Chapter 9 Flashcards
what is the function of ion-exchange chromatography?
separates molecules based on their overall charge at a given pH
How does ion-exchange chromatography work?
Resin beads are given a certain charge through a certain pH, when the sample is running through the chromatography, the ones with the opposite charge will attach to the beads and the other charge will wash away. The ones that stay attached get eluted off by the elution buffer which contains a high salt concentration, or it has a high or low pH, then it is collected.
All fractions are visualized through a PAGE
What is used so that technicians do not have to stand for hours changing collection tubes every
few minutes
fraction collectors
Why would a protein’s charge and behavior change in an ion exchange chromatography?
bc of the pH of the solution in the column
cation exchange
the molecule of interest is a positively charged protein,
then negatively charged resin is used.
anion exchange
protein of interest is negatively charged, then positively charged resin is used.
What is affinity-column chromatography based on?
on shape or molecular configuration.
how does affinity chromatography work?
- antibodies are bound to resign beads
- as sample flows, antibodies will bind to antigenic epitope on protein of interest
a molecule of a given shape
or molecular configuration can be separated from other molecules
what is the key benefit of affinity chromatography?
Since antibody-antigen interactions are very specific, affinity chromatography can
be used to isolate and remove a single type of protein from a mixture of hundreds.
what is the challenge in affinity chromatography?
is finding a complementary molecule/antibody
to attach to the resin beads. Sometimes these already exist in nature. Sometimes these
can be made in the lab.
how does hydrophobic interaction chromatography separate protein molecules?
molecules using
the differences in their hydrophobicity in buffers of high salt concentration.
How does HIC (hydrophobic interaction chromatography) work?
resin beads are made of agarose with hydrophobic group.
proteins are mixed with ammonim sulfate or sodium sulfate (high salt buffer)
high salt buffer results in the protein to change shape and expose hydrophobic regions which will bind to the hydrophobic resin beads
the proteins with low hydrophobic-ness with elute first and then the ones with high hydrophobicness with elute lass
What is an open column chromatography
is gravity flow chromatography
What is open column chromatography for
small samples and small column volumes
What is the disadvantage of open-column chromatography?
buffer runs rather slowly & the quantitation is poor & the separation is poor
What is the advantage of open column chromatography?
gives the technician an idea of how to scale-up the purification process to larger, more effective columns.
How is a fast performance liquid chromatography different from open column chromatography?
FPLC- uses a pump= more efficient than just gravity
How does an FPLC (fast protein liquid chromatography) work?
- Tubing carries the buffer from reservoirs
- Tubing is fed through a pump mechanism that pushes the sample through the column and resin at different rates
- computers and pumps set the flow rate
- as the buffer flows through the resin, the beads separate the molecules based on their characteristics
- fractions leave column through frit membrane
- pass through exit tubing, sample detector (UV spec) and chart recorder or computer and into the fraction collector
When is FPLC used?
very large volumes
What is the HPLC (high perfomance liquid chromatograpy) What are the features that makes it different from other chromatography?
- uses tiny microcolumns
- resin-containing columns are made of metal that can withstand very high
pressures. - minute resin beads, provide increased SA for better surface area
What is HPLC used for?
can study tiny amounts
of proteins, DNA, and RNA.
WHat determines how molecules will be separated in the resin?
type of resin and buffers
What factors affects the binding of sample to the resin beads?
flow rate & pressure
What is an example that ion-exchange chromatography is used for?
soften hard water- water treatment companies