bio chem midterm 2 Flashcards
(20 cards)
protein stability
noncovalent forces have both attractive and repulsive components
-electrostatic, H-bonding, hydrophobic interaction
proteins are only stable under what conditions?
physiological
electrostatic interactions
salt bridges or ion pairs
ion-dipole
dipole-dipole
van der waal’s
salt bridges or ion pairs
polar charged residues
ion-dipole
polar charged and polar uncharged residues
dipole-dipole
polar uncharged residues
van der waals
nonpolar residues
hydrogen bonds
interaction between potential acid and base
hydrophobic effect
non-polar residues and water
forces
electrostatic interactions
hydrogen bonds
hydrophobic effect
disulfide bridges
covalent bond, Cys residues
(oxidizing environment)
protein denaturation
unfolding impact structure
factors or conditions that promote unfolding
1: pH extremes
2: detergents
3: (some) water soluble organics
4: chaotropic salts
5: salts
6: heat
pH extremes
alter ionization states and H-bonding
detergents
associate with nonpolar residues and disrupt hydrophobic core
-shields water molecules from hydrophobic residues - the molecule breaks apart
(some) water soulble organics
-interfere with hydrophobic forces
chaotropic salts
-increase solubility of nonpolar substances and disrupt hydrophobic core
salts
(NaCl, KCL)
-bridge ionic charges between proteins, resulting in aggregation
heat
-kinetic energy overcomes energy of folded state
quaternary structure
nearly all proteins with molecular mass > 100 kDa are composed of muiltple polypeptide chains or subunits
