100 V 100 V No Internal Reference 130 V 130 V No Internal Reference Measured (%) Actual  (%) Measured (%) Actual  (%) Measured (%) Actual  (%) Measured (%) Actual  (%) 80.6 ± 0.2 80.0 79 ± 8.0 80.0 81.0 ± 3.0 80.0 79.3 ± 7.1 80.0 62.9 ± 0.1 60.0 63.3 ± 5.7 60.0 72.3 ± 2.4 60.0 73.7 ± 12.6 60.0 40.1 ± 0.1 40.0 44.4 ± 7.7 40.0 61.0 ± 1.4 40.0 54.6 ± 4.6 40.0 31.9 ± 1.3 30.0 38.7 ± 12.7 30.0 51.9 ± 4.6 30.0 55.1 ± 0.5 30.0 19.3 ± 0.1 20.0 34.8 ± 11.3 20.0 44.6 ± 0.9 20.0 54.0 ± 9.6 20.0 10.3 ± 0.1 10.0 13.7 ± 5.8 10.0 29.8 ± 1.8 10.0 37.6 ± 1.3 10.0

Table 1: The effect of running voltage on measurement precision. Percent cleavage was determined and compared to the actual values from known mixtures of uncleaved peptidyl-tRNA substrate and cleaved tRNA product. Values were determined for constant 100 V and 130 V with and without use of an internal 5S RNA reference from averages of three independent data sets with error determined as the standard deviation. *For 130 V with no internal reference, one gel of the three could not be meaningfully interpreted so was left out of the analysis. Inclusion of all data resulted in over an order of magnitude increase in the standard deviation reported