The long-awaited dream of chemists to observe the structural dynamics of a single molecule is now possible. Single molecules with a size of about 1 nanometer (nm, 1 billionth of a meter) exist in a volatile state under ambient conditions. Given that the coronavirus, which is about 100 nanometers in size, spreads rapidly in the air shows how difficult it is to monitor a single molecule. Recently, a Korean research team discovered a reliable way to monitor single molecules at room temperature by covering them with a thin insulating layer, like a blanket.
The research team led by Professor Kyung-dak Park and PhD candidate Mingo Kang (Department of Physics) at POSTECH, in collaboration with Professor Yong-dug Suh (Department of Chemistry) at Ulsan National Institute of Science and Technology (UNIST), has successfully investigated the conformation (arrangement of atoms in a molecule) of molecules Single molecule at room temperature for the first time, providing a close look at the structural dynamics of a single molecule, the basic unit of all things including humans.
In-depth analysis using Raman scattering signals, known as a molecular ‘fingerprint’, is difficult for molecules exposed to air due to ongoing chemical reactions and molecular motions. Ultra-low temperature (below -200 °C) and vacuum conditions have been widely used for single molecule studies to prevent the above problems, however the formations have many limitations in terms of technical difficulties and environmental conditions.
To get around this, the research team placed a single molecule on a substrate coated with a thin layer of gold and covered it with a very thin layer of aluminum oxide (Al2a3) and fasten them tightly. The molecule trapped between the layers of gold and aluminum oxide is isolated from its surroundings, which leads to chemical reactions and suppressed molecular motions.
The stable molecule is then observed through the high-sensitivity nanoendoscopy developed by the research team. The use of the method allows accurate detection of weak optical signals of a single molecule, due to the optical antenna effect of the sharp metallic tip. By this, the resolution limit of general optical microscopy (~500 nm) was overcome to clearly distinguish the conformational inhomogeneities of 1 nm single particles and check whether they lie vertically or horizontally.
POSTECH’s Mingu Kang stated, “While the James Webb Space Telescope can observe the farthest point in the visible universe to reveal the origin of the universe, our single-molecular nanoscopic observations of the smallest unit are to reveal the origin of life.” The work could reveal the molecular conformation of proteins and DNA with nanometer-level precision, leading to the identification of the cause of incurable diseases and the development of treatments for such conditions. In addition, a sample can be easily covered with a thin layer at room temperature or even higher temperatures for single molecule studies and their applications due to its direct process.
Professor Geunsik Lee and researchers Elham Oleiki and Huitae Joo from UNIST, Dr. Hyunwoo Kim and Dr. Taeyong Eom from the Korea Research Institute of Chemical Technology (KRICT), and doctoral candidates Yeonjeong Koo and Hyungwoo Lee in the Department of Physics at POSTECH participated in the research. The study was recently published in Nature Connections It was supported by the National Research Foundation of Korea.
Materials Introduction of Pohang University of Science and Technology (POSTECH). Note: Content can be modified according to style and length.