Search results for " freedom"

Orientational landscapes of peptides in membranes: prediction of (2)H NMR couplings in a dynamic context.

2009

Unlike soluble proteins, membrane polypeptides face an anisotropic milieu. This imposes restraints on their orientation and provides a reference that makes structure prediction tractable by minimalistic thermodynamic models. Here we use this framework to build orientational distributions of monomeric membrane-bound peptides and to predict their expected solid-state (2)H NMR quadrupolar couplings when labeled at specific side chain positions. Using a complete rigid-body sampling of configurations relative to an implicit lipid membrane, peptide free energy landscapes are calculated. This allows us to obtain probability distributions of the peptide tilt, azimuthal rotation, and depth of membra…

Single-Molecule Optical Switching: A Mechanistic Study of Nonphotochemical Hole-Burning

2001

Persistent spectral hole-burning of dopant chromophores embedded in solid matrices has proven to be a sensitive high-resolution spectroscopic tool to investigate structural and dynamic properties of amorphous and crystalline hosts at low temperature [1]. A commonly encountered mechanism of holeformation is the nonphotochemical process, for which it is assumed that the frequency selective laser excitation and the subsequent relaxation of guest and host eventually leads to a change of configurational degrees of freedom in the nearby environment of the photo-excited centers or in the impurities themselves (or both) [2]. However, detailed knowledge about the microscopic mechanism of the nonphot…

Glass transition in 1,4-polybutadiene: Mode-coupling theory analysis of molecular dynamics simulations using a chemically realistic model.

2006

We present molecular dynamics simulations of the glass transition in a chemically realistic model of 1,4-polybutadiene (PBD). Around 40 K above the calorimetric glass transition of this polymer the simulations reveal a well-developed two-stage relaxation of all correlation functions. We have analyzed the time-scale separation between vibrational degrees of freedom (subpicosecond dynamics) and the alpha relaxation behavior (nanosecond to microsecond dynamics) using the predictions of mode-coupling theory (MCT). Our value for the mode-coupling critical temperature Tc agrees perfectly with prior experimental estimates for PBD. The predictions of MCT for the scaling behavior of the so-called be…

Correlation of Pharmacological Properties of a Group of Hypolipaemic Drugs by Molecular Topology

1996

Abstract This investigation was undertaken to test the ability of the molecular connectivity model to predict the percentage of plasma protein binding, the percentage of total cholesterol reduction and oral LD50 in rats of a group of hypolipaemic drugs using multi-variable regression equations with multiple correlation coefficients, standard error of estimate, degrees of freedom, F-Snedecor function values, Mallow's CP and Student's t-test as criteria of fit. Regression analyses showed that the molecular connectivity model predicts these properties. Corresponding stability (cross validation) studies were made on the selected prediction models which confirmed their goodness of fit. The resul…

Humanities and Social Sciences Latvia. Vol. 23, N. 1

2015

Meson and isobar degrees of freedom in light nuclei

1983

The role of mesonic and isobar degrees of freedom in various electromagnetic processes is reviewed for light nuclei. Special emphasis is laid on the deuteron, which allows the cleanest answers within the non-relativistic framework. The origin of the photonuclear enhancement with respect to both exchange forces and exchange currents is discussed in detail.

Subnuclear Degrees of Freedom in Photoabsorption and Scattering

1986

One of the main fields of interest in medium energy nuclear physics is the study of subnuclear or non-nucleonic degrees of freedom (d.o.f.) in nuclei, like meson and isobar or quark-gluon degrees of freedom. It bridges the gap between classical or low energy nuclear physics as understood in terms of nucleon-only degrees of freedom and elementary particle or high energy physics. Hereby one may distinguish roughly two major objectives.

The Experimental Program of the MAMI-Project

1992

At Mainz university, a 100% duty-factor electron accelerator for beam current and energy up to 100 µA and 855 MeV,respectively, has become operational recently, the Mainz Microtron MAMI. The experimental program is based on three major equipments which are built up and will be run by three facility-oriented collaborations. Collaboration A1 is centered around a magnetic spectrometer setup and will do experiments with virtual photons. For experiments with real photons collaboration A2 runs a high-efficiency tagger. Collaboration A3 sets up a polarized electron source in order to exploit the polarization degrees of freedom.

Exclusive deuteron electrodisintegration with polarized electrons and a polarized target

1992

Exclusive electrodisintegration of the deuteron using a polarized beam and an oriented target is systematically investigated in a nonrelativistic framework. The structure functions are expanded in terms of Legendre functions whose coefficients are quadratic forms in the electric and magnetic multipole moments. Their experimental separation by specific experimental settings is outlined. The structure functions are studied with respect to their sensitivity to the potential model, to subnuclear degrees of freedom, and to electromagnetic form factors in different kinematical regions.

Thermodynamics of Toda lattice models: application to DNA

1993

Abstract Our generalised Bethe ansatz method is used to formulate the statistical mechanics of the classical Toda lattice in terms of a set of coupled integral equations expressed in terms of appropriate action-angle variables. The phase space as coordinatised by these action-angle variables is constrained; and both the soliton number density and the soliton contribution to the free energy density can be shown to decouple from the phonon degrees of freedom and to depend only on soliton-soliton interactions. This makes it possible to evaluate the temperature dependence of the soliton number density which, to leading order, is found to be proportional to T 1 3 .