【 Science and Technology Daily 】 Three scientific papers published in Nature in one day

The reporter learned from the University of Science and Technology of China that in the early morning of February 10, the international academic journal "Nature" published three results papers from the University of Science and Technology of China team, respectively reporting important progress in three aspects: quantum simulation based on ultra-cold atomic molecules, new electron nematic phase and protein design.

Triatomic molecules are synthesized for the first time in a mixture of ultra-cold atoms and molecules

Pan Jianwei and Zhao Bo collaborated with Bai Chunli Group of the Institute of Chemistry, Chinese Academy of Sciences to synthesize triatomic molecules for the first time in a mixture of ultra-cold atoms and molecules, taking an important step toward quantum simulation and research of ultra-cold quantum chemistry based on ultra-cold atoms and molecules.

Using highly controllable ultracold quantum gas to simulate complex physical systems that are difficult to calculate can be used for quasi-multi-directional research of complex systems, so it has a wide application prospect in chemical reactions and new material design.

The team first observed Feshbach resonances for atomic and diatomic molecules at ultra-low temperatures in 2019. In the vicinity of the Feshbach resonance, the energy of the bound state and the scattered state of the triatomic molecule tend to be the same, and the coupling between the scattered state and the bound state is greatly enhanced by resonance. The successful observation of Feshbach resonance of atomic molecules provides a new opportunity for the synthesis of triatomic molecules.

Starting from a mixture of ultra-cold atoms near absolute zero, the researchers prepared sodium-potassium ground state molecules in a single hyperfine state. In the vicinity of the Feshbach resonance of the potassium atom and the sodium potassium molecule, the scattering state of the atomic molecule and the bound state of the triatomic molecule are coupled together by the RF field. They successfully observed the RF synthesis triatomic molecular signal on the RF loss spectrum of sodium potassium molecules, and measured the binding energy of triatomic molecules near the Feshbach resonance. This achievement opens up a new way for the study of quantum simulation and ultracold chemistry.

A novel electron nematic phase has been discovered in a cage superconductor

The discovery of a new electron nematic phase in cage superconductors by Xianhui Chen, Tao Wu and Zhenyu Wang not only provides important experimental evidence for understanding the anomalous competition between charge density waves and superconductivity in cage superconductors, but also provides a new research direction for further study of interwoven sequences closely related to unconventional superconductivity in correlated electron systems.

Electron nematic phase is widely found in high temperature superconductors, quantum Hall insulators and other electronic systems, and is closely related to high temperature superconductivity, which is considered to be a kind of interweaving sequence associated with high temperature superconductivity. It is predicted that two-dimensional cage system can show novel superconductivity and abundant electron ordered states, but for a long time, there is a lack of suitable material system to realize its associated physics. The discovery of cage superconductor provides a new research system for exploration in this direction.

The research team combined three experimental techniques, scanning tunneling microscopy, nuclear magnetic resonance and elastic resistance, and found that before entering the superconducting state, the triple modulated charge density wave state will further evolve into a thermodynamically stable electron nematic phase, and determined that the transition temperature is around 35 Kelvin. Interestingly, this new electron nematic phase has also recently been observed in bilayer angular graphene systems.

A new method for protein de novo design was established

Based on the data-driven principle, Professor Liu Haiyan and Associate Professor Chen Quan's team have opened up a new protein de novo design route, and realized the original innovation of key core technologies in the frontier field of protein design, laying a solid foundation for the design of functional proteins such as industrial enzymes, biological materials, and biomedical proteins.

At present, proteins that can form stable three-dimensional structures are almost all natural proteins, and their amino acid sequences are formed by long-term natural evolution. When the structure and function of natural proteins cannot meet the needs of industrial or medical applications, it is necessary to design the structure of specific functional proteins. In recent years, the international representative work on de novo protein design mainly adopts RosettaDesign method, which uses natural structural fragments as building blocks to assemble artificial structures. However, this method has some shortcomings, such as simple design results and being too sensitive to the details of the main chain structure, which significantly limits the diversity and variability of the design main chain structure.

The research team first built the ABACUS model to design amino acid sequences for a given backbone structure, and then developed the SCUBA model to design a completely new backbone structure from scratch while the amino acid sequence is pending. Theoretical calculations and experiments show that the design of the master chain structure using SCUBA can break through the limitation of only splicing natural fragments to produce new master chain structures, thus significantly expanding the structural diversity of de novo proteins and even designing novel structures that are different from known natural proteins. The SCUBA Model +ABACUS model constitutes a complete toolchain capable of de novo design of artificial proteins with completely new structures and sequences, and is currently the only fully experimentally validated method for de novo design of proteins outside of RosettaDesign and complements it. The high-resolution crystal structures of nine de novo designed protein molecules are reported, and five of them have novel structures different from known natural proteins.

Science and Technology Daily (front page, February 11, 2022)