Microheterogeneous region

A number of multicomponent glasses have in recent years been found to show a tendency to metastable separation into two or more liquid phases. The resulting microheterogeneous regions impair the structural continuity by more or less distinct phase boundaries. The phenomenon of phase separation will be dealt with later (see Chapter II, Section 6.5). 

Thus, the value of Am characterizes the size of the microheterogeneity regions. The value of Am is calculated from the dependence mentioned above. The interdiffusion coefficients and the sizes of the microheterogeneity regions for the systems with 10, 15, and 20 mass % of PBMA are given in Table 1 [88]. 

Table 1 Interdiffusion coefficients D and microheterogeneity region sizes (X ) as functions of temperature and composition for semi-IPNs O S-PU) with different contents of PBMA [88]...

An example of recovered distribution is shown in Figure B6.1.2. It concerns the distribution of lifetimes of 2,6-ANS solubilized in the outer core region of sodium dodecylsulfate micelles8 . In fact, the microheterogeneity of solubilized sites results in a distribution of lifetimes. 

Fig. 3. Amino acid sequence of several somatic human histone HI proteins to illustrate the microheterogeneity of linker histones. The sequences for human histone HI variants (H1.1-H1.4) were obtained from Ref [373] and Hl-5 was from Ref [412]. The nomenclature followed for the designation of these histone variants was Doenecke (e.g., see Ref. [412]). The nomenclature of Parseghian et at. [373] is shown in parentheses. The regions corresponding to the trypsin-resistant (winged helix motif [96]) which is characteristic of the protein members of the histone HI family are indicated by a boxed inset.

Figure 2. Structures of the glycosaminoglycans and their linkage regions to protein. Two disaccharide repeating units are shown to emphasize the microheterogeneity that exists in some cases. Heparan sulfate and heparin show many structural similarities. However, heparan sulfate contains more GlcNAc(a-1 — 4)GlcUA repeating units fewer glucosamine residues are N-sulfated, and few iduronic acid residues are sulfated at C2.

Fig. 7. A schematic view of Nafion membrane showing the microheterogeneous environment. A hydrophobic fluorocarbon phase B hydrophilic sulfonate ionic clusters C interfacial region formed between A and B and Ru adsorbed ruthenium complex water oxidation catalyst...

It is important to emphasize that a fluorescent solute molecule samples a large number of microheterogeneities. Indeed, because the excited-state fluorescence lifetime x is relatively long (for pyrene [25] it has a value of the order of 1 x 10 x 10 s) and the diffusion coefficient D [26] is on the order of 10 cm /s, the solute samples a region charac-... 

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