Search results for "Biomolecule"
showing 10 items of 666 documents
Isotope Effects and Collective Excitations
1983
Isotopic substitution in the aqueous solvent is discussed as an effective method for probing the role of solvent dynamics in the stability of biomolecular conformation.
Photophysical behavior of norharmane related to proximity effect
1990
Abstract Solvent and temperature effects of fluorescence and its polarization characteristics for norharmane were studied. From the results obtained it is concluded that the fluorescent state changes from the φφ ∗ -type in a polar solvent (EPA) to nφ ∗ -type in a nonpolar solvent (MC), and also that lowest singlet excited states (φφ ∗ -type and nφ ∗ -type) interact by vibronic coupling. In the nonpolar solvent (MC) the lowest singlet excited states are very close in energy and consequently the vibronic coupling is stronger. At high temperatures, in a nonpolar solvent (MC), the emission is from both the φφ ∗ - and nφ ∗ -states due to thermal equilibration, while at low temperatures the emiss…
Mapping CO diffusion paths in Myoglobin with the Single Sweep Method
2010
The pathways of diffusion and escape of a CO molecule inside and out a myoglobin protein are investigated. Specifically, the three-dimensional potential of mean force (PMF or free energy) of the CO molecule position inside the protein is calculated by using the single-sweep method in concert with fully resolved atomistic simulations in explicit solvent.The results are interpreted under the assumption that the diffusion of the ligand can be modeled as a navigation on the PMF in which the ligand hops between the PMF local minima following the minimum free energy paths (MFEPs) with rates set by the free energy barriers that need to be crossed. We calculate all these quantities --local minima, …
Brewster angle microscopy and X-ray GID studies of morphology and crystal structure in monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amide
1997
First-order phase transitions from the low-density fluidlike phase to the condensed phase of monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amides at the air−water interface have been studied by π−A isotherms, Brewster angle microscopy (BAM), and synchrotron X-ray grazing incidence diffraction (GID). The thermodynamic differences between enantiomeric and racemic monolayers are too small to be measured. However, chiral discrimination is observable in the macroscopic domain morphology by BAM. The domains of the condensed phase grow dendritically. The characteristic shapes of domains of the pure S and R enantiomers are mirror images of each other. The domains of the racemic mixture are…
rac-(E,trans)-4-Bromo-10,10-dimethyl-9,11-dioxabicyclo[6.3.0]undec-4-ene
2020
In the title compound, a cyclooctene ring in a twist-boat conformation and a dioxolane ring with a distorted envelope conformation are annulated in a trans configuration. Alternating strands of single enantiomers build up the crystal. Within the strands, the molecules are connected by weak C—H...O hydrogen bonds.
How neutron scattering experiments can target the structure and dynamics of milk proteins?
2016
International audience; The powerful of neutron scattering techniques to characterize structure and dynamics of milk proteins is illustrated. Small angle neutron scattering and reflectivity are used to determine the structure and the interactions between milk proteins in solution, during gelation processes, or the protein structure at different interfaces. Experiments performed by inelastic and quasielastic neutron scattering allow one to observe the dynamics of water and proteins showing the major role of hydration on the dynamics of milk proteins.
Excess free energy of nanoparticles in a polymer brush
2008
Abstract We present an efficient method for direct determination of the excess free energy Δ F of a nanoparticle inserted into a polymer brush. In contrast to Widom's insertion method, the present approach can be efficiently implemented by Monte Carlo or Molecular Dynamics methods also in a dense environment. In the present investigation the method is used to determine the free energy penalty Δ F ( R , D ) for placing a spherical particle with an arbitrary radius R at different positions D between the grafting plane and the brush surface. Deep inside the brush, or for dense brushes, one finds Δ F ∝ R 3 whereas for shallow nanoclusions Δ F ∝ R 2 , regardless of the particle interaction (…
Structure of Polymer Brushes in Cylindrical Tubes: A Molecular Dynamics Simulation
2006
Molecular Dynamics simulations of a coarse-grained bead-spring model of flexible macromolecules tethered with one end to the surface of a cylindrical pore are presented. Chain length $N$ and grafting density $\sigma$ are varied over a wide range and the crossover from ``mushroom'' to ``brush'' behavior is studied for three pore diameters. The monomer density profile and the distribution of the free chain ends are computed and compared to the corresponding model of polymer brushes at flat substrates. It is found that there exists a regime of $N$ and $\sigma$ for large enough pore diameter where the brush height in the pore exceeds the brush height on the flat substrate, while for large enoug…
Covalently Binding of Bovine Serum Albumin to Unsaturated Poly(Globalide-Co-ε-Caprolactone) Nanoparticles by Thiol-Ene Reactions.
2019
When nanoparticles (NPs) are introduced to a biological fluid, different proteins (and other biomolecules) rapidly get adsorbed onto their surface, forming a protein corona capable of giving to the NPs a new "identity" and determine their biological fate. Protein-nanoparticle conjugation can be used in order to promote specific interactions between living systems and nanocarriers. Non-covalent conjugates are less stable and more susceptible to desorption in biological media, which makes the development of engineered nanoparticle surfaces by covalent attachment an interesting topic. In this work, the surface of poly(globalide-co-e-caprolactone) (PGlCL) nanoparticles containing double bonds i…
Single Molecules Probing the Freezing of Polymer Melts: A Molecular Dynamics Study for Various Molecule-Chain Linkages
2010
8 pages; International audience; We present molecular dynamics simulations of coarse-grained model systems of a glassforming polymer matrix containing fluorescent probe molecules. These probe molecules are either dispersed in the matrix or covalently attached to the center or the end of a dilute fraction of the polymer chains. We show that in all cases the translational and rotational relaxation of the probe molecules is a faithful sensor for the glass transition of the matrix as determined from a mode-coupling analysis or Vogel-Fulcher analysis of their R-relaxation behavior. Matrix and dumbbell related relaxation processes show a clear violation of the Stokes-Einstein-Debye laws. In accor…