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)