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Wyszukujesz frazę "76.60.-k" wg kryterium: Temat


Wyświetlanie 1-4 z 4
Tytuł:
Molecular Dynamics in Biological Systems Observed by NMR Relaxation in a Rotating Frame
Autorzy:
Wierzuchowska, D.
Skórski, L.
Blicharska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1490095.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.60.-k
76.90.+d
Opis:
NMR relaxation provides powerful tools for obtaining information on three-dimensional structures, dynamic properties and intermolecular interactions of biological macromolecules. One of these methods, called dispersion profile, is based on measuring the field dependence of spin-relaxation rates in the rotating frame, $R_{1ρ} = 1//T_{1ρ}$, in the presence of a low magnetic field $B_1$. In the presented study we use this method for investigation of molecular dynamics in protein samples. Dispersion profiles can be predicted theoretically and using two models, assuming either dipolar interaction between protons or power law dispersion, we have evaluated some molecular dynamic parameters of water adsorbed on protein surface. Our researches are focused on the connections of obtained parameters of molecular dynamics with conformation changes of protein. We have calculated the correlation times and power parameters for samples of lyophilized powder of albumins (egg white and bovine and rabbit blood serum) and lysozyme, as well as its aqueous solutions. Analysis of these parameters yields valuable information on the molecular nature of investigated biological systems. We also used this method to analyze experimental data of $T_{1ρ}$ obtained by other authors for bovine serum albumin and we have found good accordance with their conclusions concerning molecular dynamics of proteins.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 434-438
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Molecular Dynamics of Proteins Investigated by NMR Relaxation Methods
Autorzy:
Wierzuchowska, D.
Blicharska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1360657.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.60.-k
76.90.+d
Opis:
The nuclear magnetic resonance relaxation times of solvent water nuclei are known to decrease upon addition of diamagnetic solute protein. For this reason NMR relaxation methods are able to provide information on molecular dynamics changes of water protons and their interaction with macromolecules' surfaces. We present results of measurements of relaxation rates $R_1$ = 1/$T_1$, $R_2$ = 1/$T_2$ and $R_{1ρ}$ = 1/$T_{1ρ}$ in the rotating frame for three proteins: chicken egg white lysozyme, egg white albumin, and bovine serum albumin, obtained at proton resonant frequency of 60 MHz. Besides the relaxation rates dependences on concentration in the 4-23% (g/100 g solution) range, the analysis of the Carr-Purcell-Meiboom-Gill CPMG multi-echo $T_2$ experiments with variable pulse rate τ was performed. The dependences of relaxation rates on protein concentration are linear at low concentration. When protein concentration increases the slope of the straight line rapidly changes at so-called "critical" concentration which depends on MW of the diluted protein. Investigated dispersion of $T_2$, obtained using the CPMG method with a variable pulse rate, for concentrations higher and lower than the "critical" one, exhibits unequal behavior. At high concentration one-exponential curves and at low concentration two-exponential curves correspond closely with experimental data. The obtained parameters of exponents allow an estimation of the ratio of the amount of water with the determined motion freedom, that is free and bounded water, in solution. We showed that the CPMG dispersion method applied to aqueous protein solutions may widen the current understanding of the nature of molecular dynamics of hydrated water protons in non-perturbed environment.
Źródło:
Acta Physica Polonica A; 2014, 125, 4; 907-910
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Observation of Antioxidants Activity using NMR Relaxation Measurements
Autorzy:
Wierzuchowska, D.
Witek, M.
Blicharska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1030645.pdf
Data publikacji:
2018-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.60.-k
76.90.+d
76.30.Rn
Opis:
Formation of free radicals in biological solutions leads to the changes in water protons relaxation times. Therefore, NMR relaxation measurements were used to investigate kinetics of oxidation processes induced by the addition, in low amounts, of hydrogen peroxide (H_2O_2) to aqueous protein solution and to blood serum. The measured relaxation times were not stable over time because of the progressive formation of free radicals and their damaging action to the protein structure. The addition of antioxidants (ascorbic acid, gallic acid etc.) changed the relaxation time courses due to free radical scavenging. Similar time courses, thus anti-oxidant actions, were observed in various blood serum without antioxidant additive. Moreover, the observed kinetics of spin-lattice relaxation time (T_1) depended on several factors, such as: structure and concentration of protein solutions and activity and concentration of the added antioxidants.
Źródło:
Acta Physica Polonica A; 2018, 133, 2; 289-291
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
NMR Relaxation Measurements as a Tool for Observation of Oxidative Processes
Autorzy:
Wierzuchowska, D.
Skórski, L.
Blicharska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1398821.pdf
Data publikacji:
2016-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.60.-k
76.90.+d
76.30.Rn
Opis:
Water proton relaxation times, T₁ and T₂, were measured to assess the kinetics of the oxidative processes in biological samples. The oxidation in aqueous solutions of albumins was promoted by an addition of 3% hydrogen peroxide (H₂O₂). Immediately following this addition a sharp exponential decrease of both relaxation times was observed. As we confirmed experimentally, the time course of relaxation depended on several essential factors like structure and the concentration of proteins and also the presence of antioxidants added to solution. In experiments with protein solutions containing a small amount of ascorbic acid, after reaching a minimum, relaxation time increased towards the initial (pre-addition H₂O₂) values. We conclude that this T₁ and T₂ recovery is a consequence of the presence of antioxidants and may be used to evaluate its action. This study demonstrates that nuclear magnetic resonance (NMR) relaxation measurements may be useful in evaluating free radicals reactions and antioxidants capacity.
Źródło:
Acta Physica Polonica A; 2016, 129, 2; 226-228
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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