Silver staining of immunofixed group specific component on cellulose acetate membranes after isoelectric focusing in narrow pH interval gels

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Abstract
The sensitivity of group specific component (Gc) detection by immunofixation after isoelectric focusing (IEF) has been examined by using two IEF methods: ultrathinlayer IEF and immobilized pH gradient (IPG) focusing followed by two staining methods: Ponceau S and a combination of Ponceau S with silver staining (SS). Both diluted plasma and bloodstain extracts were examined by these methods at two dilutions of immunofixation antibody ‐ 1:6 and 1:24. The cellulose acetate membranes containing the Gc precipitates were washed with sodium chloride after the SS process. This greatly improved the visibility of the Gc bands. The method was found to be more sensitive than Ponceau S and its use reduced the cost of immunofixation by 75%. Ultrathin‐layer IEF was carried out in gels containing the pH 4.5–5.4 Pharmalytes. The separator N‐2‐hydroxyethylpiperazine‐N′ 2‐ethanesulfonic acid (HEPES) was added to some gels and the effect on the resolution of the Gc 1 subtypes was examined and compared with the separation achieved with IPG gels. It was found that ultrathin‐layer IEF using narrow range Pharmalytes and the separator HEPES was the more sensitive method; however, IPG gels were easier to interpret.