Lecture 2 Flashcards
(18 cards)
Amino Acids in Water
- Loses the H from the OH and gains the H at the NH2
- turns into a Zwitterionic ion
- changes the pH of water
Ionizations characteristics of AA
Depends on:
- The N terminal and C terminal groups
- Those R groups side chains that are ionizable
- Each peptide has its own isoelectric point that can be used for separation and identification purposes.
Amino Acid Titration curve
- Pk1 and Pk2 are equillibrium constants for ionization. (greatest buffering capacity happens at these points).
- pI is the isoelectric point.
Ways to separate proteins
- centrifuge
- ion chromotography
- size chromotography
- affinity chromotography
Centrifuge
-heavier things will settle out to the bottom
Ion chromatography
uses charges of the proteins
size chromatography
uses the size of the proteins/AA’s
Affinity chromatography
attach protein to another ligand and then use the ligand
- this find proteins that have a receptor that works with the ligand
- causes the protein to become solid and precipitate out (elution)
Activity
Total # of proteins in a solution
Specific Activity
Total # of just the specific protein in a solution (standardized unit of solution)
Polyacrylamide Gel Electrophoresis(PAGE)
- a gel between two plates with wells where you can put your sample
-different proteins will migrate towards the positive charge at the end of the gel.
-
Comparing Standardized values for PAGE
- Largest proteins move the least distance
- separates out by molecular weight
2D Gel electrophoresis
uses the charges to filter proteins
Isoelectric
focuses which uses the charges to filter proteins
How are Peptides named
beginning with the amino-terminal residue, towards the carboxyl-terminal end.
Amphoteric molecules (AA in water)
acts as:
-acids, proton donors
or bases, proton acceptors
Amino acids that have titration curves similar to glycine have the following
- a single alpha-amino group
- a single alpha-carboxy group
- a nonionizing R group
Disulphide bonds
Oxidation reaction forms disulphide bond
-Reduction reaction breaks disulphide bond
