title: Dynamics and mechanism of ultrafast water-protein interactions.
abstract: Protein hydration is essential to its structure, dynamics, and function, but water-protein interactions have not been directly observed in real time at physiological temperature to our awareness. By using a tryptophan scan with femtosecond spectroscopy, we simultaneously measured the hydration water dynamics and protein side-chain motions with temperature dependence. We observed the heterogeneous hydration dynamics around the global protein surface with two types of coupled motions, collective water/side-chain reorientation in a few picoseconds and cooperative water/side-chain restructuring in tens of picoseconds. The ultrafast dynamics in hundreds of femtoseconds is from the outer-layer, bulk-type mobile water molecules in the hydration shell. We also found that the hydration water dynamics are always faster than protein side-chain relaxations but with the same energy barriers, indicating hydration shell fluctuations driving protein side-chain motions on the picosecond time scales and thus elucidating their ultimate relationship.
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, OH 43210.
authors.forename: Yangzhong
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, OH 43210.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, OH 43210 zhong.28@osu.edu.
authors.forename: Dongping
authors.initials: D
authors.lastname: Zhong
mesh_terms: D000465:Algorithms; D007700:Kinetics; D008956:Models, Chemical; D056004:Molecular Dynamics Simulation; D009038:Motion; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence / Q000379:methods; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014364:Tryptophan; D014867:Water / Q000737:chemistry* / Q000378:metabolism
chemical_list: D011506:Proteins; D014867:Water; D014364:Tryptophan
keywords: coupled fluctuation; hydration shell dynamics; protein side-chain motion; tryptophan scan; water-driven relaxation