Chemical changes during

C. O. Jensen, Chemical Changes During the Curing of Cigar Eeaf Tobacco, The Pennsylvania State College, American Chemical Socief, State College, Pa., Sept. 1951. 

In addition to their protein part, most enzymes also contain a small nonprotein part called a cofactor. A cofactor can be either an inorganic ion, such as Zn2+, or a small organic molecule, called a coenzyme. A coenzyme is not a catalyst but is a reactant that undergoes chemical change during the reaction and... 

Kaplan, I.R., Galperin, Y., Alimi, H., Lee, R.P., and Lu, S.-T. Patterns of chemical changes during environmental alteration of hydrocarbon firels. Groundwater Monitor. Remed, 16(2) 113-124, 1996. 

Whereas in many metalloprotein redox systems the oxidation states +2, +3, and +4 are involved, horseradish peroxidase catalysis appears to involve five oxidation states. The interest to coordination chemists of this study goes well beyond bioinorganic systems, for here, as in several cases reported earlier, the X-rays used to obtain the high-resolution structures induced chemical changes during structure determination. The X-rays liberate electrons, which may change the oxidation state of the metal. ... 

Sodium metabisulfite is an antioxidant agent widely used in pharmaceutical preparations to reduce or prevent oxidation. There are some studies, however, that have shown that metabisulfite, under specific conditions, may have indirect oxidant properties. Baker et al. [37] demonstrated that sulfite propofol emulsion, but not EDTA propofol emulsion, underwent chemical changes during a simulated intravenous infusion. Compounds were identified as propofol oxidation products. The increase of propofol oxidation products demonstrated that sulfite from metabisulfite created a strong oxidant environment when air was introduced. Lavoie et al. [38]... 

Chemical change During this kind of change, atoms in a substance are rearranged to give a new substance having a new chemical identity. 

ESR Studies of Surface Species. ESR has been applied widely in heterogeneous catalysis as a technique for examining the nature and concentration of possible catalytic sites when a material is activated either chemically or thermally (64, 65, 66). ESR studies on the Phillips polyethylene catalyst, Cr03/Si02, are a classical example of this application (67). The interpretation of such ESR studies is questionable since the chemical changes during activation are not well understood, and the nature of the surface species may have to be assumed. 

H. Piepenbrink, Examples of chemical changes during fossilisation, Appl. Geochem. 4 (1989) 273-280. 

M. Buglione and J. Lozano, Nonenzymatic browning and chemical changes during grape juice storage, J. Food Sci., 2002, 67, 1538-1543. 

The work of Huraux, Soualmia, and Sheppard has demonstrated that it is possible to make a quantitative interpretation of the r values (within the limits of an admittedly difficult theory), and that the er value is directly linked to the chemical changes during cure. However, because of the complications introduced by dipole correlations, the relaxed permittivity is not a useful tool for routine quantitative determination of polar reactive group concentrations during cure. 

In Section 4, we have examined, from a fundamental point of view, how temperature and cure affect the dielectric properties of thermosetting resins. The principal conclusions of that study were (1) that conductivity (or its reciprocal, resistivity) is perhaps the most useful overall probe of cure state, (2) that dipolar relaxations are associated with the glass transition (i.e., with vitrification), (3) that correlations between viscosity and both resistivity and dipole relaxation time are expected early in cure, but will disappear as gelation is approached, and (4) that the relaxed permittivity follows chemical changes during cure but is cumbersome to use quantitatively. 

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