Bio-Rad CHEF Mapper® XA System - Manual (Page 54)

as desired. Switch time ramps follow the general equation: y = [x/(x+a)]*(a+1), with a<-1 or a>0.
The 27 allowable ramp shapes are shown in Figure 9.3. Each curve is uniquely defined by its ramp-
ing factor, a. Another useful value defined by these curves is the half height percent. The half height
percent is the percentage of run time required for the switch time to reach a value equal to the ini-
tial switch time plus 50% of the total ramp. Two representative ramps are shown in Figure 9.4.
Ramping factors and corresponding half height percents are indicated. The program generates 27
discrete ramp shapes. Choose a desired ramp shape from Figure 9.3, then determine the ramping fac-
tor, a, from the accompanying key. Half heights are shown in parentheses following the
corresponding a value. Enter the desired a value at the a= prompt, or press ENTER for linear ramps.
An example of linear and nonlinear ramping is shown in Figure 9.5. Lambda ladders
were separated with three different ramp shapes. The most linear band spacing was obtained
with the nonlinear ramp that had an a value of 0.357 and a 21% half height. Presumably, this
was because the switch time regimen utilized 79% of the run time ramping relatively slowly
through the longer switch time values. Conversely, the spacing between smaller DNA bands
was expanded at the expense of the larger ones when the ramping regimen emphasized shorter
switch times (a = -1.357, half height percent = 79%).
Fig. 9.3. The 27 allowable ramplng factors.
1.0 0.8 0.6 0.4 0.2 0.0
0.0
0.2
0.4
0.6
0.8
1.0
a=0.00189 (1%)
a=0.01536 (2%)
a=0.03644 (3%)
a=0.06623 6%)
a=0.10728 (9%)
a=0.16382 (12%)
a=0.24297 (16%)
a=0.35741 (21%)
a=0.53179 (26%)
a=0.82122 (31%)
a=1.37891 (37%)
a=2.84830 (43%)
a=16.16970 (49%)
Block Run Time
1.0 0.8 0.6 0.4 0.2 0.0
0.0
0.2
0.4
0.6
0.8
1.0
a=-1.00189 (99%)
a=-1.01536 (98%)
a=-1.03644 (97%)
a=-1.06623 (94%)
a=-1.10728 (92%)
a=-1.16382 (88%)
a=-1.24297 (84%)
a=-1.35741 (79%)
a=-1.53179 (74%)
a=-1.82122 (69%)
a=-2.37891 (63%)
a=-3.84830 (58%)
a=-17.16970 (52%)
Block Run Time
50