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Wyszukujesz frazę "76.90.+d" wg kryterium: Temat


Wyświetlanie 1-9 z 9
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:
Nuclear Magnetic Relaxation Dispersion Study of Human Serum Proteins Solutions
Autorzy:
Olszewski, K. J.
Powiązania:
https://bibliotekanauki.pl/articles/1920946.pdf
Data publikacji:
1992-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.90.+d
87.45.-k
Opis:
Nuclear magnetic relaxation dispersion profiles in the Larmor frequency range of 0.02-50 MHz and 277 K has been studied for human serum proteins: albumin, γ-globulins and α, β-globulins in aqueous solutions 3-14 per cent by weight of protein. The linear concentration dependences have been found both for the longitudal relaxation rates for water protons and the dispersive and non-dispersive parts of relaxation profiles. The frequency dependent relaxivities have been calculated, the hydrodynamic effect for the albumin macromolecule Brownian rotational correlation time has been observed and analyzed. The importance of molecular weight of protein for the relaxation processes and its influence for magnetic resonance imaging contrast was discussed.
Źródło:
Acta Physica Polonica A; 1992, 82, 3; 487-494
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
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:
Impact Ionization Driven Chaotic Photoluminescence Oscillations in Ga$\text{}_{0.47}$In$\text{}_{0.53}$As
Autorzy:
Godlewski, M.
Fronc, K.
Gajewska, M.
Chen, W.M.
Monemar, B.
Powiązania:
https://bibliotekanauki.pl/articles/1888119.pdf
Data publikacji:
1991-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.+z
72.70.+m
76.90.+d
Opis:
A new application of the Optically Detected Cyclotron Resonance (ODCR) is presented. We report impact ionization studies of bound exciton: (BE) and shallow donor related recombination processes in Ga$\text{}_{0.47}$In$\text{}_{0.53}$As. An appearance of chaotic oscillations in photoluminescence (PL) intensity is observed under condition of impact ionization of deeper donors.
Źródło:
Acta Physica Polonica A; 1991, 80, 2; 271-274
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hot Carrier Effects in Optically Detected Cyclotron Resonance Studies of III-V Semiconductors
Autorzy:
Karpińska, K.
Dedulewicz, S.
Godlewski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1920978.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.+z
72.70.+m
76.90.+d
Opis:
The mechanisms of irregular photoluminescence intensity oscillations, as observed in optically detected cyclotron resonance experiments, are discussed. Two possible scenarios are analyzed, both requiring impact ionization of the center(s) by electric field accelerated free carriers. The first assumes coexistence of dielectric and energy relaxation processes. The second assumes a subsequent impact ionization of two different centers.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 623-626
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
THz Spectroscopy of Extremely Shallow Acceptors States in Ge/GeSi Multiple-Quantum-Well Heterostructures
Autorzy:
Aleshkin, V. Ya.
Erofeeva, Y. V.
Gavrilenko, V. I.
Ikonnikov, A. V.
Kozlov, D. V.
Kuznetsov, O. A.
Veksler, D. B.
Powiązania:
https://bibliotekanauki.pl/articles/2041651.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Cn
76.90.+d
78.67.De
Opis:
New shallow acceptor magnetoabsorption lines in THz range have been discovered under bandgap photoexcitation in strained Ge/GeSi multiple-quantum-well heterostructures. It is shown, both theoretically and experimentally, that the resonant absorption results from the photoionization of A$\text{}^{+}$-centers and from 1s → 2p$\text{}_{+}$-type transitions from the ground state of the barrier-situated A$\text{}^{0}$-centers into excited states in the 1st and 2nd electronic subbands. The shallowest discovered ground acceptor states (E$\text{}_{B}$≤0.5 meV) are attributed to the "barrier-spaced" acceptors (a hole bound with an acceptor ion in the neighboring Ge quantum well).
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 137-141
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultramarine, Lazurite and Sodalite Studied by Positron Annihilation and EPR Methods
Autorzy:
Baranowski, A.
Dębowska, M.
Jerie, K.
Jezierski, A.
Sachanbiński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1933463.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.-g
61.90.+d
76.30.-v
Opis:
Studies of positron annihilation accompanied by EPR technique were undertaken for sodalite and lazurite and their synthetic counterparts (synthetic sodalite and ultramarines). Results of measurements performed by two techniques of positron annihilation spectroscopy (angular correlation of annihilation radiation, ACAR, and positron annihilation lifetime) revealed the undoubted influence of free radicals on positron annihilation mechanism but both inhibition of positronium formation by them and the effect of filling cages ought to be taken into account. The distinct differences between ACAR curves for sodalites, lazurites and ultramarines probably reflect the presence of different radicals in their cages and chemical heterogeneity as well as the disorder in Al, Si-site ordering in case of ultramarines. Comparison of the results of ACAR measurements with the ones of the EPR studies indicates that there is correspondence between them. Similarly to three families of the ACAR curves, different likes of EPR lines were obtained for three groups of samples; sodalites, lazurites and ultramarines. It is possible that the annihilation of positrons takes place mainly with unpaired electrons recorded by the EPR technique.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 29-41
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-9 z 9

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