ABSTRACT
Possible effects of high pressure on heat denaturation of biopolymers have been analyzed. The study was made using an equilibrium model of transition between two states. Equations used to determine the dependence of thermodynamic parameters of transition (enthalpy, entropy and transition temperature) on pressure were formulated. Pressure may have both stabilizing and destabilizing effects on the macromolecule structure depending on the change in the volume upon transition. The dependence of the transition temperature on pressure cannot have local extremums. It is demonstrated that depending on the increment (jump) of the partial expansion coefficient and the change of the transition temperature, the enthalpy of transition can both grow with the pressure growth or decrease. It is also .shown that when the pressure grows, the changes in the volume and enthalpy under denaturation cannot change their signs.
Subject(s)
Biophysical Phenomena , Biopolymers/chemistry , Thermodynamics , Entropy , Models, Theoretical , Pressure , TemperatureABSTRACT
Four-wave photon coherent scattering of laser emission was used to study the influence of DNA on the content of quasi-free ortho and para isomers of water molecules in its aqueous solution. It was shown that the concentration of quasi-free molecules that form the rotational spectrum of spin isomers increases considerably in the hydrational shell of the DNA molecule as compared to pure water. The increase in the concentration of spin isomers occurs disproportionally. In the presence of DNA, the intensity of the rotational spectrum of orthoisomers is on the average much greater than that of para isomers. It was also demonstrated that the character of hydration and the ortho/para ratio change noticeably upon DNA denaturation, which may be evidence of changes in preferable solvation of DNA during its denaturation. The data obtained allowed us to assume that the stability of different biologically important states of macromolecules can be changed by varying the relative concentration of water spin isomers in solution.
Subject(s)
DNA/chemistry , Water/chemistry , Animals , Lasers , Quantum Theory , Salmon , Scattering, RadiationABSTRACT
On the basis of molecular biophysics, a methodology for the analysis of intramolecular structural order of the polynucleotide duplex poly(A).poly(U) has been developed. It was shown that the combination of circular dichroism spectroscopy with differential scanning calorimetry is an optimal approach, which ensures the screening of a wide set of substances and interaction conditions and the choice of compound(s) that can stabilize the structure and increase the biological activity of this duplex. The study is aimed at obtaining a new and highly active antiviral remedy.
Subject(s)
Antiviral Agents/chemistry , Platinum Compounds/chemistry , Poly A-U/chemistry , Circular Dichroism/methodsABSTRACT
Scanning microcalorimetry has been used to study the high pressure effect on the main transition from the ripple gel P'(beta) phase to the liquid crystal (L(alpha)) phase in DPPC (dipalmitoylphosphatidylcholine). It has been demonstrated that an increase of the pressure by 200 MPa shifts the transition to higher temperatures by 36.4 degrees. The pressure increase does not affect the cooperativity of transition but reduces noticeably its enthalpy. The changes of the molar partial volume, isothermal compressibility as well as volume thermal expansibility during transition in DPPC suspension have been estimated. It has been shown that monovalent ions (Na(+), Cl(-)) in solution slightly affect the main thermodynamic parameters of the transition. Calcium ions significantly decrease distinction in compressibility and thermal expansibility between liquid-crystal and ripple gel phases of lipid suspension, which in its turn reflects less difference in their volume fluctuations.
Subject(s)
1,2-Dipalmitoylphosphatidylcholine/chemistry , Calorimetry/methods , Gels/chemistry , Liquid Crystals/chemistry , Phase Transition , Pressure , Suspensions , Thermodynamics , Water/chemistryABSTRACT
The effects of spin state of water molecules on its absorption on lyophilized DNA, lysozyme and some inorganic sorbents were studied. It was shown that the absorption rates of ortho and para water from vapor differ noticeably. The para isomer binding with preparations is distinctly faster than that of the ortho isomer in all cases. Clear-cut distinction in the sorption kinetics is determined by the difference in quantum statistics for spin isomers, which in its turn can give rise to remarkable differences in physico-chemical properties of ortho and para water. This finding opens a wide field of activity in studying fundamental and applied problems relating to the role of the spin state of water molecules in physics, chemistry, biology and medicine.
Subject(s)
DNA/chemistry , Muramidase/chemistry , Absorption , Animals , Chemical Phenomena , Chemistry, Physical , Kinetics , Salmon , Sensitivity and Specificity , Time Factors , Water/chemistryABSTRACT
DNA-DPPC complexes can be prepared by means of a single step procedure of mixing DNA solution and aqueous lipid dispersion in the presence of calcium ions. Interaction between DPPC and DNA brings about a biphasic shape of melting curves corresponding to the free lipid and the strongly bound one. The amount of the strongly bound lipid is 5 molecules per nucleotide which is close to the size of the first lipid monolayer around DNA molecule.
Subject(s)
1,2-Dipalmitoylphosphatidylcholine/chemistry , DNA/chemistry , 1,2-Dipalmitoylphosphatidylcholine/metabolism , Animals , Calcium/chemistry , Calcium/metabolism , Cattle , DNA/metabolism , Interferometry , Temperature , UltrasonicsABSTRACT
The inverted micellar phase, obtained by treating lecithin and Ca(2+)-DNA complex with chloroform, was used as an intermediate step in the preparation of DNA-Ca(2+)-lecithin complex. DSC analysis demonstrated the involvement of a large fraction of lipid in the interaction with DNA. Freeze-fracture electron microscopy revealed (i) rod-like structures on the hydrophobic fracture surface of membranes and (ii) regular bundles of fibrils with a repeat distance of about 6 nm, which were located free in solution. Similar regular bundles of fibrils were also revealed by staining the samples with uranyl acetate. According to the suggested model, the observed structures are hexagonally packed inverted lipid tubes, with DNA located in their central cores. The possible biological relevance of the capability of Ca(2+)-DNA to initiate polymorphic phase transitions of lecithin is discussed.
