Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “TEMPERATURE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48Linked to original sources
PubMed2005

One gene, two diseases and three conformations: molecular dynamics simulations of mutants of human prion protein at room temperature and elevated temperatures.

Fatal familial insomnia (FFI) and Creutzfeldt-Jakob disease (CJD) are associated to the same mutation at codon 178 but differentiate into clinicopathologically distinct diseases determined by this mutation and a naturally occurring methionine-valine polymorphism at codon 129 of the prion protein gene. It has been suggested that the clinical and pathological difference between FFI and CJD is caused by different conformations of the prion protein. Using molecular dynamics (MD), we investigated the effect of the mutation at codon 178 and the polymorphism at codon 129 on prion protein dynamics and conformation at normal and elevated temperatures. Four model structures were examined with a focus on their dynamics and conformational changes. The results showed differences in stability and dynamics between polymorphic variants. Methionine variants demonstrated a higher stability than valine variants. Elongation of existing beta-sheets and formation of new beta-sheets was found to occur more readily in valine polymorphic variants. We also discovered the inhibitory effect of proline residue on existing beta-sheet elongation.

Computer Simulation↗
PubMed1992

Temperature-dependent protein folding in vivo--lower growth temperature increases yield of two genetic variants of Xenopus laevis Cu,Zn superoxide dismutase in Escherichia coli.

Two genetic variants of Xenopus laevis Cu,Zn superoxide dismutase, XSODA and XSODB, have been expressed in Escherichia coli by recombinant DNA techniques. Production of both proteins was obtained, although with different yields, XSODB being more abundant than XSODA in all the conditions tested. Lowering the temperature of growth was found to be a specific factor, decisive in obtaining quantitatively abundant, active Xenopus enzymes. Impaired folding of these proteins in the E.coli cytoplasm was found to parallel their in vitro properties.

Animals↗
PubMed2001

An investigation into the effects of residual water on the glass transition temperature of polylactide microspheres using modulated temperature DSC.

The objective of the study was to ascertain residual water levels in polylactide and polylactide-co-glycolide microspheres prepared using the solvent evaporation technique and to investigate the effects of that water on the glass transitional behaviour of the microspheres. Microspheres were prepared from polylactic acid (PLA) and polylactide-co-glycolide (PLGA) 50:50 and 75:25 using a standard solvent evaporation technique. The glass transition was measured as a function of drying conditions using modulated temperature DSC. The microspheres were found to contain very low levels of dichloromethane, while residual water levels of up to circa 3% w/w were noted after freeze or oven drying, these levels being higher for microspheres containing higher glycolic acid levels. The residual water was found to lower the T(g) following the Gordon-Taylor relationship. The data indicate that the microparticles may retain significant water levels following standard preparation and drying protocols and that this drying may markedly lower the T(g) of the spheres.

Calorimetry, Differential Scanning↗
PubMed2001

Temperature relaxation in two-temperature states of dense electron-ion systems.

It is shown that the Landau-Spitzer theory for temperature relaxation between electrons and ions, which was originally derived for ideal plasmas, is in fact more general. A relaxation formula is derived, for arbitrary ion-ion coupling that follows from elementary considerations combined with the fluctuation-dissipation theorem and the f-sum rule. The conditions for the validity of this theory are weak electron-ion coupling and that the spectrum of fluctuations of the ions lies at energies far below the resonances of the electrons spectrum. It is found that the rate of energy relaxation is not sensitive to the details of the ion-excitation spectrum. For classical electrons the formula reduces to the Landau-Spitzer form with minor modifications.

Journal Article↗
PubMed2004

Inverse bremsstrahlung and temperature relaxation in moderately coupled two-temperature plasmas.

The balance equation for the energy in moderately coupled two-temperature plasmas, in the presence of an external radiation field, is derived and analyzed. The analysis is based on the Singwi-Tosi-Land-Sjolander closure assumption. The different terms in the derived equation are identified as the rate of collisional energy absorption from the external field (inverse bremsstrahlung), and the rate of energy transfer between the electrons and the ions in the presence of the radiation field (relaxation). It is shown how these terms, which have a structurally similar appearance, reduce to known expressions for relaxation and inverse bremsstrahlung in the appropriate limits. It is found that, relative to the known expressions, electron-ion correlation tends to enhance the rates of re1axation and of the inverse bremsstrahlung process.

Journal Article↗