Thursday, May 31, 2018  |  1:00 p.m. – 5:30 p.m.
Advanced Science Research Center at the Graduate Center, CUNY

Join the ASRC Nanoscience Initiative at our free, half-day symposium focusing on Functional Supramolecular SystemsWe are welcoming local, national, and international researchers on May 31st 2018 to present their research in the ASRC 5th Floor Data-Visualization Room from 1pm-5.30pm.

Confirmed speakers include:

  • Kazunori Sugiyasu, Chiba University (Japan);
  • Adam Braunschweig, Advanced Science Research Center and Hunter College, CUNY;
  • Rebecca Schulman, Johns Hopkins University;
  • Mohit Kumar, Advanced Science Research Center, CUNY;
  • Shiki Yagai, Chiba University (Japan);
  • Ankit Jain, Advanced Science Research Center, CUNY;

Full program and abstract information coming soon!

This is a catered event, please remember to register!

Please feel free to email Muaad Alody, at Muaad.Alody@asrc.cuny.edu, if you have any questions regarding this event.

Functional Supramolecular Systems | May 31, 2018
Advanced Science Research Center at the Graduate Center, CUNY

1:00 p.m.

Welcome Remarks

1:05 p.m.

Self-assembling circuit connections with biomolecules
Dr. Rebecca Schulman, John Hopkins University

1:50 p.m.

Supramolecular Polymerization under kinetic control
Kazunori Sugiyasu, National Institute for Materials Science 

2:35 p.m.

Amino Acid-Encoded Biocatalytic Self-Assembly Enables the Formation of Transient Conducting Nanostructures
Dr. Mohit Kumar, Advanced Science Research Center

3:00 p.m.

Break

3:30 p.m.

Supramolecular Polymers with Topologies
Dr. Shiki Yagai, Chiba University

4:15 p.m.

Combinatorial Diketopyrrolopyrrole-Rylene Optoelectronic Supramolecular Polymer Films
Dr. Adam Braunschweig, Advanced Science Research Center & Hunter College

5:00 p.m.

Co-factor driven Dynamic Peptide Libraries
Dr. Ankit Jain, Advanced Science Research Center

5:25 p.m.

Closing Remarks

ABSTRACTS

Functional Supramolecular Systems | May 31, 2018
Advanced Science Research Center at the Graduate Center, CUNY

1:05 p.m.

Self-assembling circuit connections with biomolecules
Dr. Rebecca Schulman, John Hopkins University

The wiring of brains illustrates how self-assembly processes can direct the formation of connections of wires from one place to another to form massive, complex circuits.   I will describe work focused on technologies for synthetically forming circuits using biomolecular assembly.  Using a process called point-to-point assembly, we can direct the formation of DNA connections between two specific types of molecules over distances as large as 10-20 microns, and different DNA can direct the formation of different connections.   I will also describe some recent work showing how we can use these DNA structures as templates for nanofluidic conduits or electronic wires.

1:50 p.m.

Supramolecular Polymerization under kinetic control
Kazunori Sugiyasu, Chiba University

Molecular self-assembly that operates under kinetic control is expected to yield nanostructures that are inaccessible through the spontaneous thermodynamic process. Moreover, time-dependent evolution, which is reminiscent of biomolecular systems, may occur under such conditions and allow the synthesis of supramolecular assemblies with enhanced complexities. Recently, we have reported the time-dependent evolution of a metastable supramolecular assembly of a porphyrin derivative. In this system, two aggregation pathways interplayed; kinetically formed nanoparticle transformed into thermodynamically stable nanofiber over time through autocatalytic process. Based on their energy landscape, we could control the lag time of the time-evolution by rational molecular design.

Herein, we will report the differentiation of a metastable supramolecular assembly. In this new system, nanoparticle of a newly designed porphyrin derivative acted as a “stem” supramolecular assembly that had the capacity of differentiation into both the nanofiber and nanosheet. Mechanistic studies unveiled the energy landscape governing unique kinetic behavior. Based on this understanding, we could control the differentiation by changing mechanical agitation and achieve both one- and two-dimensional living supramolecular polymerization using an identical porphyrin monomer.

1 “Living supramolecular polymerization realized through a biomimetic appraoch” S. Ogi, K. Sugiyasu, S. Manna, S. Samitsu, M. Takeuchi, Nat. Chem. 2014, 6, 188.

2 “Control over differentiation of a metastable supramolecular assembly in one and two dimensions” T. Fukui, S. Kawai, S. Fujinuma, Y. Matsushita, T. Yasuda, T. Sakurai, S. Seki, M. Takeuchi, K. Sugiyasu, Nat. Chem. 2017, 9, 493.

2:35 p.m.

Amino Acid-Encoded Biocatalytic Self-Assembly Enables the Formation of Transient Conducting Nanostructures
Dr. Mohit Kumar, Advanced Science Research Center

One key feature of biological systems is the existence of chemically fueled, transient structure and function, like the on-demand formation/degradation of tubulin, actin fibers etc. Supramolecular polymers as synthetic mimic of such biomaterials has shown great promise in a number of areas, including biomedicine, sensing and energy harvesting. However, the main challenge is to actively regulate the shape, function and performance of these materials, while maintaining constant, physiological conditions. This has inspired recent research towards temporal control of nanostructures, which is achieved by using (bio-)catalysis to activate building blocks and thereby drive assembly. In this regard, potential for design of active supramolecular nanostructures based on peptide nanotechnology is increasingly appreciated. The objective of this work is demonstration of active encoding of nanostructures by using simple amino acids, resulting in transient conducting nanowires.


Fig. 1: a) Chemical structure of NDI derivative 1 and various input amino acid amide investigated. b) Amino acid encoded time dependent CD signal 1 upon biocatalytic self-assembly. c) and d) TEM images of the corresponding chiral nanostructures formed in presence of input amino acid E and L respectively.

We designed a self-assembling core molecule with two in-built competing reactive sites, consisting of the organic semiconductor naphthalenediimide (NDI), conjugated with D and L enantiomer of tyrosine methyl esters (Fig. 1).[i]  The stereoselective fast enzymatic reaction at the L enantiomer compared to the D enantiomer provides the necessary kinetic competition to achieve temporal control over assembly. By simply adding one of a range of encoding amino acids in the presence of enzyme α-chymotrypsin, we achieve pathway selection between hydrolysis and acylation at both chiral ends. This results in an in situ modification of the amphiphilic structures, giving rise to unique self-assembly trajectories that are time programmed by the nature of encoding amino acid. Taking advantage of the semiconducting nature of the NDI core, electronic wires could be formed and subsequently degraded, resulting in temporally regulated electro-conductivity. Such a system holds great promise towards interfacing biology with electronics. Overall, the biocatalytic incorporation of encoding amino acids around a functional core offers a general approach to modulate, switch or fine-tune supramolecular structures over time.

[1] M. Kumar, N. Ing, V. Narang, N. Wijerathne, A. Hochbaum, R. V. Ulijn, Nat. Chem., 2018, doi:10.1038/s41557-018-0047-2

3:30 p.m.

Supramolecular Polymers with Topologies
Dr. Shiki Yagai, Chiba University

Higher-order conformations furnish a range of critical functionalities to one-dimensional polymers not only in biological systems (e.g., protein folding) but also in our daily life (functional polymers). One-dimensionally elongated molecular aggregates known as supramolecular polymers are emerging nanoscale materials with promising applications. However, to compete over covalent counterparts as well as naturally occurring polymers (polypeptides and DNA), development of supramolecular polymers with well-defined higher-order conformations (“topology”) are desired. To address this issue, we have exploited a previously reported hydrogen-bonded cyclic hexamer of barbiturated naphthalene that polymerizes noncovalently into circular supramolecular fibers (nanoring).[1] The shape persistency of nanoring along with its uniformity of diameter (ca. 14 nm) implies that a “spontaneous curvature” would occur by high degree of internal order within the continuous stacking of hexamers. In order to extend this system to “supramolecular polymers with well-defined higher-order structures”, we synthesized several new compounds based on the molecular design of the naphthalene monomer and succeeded in obtaining outstanding supramolecular systems whose higher order structures could be manipulated by external stimuli.

For examples, we introduced azobenzene chromophore to the parent molecule. By changing the polymerization condition in nonpolar solvent, this new molecule form helically coiled supramolecular polymers. Because the spontaneous curvature of the main chain can be destroyed by UV irradiation through the photoisomerization of the azobenzene unit, we realized unprecedented level of conformation change (unfolding) of supramolecular polymers by external light, which has been visualized by AFM observation for the dried samples (see the figure). The occurrence of this unfolding in solution state has also been confirmed by SAXS measurements.[2]

More recently, we have discovered supramolecular polymers that can self-fold into unprecedented higher-order topologies in the absence of specific noncovalent forces. By employing polymerization conditions with less dominant kinetic effects, we prepared partially misfolded supramolecular polymers that folded on a time scale of days into unique topologies that are reminiscent of the tertiary structures of proteins. The thermodynamic analysis of supramolecular polymers with varying degrees of folding demonstrated that the folding is accompanied by a large enthalpic gain. The self-folding is driven by ordering of misfolded domains in the main-chain using helical domains as templates, which is corroborated by the fact that fully misfolded fibres prepared under a very kinetic condition do not self-fold.[3]

[1] S. Yagai et al., Angew. Chem. Int. Ed. 2012, 51, 6643; Angew. Chem. Int. Ed. 2016 55, 9890.
[2] B. Adhikari, S. Yagai et al., Nature Commun. 2017, 8, 15254.
[3] D. D. Prabhu, S. Yagai et al., submitted.

4:15 p.m.

Combinatorial Diketopyrrolopyrrole-Rylene Optoelectronic Supramolecular Polymer Films
Dr. Adam Braunschweig, Advanced Science Research Center & Hunter College

Two diketopyrrolopyrroles (DPPs) and three rylenes were combined to form six hierarchical supramolecular polymers1,2 that assemble into hierarchical superstructures as a result of orthogonal H-bonding and π•••π stacking (Figure). The individual components and the DPP:rylene pairs were cast into films and their superstructures were examined by electron microscopy, powder X-ray diffraction, and steady-state spectroscopy. All six supramolecular polymers have different solid-state geometries, where subtle changes in the molecular structures of the components propagate across the molecular-to-micrometer length scale to alter the hierarchical order between 1D wires and 2D sheets.

The optoelectronic properties of these supramolecular polymer films were interrogated by ultrafast transient absorption spectroscopy. The photophysics were dominated by singlet fission in the stacked DPP components. Importantly, singlet fission occurs only when the DPP chromophores are scaffolded to the PDI stacks, which bring the DPP into requisite proximity for triplet formation. As a result of the delocalization along the stack, the triplets decouple and possess lifetimes approaching the innate lifetimes of the DPP triplets in solution. These studies demonstrate the benefits of combinatorial self-assembly in exploring the subtle effects of structure on complex photophysics, and here result in a deeper understanding of how self-assembly can be used to induce sophisticated and desirable optoelectronic properties into polymeric materials.

Figure. A) Library composed of three rylenes and two DPPs. B) Supramolecular assembly into supramolecular polymers via triple H-bonding and π•••π stacking results in DPP:rylene superstructures. C) Superstructures vary in the DPP and rylene components and DPP:rylene stoichiometry.

  1. Ley, D.; Guzman, C. X.; Adolfsson, K. H.; Scott, A. M.; Braunschweig, A.B. “Emergent Charge Transfer in Cooperatively Assembling Donor-Acceptor Superstructures” Journal of the American Chemical Society, 2014, 136, 7809 – 7812.
  2. Guzman, C. X.; Krick Calderon, R. M.; Xu, H.; Peurifoy, S. R.; Yamazaki, S.; Guo, C.; Davidowski, S. K.; Rosner, H. F.; Holland, G.; Scott, A. M.; Braunschweig, A. B.*“Competitive Charge and Spin Dynamics in Multicomponent Hierarchical Donor-Acceptor Films,” Journal of Physical Chemistry C, 2015, 119, 19584 – 19589.

5:00 p.m.

Co-factor driven Dynamic Peptide Libraries
Dr. Ankit Jain, Advanced Science Research Center

Proteins are an indispensible component of the modern biological metabolic machinery. A key part of understanding and emulating their function is to converge them into their minimalistic components. Considering the complexity that has evolved over billions of years this seems to be a non-trivial task. However, if an approach is to be formulated, for in vitro evolution that could potentially rival in natura evolution a co-factor driven formation of peptidic materials is to be sought. Recently, Pappas et al. showed that library of dipeptides can be used for dynamic evolution of nano materials. In this work we modified this approach to amplify peptide sequences which assemble selectively on binding with specialized co-factors. The co-factors that we chose for this work were porphyrin derivatives and highly relevant biomolecules such as RNA, DNA and ATP. Among porphyrins, we chose specifically three derivatives, Hemin (natural) TMPyP, Fe-TMPyP (synthetic). Rationale for selecting these derivatives was to eventually create functional peptidic assemblies that could partake in various photo-physical phenomena, endogenous to the porphyrin systems. We selected seven dipeptides for our dynamic library, allowing each set to evolve in solution with thermolysin and respective Co-factor. The results of evolving libraries and their consequences would be presented in the talk.

This approach has been developed as an in vitro auxiliary driven library which can further be used for finding binders of more complex molecules such as RNA and DNA expanding the signaficance of the approach into possible pre-biotic investigation.

1) C.G. Pappas, R. Shafi, I.R. Sasselli, H. Siccardi, T. Wang, V. Narang, R. Abzalimov, N. Wijerathne, R.V. Ulijn, Nat. Nanotechnol., 2016, 11, 960-967.
2) K. Kalyanasundaram, M. N-Spallart, J. Phys. Chem., 1982, 86, 5163-5169.