Biomedical subjects

L Smeller

Publications and source records attributed to L Smeller.

7 recordsLinked to original sources

PubMed2006

Refolding studies using pressure: the folding landscape of lysozyme in the pressure-temperature plane.

Refolding of hen egg white lysozyme after pressure unfolding was measured by FTIR spectroscopy. The high-pressure treatment was found to be useful for unfolding/refolding studies because pressure acts against aggregation, and therefore no irreversible aggregation takes place during the pressure treatment. After the release of the pressure, folding intermediate structures were found which were formed during the decompression of the lysozyme. These were aggregation prone when heated, as indicated by their lower stability against aggregation. The intermediates were only formed if the protein was unfolded, subdenaturing pressures could not populate these intermediates. We introduced the notion of a superfunnel to describe the free energy landscape of interacting polypeptide chains. This can explain the propensity of folding intermediates to aggregate. A possible Gibbs-free energy landscape for lysozyme was constructed for the whole pressure-temperature plane.

Animals↗

PubMed2003

High-pressure FTIR study of the stability of horseradish peroxidase. Effect of heme substitution, ligand binding, Ca++ removal, and reduction of the disulfide bonds.

The pressure stability of horseradish peroxidase isoenzyme C and the identification of possible stabilizing factors are presented. The effect of heme substitution, removal of Ca(2+), binding of a small substrate molecule (benzohydroxamic acid), and reduction of the disulfide bonds on the pressure stability were investigated by FTIR spectroscopy. HRP was found to be extremely stable under high pressure with an unfolding midpoint of 12.0 +/- 0.1 kbar. While substitution of the heme for metal-free mesoporphyrin did not change the unfolding pressure, Ca(2+) removal and substrate binding reduced the midpoint of the unfolding by 2.0 and 1.2 kbar, respectively. The apoprotein showed a transition as high as 10.4 kbar. However, the amount of folded structure present at the atmospheric pressure was considerably lower than that in all the other forms of HRP. Reduction of the disulfide bonds led to the least pressure stable form, with an unfolding midpoint at 9.5 kbar. This, however, is still well above the average pressure stability of proteins. The high-pressure stability and the analysis of the pressure-induced spectral changes indicate that the protein has a rigid core, which is responsible for the high stability, while there are regions with less stability and more conformational mobility.

Amides↗

PubMed1999

Pressure effect on the temperature-induced unfolding and tendency to aggregate of myoglobin.

This work demonstrates that pressure-induced partially unfolded states play a very important role in the aggregation of proteins. The high-pressure unfolding of horse heart metmyoglobin results in an intermediate form that shows a strong tendency to aggregate after pressure release. These aggregates are similar to those that are usually observed upon temperature denaturation. Infrared spectra in the amide I region indicate the formation of an intermolecular antiparallel beta-sheet stabilized by hydrogen bonding. The formation of the aggregates is temperature-dependent. Below 30 degrees C, no aggregation is taking place as seen from the infrared spectra. At 45 and 60 degrees C, two types of aggregates are formed: one that can be dissociated by moderate pressures and one that is pressure-insensitive. When precompressed at 5 degrees C, temperature-induced aggregation takes place at lower temperature (38 degrees C) than without pressure pretreatment (74 degrees C).

Animals↗

PubMed1998

Protein structure and dynamics at high pressure.

The effect of pressure on the structure and dynamics of proteins is discussed in the framework of the pressure-temperature stability phase diagram. The elastic (reversible) properties, thermal expansion, compressibility and heat capacity, are correlated with the entropy, volume, and the coupling between entropy and volume fluctuations respectively. The experimental approaches that can be used to measure these quantities are reviewed. The plastic (conformational) changes reflect the changes in these properties in the cold, pressure and heat denaturation.

Chemical Phenomena↗

PubMed1996

Pressure-tuning the conformation of bovine pancreatic trypsin inhibitor studied by Fourier-transform infrared spectroscopy.

A hydrostatic pressure of 1.5 GPa induces changes in the secondary structure of bovine pancreatic trypsin inhibitor (BPTI) as revealed by the analysis of the amide I' band with Fourier-transform infrared (FTIR) spectroscopy in the diamond anvil cell. The features of the secondary structure remain distinct at high pressure suggesting that the protein does not unfold. The fitted percentages of the secondary structure elements during compression and decompression strongly suggest that the pressure-induced changes are reversible. The pressure-induced changes in the tyrosine side chain band are also reversible. The results demonstrate that the infrared technique explores different aspects of the behaviour of proteins in comparison with two published molecular dynamics studies performed up to 1 GPa [Kitchen, D.B., Reed, L.H. & Levy, R.M.(1992) Biochemistry 31, 10083-10093] and 500 MPa [Brunne, R.M. & van Gunsteren, W.F.(1993) FEBS Lett. 323, 215-217]. A possible explanation for the difference is the time scale of the experiments.

Amides↗

PubMed1990

The pressure dependence of the lipid phase transitions. Effect of the pressure on the pre- and subtransition.

The pressure dependence of the pre- and subtransitions is explained by a statistical physical model. Using this theoretical model the shift of the transition temperatures can be shown to be in agreement with the experimental results. Both the hysteresis effect which appears at standard pressure and the absence of the hysteresis at high pressures are explained.

Animals↗

PubMed1989

A statistical mechanical model of the pre- and subtransitions of lecithin membranes.

A statistical mechanical model with experimentally proved facts as starting points is presented. This model explains on molecular level, the pre- and subtransitions appearing in lipid membranes. The model describes the main features of the transitions, the hysteresis of the subtransition and the mobility changes of the heads and chains at these transitions. The model was expanded for phosphatidylcholine homologues with arbitrary chain lengths, and a qualitative agreement in the case of pretransition as far as a quantitative one for the subtransition were found.

Chemical Phenomena↗