Proteins browning

In the aldehyde form, dextrose can react with amines, amides, amino acids, peptides, and proteins. Brown coloration and decomposition occur with strong alkalis. 

L-ascorbic acid, D-isoascorbic acid, and L-dehydroascorbic acid inhibited progeny by producing diet nutritionally deficient in protein (browning)... 

The following mammalian (rat, mouse, rabbit) cells have been observed to take up aminoacridines and concentrate them in the nucleus lung, heart, liver, bone-marrow, spleen, tongue, kidney, and small intestines (De Bruyn, Robertson and Farr, 1950). That aminoacridines are not accumulated by the cell s protein is not surprising because their anti-bacterial action, in vitro, is not lowered by serum protein (Browning and Gilmour, 1913). Nucleic acids, on the other hand, strongly inhibit bacteriostasis by proflavine and acriflavine (Mcllwain, 1941). The maximal amount of dye which dissolved DNA can bind follows an order for the monoaminoacridines that is the same as the order of their antibacterial action, namely 9- > 3- > 1- > 2- > 4- (Jackson and Mason, 1971). 

Hunt, J. V., and Wolff, S. P., 1992, Transition metal-catalysed oxidations as the possible causation of protein browning in aging and diabetes mellitus, in Biomarkers of Aging Expression and Regulation (F. Licastro and C. M. Caldarera, eds.), pp. 199-206, Co-operativa Libraria Universitaria Editrice Bologna, Italy. 

Requena, J. R., Vidal, R, and Cabezas-Cerrato, J., 1993, Aminoguanidine inhibits protein browning without extensive Amadori carbonyl blocking. Diabetes Res. Clin. Pract. 19 23-30. 

Natural melanins usually occur in the form of melanoproteins and thioether linkages, such as those mentioned above, may be important in the overall molecular structure. However, in this regard several attempts to demonstrate the formation of addition products between the oxidation products of either 5,6-dihydroxyindole or DOPA with certain proteins and peptides including ovalbumin [218, 224] or bovine serum albumin [224] have been unsuccessful. More recently, however, it has been shown that when tyrosine was oxidised in the presence of bovine lens protein, brown or black melanoproteins were formed [225]. On hydrolysis these pigments gave rise to a compound with similar properties to those of a (110)-type compound, which could have been formed from the oxidation of DOPA in the presence of cysteine. The thiol groups of the protein may react with some of the intermediates produced by the oxidation of tyrosine [225]. Reactions such as this may be involved in the formation of cataracts in the eye [225]. 

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