Abstract：Three cell disruption methods, i.e., liquid nitrogen grounding, liquid nitrogen grounding aided ultrasonication and liquid nitrogen grounding with glass beads were investigated to find the most appropriate one for the extraction and twodimensional electrophoresis analysis of proteins in longissimus dorsi muscles of beef cattle and yak. The same lysis buffer was used in the different cell disruption methods and the two-dimensional electrophoresis analysis was performed using isoelectric focusing and sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE) by silver staining. The protein contents of longissimus dorsi muscles were determined by the Bradford method. Analysis of the two-dimensional electrophoresis images was conducted using using PDQuest 8.0.1 software. Results showed that the protein contents of beef and yak longissimus dorsi muscles with the three cell disruption methods were significantly different, (2.59 ± 0.15) and (2.84 ± 0.29) μg/μL, (2.01 ± 0.04) and (2.21 ± 0.02) μg/μL, and (1.77 ± 0.11) and (1.95 ± 0.19) μg/μL for liquid nitrogen grounding aided ultrasonication, liquid nitrogen grounding with glass beads and liquid nitrogen grounding, respectively. The numbers of protein spots in the electrophoresis images of beef longissimus dorsi obtained using these three cell disruption methods were (279 ± 19), (581 ± 15) and (363 ± 21), respectively, whereas those of yak longissimus dorsi were (292±15), (596 ± 12) and (385 ± 17), respectively. Among these three methods, liquid nitrogen grounding aided ultrasonication yielded the highest protein contents, the greatest number of proteins and the best separation of protein spots from beef and yak longissimus dorsi. No significant differences in the protein contents of beef and yak longissimus dorsi were observed among the three cell disruption methods.
