Amphipathic helices possess hydrophobic and hydrophilic faces suited for membrane environments.
Hydrophobic residues at heptad repeat positions interlock to stabilize the coiled-coil.
RNase A spontaneously refolded after denaturation, proving sequence determines structure.
Tryptophan and tyrosine absorb ultraviolet light strongly near 280 nm.
Hydroxyproline stabilizes the collagen triple helix through hydrogen bonding.
pI = (2.34 + 9.60)/2 = 5.97.
Myoglobin has a high oxygen affinity and releases oxygen only at low oxygen tension.
Substrate binding induces conformational changes that optimize catalysis.
β-turns reverse the direction of the polypeptide chain and are stabilized by hydrogen bonding.
Oxygen binding at one site increases affinity at other sites through conformational change.
Glycine's small side chain allows conformations inaccessible to other amino acids.
Low pH and high CO₂ reduce oxygen affinity, promoting oxygen delivery.
Branched β-carbon side chains create steric hindrance in α-helices.
Most φ and ψ angle combinations are sterically forbidden for amino acids other than glycine.
Heat disrupts weak interactions but usually leaves the covalent peptide backbone intact.
Chaperones bind exposed hydrophobic regions of unfolded proteins, preventing aggregation and promoting correct folding.
Histidine's pKa is close to physiological pH, making it ideal for acid-base catalysis.
β-sheets are classified according to the orientation of adjacent strands.
The heme prosthetic group contains Fe²⁺, which reversibly binds oxygen.
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