"Crash."
Toma dropped an egg. The white began solidifying.
"Ah, I did it."
"No, it's a good experimental sample," Rei approached.
"Experiment?" Kana looked curiously.
Milia said quietly, "We can observe protein denaturation."
"Denaturation..."
Rei began explaining. "Egg white's main component is albumin. A protein."
"Raw it's transparent, but when heated it solidifies white," Toma supplemented.
"Why does it solidify?" Kana asked.
"Because the protein 'breaks,'" Rei drew a diagram on the whiteboard.
"Breaks? But it's still protein, right?"
"The amino acid sequence doesn't change. But the three-dimensional structure is lost."
Milia continued, "Proteins have specific three-dimensional structures. That structure determines function."
"Lock and key relationship," Rei used a metaphor. "When the shape collapses, it doesn't function."
Kana opened her notebook. "Why does heating collapse the structure?"
"Because hydrogen bonds break," Toma answered.
"Protein structure is maintained by hydrogen bonds, hydrophobic interactions, and disulfide bonds," Rei listed.
"When heated, molecular motion intensifies, breaking these weak bonds."
Milia supplemented, "And hydrophobic parts become exposed. That triggers aggregation."
"Aggregation?"
"Multiple protein molecules become entangled chaotically. That becomes white precipitate."
Kana looked at the egg white. "This is aggregation."
"Right. An irreversible change," Rei nodded.
Toma suddenly realized, "But proteins don't break at body temperature, right?"
"Good question," Milia smiled. "Proteins in living organisms have stabilization mechanisms."
"What mechanisms?"
Rei explained, "Chaperone proteins. They help other proteins fold correctly."
"Proteins that help proteins?" Kana was surprised.
"Yes. Heat shock proteins HSP, chaperonins, and others."
Milia elaborated, "Newly synthesized proteins don't have correct structure yet."
"Just after emerging from ribosomes, they're merely amino acid chains."
"Those chains fold spontaneously. But sometimes they fold incorrectly."
Rei continued, "Chaperones prevent that mistake. Or unfold incorrect structures."
Kana was impressed. "Like quality control."
"Exactly. The cell's quality control system," Toma said.
"But," Kana thought, "what if chaperones are insufficient?"
Milia became serious. "That causes disease."
"Disease?"
"Alzheimer's, Parkinson's. Protein aggregation is involved."
Rei supplemented, "Beta-amyloid, alpha-synuclein. These abnormally aggregate and damage nerve cells."
"When proteins break, disease occurs..." Kana murmured.
"Conversely," Milia continued, "maintaining correct structure is key to health."
Toma gave another example. "Prion disease is also abnormal protein structure, right?"
"Exactly. Normal prion protein transforms into abnormal form."
"And that abnormal form converts normal forms into abnormal ones," Rei explained.
"Chain reaction," Kana understood.
"A terrifying mechanism," Toma said.
Milia said quietly, "Protein structure carries information. When that information is lost, life functions are also lost."
Kana wrote in her notebook. "Not just sequence, but structure is important too."
"Anfinsen's dogma," Rei said. "Protein structure is determined by amino acid sequence."
"But in reality, chaperone assistance is needed."
"Right. Life cannot be explained by simple chemical principles alone."
Kana stared at the egg white. "In this white mass, life's complexity exists."
"And fragility too," Milia added.
Toma laughed. "From now on, I won't drop eggs."
"No, this was good teaching material," Rei smiled.
Silence returned to the lab. Countless proteins, protected by chaperones, continue maintaining their correct structures even now.