Optimization of an HP Scanjet for quantification of protein electrophoresis gels.

An inexpensive desktop scanner, the Hewlett-Packard Scanjet IIp (HP), has been optimized for analysis of protein electrophoresis gels by comparison with a calibrated laser densitometer (Laser). Images from both densitometers were transferred to a personal computer and analyzed with QGEL software. Without correction the HP response was often in poor agreement with the Laser. However, when the HP response to Coomassie blue stained gels and x-ray films was linearized using a HP software option called Emphasis, the HP results agreed with results from the Laser. For 2D gels scanned with appropriate Emphasis applied, spot integrated density values were a constant multiple of 1.8 +/- 0.3 times the corresponding Laser value for x-ray films (CV = 17%) and 2.1 +/- 0.5 for Coomassie blue stained gels (CV = 24%). The highest error was observed for density extremes. For proteins quantified relative to standards using sodium dodecyl sulfate-slab gel electrophoresis, the HP values were within 15% of the Laser values. Data is shown concerning linearity and reproducibility of response, optical density range (about 0 to 1.8 OD units), variability of the imaging field, and resolution of the HP.

Two-dimensional gel analysis of serum apolipoprotein A-I isoforms: preliminary analysis suggests altered ratios in individuals with heart disease.

Apolipoprotein A-I (apo A-I), the major protein component of high-density lipoprotein, is quantified in a number of ways, typically by immunochemical methods. Commercial tests do not discriminate among isoforms of apo A-I. Two-dimensional electrophoresis, however, segregates and differentiates these isoforms, primarily due to charge variations among the various species. Stained two-dimensional gels can be scanned using high-resolution laser densitometry, and the isoforms can then be quantified using image analysis software. Human sera from coronary heart disease (CHD) patients (n = 36) and sex-matched and close-age-matched individuals (n = 36) with no known CHD were analyzed, to determine the relative abundance for each isoform within a given serum. In this preliminary study, we observed statistically significant differences between the two groups, suggesting altered post-translational processing from the proapo A-I and mature apo A-I isoforms to their adjacent isoforms for patients with histories of heart disease. In two instances, the P values were less than 0.005; in two others, P values were less than 0.001.

Computerized quantitative analysis of coomassie-blue-stained serum proteins separated by two-dimensional electrophoresis.

Two-dimensional electrophoresis in combination with Coomassie Blue staining was refined for use as a quantitative method. Microcomputer software was developed for use with the IBM AT and compatible computers for analyzing the gels. To test the refined method to determine its usefulness in simultaneous measurements of 28 human serum proteins, we measured each protein relative to a single standard (bovine serum albumin) polymerized at different concentrations in a calibration scale, rather than using 28 individual standards. All samples were analyzed in triplicate. We evaluated calibration, linearity of response, recoveries, units, within-run CV, and between-run CV. The five isoforms of apolipoprotein A-I were analyzed in samples from 16 healthy donors and the isoform ratios determined. The method as presented here should prove useful for diagnosis of non-urgent disease states and for analysis for protein isoforms in relation to disease; it should also be applicable to assays of proteins in other fluids and tissues.