Ara P. Antonyan

Influence of Low Intensity Coherent Electromagnetic Millimeter Radiation (Emr) on Aqua Solution of Dna

The thermostability and density of water-salt solutions of DNA, irradiated by non thermal coherent millimeter electromagnetic waves with frequency 64.5 GHz have been investigated using the methods of spectrophotometry and densitometry. It is shown that the thermostability of DNA and density of its solutions are increased, depending on time of irradiation. It is expected that under the influence of millimeter electromagnetic radiation the hydration of DNA and ions of Na+ that are present in solution decrease. As a result, the physicochemical characteristics of DNA are changed.

Complex-formation of Ethidium Bromide with poly[d(A-T)].poly[d(A-T)].

Abstract The interaction of Ethidium Bromide (EtBr) with double-stranded (ds-) and single-stranded (ss-) poly[d(A-T)] was studied in different ionic strengths solutions. Optical spectroscopy and Scatchard analysis results indicate that the ligand interacts to both helix and coiled structures of the polynucleotide by “strong” and “weak” binding modes. The association parameters (binding constant—K—and the number of nucleotides corresponding to a binding site—n) of the strong type of interaction were found to be independent of Na+ concentration. Weak interaction occurs at low ionic strength and/or high EtBr concentration. Estimated binding parameters of EtBr with ss- and ds-polynucleotide are in good agreement with those for EtBr-B-DNA complexes. Data obtained provided an evidence for a stacking interaction of EtBr with single stranded poly[d(A-T)].

Study of ethidium bromide interaction peculiarities with DNA

The helix-coil transition of DNA-ethidium bromide complexes in an interval of ionic strength of 2.0 x 10(-3) M ≤ muNa+ ≤ 2.0 x 10(-2) M has been investigated. It has been revealed that at the certain high ligand-DNA ratios (r(b)) the transition interval of the complex-(ΔT) becomes equal to that of DNA itself (ΔTo). It has been shown that the values of r(b) at which δ ΔT=ΔT-ΔT0=0 depends on ionic strength of a solution. Further increasing of ligand concentration leads to its conversion from stabilizer into the destabilizer of the double-stranded DNA.

The influence of GC/AT composition on intercalating and semi-intercalating binding of ethidium bromide to DNA

The binding parameters of ethidium bromide (EtBr) with DNA of various GC/AT ratios were determined using absorption and fluorescence spectroscopy. Our experimental data clearly demonstrate the co-existence of fluorescing and non-fluorescing types of “strong” binding at low concentration of EtBr. The fluorescent complex corresponds to the ordinary intercalative model. The non-fluorescent complex is referred to semi-intercalative binding of EtBr. The binding constant (K) and the number of base pairs corresponding to a binding site (n) of the fluorescent (K f and n f ) and non-fluorescent (K nf, nnf) types of interactions were determined. The average size of binding site (n) is equal to 1.5 bp (absorption spectroscopy), and nf ca. 2 bp (fluorescence spectroscopy). It was shown that nnf is dependent on GC-content and total n is independent of it.

Analysis of experimental binding curves of EtBr with single- and double-stranded DNA at small fillings

In this paper, a method that allows to analyze the binding curves of ligand (EtBr) with single-stranded (ss) and double-stranded (ds) DNA, when there are at least two modes of ligand binding to DNA at small fillings has been proposed. The obtained experimental binding curves for EtBr–ssDNA and EtBr–dsDNA have two clearly expressed linear regions. These curves were analyzed by two modes: Experimental points on linear regions were described by two different lines and all experimental points were described by single curve. It was revealed that the description by single curve permits obtaining more precise data of binding parameters (i.e. binding constant and number of base pairs that bind one ligand molecule). Moreover, the proposed method permits determining the value of proportion of binding sites of each binding mode.

Joint interaction of ethidium bromide and methylene blue with DNA. The effect of ionic strength on binding thermodynamic parameters

Large amount of data of experimental and theoretical studies have shown that ethidium bromide (EtBr) and methylene blue (MB) may bind to nucleic acids via three modes: intercalation between two adjacent base pairs, insertion into the plane between neighboring bases in the same strand (semi-intercalation), and outside binding with negatively charged backbone phosphate groups. The aim of the given research is to examine the behavior of these two ligands at both separate and joint DNA binding. The obtained experimental data show that the effect of simultaneous binding of EtBr and MB on double-stranded DNA has a non-additive effect of separate binding. The analyses of the melting thermodynamic parameters of DNA complexes with two bound ligands suggest competitive mechanism of interaction.

Ethidium bromide binding to native and denatured poly(dA)poly(dT)

Isotherms of the EtBr adsorption on native and denatured poly(dA)poly(dT) in the temperature interval 20–70°C were obtained. The EtBr binding constants and the number of binding sites were determined. The thermodynamic parameters of the EtBr intercalation complex upon changes of solution temperature 20–48°C were calculated: 1.0·106 M−1≤K≤1.4·106 M−1, free energy ΔGo=−8.7±0.3 kcal/mol, enthalpy ΔHo≅0, and entropy ΔSo=28±0.5 cal/(mol deg). UV melting has shown that the melting temperature (Tm) of EtBr-poly(dA)poly(dT) complexes (μ=0.022,4.16·10−5 M EtBr) increased by 17°C as compared with the ΔTm of free homopolymer, whereas the half-width of the transition (Tm) is not changed. It was shown for the first time that EtBr forms complexes of two types on single-stranded regions of poly(dA)poly(dT) denatured at 70°C: strong (K1=1.7·105 M−1; ΔGo=−8.10±0.03 kcal/mol) and weak (K2=2.9·103 M−1; ΔGo=−6.0±0.3 kcal/mol).The ΔGo of the strong and weak complexes was independent of the solution ionic strength, 0.0022≤μ≤0.022. A model of EtBr binding with single-stranded regions of poly(dA)poly(dT) is discussed.

Study of influence of millimeter range electromagnetic waves on water–saline solutions of albumin

In this work, the effect of electromagnetic waves of millimeter diapason (EMW MM) on both melting parameters of serum albumin from human blood and its solution density has been studied. It was shown that the irradiation of albumin solution results in protein denaturation at higher temperatures than in the case of nonirradiated samples, which indicates the increase of albumin packing degree. It was also shown that the enhancement of albumin solution density takes place which indicates the protein packing degree change as well. The obtained data show that the effect of EMW MM does not depend on frequency of these waves, because alterations are revealed at all studied frequencies — 41.8, 48 and 51.8GHz.

Absorption and fluorescence spectra of polynucleotide complexes with ethidium bromide

We study the ethidium bromide (EtBr) interaction with the poly(dA)-poly(dT) and poly[d(A-T)]-poly[d(A-T)] polynucleotides at 0.02 M ionic strength of solution and pH = 7.2. It was revealed that the EtBr binds to the poly[d(A-T)]-poly[d(A-T)] by three modes: the intercalation, semiintercalation and weak (electrostatic), while with the poly(dA)-poly(dT) by two modes: the intercalation and semi-intercalation. Moreover, EtBr binds to the poly(dA)-poly(dT) cooperatively and to the poly[d(A-T)]-poly[d(A-T)] non-cooperatively.

Behavior of Ethidium Bromide-Hoechst 33258-DNA and Ethidium Bromide-Methylene Blue-DNA Triple Systems by means of UV Melting

The study of EtBr and H33258 interaction as well as EtBr and MB interaction with DNA has been carried out. It was revealed that, at joint interaction, the effect of two ligands on the change of melting thermodynamic parameters of EtBr-DNA-H33258 or EtBr-DNA-MB complexes is not an addition of separate interaction influences. It was shown that, at joint, binding of EtBr and MB with DNA competition occurs, while in the case of EtBr and H33258, the mutual strengthening of stabilizing effect of each of them on DNA double-stranded structure mainly takes place.