Amino Acids, Peptides and Proteins Flashcards
(30 cards)
What do you get when you do acid-catalyzed hydrolysis of amides? Base-catalyzed?
acid- get carboxylic acid
base- get conjugate base
Which form are most naturally occurring AAs?
L
Name the 3 basic amino acids
histidine
lysine
arginine
Name the 2 acidic amino acids
aspartic acid
glutamic acid
Name the 6 polar amino acids. Which is sometimes considered to be non polar?
serine threonine cysteine asparagine glutamine tyrosine (sometimes considered to be non polar)
Name 2 non polar amino acids that you would think are polar, acidic or basic
tryptophan
methionine
What is the approximate pKa of the NH3+ group on an amino acid?
9 or 10
What is the approximate pKa of the carboxyl group on an amino acid?
2
Why are AAs not very soluble at near-neutral pH?
they form ion pairs because they are charged on both ends
What is the isoelectric point?
the pH of a solution at which the collection of molecules has no charge
Which AAs come out of the ion-exchange tube of HPLC first?
negative ones because they’re repulsed by the negative column
(positively charged are last)
Give the order that the types of AAs come out of HPLC
negative
polar
non polar
positive
Name 3 AAs that can’t be separated using AAA because they are destroyed by acid hydrolysis
Gln
Asn
Trp
Where does CNBr cleave proteins?
After Met
Where does Edman degradation cleave proteins?
the N-terminal amino acid
Where does trypsin cleave proteins?
after Arg and Lys
Where does chemotrypsin cleave proteins?
after Phe, Trp and Tyr
Where does carboxypeptidase A cleave proteins?
at the C-terminal amino acid
How many AAs can be sequenced using Edman degradation at once?
40-60
When doing Edman degradation does every amino acids give a different PTH derivative?
yes
When doing N-terminal identification how can you tell if lysine was on the N terminal or not?
if it was on the N terminal, will have 2 DNP groups attached, if not will only have one
When doing C-terminal sequencing the amino acid you have the most of is found at which end? The least?
most is found at the C terminus
least is at the N terminus
How do we protect the COOH of an amino acid?
make it a benzyl ester
How do we remove a benzyl ester from an amino acid?
HBr and HOAc (dry acetic acid)
