Silver staining mechanisms

There are a number of different silver staining methods. Some are available in kit form from various manufacturers. Others do not lend themselves to commercial kits. For a discussion of the mechanisms of silver staining, see Reference 54. Silver staining can be as much as 100 times more sensitive than CBB dye staining. All silver staining procedures have many manual steps and the decision as to when to terminate color development is quite subjective. 

Heukeshoven, J. and Dernick, R. 1985. Simplified method for silver staining of proteins in polyacrylamide gels and the mechanism of silver staining. Electrophoresis 6 103-112. 

The first step in this new stain protocol employs copper acetate, a metal salt that is both a good fixative ( ) and a silver stain enhancer. The mechanism of copper s stain enhancement, in this and other silver stains, may be similar to its action in the biuret reaction (15.), in which a characteristic color shift, from violet to pink, is achieved by titrating peptides in the presence of copper ions. Copper complexes formed with the N-peptide atoms of the peptide bonds are primarily responsible for this reaction. There are also some number of secondary sites which may interact with copper. Any elemental copper formed may displace positive silver ions from solution as copper has a greater tendency to donate electrons than silver, indicated by its position in the electromotive series of the elements. Following the treatment with copper acetate, the membrane is sequentially soaked in a solution containing chloride and citrate ions and then in a solution containing silver nitrate. The membrane is then irradiated with light while it is in the silver nitrate... 

Comparison Of Silver Stain Reactive Groups With Commassie Stain Reactive Groups Recent studies concerning the mechanisms of... 

The mechanism of GELCODE silver staining may be analogous to tTiTs process, however, the reader should be reminded that this is a working hypothesis and more data are needed. 

Merril, C. R. (1986) Development and mechanisms of silver stains for electrophoresis. Acta Histochem. Cytochem. 19, 655-667. 

Mechanism studies of Coomassie Blue and silver staining of proteins. J. Pharm. Sci. 1986, 75, 907-911. 

A silver staining can significantly increase the sensitivity of label-fiee protein SERS detection. It is available for detection of proteins separated by gel electrophoresis. The basic mechanism underlying silver staining of proteins is that silver ions bound to amino acid side-chains (primary COO-, -SH) are reduced to free silver by a reductant (citric acid, formaldehyde, or photoreduction). The... 

Evidence for metals (e.g. iron, copper, tin, silver, etc) causing stain formation appears to be significant only for individuals exposed to metals and their salts, typically in connection with their occupation or certain medicines [140, 147], Stannous-fluoride-containing toothpastes have been reported to promote golden brown discolourations [63], The mechanism for stain formation probably involves interaction of dietary chromogens and metal ions forming coloured complexes on the tooth surfaces, as indicated by in vitro and in vivo studies [159,161]. 

Mechanical surface pretreatment, followed by very careful degreasing. Carry out bonding immediately, since especially silver surfaces can change due to silver sulfide formation (dark staining). 

The importance of the basic amino acids has been further substantiated by evaluations of the relationship between a denatured protein s amino acid mole percentages and its ability to stain with silver. The best correlations were achieved when a comparison was made between the slope of the linear portion of a denatured protein s staining curve and the protein s mole percentages of the basic amino acids, histidine and lysine ( ). A similar correlation was observed by Dion and Pomenti(4 ). Dion and Pomenti suggested that this correlation may be due to an interaction between lysine and glutaraldehyde, which was used in their stain protocol. The bound glutaraldehyde could supply aldehyde groups to facilitate the reduction of ionic silver. While this mechanism may play a role in... 

At the time of initial nucleation most spots appear yellow to brown. As the reaction continues in the carbonate solution some proteins stain red or blue, or black while others remain yellow or brown. It is generally accepted that the smaller silver colloidal particle (approximately . 2 urn) are seen as yellow - red coloration and that larger particles (above >. 3um) are blue to black in coloration. The mechanism of different coloration of proteins may be dependent on protein sequence or structure. Thus coalescence of differing amounts of silver colloidal particles onto precipitated proteins is at least one plausible explanation of the colors seen in the gels. Therefore, colors observed in the pro tein pattern are influenced by the chemical environment as well as the charge and steric characteristics of the precipitated protein. 

HerickholT, L., Stack, S., and Robertson. J. (1992). Staining plant cells with silver. 111. The mechanism. Bioieehnic Hislochem. 67, 171-182. 

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