The rational design of chiral nanomaterials demands precise control over helical handedness across multiple length scales. This study demonstrates a transformative approach to achieving macroscopic helicity through coassembly of N-terminal aromatic amino acids with melamine (Mm), revealing an unprecedented inversion of supramolecular chirality from molecular to macroscopic levels. The process is governed by hydrogen-bond-directed structural reorganization, enabling the emergence of stable helical architectures with tailored handedness.
Fmoc-protected aspartic acid (Asp), norvaline (NV), and homophenylalanine (HP) were selected as model systems due to their ability to form well-defined self-assemblies in water. Individual self-assembly yielded achiral nanostructures—plates for Asp, hydrogels for NV and HP—with no observable macroscopic chirality. However, single-crystal X-ray analysis revealed inherent supramolecular tilt chirality at the molecular level: L-Asp exhibited M-handedness via a “left-front/right-rear” hydrogen-bonded array along the b-axis, while D-Asp showed P-chirality. Despite this, the chirality remained confined to the molecular scale and failed to propagate to higher orders.
Upon coassembly with Mm, a dramatic shift occurred. CD spectroscopy revealed strong exciton-coupled Cotton effects centered around 270–300 nm, indicating long-range chiral organization. For L-Asp/Mm systems, the initial negative band inverted to a positive one with increasing Mm content, signaling a reversal from M- to P-handedness. This was confirmed by SEM and AFM images showing uniform helical fibers with pitches up to 2 µm, in stark contrast to the flat morphologies of pure Asp aggregates.Androgen Receptor Antibody Autophagy
The driving force behind this inversion lies in the formation of directional, duplex hydrogen bonds between Mm’s amine groups and the carboxylic acid termini of the amino acids.XRCC6BP1 Antibody Epigenetics FT-IR spectra confirmed the disappearance of free carboxylic acid bands and a blue shift in amide II vibrations, indicating stronger hydrogen bonding. Grazing incidence X-ray scattering (GIXS) further revealed structural evolution: Asp/Mm adopted hexagonal columnar packing, while NV/Mm and HP/Mm formed lamellar arrangements with interlayer spacings of ~2.85 nm, consistent with Mm intercalation.
Molecular dynamics simulations supported these findings. In the presence of Mm, the number of hydrogen bonds per amino acid increased from ~0.4 to ~3.0, stabilizing one-dimensional growth. The simulation captured the spontaneous formation of screw-like structures after 30 ns, confirming that Mm induces a preferred helical conformation through enhanced noncovalent interactions. Moreover, Mm showed high binding affinity for the amino acids, minimizing self-aggregation and ensuring efficient coassembly.
This phenomenon was observed not only in Asp but also in NV and HP systems. For NV/Mm, the helical pitch expanded 20-fold, and chirality reversed from right- to left-handed.PMID:35233578 Similarly, HP/Mm systems transitioned from achiral hydrogels to spring-like helices with M-handedness. The consistency across different amino acids suggests a generalizable mechanism: Mm acts as a structural director that overrides intrinsic self-assembly pathways by introducing new hydrogen-bonding motifs that favor helical growth.
Crucially, the helicity inversion is not random—it is dictated by the absolute configuration of the amino acid residue. L-enantiomers consistently produced one handedness, while D-enantiomers yielded the mirror image, demonstrating that point chirality is faithfully transmitted through the coassembly process. This enables precise engineering of macroscopic chirality with predictable outcomes.
In summary, this work establishes a robust protocol for the inverse transmission of helicity—from molecular tilt chirality to macroscopic helical architecture—via hydrogen-bond-mediated coassembly. By leveraging small organic binders like Mm, it becomes possible to precisely control the emergence, handedness, and stability of chiral nanostructures. These findings provide a foundational framework for the rational design of functional chiral materials with applications in asymmetric catalysis, chiroptical sensing, and advanced soft robotics.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com