DNA-guided self-assembly brings novel nanometer rope ladders

According to a report recently organized by the Physicist Organization Network, scientists at the Brookhaven National Laboratory of the US Department of Energy have developed a DNA "connector" that can link nanorods together like a rope, forming a kind of rope ladder. Structure. The researchers pointed out that this kind of assembly is achieved through the joint action of DNA "ropes" and is expected to bring about a new kind of nanofibers and give them various attributes that people want. Related papers were published in the American Chemical Society's "ACS Nano" magazine.

It is known that DNA molecular chains carry genetic information in living organisms. Using synthetic DNA as a molecular gel can guide nanoparticle self-assembly. When the DNA contains complementary nucleotide base pairs, the chains act like ropes, pulling the nanoparticles together and inhibiting their binding when bases are not matched. Careful control of this attraction and suppression force is a delicate nano-engineering.

In the latest study, the researchers developed a new permutation combination using gold nanorods and single strands of DNA, linking adjacent nanorods together through complementary DNA strands, and examined the effects of multiple joining combinations. Then, they used an ultraviolet spectrometer and a synchrotron light source X-ray scattering technology in combination with an electron microscope to detect the assembly structure and learned how the entire assembly process proceeded.

Various analytical methods have proved that in the early stage of assembly, the nanorods are arranged like rope ladders, and then these tapes are stacked up and finally become larger three-dimensional stacks because DNA links are formed between the rope ladders. bridge. This staged assembly process, known as multi-level assembly, occurs in the self-assembly of many biological systems, such as the amino acid is first connected to the long chain, and then the long chain is folded to form a functional protein.

This stepped assembly nature also shows that the grading process may stop at the intermediate stage. The researchers demonstrated that using DNA to "block" chains can bind the remaining free cords together in a linear ribbon structure, avoiding the formation of stacked structures in the next stage.

This “rope ladder” arrangement is due to breaking the basic symmetry of the nanorods. The author of the paper, Brooke Haiwen, a physicist, said: "This is a new self-assembly mechanism, not a direct simulation of the molecular domain or microscopic system. It interrupts the next assembly process in the 'rope ladder' phase. , It is expected to bring a kind of linear structural fiber and give it its desired attributes. For example, to control cytoplasmic genes or fluorescent properties, we can create a nano-concentrator or light guide and switch them on and off as needed.” ( Chang Lijun)

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