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How a memory gets physically written into your brain — at the molecular level: ACTIVATION … The synapse fires, a glutamate signal arrives, then the NMDA receptor opens and Ca²⁺ floods into the post-synaptic spine. Calmodulin — a small dumbbell-shaped sensor protein — cradles four Ca²⁺ ions, two per lobe. Loaded calmodulin clamps onto CaMKII, the central memory enzyme of the brain. CaMKII isn’t one kinase. It’s a holoenzyme: 12 kinase domains arranged as two stacked hexagonal rings of 6, all radiating from a violet hub. When Ca²⁺/calmodulin binds, the kinase arms swing out from their folded inactive state into the activated starburst. Then each kinase autophosphorylates its neighbor at Thr286. That single modification locks the enzyme ON — even after Ca²⁺ leaves. The switch is now a latch. The memory trace begins here. DOCKING … A microtubule is a hollow cylinder built from α/β-tubulin dimers — 13 protofilaments, 25 nm outer diameter, 15 nm inner lumen. The tubulins tile its surface in a near-hexagonal lattice. CaMKII’s hexagonal foot is ~20 nm across. The numbers aren’t coincidence — the kinase hexagon matches the tubulin lattice exactly. When activated CaMKII lands on a microtubule, six of its kinase feet contact six tubulins arranged in a hexagonal ring around one untouched central “address” dimer. Complementary surface charges hold it in place with 6 to 36 kcal/mol of electrostatic attraction — strong, specific, reversible. The enzyme isn’t just sitting on the lattice. It’s registered to it. Like a print head locking onto paper. ENCODING — the write step Now CaMKII writes… Each of the six feet transfers a phosphate group (one ATP per contact) onto its target tubulin’s C-terminus — or doesn’t. Six independent decisions. Six bits. One byte. The phosphorylation sites are real and identified: Thr312 and Ser444 on βIII-tubulin. Each phosphate flips that tubulin into a glowing amber conformational state, distinguishable from the unphosphorylated teal/indigo dimers around it. The information capacity is staggering: •A-lattice binary (β-tubulin only): 2⁶ = 64 states per byte •A-lattice ternary (α or β phosphorylation): 3⁶ = 729 states per byte •B-lattice 9-dimer (ternary, 6 of 8 dimers writable): 5,281 states per byte Multiply that across the billions of tubulins in every single one of our neurons and you get memory density that dwarfs anything we build in silicon. COMPUTATION — the pattern isn’t inert; it computes… The phosphorylation pattern isn’t a passive record. It actively shapes the microtubule lattice, and thus the cell: C-terminal tails flip between up/down conformations, seeding hexagonal Turing waves that propagate the pattern across the lattice. MAPs (microtubule-associated proteins) dock preferentially at amber phospho-sites, templating bundle architecture and synaptic stability. Kinesin — the two-legged molecular motor — reads the amber path and walks cargo vesicles along it. The memory becomes a routing map for transport. The whole lattice resonates at MHz frequencies — millions of state updates per second. Storage and processing collapse into the same substrate. The brain may literally write in hexagonal bytes! Craddock, Tuszynski & Hameroff (2012), PLoS Comput Biol 8(3):e1002421 — https://t.co/InJdmdYv8d

JosephJacks_'s tweet photo. How a memory gets physically written into your brain — at the molecular level:

ACTIVATION …

The synapse fires, a glutamate signal arrives, then the NMDA receptor opens and Ca²⁺ floods into the post-synaptic spine.

Calmodulin — a small dumbbell-shaped sensor protein — cradles four Ca²⁺ ions, two per lobe. Loaded calmodulin clamps onto CaMKII, the central memory enzyme of the brain.

CaMKII isn’t one kinase. It’s a holoenzyme: 12 kinase domains arranged as two stacked hexagonal rings of 6, all radiating from a violet hub.

When Ca²⁺/calmodulin binds, the kinase arms swing out from their folded inactive state into the activated starburst.

Then each kinase autophosphorylates its neighbor at Thr286. That single modification locks the enzyme ON — even after Ca²⁺ leaves. The switch is now a latch. The memory trace begins here.

DOCKING …

A microtubule is a hollow cylinder built from α/β-tubulin dimers — 13 protofilaments, 25 nm outer diameter, 15 nm inner lumen. The tubulins tile its surface in a near-hexagonal lattice.

CaMKII’s hexagonal foot is ~20 nm across. The numbers aren’t coincidence — the kinase hexagon matches the tubulin lattice exactly.

When activated CaMKII lands on a microtubule, six of its kinase feet contact six tubulins arranged in a hexagonal ring around one untouched central “address” dimer.

Complementary surface charges hold it in place with 6 to 36 kcal/mol of electrostatic attraction — strong, specific, reversible.

The enzyme isn’t just sitting on the lattice. It’s registered to it. Like a print head locking onto paper.

ENCODING — the write step

Now CaMKII writes…

Each of the six feet transfers a phosphate group (one ATP per contact) onto its target tubulin’s C-terminus — or doesn’t. Six independent decisions. Six bits. One byte.

The phosphorylation sites are real and identified:

Thr312 and Ser444 on βIII-tubulin.

Each phosphate flips that tubulin into a glowing amber conformational state, distinguishable from the unphosphorylated teal/indigo dimers around it.

The information capacity is staggering:

•A-lattice binary (β-tubulin only): 2⁶ = 64 states per byte

•A-lattice ternary (α or β phosphorylation): 3⁶ = 729 states per byte

•B-lattice 9-dimer (ternary, 6 of 8 dimers writable): 5,281 states per byte

Multiply that across the billions of tubulins in every single one of our neurons and you get memory density that dwarfs anything we build in silicon.

COMPUTATION — the pattern isn’t inert; it computes…

The phosphorylation pattern isn’t a passive record. It actively shapes the microtubule lattice, and thus the cell:

C-terminal tails flip between up/down conformations, seeding hexagonal Turing waves that propagate the pattern across the lattice.

MAPs (microtubule-associated proteins) dock preferentially at amber phospho-sites, templating bundle architecture and synaptic stability.

Kinesin — the two-legged molecular motor — reads the amber path and walks cargo vesicles along it. The memory becomes a routing map for transport.

The whole lattice resonates at MHz frequencies — millions of state updates per second. Storage and processing collapse into the same substrate.

The brain may literally write in hexagonal bytes!

Craddock, Tuszynski & Hameroff (2012), PLoS Comput Biol 8(3):e1002421 — https://t.co/InJdmdYv8d

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