Social and Behavioral Sciences Commons^™

Switching Radical Stability By Ph-Induced Orbital Conversion, Ganna Gryn'ova, David L. Marshall, Stephen J. Blanksby, Michelle L. Coote

Faculty of Science, Medicine and Health - Papers: part A

In most radicals the singly occupied molecular orbital (SOMO) is the highest-energy occupied molecular orbital (HOMO); however, in a small number of reported compounds this is not the case. In the present work we expand significantly the scope of this phenomenon, known as SOMO–HOMO energy-level conversion, by showing that it occurs in virtually any distonic radical anion that contains a sufficiently stabilized radical (aminoxyl, peroxyl, aminyl) non-π-conjugated with a negative charge (carboxylate, phosphate, sulfate). Moreover, regular orbital order is restored on protonation of the anionic fragment, and hence the orbital configuration can be switched by pH. Most importantly, our theoretical …

The Effect Of Band-Tail States On The Thermal Stability Of The Infrared Stimulated Luminescence From K-Feldspar, Bo Li, Sheng-Hua Li

Faculty of Science, Medicine and Health - Papers: part A

The thermal stability of the infrared stimulated luminescence (IRSL) signal from a sedimentary K-feldspar was investigated using isothermal decay study. It is observed that the isothermal decay of IRSL signal cannot be described using a first-order exponential decay function. Instead, the decay can be well described by considering the presence of band-tail states. Based on the isothermal decay results, a trap depth of ∼1.92 eV was obtained for the IRSL stimulated at 50 °C and the width of the band-tail states was found to be ∼0.37 eV below the conduction band edge. Deeper trap depths (up to ∼2.06 eV) were …

Thermal Stability Of Infrared Stimulated Luminescence Of Sedimentary K-Feldspar, Bo Li, Sheng-Hua Li

Faculty of Science, Medicine and Health - Papers: part A

The thermal stability of the infrared stimulated luminescence (IRSL) signal measured at 50 °C as a function of IR stimulation time was investigated using KF grains extracted from sediments from central China. A dependence of thermal stability of IRSL signal on IR stimulation time and stimulation temperature were observed in pulse annealing studies. Relatively lower thermal stability is given by the initial part of the IRSL measured at 50 °C, than the later part of IRSL curve. Based on these observations, the thermal stability of the post-IR IRSL signal stimulated at elevated temperatures (100–200 °C) was also investigated. It was …

Protein Dynamics And Stability: The Distribution Of Atomic Fluctuations In Thermophilic And Mesophilic Dihydrofolate Reductase Derived Using Elastic Incoherent Neutron Scattering, Lars Meinhold, David Clement, Moeava Tehei, Roy Daniel, John L. Finney, Jeremy C. Smith

Faculty of Science, Medicine and Health - Papers: part A

The temperature dependence of the dynamics of mesophilic and thermophilic dihydrofolate reductase is examined using elastic incoherent neutron scattering. It is demonstrated that the distribution of atomic displacement amplitudes can be derived from the elastic scattering data by assuming a (Weibull) functional form that resembles distributions seen in molecular dynamics simulations. The thermophilic enzyme has a significantly broader distribution than its mesophilic counterpart. Furthermore, although the rate of increase with temperature of the atomic mean-square displacements extracted from the dynamic structure factor is found to be comparable for both enzymes, the amplitudes are found to be slightly larger for the …

Decreased Heat Stability And Increased Chaperone Requirement Of Modified Human Βb1-Crystallins, Kirsten J Lampi, Yung H. Kim, Hans Peter Bachinger, Bruce A. Boswell, Robyn A. Lindner, John A. Carver, Thomas R Shearer, Larry L. David, Deborah M. Kapfer

Faculty of Science, Medicine and Health - Papers: part A

Purpose: To determine how deamidation and partial loss of the N- and C-terminal extensions alter the heat stability of βB1-crystallin.

Methods: Human lens βB1, a deamidated βB1, Q204E, and αA-crystallins were expressed. Truncated βB1 was generated by proteolytic removal of part of its terminal extensions. The aggregation and precipitation of these proteins due to heating was monitored by circular dichroism and light scattering. The effect of heat on the stability of both monomers and oligomers was investigated. The flexibility of the extensions in wild type and deamidated βB1 was assessed by ¹H NMR spectroscopy.

Results: With heat, deamidated βB1 …