ЕФЕКТИВНI РАДIУСИ МАКРОМОЛЕКУЛ У РОЗБАВЛЕНИХ РОЗЧИНАХ ПОЛIВIНIЛОВОГО СПИРТУ УДК 532.13, 544.777 На основi експериментальних даних в'язкостi розбавлених розчинiв полiвiнiлового спир-ту (ПВС) у диметилсульфоксидi (ДМСО) та водi за допомогою теорiї зсувної в'язкостi розчинiв макромолекул Маломужа-Орлова дослiджуються температурнi та концен-трацiйнi залежностi ефективних радiусiв макромолекул полiвiнiлового спирту. Пока-зано, що в iнтервалi температур 293-353 К температурнi залежностi ефективних ра-дiусiв макромолекул ПВС у ДМСО мають лiнiйний характер, тодi як у водних розчинах ПВС такi залежностi є бiльш складними: за вiдносно низьких температур i концен-трацiй величини ефективних радiусiв макромолекул залишаються незмiнними, а зро-стання температури i концентрацiї призводить до нелiнiйного зменшення ефективних радiусiв макромолекул. Концентрацiйнi залежностi ефективних радiусiв макромолекул в обох розчинниках для iнтервалу концентрацiй 0,3-3 мас.% носять нелiнiйний спадний характер.К л ю ч о в i с л о в а: розчин полiвiнiлового спирту, ефективний радiус макромолекули, ди-метилсульфоксид, теорiя Маломужа-Орлова.
The Malomuzh–Orlov theory is used to analyze the experimental shear viscosity data obtained for aqueous solutions of human serum albumin (HSA) at pH = 7.0 in wide temperature and concentration intervals, which allowed the effective radii of HSA macromolecules to be calculated. It is shown that three intervals of the effective molecular radius of HSA with different behaviors can be distinguished in a temperature interval of 278–318 K: 1) below the crossover concentration, the effective molecular radius of HSA remains constant; 2) in the interval from the crossover concentration to about 10 wt%, the effective molecular radius of HSA in the aqueous solution nonlinearly decreases; and 3) at concentrations of 10.2–23.8 wt%, the effective radius of HSA macromolecules linearly decreases, as the concentration grows. The assumption is made that the properties of water molecules in the solution bulk play a crucial role in the dynamics of HSA macromolecules at the vital concentrations of HSA in the solutions. The role of water near the surface of HSA macromolecules and the corresponding changes of its physical properties have been discussed.
Experimental researches are carried out for the concentration and temperature dependences of the kinematic viscosity and the density of diluted and semidiluted solutions of polyvinyl alcohols (PVAs) with hydrolysis degrees of 85.2 ± 1.0 mol.% and 98.4 ± 0.4 mol.% in dimethyl sulfoxide and water. Critical concentrations of the transition from the diluted solution to more concentrated regimes are calculated. The results of calculations show that the critical crossover concentrations for PVA solutions in dimethyl sulfoxide are lower than that for PVA aqueous solutions. The obtained temperature dependences of the effective hydrodynamic radii of macromolecules in the diluted PVA solutions testify that this parameter decreases, as the temperature grows.
On the basis of experimental data for the shear viscosity in the aqueous solutions of ovine serum albumin and using the cellular model describing the viscosity in aqueous solutions, the concentration dependences of the effective radius of ovine serum albumin macromolecules in the aqueous solutions within a concentration interval of 3.65–25.8 wt% and a temperature interval of 278–318 K at the constant pH = 7.05 are calculated. The concentration and temperature dependences of the effective radii of ovine, bovine, and human serum albumin macromolecules are compared. It is shown that they are partially similar for the solutions of ovine and human serum albumins within concentration intervals of 0.12–0.49 vol% and 0.18–0.48 vol%, respectively, provided an identical acid-base balance (pH) in those solutions. The following conclusions are drawn: (i) the concentration dependences of the effective radii of structurally similar macromolecules of various albumins are similar, but provided an identical pH, and (ii) the dependence of the volume concentration of aqueous albumin solutions on the temperature at the constant radius of a macromolecule confirms the hypothesis about the existence of a dynamic phase transition in aqueous solutions at a temperature of 42 ∘C, at which the thermal motion of water molecules significantly changes.
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