Mesopores provide an amorphous state suitable for studying biomolecular structures at cryogenic temperatures

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 34; pp. 14145 - 14150
• Main Authors: Huang, Ya-Wen, Lai, Yei-Chen, Tsai, Chia-Jung, Chiang, Yun-Wei
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 23.08.2011; National Acad Sciences
• Subjects: Aqueous solutions; Biological Sciences; Biomolecules; Cold Temperature; Cryogenic temperature; Electron paramagnetic resonance; Electron Spin Resonance Spectroscopy; Ice; Line spectra; Liquids; Low temperature; Molecular Conformation; Molecules; Nanoparticles - chemistry; Peptides; Peptides - chemistry; Porosity; Prions; Proteins; Solutions; Solvents; Spin Labels; Temperature; Time Factors; Vitrification
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1102395108

In nano-confinements, aqueous solutions can be found to remain in a liquid state at subfreezing temperatures. The finding provides a means of entering into previously inaccessible temperature regions for studying the dynamics and structure of bulk liquid. Here we show that studying biomolecular structures in nano-confinements improves the accuracy of cryostructures and provides better insight into the relationship between hydration water and biomolecules. Synthetic prion protein peptides are studied in two experimental conditions: (i) in confined nanochannels within mesoporous materials, and (ii) in vitrified bulk solvents, with a temperature range of 50–275 K, using cw/pulse ESR techniques. A large inhomogeneous lineshape broadening is only observed for the spectra from the vitrified bulk solvent below 70 K, suggesting a possible peptide clustering in the solution. The spin-counting and distance measurements by DEER-ESR provide further evidence that peptides are dispersed homogeneously in mesopores but heterogeneously in vitrified solvents wherein the biomolecular structure is disturbed due to heterogeneity in the bulk solvent structure. Our study demonstrates that the nanospace within mesoporous materials provides an amorphous environment that is better than vitrified bulk solvent for studying biostructures at cryogenic temperatures.