Table 1.

DNA transport through α-hemolysin channels

No. of channels	Blockades/min	Molecules/min
35	1300	1250
8	220	280
6	150	80

The number of blockades/min is compared with the number of molecules/min that moved to the trans chamber during experiments in which the cis chamber contained 0.27 mg/ml of 150-nt single-stranded DNA and an equivalent number of 100-nt strands of double-stranded DNA. Multiple channels were used in these experiments to show the proportionality between channel number and DNA movement. Because frequent current reversals were required during the experiments (see Materials and Methods), the precision of the blockade rate calculation is limited to ±30%. The number of molecules transported to the trans chamber per minute was calculated from the total number of molecules found in the trans chamber at the end of each experiment, as measured by competitive PCR analysis which can reliably discriminate 2-fold differences in copy number (25).