Chemists visualize building blocks of synthetic polymers

Chemists visualize building blocks of synthetic polymers

This article has been reviewed in accordance with Science

Fact check

Peer-reviewed publication

trusted source

Proofreading


CREATS for single-molecule super-resolution imaging of ROMP at high monomer concentrations. athe design of CREATS, is demonstrated by coupling a surface-grafted chain growth polymerization reaction (e.g., ROMP catalyzed by G2) and a non-photo-restricted fluorescence reaction, allowing the overall reaction to be effectively fluorogenic for single-molecule super-resolution imaging. NHC, heterocyclic carbene. BLaser and camera timing diagram for repeated cycles of deconjugation, imaging (chromatin) and bleaching of incorporated monomers during polymerization. CScheme of the experimental setup for imaging real-time polymerization reactions in operation via TIRF microscopy. DrFstructures of three trapped monomers (monomer a in Dr; Monomerial B in H; Monomerial C in F) and the unconstrained interaction scheme (as shown in Dr). Fluorophores are coded by their emission colors. The cage assembly is highlighted in grey. gmonomer fluorescence spectra a, B And C After removing the images; Their limited spectral overlap allows simultaneous detection of different monomers through spectral separation. Hmonomer fluorescence spectra a uncaging under 375 nm radiation (~30 mW cm).-2) over time in CHCl3showing the uncaging process. IFluorescence intensity at 518 nm versus time H. The line is proportional to the saturation function y= abx/(1+ bx) + C with appropriate parameters a= 73±1, B= 1.21±0.07 min-1 And C= 0±1. Ygreen labeled BODIPY chart G2 After vaccination on a norbornene-activated magnetic particle. credit: Nature chemistry (2023). doi: 10.1038/s41557-023-01363-2

× Close


CREATS for single-molecule super-resolution imaging of ROMP at high monomer concentrations. athe design of CREATS, is demonstrated by coupling a surface-grafted chain growth polymerization reaction (e.g., ROMP catalyzed by G2) and a non-photo-restricted fluorescence reaction, allowing the overall reaction to be effectively fluorogenic for single-molecule super-resolution imaging. NHC, heterocyclic carbene. BLaser and camera timing diagram for repeated cycles of deconjugation, imaging (chromatin) and bleaching of incorporated monomers during polymerization. CScheme of the experimental setup for imaging real-time polymerization reactions in operation via TIRF microscopy. DrFstructures of three trapped monomers (monomer a in Dr; Monomerial B in H; Monomerial C in F) and the unconstrained interaction scheme (as shown in Dr). Fluorophores are coded by their emission colors. The cage assembly is highlighted in grey. gmonomer fluorescence spectra a, B And C After removing the images; Their limited spectral overlap allows simultaneous detection of different monomers through spectral separation. Hmonomer fluorescence spectra a uncaging under 375 nm radiation (~30 mW cm).-2) over time in CHCl3showing the uncaging process. IFluorescence intensity at 518 nm versus time H. The line is proportional to the saturation function y= abx /(1+ bx) + Cwith appropriate parametersa= 73±1,B= 1.21±0.07 min-1 AndC= 0±1. Ygreen labeled BODIPY chart G2 After vaccination on a norbornene-activated magnetic particle. credit:Nature chemistry(2023). doi: 10.1038/s41557-023-01363-2

Synthetic polymers are everywhere in our society, from nylon and polyester clothing to Teflon cookware and epoxy glue. At the molecular level, the molecules of these polymers are composed of long chains of monomer building blocks, the complexity of which increases functionality in many of these materials.

In particular, copolymers, which are composed of different types of monomers in the same chain, allow the properties of the material to be fine-tuned, said Ping Chen, the Peter J. W. Debye Professor of Chemistry in the College of Arts and Sciences (A&S). Monomer sequence plays a crucial role in a material’s properties, but until now scientists have lacked a way to sequence synthetic copolymers.

Chen and his colleagues developed CREATS (Coupled Reaction Approach Toward Ultra-Resolution Imaging), which allows them to image polymerase catalytic reactions at the resolution of a single monomer and, through fluorescent signals, to distinguish monomers from one another. Both are important steps in discovering the molecular structure of a synthetic polymer.

They describe this technique and their first discoveries in “Optical sequencing of single synthetic polymers,” published inNature chemistry.

Co-lead authors are Rong Yi, Xiangqing Sun, and Xianwen Mao, all of whom are former postdoctoral researchers in Chen’s group. Co-authors are former postdoctoral researchers in Chen’s group, Susil Baral and Chunming Liu, current postdoctoral researcher Felix Alfonso, and Jeffrey Coates, professor of chemistry and chemical biology at Tisch.

“Synthetic polymers are made of monomer units linked together like a string of beads,” Chen said. In the simplest polymers, the monomers are identical, but more complex properties appear when polymers contain monomers of different types called copolymers. The precise arrangement of monomers in a copolymer plays an important role in its properties, such as rigidity or flexibility.

Sequence plays a role in the properties of natural polymers as well, Chen said. A protein, for example, consists of 20 monomers of amino acids arranged in a very specific sequence.

“In a natural polymer, nature is in control,” Chen said. “In synthetic polymers, humans do the arrangements, and chemists generally don’t have that precise control.”

Chen said that sequencing copolymers is extremely difficult largely because of the heterogeneity in synthetic polymers. Individual chains vary in length, composition, and sequence, requiring single-polymer sequencing methods that can analyze and identify individual monomers.

Some newer methods allow scientists to control the order of monomers in the chain, but only for very short polymers — 10 to 20 monomers in length, Chen said.

Using CREATS, researchers can sequence a polymer as it is manufactured, one monomer at a time, by photographing and identifying each monomer as it is added to the polymer. To make monomers visible, CREATS combines the polymerase reaction with another reaction that produces fluorescent signals.

“Every monomer that comes in gives off a burst of light,” Chen said. “Light is produced by a laser, and the light puff has a color. In our case, it’s either green or yellow. By seeing whether it’s yellow or green, we see what goes into the monomer.”

The laboratory is already equipped to measure the properties of the synthetic polymer. Now that they can determine the sequence of the individual polymer, the next step is to combine the two experiments to correlate structure and function, ultimately providing guidelines for designing the polymer to achieve certain properties.

“If you know how a sequence controls a property, you can really think about designing any sequence you want to achieve a particular property,” Chen said. “This knowledge should help people design their materials for the desired application.”

more information:
Rong Yi et al., Optical sequencing of single synthetic polymers,Nature chemistry(2023). doi: 10.1038/s41557-023-01363-2

Magazine information:
Nature chemistry

You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *