2-DE Gel Image Analysis Protocol

The ImageQuant™ LAS500 (GE Healthcare Bioscience, Uppsala, Sweden) was used to visualize and store the silver-stained 2-DE gel images. Detection, matching, and quantification of the distinct protein spots were performed using the Image Master 2D Platinum Software, version 7.0 (GE Healthcare Bioscience, Uppsala, Sweden). Normalization was subsequently performed to evaluate proteins that were differentially expressed in the serum by correcting the spot quantification values and gel-to-gel variation unrelated to expression changes. This was achieved by taking into account total densities from the gel images (i.e., raw quantity of each gel spot was divided by the total quantity of all spots within the gel). The percentage of a given protein taken against total spot volume of all proteins (including the unresolved peptides) in the gel was calculated to give a percent of volume contribution (vol%) (Chen et al., 2008 (link)). All protein concentration values are presented as means of percentage volume (% volume) ± standard deviations (SD). Statistical analysis was done using the Student’s t-test to analyse differences between controls and patients. A p-value of less than 0.05 (p < 0.05) was considered to be statistically significant.