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In situations where the molecular mechanism of many ocular disorders is unknown, owing to the difficulties associated with sampling from ocular tissues, human tear film can be a promising medium in ophthalmic research. The present study demonstrates an in-depth gel-based proteome optimization survey to approach more appropriate and efficient systems in various situations such as normal and dry-eye syndromes. Therefore, systematic and statistical evaluations were performed on different preparation methods, including acetone, acetone-methanol, chloroform-methanol-water, trichloroacetic acid (TCA)-acetone, tri-n-butylphosphate-acetone-methanol precipitations and ammonium sulfate fractionation at three different percentages of saturations (50, 70 and 90%). Methods were compared quantitatively on both one- and two-dimensional patterns. Some important parameters such as total protein recovery yield, densitometric analysis of some protein contaminants, banding patterns and total spot numbers along with statistical models for proper clustering were considered. Findings revealed noticeable impacts of preparation methods on all aspects of gel-based separations as well as recovery yield (ranging from 5.29 ± 0.96 to 22.56 ± 1.77 µg/mm) and banding and pattern resolution. In addition to all these, the most important point is that the total protein spot number on the final two-dimensional patterns (varied from 528.00 ± 19.00 to 657.00 ± 21.52 for different methods) were also noticeably increased in comparison with previously published reports (maximum of 250 spots), which is essential for a more comprehensive analysis. Increasing the proteome coverage in the present study is supposed to originate from improved solubility and effective rehydration during the sample application and isoelectric focusing (IEF) procedure along with proper sample preparation., (Copyright © 2014 John Wiley & Sons, Ltd.)

Patterns obtained in two-dimensional gel electrophoresis (2-DE) in the previously published articles suggest a varying number of proteins. To seek the cause of this variation, we investigated the effect of reduction power on the overall tear proteome maps. To this end, the buffers of two reducing agents, dithiothreitol (DTT) at nine different concentrations and di-(2-hydroxyethyl) disulfide (HED), were examined. The assay showed that HED clearly improved 2-DE resolution, increased the number of detectable protein spots, and offered well-resolved chain regions in comparison with those treated with DTT. Furthermore, this study introduced increasing the reduction power as a remedy to increase the reproducibility of two-dimensional human tear proteome maps. In addition, the results of our assessment showed that improved reduction efficiency was accompanied by increased procedure reproducibility from 42% to 89%., (© 2014 International Union of Biochemistry and Molecular Biology, Inc.)