Protein Sequencing & Secondary Structure Flashcards
(31 cards)
What does cyanogen bromide cleave?
Breaks apart proteins after Met; except if preceding residue is a Pro
What does ammonium sulfate do?
purify proteins by salt fractionation
What does phenyl isothiocyanate do?
react with N-terminal free amino acid group
What does iodoacetate do?
alkylate sulfhydryl group of cysteine to keep reformation of disulfide bonds
In all B-Sheets, how are the side chains oriented?
successive side chains of polypeptide chains occur on opposite ends of the sheet
What residues are found in high proportions in silk fibroin?
Gly, Ala, Ser
Folded states of globular proteins in aqueous solution are stabilized by…
hydrophobic interactions
What is the quaternary structure?
spatial arrangement of protein subunits
What is the slowest step of protein folding?
conformational adjustments to optimize the orientation of the side chains
How are the side chains found in alpha helices?
side chains of amino acid residues are found on outside of the helix spiral
What is the structure of silk fibrion?
antiparallel B-Sheets
A peptide bond has…
partial bond character
What is the structure of collagen?
triple helix with every third residue a Gly facing the interior of the helix
What type of B-sheet is more stable?
Antiparallel more stable than parallel
What are the three amino acid residues found in high proportions of collagen?
Gly, Pro, 4-hydroxyproline
What does Trypsin cleave?
cuts after Arg and Lys; except when preceded by Pro
What does elastase cleave>
cut after Gly, Ala, Val; except when preceded by Pro
What does chymotrypsin cleave?
cuts after Phe, Tyr, Trp; except when preceded by a Pro
What does B-mercapto cleave?
All disulfide bonds
What does carboxypeptidase A cleave?
cleaves the C-terminal group; except Arg and Lys
What type of stereochemistry do amino acids take in proteins?
19/20 take the trans orientation while Pro takes the cis orientation
Where is the Phi bond?
between the alpha carbon and N terminal bond
Where is the Psi bond?
between the alpha carbon and the C-terminal bond
What is N?
the number of residues per helical turn
