123rd General Meeting of the KCS

Type Symposium
Area Advanced Instrumental Analysis Chemistry for Protein Dynamics Studies
Room No. Room 202
Time THU 16:05-16:30
Code ANAL1-2
Subject X-ray Studies of Water’s Anomalous Properties and Ground-State Protein Dynamics with Free Electron Lasers
Authors Kyung Hwan Kim
Department of Chemistry, POSTECH, Korea
Abstract X-ray science has evolved dramatically with the use of X-ray free electron lasers (XFELs) such as LCLS, SACLA, PAL-XFEL, European XFEL, and SwissFEL. They can generate ultrashort X-ray pulses with unprecedented brilliance and coherence, and this has been a breakthrough for many X-ray related techniques on a broad range of scientific disciplines and brought us to investigate many interesting new sciences which was previously not possible. In this talk, two recent X-ray studies about the origin of anomalous properties of water and ground-state protein dynamics with free electron laser facilities will be shown. In the liquid form, water has numerous anomalous properties as compared to other liquids such as density maximum at 4-degree C. As an explanation for these anomalous experimental observations, a hypothetical liquid-liquid transition (LLT) and a liquid-liquid critical point (LLCP) has been proposed but has never been proved experimentally. Recently, we developed a new experimental technique utilizing FELs and found the first experimental evidence of the existence of the Widom line which is supposed to emanate from the LLCP [1-2]. With the FELs which provide coherent beams, a new domain for X-ray diffraction of disordered materials becomes possible which can be used to probe the dynamics of the system on a molecular level. The technique is called X-ray Photon Correlation Spectroscopy (XPCS) (3). While other pump-probe type experiments measure the exited-state dynamics, XPCS is a probe-probe type experiment and thus can investigate the true ground-state equilibrium dynamics of proteins or other materials. Reference [1] K. H. Kim et al., Science, 358, 1589-1593 (2017) [2] K. H. Kim et al., Phys. Rev. Lett. 119, 075502 (2017) [3] F. Perakis et al., Nat. Commun., 9, 1917 (2018).
E-mail kimkyunghwan@postech.ac.kr