Biology Reference
In-Depth Information
the component, since the larger the stoichiometry of the component,
the more dramatic the influence of the component concentration
(dilution factor) on the reaction. In the plot curve, the y -axis is the
log of the yield of the reaction, and the x -axis is the log of the step-
up concentration, or the log of the inverse of the dilution factor start-
ing from high dilution. The larger the stoichiometry of one
component, the larger the slope of the log/log plot curve for this
component will be. The slope is defined as the tangent of the angle
between the curve and the x -axis. When plotting the curve for meas-
uring the slope, the unit length for the x -axis (log of concentration)
must be the same as that of the y -axis (log of yield).
Approaches
The dose response curves of in vitro viral assembly versus the con-
centration of various assembly components have been used as a
method to estimate stoichiometry. In these dose response curves, the
larger the stoichiometry of the component, the more dramatic is the
influence of the dilution factor on the reaction. A slope of one indi-
cates that one copy of the component is involved in the assembly of
one virion, as is the case, for instance, in genomic DNA in phi29
assembly. A slope larger than one would indicate multiple-copy
involvement (cooperative binding).
To test one parameter, all other components should be kept in
excess in this assay. The relative concentration ( x -axis, from low to
high) was plotted against the yield ( y -axis) of phi29 virions assem-
bled (PFU/ml). The log scale was used for both the concentration
and the yield, with the unit length of the log scale of the x -axis
equal to that of the y -axis. 107,108,134,151 The angle between the x -axis
and the concentration-dependent curve was measured, and the
slopes (tan) of all curves were plotted against their stoichiometry.
Computer programs such as Cricket Graph or Prism can be utilized
to find a best-fit curve and to deduce the formula for stoichiome-
try determination.
The log/log plot method only considers the functional unit
(oligo or complex), not the copy number of the subunits, as described
Search WWH ::




Custom Search