Why is the SDS solubilization buffer added after the bacteria cells are treated with lysozyme?
SDS solubilizes the lipoproteins that make up the plasma membrane of the bacterial protoplast. This results in rupturing of the cell by inducing osmotic shock. The effect of the SDS solubilization buffer is minimal on bacterial cells whose bacterial cells have an intact peptidoglycan layer. Discuss the function of a reducing agent such as B-mercaptoethanol. Answer: A reducing agent cleaves the disulfide bonds that hold together the polypeptide constituents of whole proteins, making possible direct comparison of individual gene products, or polypeptides. For example, if a 125,000 Dalton untreated protein is electrophoresed it will yield one band. However, if the protein is treated with a reducing agent, it will yield several bands with a combined molecular weight of 125,000 Daltons-the same as the original protein. Examine your electrophoresis lanes. Based on the band patterns in these lanes, the background information in the introduction, and Figure 1, determine which samples are gram-
