Contamination problems electrophoresis

Contamination Problems. As analytical techniques become more sensitive, contamination becomes more of a problem. For example, Ochs (25) reported that many erroneous bands in polyacrylamide gels run with SDS were from proteins found on the skin of the researchers handling the gels. Her work indicates the need to exercise extreme care in sample preparation. In addition, suitable sample blanks handled in a parallel fashion would enable the researcher to identify contamination problems. Secondary checking of materials by two-dimensional electrophoresis would also help identify the nature and type of contamination. 

This is a CE analog of conventional zone gel electrophoresis for the separation of macromolecules based on size. The capillary is filled with a porous polymer gel, and molecular sieving occurs as the molecules move through the gel, that is, separation is based on both electrophoretic mobility and molecular size. Very high resolution is achieved. The trend is to fill the capillary with a liquid gel matrix (pumpable gel solutions, such as deriyatized celluloses dissolved in the run buffer). This allows replacement of the gel in the capillary to eliminate contamination problems from the sample matrix that occurs with fixed gels.. This technique is widely used for separation of nucleotides in deoxyribonucleic acid (DNA) sequencing (Chapter 25). 

Removal of interfering matrix contaminants and/or improving the detection limits represent frequent problems in the analysis of natural, and particularly biological, samples. This potential has not yet been exploited fully in capillary electrochromatography. A typical example that demonstrates a combination of biorecognition-based separation with a subsequent capillary electrophoresis step is presented [180]. 

CP24 resolved from NaSCN treated PSII membranes by mild electrophoresis, was found to consist of only one polypeptide with the apparent molecular weight of 20 kDa (Fig. 1, lane D). When CP24 was isolated from untreated PSII membranes, it showed a multipolypeptide composition and thus the identity of the pigment binding polypeptide(s) could not be firmly established. This problem was overcome by the NaSCN treatment which removes several extrinsic polypeptides contaminating the CP24. 

Analysis of proteins following gel electrophoresis is complicated by the relatively low amounts (low pmol to fmol range), the possibility of artifactual modifications, and the large number of samples to be processed. Furthermore, sample preparation is necessarily an off-line technique accompanied by the possibilities of sample loss and contamination [58]. The development of robotic systems for sample preparation may alleviate some of these limitations but will not overcome all of the problems [59]. 

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