugars appear in Nature mainly as one enantiomer. The origin of "homo chirality" in Nature, was -and is -discussed very intensively in the literature 1 . However, the focus of this work is related to a more fundamental question, i.e., why did Nature preserve chirality so persistently over the many millions years of evolution? In other words, does chirality per se, independent on the speci c handedness, provide properties that serve an important role in Life?The ability of biological molecules to interact selectively with each other is at the heart of all biological processes and the basis of many pharmaceutical concepts. Two important properties -related to chirality -characterize interactions in nature, i.e., very strong enantioselectivity

Anomalous Viscosity of a Racemate: A Simple Experiment Demonstrating Chirally Induced Spin Selectivity

“…In conclusion, the most parsimonious explanation of the effect we observe is a decrease in intermolecular force similar to the one predicted by SDCR and seen in atomic force measurements . It may be possible to detect a reduction in hydrogen bond strength in racemates directly by vibrational spectroscopy .…”

“…Specifically, a novel magnetic force is predicted to exist, attractive between homochiral pairs and repulsive in heterochiral ones. This was confirmed by atomic force microscopy . We speculated that this force might cause a measurable depression in the kinematic viscosity of a racemic mixture.…”

“…This was confirmed by atomic force microscopy. 10 We speculated that this force might cause a measurable depression in the kinematic viscosity of a racemic mixture.…”

“…In conclusion, the most parsimonious explanation of the effect we observe is a decrease in intermolecular force similar to the one predicted by SDCR and seen in atomic force measurements. 10 It may be possible to detect a reduction in hydrogen bond strength in racemates directly by vibrational spectroscopy. 23 If its origin in SDCR is established, the anomalous viscosity of racemates would be a classroom demonstration of the first fluid mechanical effect since superfluidity to require a quantum mechanical explanation.…”

Understanding the Adhesion Mechanism of Hydroxyapatite-Binding Peptide

“…To further investigate the contribution of lysine to the interaction with HAp, we performed SMFS analysis using an AFM. Recently, force spectroscopy was used to study how peptides, proteins, and even single amino acids interact in different systems, including ligand–receptor interactions, − chiral induced spin exchange, , and adhesion to solid surfaces. ,− We coupled peptide molecules to an AFM tip and performed an adhesion assay against a polycrystalline HAp surface. In this experiment, the probe was approached to the substrate to allow the peptide to adhere, and the tip was then retracted until full separation was obtained.…”