A fully automated system with online sample loading, isotope dimethyl labeling and multidimensional separation for high-throughput quantitative proteome analysis.

Multidimensional separation is often applied for large-scale qualitative and quantitative proteome analysis. A fully automated system with integration of a reversed phase-strong cation exchange (RP-SCX) biphasic trap column into vented sample injection system was developed to realize online sample loading, isotope dimethyl labeling and online multidimensional separation of the proteome samples. Comparing to conventionally manual isotope labeling and off-line fractionation technologies, this system is fully automated and time-saving, which is benefit for improving the quantification reproducibility and accuracy. As phosphate SCX monolith was integrated into the biphasic trap column, high sample injection flow rate and high-resolution stepwise fractionation could be easily achieved. Approximately 1000 proteins could be quantified in approximately 30 h proteome analysis, and the proteome coverage of quantitative analysis can be further greatly improved by prolong the multidimensional separation time. This system was applied to analyze the different protein expression level of HCC and normal human liver tissues. After three times replicated analysis, finally 94 up-regulated and 249 down-regulated (HCC/Normal) proteins were successfully obtained. These significantly regulated proteins are widely validated by both gene and proteins expression studies previously. Such as some enzymes involved in urea cycle, methylation cycle and fatty acids catabolism in liver were all observed down-regulated.