107 research outputs found
Mechanical Strength of 17 134 Model Proteins and Cysteine Slipknots
A new theoretical survey of proteins' resistance to constant speed stretching
is performed for a set of 17 134 proteins as described by a structure-based
model. The proteins selected have no gaps in their structure determination and
consist of no more than 250 amino acids. Our previous studies have dealt with
7510 proteins of no more than 150 amino acids. The proteins are ranked
according to the strength of the resistance. Most of the predicted top-strength
proteins have not yet been studied experimentally. Architectures and folds
which are likely to yield large forces are identified. New types of potent
force clamps are discovered. They involve disulphide bridges and, in
particular, cysteine slipknots. An effective energy parameter of the model is
estimated by comparing the theoretical data on characteristic forces to the
corresponding experimental values combined with an extrapolation of the
theoretical data to the experimental pulling speeds. These studies provide
guidance for future experiments on single molecule manipulation and should lead
to selection of proteins for applications. A new class of proteins, involving
cystein slipknots, is identified as one that is expected to lead to the
strongest force clamps known. This class is characterized through molecular
dynamics simulations.Comment: 40 pages, 13 PostScript figure
Die Qualitätskontrolle der Lebensmittelkonzentrate
Az úgynevezett készételek fogalmi meghatározása után tárgyalja e termékek legfontosabb csoportjait és alapvető tulajdonságaikat. Foglalkozik továbbá azokkal a tényezőkkel, amelyek ezeknek a termékeknek a minőségét befolyásolják, áttekintést nyújt vizsgálati eljárásaikról és az ipari minőségvizsgálat szervezetéről, különös tekintettel az üzemen belüli minőségvizsgálat eljárásaira. Végül felsorolja a készletek minőségi értékelésének kritériumait. After presenting the concept of convenience foods, ready-made meals, the main groups of these products are listed and their fundamental properties described. Also the factors affecting the quality of products are surveyed and the organisation of quality control of the industry described, on paying particular attention to the quality control carried out within the plants producing the foods of this type. Lastly, the criteria of the evaluation of the quality of the products are summed up
LinkProt : a database collecting information about biological links
Protein chains are known to fold into topologically complex shapes, such as knots, slipknots or complex lassos. This complex topology of the chain can be considered as an additional feature of a protein, separate from secondary and tertiary structures. Moreover, the complex topology can be defined also as one additional structural level. The LinkProt database (http://linkprot.cent.uw.edu.pl) collects and displays information about protein links - topologically non-trivial structures made by up to four chains and complexes of chains (e.g. in capsids). The database presents deterministic links (with loops closed, e.g. by two disulfide bonds), links formed probabilistically and macromolecular links. The structures are classified according to their topology and presented using the minimal surface area method. The database is also equipped with basic tools which allow users to analyze the topology of arbitrary (bio)polymers
Stretching and twisting of the DNA duplexes in coarse grained dynamical models
Three coarse-grained models of the double-stranded DNA are proposed and
compared in the context of mechanical manipulation such as twisting and various
schemes of stretching. The models differ in the number of effective beads
(between two and five) representing each nucleotide. They all show similar
behavior and, in particular, lead to a torque-force phase diagrams
qualitatively consistent with experiments and all-atom simulations
Influence of Hydrodynamic Interactions on Mechanical Unfolding of Proteins
We incorporate hydrodynamic interactions in a structure-based model of
ubiquitin and demonstrate that the hydrodynamic coupling may reduce the peak
force when stretching the protein at constant speed, especially at larger
speeds. Hydrodynamic interactions are also shown to facilitate unfolding at
constant force and inhibit stretching by fluid flows.Comment: to be published in Journal of Physics: Condensed Matte
The Energy Landscape, Folding Pathways and the Kinetics of a Knotted Protein
The folding pathway and rate coefficients of the folding of a knotted protein
are calculated for a potential energy function with minimal energetic
frustration. A kinetic transition network is constructed using the discrete
path sampling approach, and the resulting potential energy surface is
visualized by constructing disconnectivity graphs. Owing to topological
constraints, the low-lying portion of the landscape consists of three distinct
regions, corresponding to the native knotted state and to configurations where
either the N- or C-terminus is not yet folded into the knot. The fastest
folding pathways from denatured states exhibit early formation of the
N-terminus portion of the knot and a rate-determining step where the C-terminus
is incorporated. The low-lying minima with the N-terminus knotted and the
C-terminus free therefore constitute an off-pathway intermediate for this
model. The insertion of both the N- and C-termini into the knot occur late in
the folding process, creating large energy barriers that are the rate limiting
steps in the folding process. When compared to other protein folding proteins
of a similar length, this system folds over six orders of magnitude more
slowly.Comment: 19 page
Mechanical unfolding of proteins – comparative non-equilibrium molecular dynamics study
Mechanical signals regulate functions of mechanosensitive proteins by inducing structural changes that are determinant for force-dependent interactions. Talin is a focal adhesion protein that is known to extend under mechanical load, and it has been shown to unfold via intermediate states. Here, we compared different nonequilibrium molecular dynamics (MD) simulations to study unfolding of the talin rod. We combined boxed MD (BXD), steered MD, and umbrella sampling (US) techniques and provide free energy profiles for unfolding of talin rod subdomains. We conducted BXD, steered MD, and US simulations at different detail levels and demonstrate how these different techniques can be used to study protein unfolding under tension. Unfolding free energy profiles determined by BXD suggest that the intermediate states in talin rod subdomains are stabilized by force during unfolding, and US confirmed these results
Tests of the Structure-Based Models of Proteins
The structure-based models of proteins are defined through the condition that their ground state coincides with the native structure of the proteins. There are many variants of such models and they yield different properties. Optimal variants can be selected by making comparisons to experimental data on single-molecule stretching. Here, we discuss the 15 best performing variants and focus on fine tuning the selection process by adjusting the velocity of stretching to match the experimental conditions. The very best variant is found to correspond to the 10-12 potential in the native contacts with the energies modulated by the Miyazawa-Jernigan statistical potential and variable length parameters. The second best model incorporates the Lennard-Jones potential with uniform amplitudes. We then make a detailed comparison of the two models in which theoretical surveys of stretching properties of 7510 proteins were made previously
Tests of the Structure-Based Models of Proteins
The structure-based models of proteins are defined through the condition that their ground state coincides with the native structure of the proteins. There are many variants of such models and they yield different properties. Optimal variants can be selected by making comparisons to experimental data on single-molecule stretching. Here, we discuss the 15 best performing variants and focus on fine tuning the selection process by adjusting the velocity of stretching to match the experimental conditions. The very best variant is found to correspond to the 10-12 potential in the native contacts with the energies modulated by the Miyazawa-Jernigan statistical potential and variable length parameters. The second best model incorporates the Lennard-Jones potential with uniform amplitudes. We then make a detailed comparison of the two models in which theoretical surveys of stretching properties of 7510 proteins were made previously
- …