Lecture 9
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What is the Beer-Lambert Law equation?
A= E x l x c
What is A?
Absorbance measured by the spectrophotometer
What is E?
Extinction Coefficient
What is the extinction coefficient?
A measurement of how strongly a chemical attenuates light at a given wavelength
What is l?
Path length
What is path length?
The length of cuvette (1cm)
What is c?
Concentration
What are 2 applications of the Beer-Lambert Law?
Compare the protein concentration with known absorbance for two different samples. Calculate the protein concentration with the known extinction coefficient and path length.
True or False. Proteins with higher concentration show higher absorbance
True
Protein is usually measured at _____ nm
280
What are the aromatic amino acids?
Tryptophan, tyrosine, and phenylalanine
What is the denaturation temperature of conalbumin (ovotransferrin)
61.5
What happens when proteins unfold?
Protein denaturation
What factors affect denaturation and coagulation?
Heat, pH, Sugar, and Salt
______ should be slow and mild.
Heat
What temp does egg white denature, coagulate, and become solid?
63-65
As _____ shift, strong intramolecular electrostatic repulsion causes swelling and unfolding.
pH
Sugar _____ the temperature required for coagulation.
Raises
______ decreases the denaturation temperature.
Salt
What promotes denaturation, coagulation, and gelation?
Salt
Why is 280 nm commonly used to measure the absorbance of proteins?
It can identify aromatic aa which is a unique functional group