protein denaturation Flashcards
When a protein loses it function because of a change in its secondary, tertiary, or quaternary structure, then this process is known
denaturation
Denatured proteins have ___ solubility and often _____ from solution
lower solubility, precipitate (coagulation)
bonds broken during denaturation:
weak noncovalent bonds, hydrogen bonds, disulfide bonds, ionic bonding, hydrophobic attractions
Proteins can denatured by what?
heat, detergents, mechanical or whipping action and certain acids or bases
During digestion, ____ proteins are denatured and then _____ to form _______
dietary proteins, hydrolyzed, amino acids
process used to breakdown polypeptides to find the amino acid composition of a peptide
hydrolysis
how to hydrolyze in lab?
6M HCl (strong solution of HCl)
principles for 6M HCl
Trp is destroyed
Gln becomes Glu
Asn becomes Asp
+ sign is used, because the HCl attacks the amide linkages in side chains
digestion of proteins in food, what enzyme?
protease
what are the amino acids that these enzymes cleave: trypsin, chymotrypsin, and pepsin?
trypsin: Arg, Lys
chymotrypsin: Phe, Trp, Tyr
pepsin: Phe, Trp, Tyr, Met, Leu
only the right side is cleaved, hence the plus sign
meat tenderizer similar to pepsin
papain
what are the tests for proteins and amino acids?
xanthoproteic test
biuret test
lowry assay
bradford assay
ninhydrin test
Yellow products for proteins with benzene rings
xanthoproteic
Violet color peptides/ proteins with two or more peptide bonds, (test is negative for amino acids/dipeptides)
biuret test
dark violet-blue for tyrosine and tryptophan containing proteins
lowry assay
dark blue color for proteins, most sensitive common test for proteins
bradford assay
blue solution for all amino acids except proline and hydroxypoline
ninhydrin test
xanthoproteic reagent
HNO3 (nitric acid)
biuret reagent
CuSO4 (copper sulfate)
lowry assay reagent
CuSO4 and molybdates/tungstates
bradford assay reagent
coomassie brilliant blue dye
ninhydryin reagent
ninhydrin
a separation technique used to separate complex mixtures of amino acids
chromatography
Proteins are separated using ___ chromatography (..in particular ______) because proteins tend to ______ when separated using TLC
column chromatography (high-performance liquid chromatography), denature
in the TLC, from heaviest to lightest
Asparagine, Glycine, Histidine, Arginine
is a separation technique used to separate proteins based on charge and size
electrophoresis
Protein electrophoresis is typically carried out in a _______
gel matrix
zwitterions are only in the what part of electrophoresis?
middle
sanger’s reagent is what?
2,4-dinitrofluorobenzene (DNFB)
sanger’s reagent is used to determine _____ of a protein
amino acid sequence
sanger’s reagent is named after ____ who determined the ?
frederick sanger, primary structure of insulin
DNFB reacts with the ______ of the polypeptide chain and this substituted polypeptide in turn is _______ to free amino acids
N-terminal residue, hydrolyzed
steps in sanger’s reagent
DNFB - N-terminal residue, alkaline, combined, hydrolysis, amino acids
Sanger determined the amino acids present in insulin using ____ and ____
DFNB and acid hydrolysis
He determined the amino acid sequence of insulin by ________ with ______ structures at their ends
combining fragments, overlapping
The ________ is a lab method used in determining the amino acid sequence in a polypeptide.
Edman degradation
edman degradation reagent
phenylisothiocyanate
Edman degradations are carried out automatically in devices known as _________
protein sequenators
kung ano ang gustong idugtong, yung ang du-dugtong
blocking groups
decreases the reactivity of the functional group toward the reagent being used
blocking groups
first breakthrough in speeding up protein synthesis was the development of a device in 1960 by ______ that could automatically synthesize polypeptide chains
R. Bruce Merrifield
what proteins were used in the first protein synthesis?
pancreatic ribonuclease and human growth hormone
