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And by a prudent flight and cunning save A life which valour could not, from the grave. A better buckler I can soon regain, But who can get another life again? Archilochus

Tuesday, February 3, 2026

The Metric Tensor...

...and Twistor Theory:
Google AI on Chirality:
Ting Zhu's Quest to Reverse Chirality and Create a New Life Form
The chirality of life refers to the universal preference of Earth's living systems for specific "handedness" (homochirality), where essential molecules like amino acids are exclusively left-handed (L-form) and sugars in DNA/RNA are right-handed (D-form). This molecular asymmetry, like our left and right hands, is crucial for biological function and efficiency, ensuring molecules fit together correctly, but how this single-handedness emerged from a random chemical world remains a fundamental mystery in the origin of life.
What is Chirality?
  • Handedness: 
    Chirality (from the Greek "cheir" for hand) describes molecules that exist in non-superimposable mirror-image forms, called enantiomers, like your left and right hands.
  • Homochirality: 
    Life's signature is homochirality—a strict preference for only one enantiomer (e.g., L-amino acids) for a given molecule, even though laboratory synthesis produces equal mixtures (racemic mixtures) of both.
This video explains the concept of chirality and how it relates to the building blocks of life:
Key Examples in Life
  • Proteins: Built from only left-handed (L-) amino acids.
  • DNA & RNA: Their sugar backbones (deoxyribose and ribose) are only right-handed (D-sugars).
Watch this video to learn why life is chiral:
Why is it Important?
  • Function: 
    Ensures specific molecular interactions, like enzymes recognizing only one shape of substrate, enabling complex biochemical pathways.
  • Efficiency: 
    Prevents conflicting interactions that would arise from mixed chiralities (e.g., protein chains with mixed amino acids don't fold or function well).
This video discusses the origin of homochiral life on Earth:
The Mystery of its Origin
  • The Problem: 
    Early Earth chemistry produced racemic mixtures, so how did a single handedness become established?.
  • Hypotheses: 
    Theories involve extraterrestrial delivery, cosmic rays, or magnetic fields influencing prebiotic chemistry to favor one form, leading to the RNA world and subsequent life.
Significance
  • Signature of Life: 
    Homochirality is a fundamental signature of life, essential for its existence as we know it.
  • Astrobiology: 
    Scientists look for homochirality in potential extraterrestrial life as a key indicator.
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