Search results for "Biophysic"

Oxygenation Status of Rhabdomyosarcoma Spheroids with Different Stages of Differentiation

1994

Multicellular tumor spheroids with regional heterogeneities of proliferation and substrate concentrations have been investigated recently to study the biological properties of small tumor nodules prior to onset of vascularization (for reviews see: Mueller-Klieser, 1987; Sutherland, 1988).

NMR relaxation in modern wood and treated and untreated wood from a XVI century wooden statue

2007

Longitudinal (T1) relaxation data are presented for European lime (Tilia cordata Mill) wood samples, a modern sample and two from a XVI century wooden statue, one of which samples is treated with Paraloid B72 for preservation. The 1H signals from liquid and solid are separated in the free induction decays (FID). T1 distributions are obtained by UPEN and show two resolved peaks for the liquid component of either untreated wood but a wide distribution for the liquid of the treated sample. In each case, the solid component showed a single peak, which for either untreated sample was at about the position of the longer T1 liquid peak. We compute geometric-mean times, T1-gm, 2.1 and 36 ms for the…

Synergistic and Antagonistic Effects of Combined Subzero Temperature and High Pressure on Inactivation of Escherichia coli

2006

ABSTRACT The combined effects of subzero temperature and high pressure on the inactivation of Escherichia coli K12TG1 were investigated. Cells of this bacterial strain were exposed to high pressure (50 to 450 MPa, 10-min holding time) at two temperatures (−20°C without freezing and 25°C) and three water activity levels (a w ) (0.850, 0.992, and ca. 1.000) achieved with the addition of glycerol. There was a synergistic interaction between subzero temperature and high pressure in their effects on microbial inactivation. Indeed, to achieve the same inactivation rate, the pressures required at −20°C (in the liquid state) were more than 100 MPa less than those required at 25°C, at pressures in t…

Probing Protein−Membrane Interactions Using Solid Supported Membranes

2011

International audience; Tethered bilayer lipid membranes have been used as a model system to mimic the interactions between the whey protein β-lactoglobulin and a lipid interface. The approach allowed for a detailed study of the lipid-protein interactions, the results being of possible importance in food and cosmetic applications. For such applications, lipid-protein interactions and the interfacial behavior are vital factors in controlling and manipulating process conditions such as emulsion stabilization and gelification. Lipid composition as well as the structural properties of the protein governed their interactions, which were probed by a combination of surface plasmon spectroscopy, ne…

Effect of Ligands on HP-Induced Unfolding and Oligomerization of β-Lactoglobulin

2020

ABSTRACTTo probe intermediate states during unfolding and oligomerization of proteins remains a major challenge. High pressure (HP) is a powerful tool for studying these problems, revealing subtle structural changes in proteins not accessible by other means of denaturation. Bovine β-lactoglobulin (BLG), the main whey protein, has a strong propensity to bind various bioactive molecules, such as retinol and resveratrol, two ligands with different affinity and binding sites. By combining in situ HP-small-angle neutron scattering (SANS) and HP-UV/visible absorption spectroscopy, we report the specific effects of these ligands on 3D conformational and local changes in BLG induced by HP. Dependin…

Regulation of tyrosinase by tetrahydropteridines—What is real?

2005

Analytic evaluation of Raman intensities in coupled-cluster theory

2007

We present the first implementation for the analytic calculation of polarizability derivatives using coupled-cluster theory. These derivatives are related to the intensity of bands seen in Raman spectroscopy, and are therefore important quantities that can also be measured experimentally. The required theory of analytic third derivatives is discussed and also connected to response theory to allow the calculation of frequency-dependent quantities. This work includes the use of a string-based general coupled-cluster/configuration-interaction program which makes the calculation of Raman intensities for arbitrary coupled-cluster or configuration-interaction methods up to the full configuration-…

Resonant activation in polymer translocation: new insights into the escape dynamics of molecules driven by an oscillating field

2010

The translocation of molecules across cellular membranes or through synthetic nanopores is strongly affected by thermal fluctuations. In this work we study how the dynamics of a polymer in a noisy environment changes when the translocation process is driven by an oscillating electric field. An improved version of the Rouse model for a flexible polymer has been adopted to mimic the molecular dynamics, by taking into account the harmonic interactions between adjacent monomers and the excluded-volume effect by introducing a Lennard–Jones potential between all beads. A bending recoil torque has also been included in our model. The polymer dynamics is simulated in a two-dimensional domain by num…

Thermodynamics of small systems embedded in a reservoir: a detailed analysis of finite size effects

2012

International audience; We present a detailed study on the finite size scaling behaviour of thermodynamic properties for small systems of particles embedded in a reservoir. Previously, we derived that the leading finite size effects of thermodynamic properties for small systems scale with the inverse of the linear length of the small system, and we showed how this can be used to describe systems in the thermodynamic limit [Chem. Phys. Lett. 504, 199 (2011)]. This approach takes into account an effective surface energy, as a result of the non-periodic boundaries of the small embedded system. Deviations from the linear behaviour occur when the small system becomes very small, i.e. smaller tha…

Spinodal lines and Flory-Huggins free-energies for solutions of human hemoglobins HbS and HbA

1991

Gelation of deoxygenated solutions of sickle-cell human Hemoglobin (HbS) is of high theoretical interest and it has serious pathological consequences. For this reason HbS is probably the most studied protein capable of self-organization. This notwithstanding, the location in the T, c plane of the region of thermodynamic instability of solutions of deoxy-HbS (as bounded by the spinodal line and as distinct from the gelation region) has remained unknown, along with related values of Flory-Huggins enthalpies and entropies. In the present work this information is derived from experiments for the two cases of (deoxy) HbS and of human adult hemoglobin (HbA). Experiments also show critical exponen…