Intrinsic factor properties

It is noted that all systems in turmoil tend to subside spontaneously to simple states, independent of previous history. It happens when the effects of previously applied external influences damp out and the systems evolve toward states in which their properties are determined by intrinsic factors only. They are called equilibrium states. Experience shows that all equilibrium states are macroscopically completely defined by the internal energy U, the volume V, and the mole numbers Nj of all chemical components. 

The rate of reduction of a vat dye depends partly on the intrinsic chemical properties of the dye and partly on the size and physical form of the dispersed particles undergoing this reaction. The physical factors are much less important than the chemical aspects [26]. The vatting process entails conversion of the insoluble keto form into the soluble sodium enolate (section 1.6.1). The reaction takes place in two stages at ambient temperature. Extremely rapid reduction to the hydroquinone is followed by slower dissolution in the alkaline solution. At higher temperatures, however, the dissolution rate approximates more closely to the rate of reduction. Temperature and dithionite concentration are the important variables and the rate of reduction is much less dependent on dye or alkali concentration. 

Green plants may have diverged from a common ancestor with animals 1.6 billion (1.6 x 109) years ago. How do the genomes of present-day plants and animals compare There are many similarities in basic metabolism. These arise from the intrinsic chemical properties and reactivities of cellular components and from the coevolution of plants and animals. Plants and animals also utilize similar structures and similar control of chromatin. However, in the control of development there are great differences.464 For example, the Arabidopsis genome contains no relative of the Drosophila Gurken, no receptor tyrosine kinases, no relatives of transcription factor NF-kB. However, there are similarities in parallel pathways utilized by plants and animals. 

Unusual features of vitamin Bn observed by some investigators include (1) the cyanide group is an artifact of preparation (2) the only vitamin synthesized in appreciable amounts only by microorganisms (possible in tumors) (3) only vitamin with a metal ion (4) works with glutathione (5) glutathione content decreased on B12 deficiency (6) mitosis retarded in B12 deficiency (7) requires intrinsic factor (enzyme) for oral activity (8) increases tumor size (Rous sarcoma) (9) diamagnetic properties (10) no acidic or basic groups revealed on titration (no pKa). 

The separation factor, /3pervap, contains contributions from the intrinsic permeation properties of the membrane, the composition and temperature of the feed liquid, and the permeate pressure of the membrane. The contributions of these factors are best understood if the pervaporation process is divided into two steps, as shown in Figure 9.3 [18]. The first step is evaporation of the feed liquid to form a saturated vapor in contact with the membrane the second step is diffusion of this vapor through the membrane to the low-pressure permeate side. This two-step description is only a conceptual representation in pervaporation no vapor phase actually contacts the membrane surface. Nonetheless, the representation of the process shown in Figure 9.3 is thermodynamically completely equivalent to the actual pervaporation process shown in Figure 9.F... 

Equation (9.11) identifies the three factors that determine the performance of a pervaporation system. The first factor, pevAp, is the vapor-liquid equilibrium, determined mainly by the feed liquid composition and temperature the second is the membrane selectivity, G-men, an intrinsic permeability property of the membrane material and the third includes the feed and permeate vapor pressures, reflecting the effect of operating parameters on membrane performance. This equation is, in fact, the pervaporation equivalent of Equation (8.19) that describes gas separation in Chapter 8. 

All orally administered chugs must pass through the gastrointestinal tract to reach the blood and thus pass the barrier formed by the enterocytes in the intestine. For years, low first-pass bioavailability of a drug was attributed mainly to clearance via hepatic metabolism and biliary clearance or incomplete absorption in the intestine due to poor solubility or intrinsic permeability properties. Although these are important factors in determining the overall oral bioavailability of certain... 

Once a chemical enters the body of animal or human, it undergoes metabolic reaction. A host of factors modulate the reaction rate and the induction of toxicological effects. These factors have been termed intrinsic factors and include animal species, gender, age, nutritional status, pregnancy, other health status, and circadian rhythms. In addition, there are certain extrinsic factors (e.g., physicochemical properties of chemicals, solvent or vehicle, route of exposure, temperature, and humidity) during exposure to chemicals that also influence the effect of a test chemical. We shall discuss these factors in greater detail. 

A2. Allen, R. H., and Mehlman, C. S., Isolation of gastric vitamin B12 binding proteins using affinity chromatography. I. Purification and properties of human intrinsic factor. /. Biol. Chem. 248, 3660-3669 (1973). 

V2. Visuri, K., and Gras beck, R., Human intrinsic factor, isolation by improved conventional methods and properties of the preparation. Biochim. Biophys. Acta 310, 508-517 (1973). 

C2. Capraro, V., Cresseri, A., and Cantone, A., Some biological properties of gastric mucin preparations. Vitamin Bjg und Intrinsic Factor, I. Europ. Symp., Hamburg, 19S6, pp. 283-291. Enke, Stuttgart, 1957. 

E3. Ellenbogen, L., Purification, properties and assay of intrinsic factor. Vitamin Bj2 und Intrinsic Factor, 2. Europ. Symp., Hamburg, 1961 pp. 443-456. Enke, Stuttgart, 1962. 

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