Photon Correlation Spectroscopy and Applications

Contains report on research project.National Science Foundation (Grant PCM81-11534

Photon Correlation Spectroscopy and Applications

Contains report on one research project.National Science Foundation (Grant PCM81-11534

Photon Correlation Spectroscopy and Applications

Contains report on one research project.National Science Foundation (Grant PCM81-11534

Photon Correlation Spectroscopy and Applications

Contains a report on the research program.National Science Foundation (Grant PCM78-15844

Photon Correlation Spectroscopy and Applications

Contains report on research program.National Science Foundation (Grant PCM78-15844

Logarithmic decay in single-particle relaxations of hydrated lysozyme powder

We present the self-dynamics of protein amino acids of hydrated lysozyme powder around the physiological temperature by means of molecular dynamics (MD) simulations. The self-intermediate scattering functions (SISF) of the amino acid residue center-of-mass and of the protein hydrogen atoms display a logarithmic decay over 3 decades of time, from 2 picoseconds to 2 nanoseconds, followed by an exponential alpha-relaxation. This kind of slow dynamics resembles the relaxation scenario within the beta-relaxation time range predicted by the mode coupling theory (MCT) in the vicinity of higher-order singularities. These results suggest a strong analogy between the single-particle dynamics of the protein and the dynamics of colloidal, polymeric and molecular glass-forming liquids.Comment: 4 pages, 5 figure

Photon Correlation Spectroscopy and Applications

Contains report on the research program.National Science Foundation (Grant PCM78-15844

Detection of the liquid-liquid transition in the deeply cooled water confined in MCM-41 with elastic neutron scattering technique

In this paper we present a review on our recent experimental investigations into the phase behavior of the deeply cooled water confined in a nanoporous silica material, MCM-41, with elastic neutron scattering technique. Under such strong confinement, the homogeneous nucleation process of water is avoided, which allows the confined water to keep its liquid state at temperatures and pressures that are inaccessible to the bulk water. By measuring the average density of the confined heavy water, we observe a likely first-order low-density liquid (LDL) to high-density liquid (HDL) transition in the deeply cooled region of the confined heavy water. The phase separation starts from 1.12 ± 0.17 kbar and 215 ± 1K and extends to higher pressures and lower temperatures in the phase diagram. This starting point could be the liquid-liquid critical point of the confined water. The locus of the Widom line is also estimated. The observation of the liquid-liquid transition in the confined water has potential to explain the mysterious behaviors of water at low temperatures. In addition, it may also have impacts on other disciplines, because the confined water system represents many biological and geological systems in which water resides in nanoscopic pores or in the vicinity of hydrophilic or hydrophobic surfaces

An effective long-range attraction between protein molecules in solutions studied by small angle neutron scattering

Small angle neutron scattering intensity distributions taken from cytochrome C and lysozyme protein solutions show a rising intensity at very small wave vector, Q, which can be interpreted in terms of the presence of a weak long-range attraction between protein molecules. This interaction has a range several times that of the diameter of the protein molecule, much greater than the range of the screened electrostatic repulsion. We show evidence that this long-range attraction is closely related to the type of anion present and ion concentration in the solution