Carbonyl content

Friedrich et al. also used XPS to investigate the mechanisms responsible for adhesion between evaporated metal films and polymer substrates [28]. They suggested that the products formed at the metal/polymer interface were determined by redox reactions occurring between the metal and polymer. In particular, it was shown that carbonyl groups in polymers could react with chromium. Thus, a layer of chromium that was 0.4 nm in thickness decreased the carbonyl content on the surface of polyethylene terephthalate (PET) or polymethylmethacrylate (PMMA) by about 8% but decreased the carbonyl content on the surface of polycarbonate (PC) by 77%. The C(ls) and 0(ls) spectra of PC before and after evaporation of chromium onto the surface are shown in Fig. 22. Before evaporation of chromium, the C(ls) spectra consisted of two components near 284.6 eV that were assigned to carbon atoms in the benzene rings and in the methyl groups. Two additional... 

As a result of oxidation, the adhesion strength between PE and A1 is found to increase by about 8 to 28 times. The adhesion strength increases with an increase in carboxyl content, total amount of oxo- groups, and the combined carboxyl and carbonyl content. 

Chapman, M.L., Rubin, B.R and Gracy, RW. (1989). Increased carbonyl content of proteins in synovial fluid from patients with rheumatoid arthritis. J. Rheumatol. 16, 15-18. 

It must be pointed out that a correction is needed to account for the change in thickness upon stretching of the films. For that reason all carbonyl contents have been referred to the thickness of the non-strained film which has been photooxidized at the same temperature for the same period. The 2840 cm-l band, which corresponds to the symmetric C-H stretching of the methylene groups (14) was chosen as reference for thickness correction (other bands can be used, but the choice was decided by the fact that the 2840 cm l band changed in intensity as the strain varied, but its location and shape were not affected by the strain variation.) Thus, all the photooxidation data are given on a relative scale. 

The neck is more or less fully developed and a fibrillar structure is obtained. This structure is less susceptible to degradation because of its high degree of orientation and high crystallinity. This explains the drop and then levelling off of the carbonyl content in this latter stage. 

In earlier studies the in vitro transition metal-catalyzed oxidation of proteins and the interaction of proteins with free radicals have been studied. In 1983, Levine [1] showed that the oxidative inactivation of enzymes and the oxidative modification of proteins resulted in the formation of protein carbonyl derivatives. These derivatives easily react with dinitrophenyl-hydrazine (DNPH) to form protein hydrazones, which were used for the detection of protein carbonyl content. Using this method and spin-trapping with PBN, it has been demonstrated [2,3] that protein oxidation and inactivation of glutamine synthetase (a key enzyme in the regulation of amino acid metabolism and the brain L-glutamate and y-aminobutyric acid levels) were sharply enhanced during ischemia- and reperfusion-induced injury in gerbil brain. 

In contrast to the findings obtained in Ref. [34], it was concluded [36,37] that exposure of proteins to peroxynitrite leads to a very small increase in carbonyl content at physiological pH and C02 concentration. At the same time, carbonyl contents in glutamine synthetase and BSA increased in the absence of C02. These data show the importance of C02 in the... 

Studies on the polymerization of various 4-methylene-l,3-dioxolans [94] by BF3Et20 or A1C13 showed that 4-methylene-l,3-dioxolan itself polymerises mainly through the double bond the 2-methyl and 2,2-dimethyl compounds gave polymers with a variable carbonyl content. This arises from a co-polymerization in which units of type (VII) and (VIII) are incorporated in the chain in different proportions, according to the reaction conditions ... 

In addition to the previously mentioned chemical tests, methods based on the carbonyl content of oxidized fats have also been suggested (Henick et al 1954 Lillard and Day 1961) as a measure of oxidative deterioration. The procedures determine the secondary products of autoxidation and have been reported to correlate significantly with the degree of off-flavor in butter oil (Lillard and Day 1961). The methods, however, are cumbersome and are not suited for routine analysis. 

Comparative studies by Forss and co-workers (1960A.C) on the fishy, tallowy, and painty flavors of butterfat tended to emphasize the importance of the relative and total carbonyl contents in dairy products with different off-flavors. These researchers showed that three factors distinguished painty and tallowy butterfat from fishy butterfat. First, there was a relative increase in the n-heptanal, re-octanal, n-non-... 

The mesomeric quinonemethides and 0-quinonemethides described above are somewhat more stable than the simple p-quinonemethides whose properties are already well known even from classical studies. The o-quinonemethides XX and XVII do not add on water even in solution in aqueous organic solvents their solution in dioxane/water is stable for months. They do not add on methanol or higher alcohols and react only slowly with phenols and organic acids. The addition of water is not catalyzed by mild alkalies the red color of the phenoxide ion (XVIII) prevails for weeks in soda solution. Addition of water occurs more rapidly in strongly alkaline solution. The addition of mineral acids and reduction by sodium borohydride are instantaneous. The addition of HC1 is rapid even at pH 4.0, the conditions used for determining the carbonyl content of lignin by the hydroxylamine hydrochloride reaction 13). 

The quantitation of carbonyl groups in cellulose was so far limited to the measurement of the total carbonyl content by different methods, which are summarized in Table 1. 

The label is completely stable in this solvent system at ambient temperature. Calibration, which is required for quantification of the carbonyl content,... 

Fig. 6 MWD of different dissolving pulps (s2-s8), the vertical lines limit DP ranges of 100 and 2000, corresponding to the carbonyl contents in Fig. 7 below...

Fig. 8 Ozone bleaching (Z) of a beech sulfite pulp, increasing numbers reflect increasing intensity of the ozone treatment. Left differential MWD und carbonyl DS. Right ADSco plots showing the differences in carbonyl content between the bleached sample and the starting material (SM). Reprinted with permission from Biomacromolecules (2002) 3 969. Copyright (2002) American Chemical Society...

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