Hydrophilic microenvironment

A slight increase in the turbidity upon heating of aqueous solutions of the s-fractions of the NVCl/NVIAz-copolymers obtained from the feeds with initial comonomer molar ratios of 75 25 (Tcp 65 °C) and 80 20 (Tcp 66 °C) could be due to the micellization phenomena, although the absence of DSC peaks over the same temperature range testified to the non-cooperative character of the process. This could indicate that the chains of these s-type copolymers had, nevertheless, a certain amount of oligoNVCl blocks non-buried by the hydrophilic microenvironment sufficiently well and thus capable of participating in the hydrophobically-induced associative intermolecular processes at elevated temperatures. At the same time, the sequence of monomer units in the s-copolymers obtained from the feeds with the initial comonomer ratios of 85 15 and 90 10 (mole/mole) corresponded to the block-copolymers of another type. The basis for such a conclusion is the lack of macroscopic heat-induced phase separation at elevated temperatures (Fig. 3 a and b) and, simultaneously, the transi-... 

In the anhydrous microencapsulation, protein and excipients were suspended/dissolved in PLA/acetonitrile solution and then added to cottonseed oil to form an o/o emulsion with Span 85 as an emulsifier. Petroleum ether was then added to extract the acetonitrile and the microspheres were hardened. The microspheres were then recovered by filtration and dried under vacuum. As shown in Table 5 and Fig. 5, without the pore-forming PEG, only 36% BSA was released from PLA microspheres in 1-month of incubation with a total recovery (released-fall soluble and aggregated residue in polymer after release) of 76%. Blending in 30% of 35 kDa PEG with the PLA eliminated the BSA aggregation in polymer completely, with 82% of encapsulated BSA released in 1 month. The improved BSA stability in PLA/PEG microspheres could be attributed to a less acidic and more hydrophilic microenvironment in the polymer. As seen in Fig. 6, unlike PLGA 50/50, which caused a dramatic pH drop in the release medium after a 4-week incubation (41), a relatively neutral pH was retained in the release medium for both PLA and PLA/PEG microspheres. A slightly lower pH in the release medium incubated with PLA/PEG microspheres relative to that in PLA was also... 

Glycolipids of tho kind LVlI o can be envisaged as contributing to a hydrophilic microenvironment for the erythrocjdie (other substances like the erythrocyte MN glycoproteins presumably so contribute in this way) (Winzler et al., 1967) but the functions and intramembrane locations of... 

To obviate such problems, several surface modification techniques have been studied and their efficacy tested both in vitro and in vivo. Physical methods involve oxidation of PDMS surface and adsorption of (natural or synthetic) polymers. Often, the hydrophilic microenvironment provided by... 

Scheme 10.26 Illustration of the encapsulation of Ru-TsDPEN in the nanocage with different hydrophobic/hydrophilic microenvironments. Reprinted with permission from Ref [72]. Copyright 2010 Royai Society of Chemistry.

Initial efforts gave rise to well-characterized dendritic macromolecules, but applications remained limited because of the lack of specific functionalities. An exponential increase of publication volume observed for about 15 years testified the growing interest for dendrimers and has led to versatile and powerful iterative methodologies for systematically and expeditiously accessing complex dendritic structures. The perfect control of tridimensional parameters (size, shape, geometry) and the covalent introduction of functionalities in the core, the branches, or the high number extremities, or by physical encapsulation in the microenvironment created by cavities confer such desired properties as solubility, and hydrophilic/hydrophobic balance. Thus, creativity has allowed these structures to become integrated with nearly all contemporary scientific disciplines. 

In many biological systems the biological membrane is a type of surface on which hydrophilic molecules can be attached. Then a microenvironment is created in which the ionic composition can be tuned in a controlled way. Such a fluffy polymer layer is sometimes called a slimy layer. Here we report on the first attempt to generate a realistic slimy layer around the bilayer. This is done by grafting a polyelectrolyte chain on the end of a PC lipid molecule. When doing so, it was found that the density in which one can pack such a polyelectrolyte layer depends on the size of the hydrophobic anchor. For this reason, we used stearoyl Ci8 tails. The results of such a calculation are given in Figure 26. 

Considerable progress has been made within the last decade in elucidating the effects of the microenvironment (such as electric charge, dielectric constant and lipophilic or hydrophilic nature) and of external and internal diffusion on the kinetics of immobilized enzymes (7). Taking these factors into consideration, quantitative expressions have been derived for the kinetic behavior of relatively simple enzyme systems. In all of these derivations the immobilized enzymes were treated as simple heterogeneous catalysts. 

It is evident that a single electron transfer photoproduct is transformed into a doubly reduced charge relay in two phase systems. The primary processes in the natural photosynthetic apparatus involve single electron transfer reactions that proceed in hydrophobic-hydrophilic cellular microenvironment. Thus, we suggest similar induced disproportionation mechanisms as possible routes for the formation of multi-electron charge relays, effective in the fixation of CO2 or N2. 

The energetically unfavorable interactions of the hydrophobic tails with the water molecules are then minimized by the surfactants forming aggregates with other surfactant molecules. In those aggregates, the hydrophilic headgroups remain solvated by water molecules while the hydrocarbon moieties are shielded from water and create a hydrophobic microenvironment. Examples of these spontaneously formed aggregates are micelles and lamellae. The intersection of the extrapolations of the linear parts of the surface tension curve (Figure 17.2) is the critical micelle concentration (CMC). 

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