Key Takeaways
- Researchers at Chiba University, Shizuoka University, Keele University, Kanazawa University, and Ritsumeikan University have developed a chlorophyll-based supramolecular polymer that transforms from nonhelical fibers into helical structures through discrete intermediate stages, with findings published in the Journal of the American Chemical Society on April 20, 2026.
- The study, led by Professor Shiki Yagai at Chiba University’s Institute for Advanced Academic Research, identified four structural states: one nonhelical form (NF) and three right-handed helical forms (HF1, HF2, HF3) with pitches of 26 nm, 13 nm, and 8 nm respectively.
- The transformation follows a stepwise timeline: nonhelical fibers convert to HF1 and HF2 within 30 minutes, HF1 converts almost entirely to HF2 within hours, and the final HF2-to-HF3 transition takes several days.
- The structural shift is cooperative — once a small region of a fiber reorganizes into a more stable helical form, the change propagates to neighboring regions along the polymer backbone.
- The chlorophyll derivative is functionalized with barbituric acid groups and long alkyl chains that assemble into rosette ring structures through hydrogen bonding, stacking into one-dimensional fibers in low-polarity solvents.
Chiba University-Led Team Creates DNA-Inspired Polymer with Time-Evolving Helical Structure
Researchers from Chiba University, Shizuoka University, Keele University, Kanazawa University, and Ritsumeikan University have developed a chlorophyll-based supramolecular polymer that transitions from nonhelical fibers to helical structures through a series of intermediate stages, drawing on the structural adaptability observed in biological molecules such as DNA and proteins. The study was led by Professor Shiki Yagai at the Institute for Advanced Academic Research, Chiba University, with Balaraman Vedhanarayanan and Ryoma Tsuchida of Chiba University’s Graduate School of Engineering, Shinnosuke Kawai of Shizuoka University, and Martin J. Hollamby of Keele University, UK. The findings were published online in the Journal of the American Chemical Society on April 20, 2026.
Molecular Assembly and Fiber Formation
The researchers synthesized a chlorophyll derivative functionalized with barbituric acid groups and long alkyl chains. In low-polarity solvents, these molecules assemble through hydrogen bonding into ring-like rosette structures, which then stack into long, one-dimensional fibers. The large and complex geometry of each chlorophyll unit prevents the rosettes from immediately adopting a stable arrangement, causing the system to initially form nonhelical fibers that gradually reorganize into helices over time.
Chiba University Researchers Identify Four Structural States and Stepwise Transformation
Using atomic force microscopy, the team characterized four structural forms: a nonhelical form (NF), in which rosettes stack without offset, and three right-handed helical forms — HF1, HF2, and HF3 — arising from slight translational shifts between stacked rosettes. The three helical forms differ in pitch: 26 nm for HF1, 13 nm for HF2, and 8 nm for HF3.
Time-resolved imaging tracked how these states evolved. Within the first 30 minutes, the majority of nonhelical fibers converted to HF1 and HF2. Over the following hours, HF1 converted almost entirely into HF2. The final transition from HF2 to HF3 proceeded over a period of several days.
“Examples of synthetic supramolecular polymers in which multiple helicity arises dynamically from kinetically trapped, nonhelical structures are rare,” said Professor Shiki Yagai, Institute for Advanced Academic Research, Chiba University.
Cooperative Propagation and Implications for Adaptive Materials
The team also established that the transformation is cooperative. Once a small region of a fiber adopts a more stable helical configuration, the reorganization promotes similar changes in neighboring regions, allowing the structural shift to propagate along the polymer backbone.
“We demonstrate that helicity in a one-dimensional supramolecular polymer can emerge and mature through discrete, cooperative reorganizations occurring within the polymer backbone across a rugged energy landscape, representing a rare behavior,” said Professor Shiki Yagai, Institute for Advanced Academic Research, Chiba University.
The researchers note that it remains unclear whether structural changes initiate randomly along fibers or propagate directionally from specific sites. Understanding this process could support the design of materials that more closely replicate the adaptive structural behavior observed in biological systems.
