Abstract
The apparent piezoelectricity of biological materials is not yet fully understood at the molecular level. In particular, dynamic noncovalent interactions, such as host–guest binding, are not included in the classical piezoelectric model, which limits the rational design of eco-friendly piezoelectric supramolecular materials. Here, inspired by the conformation-dependent mechanoresponse of the Piezo channel proteins, we show that guest–host interactions can amplify the electromechanical response of a conformationally mobile peptide metal–organic framework (MOF) based on the endogenous carnosine dipeptide, demonstrating a new type of adaptive piezoelectric supramolecular material. Density functional theory (DFT) predictions validated by piezoresponse force microscopy (PFM) measurements show that directional alignment of the guest molecules in the host carnosine–zinc peptide MOF channel determines the macroscopic electromechanical properties. We produce stable, robust 1.4 V open-circuit voltage under applied force of 25 N with a frequency of 0.1 Hz. Our findings demonstrate that the regulation of host–guest interactions could serve as an efficient method for engineering sustainable peptide-based power generators.
Highlights
The conversion of mechanical force into cellular signals is a core biological function conserved throughout mammalian evolution,[1] enabling essential biological functions including sense of touch,[2] location and movement,[3] pain,[4] and lung inflation.[5]
We show the guest molecule MeCN selectively alters the crystal morphology and acts as a structure-directing agent to lower the symmetry of the unit cell
Unlike the four other guests we tested, the Car_Zn·(MeCN) metal−organic framework (MOF) crystallized into the lowest symmetric system with unconstrained polarization, which created a significant piezoresponse as mapped by using Density functional theory (DFT) calculations and microscopy
Summary
The conversion of mechanical force into cellular signals is a core biological function conserved throughout mammalian evolution,[1] enabling essential biological functions including sense of touch,[2] location and movement (proprioception),[3] pain (nociception),[4] and lung inflation.[5]. Owing to the flexible alkyl segments in the β-alanine-histidine peptide, carnosine-based linkers can adopt a wide range of conformational states through low-energy torsional rearrangements, which enables guest-specific flexible response of the Car_Zn framework; that in turn affects the electromechanical behavior.[40] Even though bio-inspired host−guest interactions have been exploited in materials design,[41−43] studies involving guest-modulated electromechanical behavior are relatively underexplored.[44,45] The unambiguous demonstration of guest molecule-directed electromechanical properties would offer a means of dynamically modulating piezoelectric response, allowing better understanding of piezoelectricity in soft materials and providing an additional functionality for emerging eco-friendly piezoelectric devices.[46−51]. (f, g) Hydrogen-bonding pattern of (f) Car_Zn·(IPA) and (g) Car_Zn·(MeCN) illustrates how the nature of the guest molecule in the channel affects the conformation of the peptide linker through hydrogen bonds (MeCN) shows the change in channel shape and orientation caused by the guest molecule. (f, g) Hydrogen-bonding pattern of (f) Car_Zn·(IPA) and (g) Car_Zn·(MeCN) illustrates how the nature of the guest molecule in the channel affects the conformation of the peptide linker through hydrogen bonds
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