Immunoassay Storage Buffer Example
DESCRIPTION:
This experiment was conducted to study how changing the storage buffer
would affect the stability of a macromolecule (enzyme-antibody
conjugate) after storage for one month at room temperature. The
response is the rate of degradation observed. The experimental
design,
ff0516
is a fractional factorial design with 5
experimental factors each at two levels. The design consists of 16 runs and is
a resolution V, 1/2 fraction of the full factorial.
See Chapter 4 of Haaland (1989) for a more complete description
of the experiment.
ARGUMENTS:
- pH
-
an experimental factor indicating the pH level of the buffer. The pH of
the buffer may affect general reactivity including hydrolysis and
other types of binding.
- gent
-
an experimental factor indicating whether gentamicin, an antimicrobial
agent, is included in the buffer. It is thought that microbial
contamination may lead to clipping of the protein and result in loss
of activity. The low level is no gentamycin.
- thimer
-
an experimental factor indicating whether thimerosal, another
antimicrobial agent, is included in the buffer. The low level is no
thimerosal.
- azide
-
an experimental factor indicating whether azide, another antimicrobial
agent, is included in the buffer. The low level is no azide.
- chelex
-
an experimental factor indicating whether a chelating agent that binds
calcium and magnesium and other metal ions is added to the buffer at a
low or high level. Binding with calcium or magnesium may inactivate
the protein due to resulting conformational changes. It is also
unknown to what extent the presence of ions in the solution may help
or inhibit activity.
- rate
-
the response variable, degradation rate, is expressed as the
amount of degradation observed per month at room temperature.
The response should be minimized.
REFERENCES:
Haaland, P. D. (1989).
Experimental Design in Biotechnology.
New York: Marcel Dekker.
SOURCE:
Used by permission of Marcel Dekker, Inc.
EXAMPLES:
# This design is already available in S-PLUS
# under the name buffer.df. The following commands
# were used to create the data frame:
buffer.design <- design.digest('ff0516',c('pH','chelex',
'azide','gent','thimer'))
buffer.rate <-c(6.90,9.81,8.78,7.92,8.42,7.04,7.21,9.96,
2.34,1.22,1.29,1.73,1.55,1.68,1.81,1.36)
buffer.df <- cbind(buffer.design, rate = buffer.rate)
# sample analysis
summary(buffer.design)
plot(buffer.df)
buffer.fac <- fac.aov(buffer.df)
summary(buffer.fac)
pareto(buffer.fac)
qqnorm(buffer.fac)
tfiplot(buffer.fac,~pH:thimer+pH:gent)
acplot(buffer.fac)
acplot(buffer.fac,.2,5)
ebplot(buffer.fac)
buffer.rmod <- update(buffer.fac,.~pH*thimer+pH*gent)
summary(buffer.rmod)
pareto(buffer.rmod)
plot(buffer.rmod)