1977
|
Kutnik, Jan Bioelectric potentials of Charophyta cells Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 2, pp. 5-13, 1977, ISSN: 1232-9630. @article{ZBW_1976(2)5-13,
title = {Bioelectric potentials of Charophyta cells},
author = {Jan Kutnik},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue2/v2_5.pdf},
issn = {1232-9630},
year = {1977},
date = {1977-01-01},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {2},
pages = {5-13},
abstract = {Bioelectric potentials are generated due to cell membranes. Two kinds of potentials can be distinguished: resting potential and action potential. Potentials of the Chorophyta cells differ from analogical potentials of animal cells in value, time of duration, velocity of extending and participation of particular ions flowing through the membrane. Resting potentials are of the diffusion kind. Action potentials are explained by the increase in permeability of the membrane for certain kinds of ions. There remain some problems which have not been fully explained yet, e.g. selectivity of membranes, mobility of ions in the membranes, mechanisms acting in membranes in excited state etc. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Bioelectric potentials are generated due to cell membranes. Two kinds of potentials can be distinguished: resting potential and action potential. Potentials of the Chorophyta cells differ from analogical potentials of animal cells in value, time of duration, velocity of extending and participation of particular ions flowing through the membrane. Resting potentials are of the diffusion kind. Action potentials are explained by the increase in permeability of the membrane for certain kinds of ions. There remain some problems which have not been fully explained yet, e.g. selectivity of membranes, mobility of ions in the membranes, mechanisms acting in membranes in excited state etc. |
Bulanda, Wladyslaw Electric conductivity of organic compounds and its significance in biology Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 2, pp. 15-41, 1977, ISSN: 1232-9630. @article{ZBW_1976(2)15-42,
title = {Electric conductivity of organic compounds and its significance in biology},
author = {Wladyslaw Bulanda},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue2/v2_15.pdf},
issn = {1232-9630},
year = {1977},
date = {1977-01-01},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {2},
pages = {15-41},
abstract = {The paper reviews experimental and theoretical investigations concerning semiconducting properties of organic compounds. Principal parameters of semiconductors and methods of their measurements are presented as well as results of semiconducting parameter measurements of organic compounds and some models explaining electronic conductivity of them are discussed. Semiconducting properties of proteins, nucleic acids, amino acids and the possible occurrence of semiconductivity in biological systems are described. The results of the experiments carried out in the Biophysics Laboratory of Physic's Institute of UMCS in Lublin concerning electronic conductivity in intermodal cells of Characeae are presented.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The paper reviews experimental and theoretical investigations concerning semiconducting properties of organic compounds. Principal parameters of semiconductors and methods of their measurements are presented as well as results of semiconducting parameter measurements of organic compounds and some models explaining electronic conductivity of them are discussed. Semiconducting properties of proteins, nucleic acids, amino acids and the possible occurrence of semiconductivity in biological systems are described. The results of the experiments carried out in the Biophysics Laboratory of Physic's Institute of UMCS in Lublin concerning electronic conductivity in intermodal cells of Characeae are presented. |
Wadas, Romuald Magnetism in biological molecules Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 2, pp. 43-70, 1977, ISSN: 1232-9630. @article{ZBW_1976(2)43-70,
title = {Magnetism in biological molecules},
author = {Romuald Wadas},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue2/v2_43.pdf},
issn = {1232-9630},
year = {1977},
date = {1977-00-00},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {2},
pages = {43-70},
abstract = {The paramagnetic, antiferromagnetic, ferrimagnetic and ferromagnetic biological molecules were described. The effect of the magnetic properties of biological molecules on metabolic processes was presented. The effect of the externally applied magnetic field on magnetic biological molecules and liquid crystals in living cells was investigated both experimentally and theoretically.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The paramagnetic, antiferromagnetic, ferrimagnetic and ferromagnetic biological molecules were described. The effect of the magnetic properties of biological molecules on metabolic processes was presented. The effect of the externally applied magnetic field on magnetic biological molecules and liquid crystals in living cells was investigated both experimentally and theoretically. |
Jóźwiak, Zofia; Bartosz, Grzegorz Superoxide dismutase Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 2, pp. 71-98, 1977, ISSN: 1232-9630. @article{ZBW_1976(2)71-98,
title = {Superoxide dismutase},
author = {Zofia Jóźwiak and Grzegorz Bartosz},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue2/v2_71.pdf},
issn = {1232-9630},
year = {1977},
date = {1977-00-00},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {2},
pages = {71-98},
abstract = {Superoxide dismutase (oxidoreductase superoxide: E. C. 1.15.1.1) catalyses the reaction of dismutation of superoxide radical anion, 02'. This enzyme is an universal cellular constituent of aerobic organisms. A dimeric metalloprotein of molecular weight of about 33 000 daltons containing Cu and Zn is present in cytosol of eukaryotic organisms. Cu-Zn-superoxide dismutase from bovine erythrocytes is the best characterrized protein of this group and its complete amino acid sequence is established. On the other hand, prokaryotic organisms possess dismutases of different structure, containing either Mn or Fe, of molecular weight of about 40000 daltons. A tetrameric from of Mn-superoxide dismutase (molecular weight of about 80000 daltons) is present in mitochondria of eukaryotes, what has been interpreted' in favour of the theory of endosymbiothic origin of mitochondria. Extensive studies have been performed on the mechanism of action of superoxide dismutase. The enzyme has also been used as a specific probe for involvement of the superoxide radical anion in various enzymatic and non-enzymatic processes. The ubiquitous presence of this enzyme in aerobic organisms suggests its important role as a protective agent against 02-.. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Superoxide dismutase (oxidoreductase superoxide: E. C. 1.15.1.1) catalyses the reaction of dismutation of superoxide radical anion, 02'. This enzyme is an universal cellular constituent of aerobic organisms. A dimeric metalloprotein of molecular weight of about 33 000 daltons containing Cu and Zn is present in cytosol of eukaryotic organisms. Cu-Zn-superoxide dismutase from bovine erythrocytes is the best characterrized protein of this group and its complete amino acid sequence is established. On the other hand, prokaryotic organisms possess dismutases of different structure, containing either Mn or Fe, of molecular weight of about 40000 daltons. A tetrameric from of Mn-superoxide dismutase (molecular weight of about 80000 daltons) is present in mitochondria of eukaryotes, what has been interpreted' in favour of the theory of endosymbiothic origin of mitochondria. Extensive studies have been performed on the mechanism of action of superoxide dismutase. The enzyme has also been used as a specific probe for involvement of the superoxide radical anion in various enzymatic and non-enzymatic processes. The ubiquitous presence of this enzyme in aerobic organisms suggests its important role as a protective agent against 02-.. |
Chławiczka, Stanisław; Wardas, Władysław Kinetic formaldehyd metod investigation of DNA secondary structure changes Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 2, pp. 99-110, 1977, ISSN: 1232-9630. @article{ZBW_1977(2)99-110,
title = {Kinetic formaldehyd metod investigation of DNA secondary structure changes },
author = {Stanisław Chławiczka and Władysław Wardas },
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue2/v2_99.pdf},
issn = {1232-9630},
year = {1977},
date = {1977-00-00},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {2},
pages = {99-110},
abstract = {The effect of various physical and chemical factors on the secondary structure of DNA molecules in solution is discussed. The mathematical aspect of interaction DNA·formaldehyd (CH20) and some theoretical principles of the so called kinetic formaldehyd method (KF) are presented. Using the KF method the determination of defect concentration in DNA secondary structure is possible basing on differences in the unwinding velocity of the DNA bihelix observed under action of CH20 when analysed DNA samples have different numbers of structural defects. The detailed procedure of DNA secondary structure investigation by use of this method is presented. Effects of other parameters as chosen wavelength, pH, temperature, kind of DNA and formaldehyde concentration on the characteristic of the obtained KF curves are reviewed and discussed. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The effect of various physical and chemical factors on the secondary structure of DNA molecules in solution is discussed. The mathematical aspect of interaction DNA·formaldehyd (CH20) and some theoretical principles of the so called kinetic formaldehyd method (KF) are presented. Using the KF method the determination of defect concentration in DNA secondary structure is possible basing on differences in the unwinding velocity of the DNA bihelix observed under action of CH20 when analysed DNA samples have different numbers of structural defects. The detailed procedure of DNA secondary structure investigation by use of this method is presented. Effects of other parameters as chosen wavelength, pH, temperature, kind of DNA and formaldehyde concentration on the characteristic of the obtained KF curves are reviewed and discussed. |
Kanclerz, Andrzej; Zbytniewski, Zbigniew Application of the electron spin resonance (ESR) technique in oncology Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 2, pp. 111-118, 1977, ISSN: 1232-9630. @article{ZBW_1977(2)111-118,
title = {Application of the electron spin resonance (ESR) technique in oncology },
author = {Andrzej Kanclerz and Zbigniew Zbytniewski},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue2/v2_111.pdf},
issn = {1232-9630},
year = {1977},
date = {1977-00-00},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {2},
pages = {111-118},
abstract = {During the last years the ESR technique is becoming more and more applicable in the investigations of biological systems. There exists a free-radical theory of oncogenesis which is supported by the findings available by the use of ESR technique. It has been stated that many chemical carcinogens in the cell are transformed into free-radical forms reacting with nucleic acids. In the early stages of carcinogenesis the free-radical level increases, and after the occurrence of the tumour it decreases below the normal level. The observed changes in the free-radical concentrations take place not only in the tumour itself, but also in other tissues of the tumour bearing animals and human beings},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
During the last years the ESR technique is becoming more and more applicable in the investigations of biological systems. There exists a free-radical theory of oncogenesis which is supported by the findings available by the use of ESR technique. It has been stated that many chemical carcinogens in the cell are transformed into free-radical forms reacting with nucleic acids. In the early stages of carcinogenesis the free-radical level increases, and after the occurrence of the tumour it decreases below the normal level. The observed changes in the free-radical concentrations take place not only in the tumour itself, but also in other tissues of the tumour bearing animals and human beings |
1976
|
Kotłowska, Maria; Kielich, Stanislaw Determination of the optical and electric properties of biomacromolecules by the method of anisotropic light scattering Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 1, pp. 7-16, 1976, ISSN: 1232-9630. @article{ZBW_1976(1)7-16,
title = {Determination of the optical and electric properties of biomacromolecules by the method of anisotropic light scattering },
author = {Maria Kotłowska and Stanislaw Kielich },
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue1/Abstract-v1_7.pdf},
issn = {1232-9630},
year = {1976},
date = {1976-01-01},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {1},
pages = {7-16},
abstract = {Anisotropic light scattering by solutions of biomacromolecules, arrayed in an external DC electric field, is a source of data concerning their dipole moment and anisotropy, both optical and electric. A theory of the effect is proposed for biomacromolecules of linear dimensions l less than incident light wavelength λ (l<1/20 λ) as well for ones of linear dimensions of wavelength order (l ~ λ). Formulae are derived for the relative changes in scattered light intensity versus the square of the external field strength permitting to determine the sign and numerical value (α3 – α1) of the electric anisotropy (α3 - the electric polarizabilitv of the biornacromolecule in the direction of its symmetry axis, α1 - that perpendicular to the latter). Very high external field strengths lead to electric saturation (the biomacromolecutes are completely oriented with their axis of maximal polarizability into the field direction). Relative changes in intensity, scattered at electric saturation, are considered, and formulae are proposed permitting to determine the sign and numerical value of the optical anisotropy of such biomacrornolecules. Cases of reorientation by other external agents (a magnetic field or the electric field of a laser beam) are also discussed. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Anisotropic light scattering by solutions of biomacromolecules, arrayed in an external DC electric field, is a source of data concerning their dipole moment and anisotropy, both optical and electric. A theory of the effect is proposed for biomacromolecules of linear dimensions l less than incident light wavelength λ (l<1/20 λ) as well for ones of linear dimensions of wavelength order (l ~ λ). Formulae are derived for the relative changes in scattered light intensity versus the square of the external field strength permitting to determine the sign and numerical value (α3 – α1) of the electric anisotropy (α3 - the electric polarizabilitv of the biornacromolecule in the direction of its symmetry axis, α1 - that perpendicular to the latter). Very high external field strengths lead to electric saturation (the biomacromolecutes are completely oriented with their axis of maximal polarizability into the field direction). Relative changes in intensity, scattered at electric saturation, are considered, and formulae are proposed permitting to determine the sign and numerical value of the optical anisotropy of such biomacrornolecules. Cases of reorientation by other external agents (a magnetic field or the electric field of a laser beam) are also discussed. |
Wróbel, Danuta Spectral methods of investigation of biological systems Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 1, pp. 17-37, 1976, ISSN: 1232-9630. @article{ZBW1976(1)17-37,
title = {Spectral methods of investigation of biological systems },
author = {Danuta Wróbel },
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue1/Abstract-v1_17.pdf},
issn = {1232-9630},
year = {1976},
date = {1976-01-01},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {1},
pages = {17-37},
abstract = {In the article various methods used in the study of the biological systems are described. Several methods of radiative transitions spectroscopy such as: vibrational – rotational spectroscopy, spectroscopy of singlet and triplet states, two – photon absorption, electron impact spectroscopy, also degree of polarization and lifetime of the excited states measurements are characterized. Radiationless spectroscopy (internal conversion and intersystem crossing) is reported too. From absorption and fluorescence measurements done on biological systems, the information concerning the structure of biological systems, mutual ordering and shape of biomolecules, interaction and energy migration between them, and the role of individual compounds of live organism in metabolic processes is derived. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In the article various methods used in the study of the biological systems are described. Several methods of radiative transitions spectroscopy such as: vibrational – rotational spectroscopy, spectroscopy of singlet and triplet states, two – photon absorption, electron impact spectroscopy, also degree of polarization and lifetime of the excited states measurements are characterized. Radiationless spectroscopy (internal conversion and intersystem crossing) is reported too. From absorption and fluorescence measurements done on biological systems, the information concerning the structure of biological systems, mutual ordering and shape of biomolecules, interaction and energy migration between them, and the role of individual compounds of live organism in metabolic processes is derived. |
Łazarski, Roman Natural photoprotectors Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 1, pp. 89-101, 1976, ISSN: 1232-9630. @article{ZBW_1976(1)89-101,
title = {Natural photoprotectors },
author = {Roman Łazarski},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue1/v1_89.pdf},
issn = {1232-9630},
year = {1976},
date = {1976-01-01},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {1},
pages = {89-101},
abstract = {Light can be considered one of those environmental factors which are not only beneficial but even indispensable for the existence of life. Nevertheless, one can suppose that photochemical reactions are, as a rule, deleterious if uncontrolled by the organism. Such a point of view is substantiated by numerous experimental data. The present paper describes various ways of this harmful action, including the role of photodynamic effect, and analyses several possible mechanisms of photo-protection. The question is then discussed what are the general features of substances capable of functioning as natural photoprotectors, particular attention being paid to two especially interesting groups of chemical compounds, namely to melanins and carotenoids. In the light of contemporary research, the significance of melanins as protectors against damage produced by electromagnetic waves is manifold. This hold true for both the wavelength (from infrared until gamma radiations) and the mechanisms of action (from simple screening until radical reactions and oxidation-reductions). As regards carotenoids, their radio-protective activity is still disputable and the mechanism of physical careening seems to be of second importance. On the contrary, the photo-protection based on physico-chemical interactions is quite essential for the organism and much better understood. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Light can be considered one of those environmental factors which are not only beneficial but even indispensable for the existence of life. Nevertheless, one can suppose that photochemical reactions are, as a rule, deleterious if uncontrolled by the organism. Such a point of view is substantiated by numerous experimental data. The present paper describes various ways of this harmful action, including the role of photodynamic effect, and analyses several possible mechanisms of photo-protection. The question is then discussed what are the general features of substances capable of functioning as natural photoprotectors, particular attention being paid to two especially interesting groups of chemical compounds, namely to melanins and carotenoids. In the light of contemporary research, the significance of melanins as protectors against damage produced by electromagnetic waves is manifold. This hold true for both the wavelength (from infrared until gamma radiations) and the mechanisms of action (from simple screening until radical reactions and oxidation-reductions). As regards carotenoids, their radio-protective activity is still disputable and the mechanism of physical careening seems to be of second importance. On the contrary, the photo-protection based on physico-chemical interactions is quite essential for the organism and much better understood. |
Retelewska, Wanda Effect of ionising radiation on lymphocytes Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 1, pp. 103-121, 1976, ISSN: 1232-9630. @article{ZBW_1976(1)103-121,
title = {Effect of ionising radiation on lymphocytes },
author = {Wanda Retelewska},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue1/v1_103.pdf},
issn = {1232-9630},
year = {1976},
date = {1976-01-01},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {1},
pages = {103-121},
abstract = {Radiation-induced changes of lymphocytes, which belong to the most radiosensitive cells, are described. Depending on the radiation dose, conditions of irradiation and nature of the irradiated object (whole organism or isolated lymphocytes from different tissues) the radiation-induced changes may be of different character. The most frequently observed radiation-induced changes of lymphocytes consist in a partial disappearance of these cells and deterioration of immunologic capacity of irradiated animals. Among the visible morphologic changes preceding the radiation-induced lymphocyte death one should mention: pycnotic degeneration of the cell nucleus, disintegration of mitochondria and cell membranes and cytoplasmic alterations. Radiation affects, first of all, energetic metabolism of the lymphocyte. It is generally suggested that energetic metabolism of the cell nucleus belongs to the first signals of irradiation both in vivo and in vitro. Radiation-induced inhibition of nuclear and mitochondrial oxidative phosphorylation involving a decrease of ATP level precedes other detectable radiaton-induced injuries of the lymphocyte. It has been shown recently that degradation of adenine nucleotides to hypoxanthine begins already in 30 min after irradiation of rat thymocytes, preceding inhibition of ATP synthesis. Oxidative phosphorylation is very sensitive to the action of radiation, however its inhibition is observed not immediately but about 60 min following irradiation of rat thymocytes with a dose of 1000 R. Restoring effect of adenine on radiation-induced damage of rat thymocytes is also rewieved. Adenine added within one hour after irradiation prevents the degradation of ATP to' hypoxanthine and nucleoprotein dissociation. It affects the lymphocyte viability, too. Mechanism of the restoring effect of adenine on nucleotide degradation is not cleared up. The extraordinary sensitivity of lymphocytes to the action of radiation may be utilized in biological dosimetry. On the basis of quantitative alterations induced by radiation in chromosomes of peripheral blood lymphocytes the dose of radiation absorbed by the organism, may be evaluated. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Radiation-induced changes of lymphocytes, which belong to the most radiosensitive cells, are described. Depending on the radiation dose, conditions of irradiation and nature of the irradiated object (whole organism or isolated lymphocytes from different tissues) the radiation-induced changes may be of different character. The most frequently observed radiation-induced changes of lymphocytes consist in a partial disappearance of these cells and deterioration of immunologic capacity of irradiated animals. Among the visible morphologic changes preceding the radiation-induced lymphocyte death one should mention: pycnotic degeneration of the cell nucleus, disintegration of mitochondria and cell membranes and cytoplasmic alterations. Radiation affects, first of all, energetic metabolism of the lymphocyte. It is generally suggested that energetic metabolism of the cell nucleus belongs to the first signals of irradiation both in vivo and in vitro. Radiation-induced inhibition of nuclear and mitochondrial oxidative phosphorylation involving a decrease of ATP level precedes other detectable radiaton-induced injuries of the lymphocyte. It has been shown recently that degradation of adenine nucleotides to hypoxanthine begins already in 30 min after irradiation of rat thymocytes, preceding inhibition of ATP synthesis. Oxidative phosphorylation is very sensitive to the action of radiation, however its inhibition is observed not immediately but about 60 min following irradiation of rat thymocytes with a dose of 1000 R. Restoring effect of adenine on radiation-induced damage of rat thymocytes is also rewieved. Adenine added within one hour after irradiation prevents the degradation of ATP to' hypoxanthine and nucleoprotein dissociation. It affects the lymphocyte viability, too. Mechanism of the restoring effect of adenine on nucleotide degradation is not cleared up. The extraordinary sensitivity of lymphocytes to the action of radiation may be utilized in biological dosimetry. On the basis of quantitative alterations induced by radiation in chromosomes of peripheral blood lymphocytes the dose of radiation absorbed by the organism, may be evaluated. |
Bartosz, Grzegorz Sprawozdanie z V Międzynarodowego Kongresu Biofizyki Miscellaneous 1976, ISSN: 1232-9630. @misc{ZBW_1976(1)123-125,
title = {Sprawozdanie z V Międzynarodowego Kongresu Biofizyki},
author = {Grzegorz Bartosz},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue1/Abstract-v1_123.pdf},
issn = {1232-9630},
year = {1976},
date = {1976-01-01},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
|
Wanik, Barbara; Lidwin, Maria Optical activity of deoxyribonucleic acid Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 1, pp. 39-54, 1976, ISSN: 1232-9630. @article{ZBW1976(1)39-54,
title = {Optical activity of deoxyribonucleic acid},
author = {Barbara Wanik and Maria Lidwin},
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue1/Abstract-v1_39.pdf},
issn = {1232-9630},
year = {1976},
date = {1976-00-00},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {1},
pages = {39-54},
abstract = {It is known that the explanations of CD and ORD phenomenon of nucleic acids should take into account rather the base-base interactions than the base-pentose rings interactions. In the light of the neighbour-neighbour approximation theory the base-stacking interaction seems to have the greatest importance. DNA macromolecules in aqueous environments are available to disorganization accompanied by the weakening of basestacking hydrophobic interactions that are reflected in the diminution of the Cotton effect amplitude. The ionic strength of the solution in the range of 5.10-5 - 5.10-3 influences in different ways the stability of the structure of DNA molecule. Basing on the analysis of ORD and CD profiles, DNA molecules in solution of the ionic strength of.5 .10-3 - 1 seem to have the greatest stability. The appearance of new peaks on ORD
curves (e.g. as a result of protonation from pH = 7 to pH = 3.5) indicates the existence of an intermediate DNA form not fully native and not completely denatured. The formation of the intermediate DNA structure is probably evoked by conformational changes which occur in the G+C rich fragments of DNA double-helical chains as a result of cytosine protonation. The increase of temperature disrupts the "DNA double-helical
structure. This phenomenon can be analyzed through ORD profiles as a function of temperature. The divalent cations (Mg+2, Mn+2, Cu+2, Hg+2, Zn+2) cause some subtle reversible changes in the DNA structure which are reflected in different deformations of the ORD profiles. Sometimes the interactions of divalent cations with DNA macromolecules produce even a lowering of the peaks. The interactions of dyes such as acridine
orange or proflavine with DNA macromolecules which form DNA-dyes complexes are accompanied by appearance of new Cotton effects.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
It is known that the explanations of CD and ORD phenomenon of nucleic acids should take into account rather the base-base interactions than the base-pentose rings interactions. In the light of the neighbour-neighbour approximation theory the base-stacking interaction seems to have the greatest importance. DNA macromolecules in aqueous environments are available to disorganization accompanied by the weakening of basestacking hydrophobic interactions that are reflected in the diminution of the Cotton effect amplitude. The ionic strength of the solution in the range of 5.10-5 - 5.10-3 influences in different ways the stability of the structure of DNA molecule. Basing on the analysis of ORD and CD profiles, DNA molecules in solution of the ionic strength of.5 .10-3 - 1 seem to have the greatest stability. The appearance of new peaks on ORD
curves (e.g. as a result of protonation from pH = 7 to pH = 3.5) indicates the existence of an intermediate DNA form not fully native and not completely denatured. The formation of the intermediate DNA structure is probably evoked by conformational changes which occur in the G+C rich fragments of DNA double-helical chains as a result of cytosine protonation. The increase of temperature disrupts the "DNA double-helical
structure. This phenomenon can be analyzed through ORD profiles as a function of temperature. The divalent cations (Mg+2, Mn+2, Cu+2, Hg+2, Zn+2) cause some subtle reversible changes in the DNA structure which are reflected in different deformations of the ORD profiles. Sometimes the interactions of divalent cations with DNA macromolecules produce even a lowering of the peaks. The interactions of dyes such as acridine
orange or proflavine with DNA macromolecules which form DNA-dyes complexes are accompanied by appearance of new Cotton effects. |
Olichwier-Holwek, Jolanta Paramagnetic resonance studies of hemoproteins Journal Article In: Zagadnienia Biofizyki Współczesnej, vol. 1, pp. 55-88, 1976, ISSN: 1232-9630. @article{ZBW1976(1)55-88,
title = {Paramagnetic resonance studies of hemoproteins},
author = {Jolanta Olichwier-Holwek },
editor = {Wanda Leyko},
url = {http://ctbo.home.amu.edu.pl/issue1/v1_55.pdf},
issn = {1232-9630},
year = {1976},
date = {1976-00-00},
journal = {Zagadnienia Biofizyki Współczesnej},
volume = {1},
pages = {55-88},
abstract = {Metallo-proteins, and in particular heme proteins, perform a wide variety of biological functions and have diverse chemical and physical characteristics. Physical methods such as EPR have often been used as aids to determine the electronic state at the heme site in order to relate the structure of the protein at its active site to its chemical function. Home proteins can exist in a variety of oxidation and spin states, each dependent upon the immediate environment of the heme. The oxidation states most commonly encountered are the ferrous and ferric. The states have 6 and 5 magnetic electrons respectively, in the iron-porphyrin system (the d electrons) and it is the geometrical relationship of
these magnetic electrons, which is sensitive to the influence of the environment of heme. When examined at low temperatures all heme proteins containing mononuclear high spin ferric heme, exhibit electron paramagnetic resonance (EPR) absorptions extending from near g=6 to g=2 which arise from transients of the lowest Kramers doublet. Absolute quantitation of high spin ferric EPR spectra has to be made from
experiments at very low temperature or at the basis of the zero field splitting. The characteristics of the EPR spectrum may be used to describe the symmetry of heme. The incorporation of hemin into a protein constains the heme in such a manner that there is a departure from tetragonal symmetry towards rhombic (gx ≠ gy). In these cases the resonance absorption derivative near g=6 is either broadened or split into two resolvable g values dependent upon the interaction of the protein with heme. Thus, the EPR of high spin heme proteins can be used as a protein conformational probe. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Metallo-proteins, and in particular heme proteins, perform a wide variety of biological functions and have diverse chemical and physical characteristics. Physical methods such as EPR have often been used as aids to determine the electronic state at the heme site in order to relate the structure of the protein at its active site to its chemical function. Home proteins can exist in a variety of oxidation and spin states, each dependent upon the immediate environment of the heme. The oxidation states most commonly encountered are the ferrous and ferric. The states have 6 and 5 magnetic electrons respectively, in the iron-porphyrin system (the d electrons) and it is the geometrical relationship of
these magnetic electrons, which is sensitive to the influence of the environment of heme. When examined at low temperatures all heme proteins containing mononuclear high spin ferric heme, exhibit electron paramagnetic resonance (EPR) absorptions extending from near g=6 to g=2 which arise from transients of the lowest Kramers doublet. Absolute quantitation of high spin ferric EPR spectra has to be made from
experiments at very low temperature or at the basis of the zero field splitting. The characteristics of the EPR spectrum may be used to describe the symmetry of heme. The incorporation of hemin into a protein constains the heme in such a manner that there is a departure from tetragonal symmetry towards rhombic (gx ≠ gy). In these cases the resonance absorption derivative near g=6 is either broadened or split into two resolvable g values dependent upon the interaction of the protein with heme. Thus, the EPR of high spin heme proteins can be used as a protein conformational probe. |
