Solubility basic units

The two polymers most often used in these applications are dextran and PEG. Both polymers consist of repeating units of a single monomer—glucose in the case of dextran and an ethylene oxide basic unit in the case of PEG. The polymers may be composed of linear strands (PEG or dextran) or branched constructs (dextran). An additional similarity is that both of them possess hydroxyl and ether linkages, lending hydrophilicity and water solubility to the molecules. Dextran and PEG can be activated through their hydroxyl groups by a number of chemical methods to allow... 

Poly(A-vinylamides) are another class of synthetic thermo-responsive polymers. Two of the most common polymers of this class are poly(Al-vinylpyrrolidone) (PVP) and poly(A-vinylcaprolactam) (PVCL) (Figure 1.3). PVCL is a water-soluble nonionic amphiphilic polymer with its basic unit comprising a seven-membered cyclic amide with a polar hydrophilic carboxyl group and an amide group connected directly to a hydrophobic vinyl chain. 

Solutions of F-actin and myosin at high ionic strength = 0.6) in vitro form a complex called actomyosin. The formation of the complex is reflected by an increase in viscosity and occurs in a deflnite molar ratio 1 molecule of myosin per 2 molecules of G-actin, the basic unit of the double-helical F-actin strand. It appears that a spike-like structure is formed, which consists of myosin molecules embedded in a backbone made of the F-actin double helix. Addition of ATP to actomyosin causes a sudden drop in viscosity due to dissociation of the complex. When this addition of ATP is followed by addition of Ca +, the myosin ATPase is activated, ATP is hydrolyzed and the actomyosin complex again restored after the ATP concentration decreases. Upon spinning of an actomyosin solution into water, flbers are obtained which, analogous to muscle flbers, contract in the presence of ATP. Glycerol extraction of muscle fibers removes all the soluble components and abolishes the semipermeability of the membrane. Such a model muscle system shows all the reactions of in vivo muscle contraction after the readdition of ATP and Ca +. This and similar model studies demonstrate that the muscle contraction mechanism is understood in principle, although some molecular details are still not clarified. 

Instant tea is manufactured in the United States, Japan, Kenya, Chile, Sri Lanka, India, and China. Production and consumption in the United States is greater than in the rest of the world. World production capacity of instant teas depends on market demand but is in the range of 8,000 to 11,000 t/yr (3). The basic process for manufacture of instant tea as a soluble powder from dry tea leaf includes extraction, concentration, and drying. In practice, the process is considerably more compHcated because of the need to preserve the volatile aroma fraction, and produce a product which provides color yet is soluble in cold water, all of which are attributes important to iced tea products (88). 

A soluble gas is absorbed into a liquid with which it undergoes a second-order irreversible reaction. The process reaches a steady-state with the surface concentration of reacting material remaining constant at (.2ij and the depth of penetration of the reactant being small compared with the depth of liquid which can be regarded as infinite in extent. Derive the basic differential equation for the process and from this derive an expression for the concentration and mass transfer rate (moles per unit area and unit time) as a function of depth below the surface. Assume that mass transfer is by molecular diffusion. 

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