Calorimetric and Compressibility Study of Aqueous Solutions of Dextran with Special Reference to Hydration and Structural Change of Water

Abstract

ABSTRACT:Interactions between water and dextran have been investigated by measuring specific heat capacity, adiabatic compressibility, and viscosity, with dextran samples of molecular weight above 10 4 . For these measurements, a laboratory-constructed isoperibol twin calorimeter and an ultrasonic interferometer were used. The compressibility data show the existence of the water hydrated to dextran molecules, and the amount of hydration water was determined. The partial molar heat capacity was calculated for the structural unit of the dextran molecule. In the plot of log [11] against log Mw, a downward deviation from the linear relation was observed, and this was interpreted as due to branching of the dextran molecule. The amount of hydration water and the partial molar heat capacity decreased with the increasing molecular weight of dextran. The quantity !•,."Cp, 0 =Cp, 0 -Cp, (pure state) indicates that the structural change of water caused by the dissolution of one structural unit of the dextran molecule is smaller than in the case of glucose and that the degree of the structural change of water decreases sharply with the increasing molecular weight of polymers. These results are interpreted in terms of the combination of branching and increased entanglement of the polymer chain.

Temperature dependence of the heat capacities in the solid state of 18 mono-, di-, and poly-saccharides

“…Regarding C p,m (T), the comparisons between the present results and literature values are displayed in figure 2. For four monoand two di-saccharides, literature values are available in the (290 to 325) K temperature interval [19]. Figure 2a shows that the two sets of results agree within 2%, except for MAN (at low temperatures) and LAC where deviations are larger.…”

Flexibility and Hydration of Amphiphilic Hyperbranched Arabinogalactan-Protein from Plant Exudate: A Volumetric Perspective

“…We then obtained for HIC-F1 an average K • sh value of 5.2 × 10 −11 cm 3 •mol −1 •Pa −1 or 29 × 10 −11 Pa −1 , corresponding to a 37% decrease as compared to bulk water ( Table 5). Please note that this value is larger than the 18 × 10 −11 Pa −1 arbitrary value that is usually used for characterizing the adiabatic compressibility of strongly hydrogen-bonded hydrating water of polysaccharides [45,47,50,51,54], but still of the same magnitude.…”

“…• s , are macroscopic thermodynamic observables that are particularly sensitive to the hydration properties of solvent exposed atomic groups, as well as to the structure, dynamics, and conformational properties of the solvent inaccessible biopolymer interior [29,30]. This has motivated many efforts to experimentally measure these quantities on small solutes (amino acids, sugars, minerals) and on biopolymers, such as globular, fibrous, and unfolded proteins [31][32][33][34][35][36][37][38][39][40], nucleic acids [33,35,[41][42][43] and linear or branched polysaccharides [33,[44][45][46][47][48][49][50][51][52][53][54].…”

Preferential Solvation of Dextran in Water–Ethanol Mixtures

“…15 The weight-average molecular weights were 1.0 x 10 4 , 3.30 x 10 4 , 4.61 x 10 5 , 7.58 x 10 5 , and 2.0 x 10 6 . All saccharides used, i.e., glucose, maltose, and raffinose, were extra-pure reagents supplied from Nakarai Chemical Co., Ltd.…”

“…The results of the molecular weight dependence of the amount of bound water have already been discussed in connection with the structural change in water as a result of dissolution of the dextran molecule, as shown by the partial molar heat capacity data of aqueous solution of dextran. 15 In these papers, the compressibility of solute dextran has been assumed to be zero. As mentioned above, this assumption does not seem entirely sound for high polymers.…”