Geometric Derivation from First Principles
The double helix is not discovered. It is derived. The geometry demands it.
Everything in the Epoch Model derives from a single closure constant. One number that generates all others.
From κ, we derive everything: atomic structure, molecular geometry, helix parameters, and the very structure of DNA.
| Constant | Derivation | Value | Role |
|---|---|---|---|
| κ | 2π/180 | 0.0349 rad | Closure constant |
| κ_shadow | 1/κ | 28.6479 | Hidden witness |
| σ | 5/16 | 0.3125 | Helix overlap |
| cos(BC) | 2/3 | 0.6667 | Tetrahelix angle |
| coupling | σ × cos(BC) | 5/24 ≈ 0.208 | Universal coupling |
DNA rotates 36 degrees per base pair. This is exactly 18κ.
This is not coincidence. This is geometry demanding a specific structure.
Most biology textbooks present DNA as a discovery - something found in nature and described empirically. But the Epoch approach asks: why MUST DNA be shaped this way?
The answer: because the mathematics of space itself demands it. The tetrahelix - a structure of pure geometry - projects into molecular reality as the double helix. Life didn't invent this shape. Life found the shape that reality permits.
DNA has 10 bp per turn because... that's what we measured.
DNA has 10 bp per turn because 360°/36° = 10, and 36° = 18κ.
Before we can understand DNA, we must understand the tetrahelix - a chain of face-sharing regular tetrahedra that forms a helical structure of pure geometry.
The tetrahelix - a helical chain of face-sharing tetrahedra
Take a regular tetrahedron. Attach another tetrahedron by sharing one face. Continue. The result is not straight - it twists.
Four equilateral triangular faces, four vertices, six edges.
Attach second tetrahedron by sharing one triangular face.
Each new tetrahedron rotates ~131.8° relative to the previous.
After ~10 tetrahedra, the structure nearly returns to its starting orientation.
| Property | Value | Significance |
|---|---|---|
| cos(BC) angle | 2/3 ≈ 0.6667 | Inter-tetrahedral relationship |
| Twist per unit | ~131.8° (arccos(2/3)) | Rotation between tetrahedra |
| Simplified projection | ~36° per unit | Matches DNA rotation exactly |
| Period | ~10 units | Returns near starting position |
| Chirality | Left or Right | Two mirror forms exist |
The Boerdijk-Coxeter angle is defined by the relationship between adjacent tetrahedra. This angle, expressed as cos(BC) = 2/3, is one of our fundamental constants.
Combined with the helix overlap σ = 5/16, we get the universal coupling constant:
The tetrahelix actually has four distinct strands - the four edges of each tetrahedron trace four intertwined helices. When projected onto molecular space, we typically see only two - the famous double helix.
The other two are silent - present in the geometry but not expressed in the physical structure. This mirrors the Epoch Model's concept of apparent and hidden components.
The DNA double helix is the molecular expression of tetrahelix geometry. The parameters match because they must - the geometry demands it.
~36°
Simplified rotation per unit
36°
Rotation per base pair
| Parameter | Value | Geometric Origin |
|---|---|---|
| Rotation per bp | 36° | 18κ exactly |
| Base pairs per turn | 10 | 360°/36° = 10 |
| Rise per bp | 3.4 Å | Pitch/10 |
| Pitch (rise per turn) | 34 Å | 3.4 × 10 |
| Diameter | 20 Å | Nucleotide geometry |
| Major groove | 22 Å wide | Apparent side |
| Minor groove | 12 Å wide | Shadow side |
The double helix has two grooves of different widths: the major groove (22 Å) and the minor groove (12 Å).
In Epoch terms:
The tetrahelix has four strands. DNA expresses two. Why?
The answer lies in the complementary base pairing - Adenine with Thymine, Guanine with Cytosine. This pairing represents the apparent/shadow duality.
DNA (in its common B-form) is right-handed. The tetrahelix can be left or right-handed. Why did life choose right?
The answer involves the chirality of the sugar-phosphate backbone. L-amino acids and D-sugars dominate biology, creating a consistent handedness throughout molecular machinery.
This is chirality selection - one of the silent fourth becomes expressed, the other remains silent. The choice was made once, early in life's history, and propagated ever since.
DNA helicase is an enzyme that unwinds the double helix during replication and transcription. It is a molecular motor that rotates at approximately 10,000 RPM.
DNA helicase - a hexameric ring motor that unwinds the double helix
Most DNA helicases form a ring of six subunits - a hexamer. This is not random. The hexamer is geometrically optimal.
Top view of a hexameric ring motor - six subunits with 60° symmetry
6
Hexameric structure
60°
360°/6 per subunit
C6
Six-fold rotational
Here is where our geometric derivation connects to the macroscopic world. DNA helicase demonstrates the exact same paradox we see in vinyl records, gears, and propellers.
Outer edge faster than center
Same at contact point
Radial velocity gradient
At 10,000 RPM (167 Hz), the angular velocity is constant: ω = 1047 rad/s
But linear velocity varies with radius: v = ω × r
| Location | Radius | Linear Velocity |
|---|---|---|
| Central pore | 6.5 Å | 6,806 Å/s |
| Mid-ring | 25 Å | 26,175 Å/s |
| Outer edge | 50 Å | 52,350 Å/s |
The DNA passing through the central pore moves at a different speed than the outer edge of the helicase ring. Same rotation, different speeds. The geometry cannot lie.
| Helicase Type | Rate (bp/s) | Conditions |
|---|---|---|
| E. coli DnaB | 35 - 500 | In vitro / In vivo |
| T7 gp4 | ~130 | Optimal |
| Human MCM | 15 - 30 | Cell cycle dependent |
| Viral helicases | 100 - 300 | Variable |
Can we predict unwinding rates from geometry?
This theoretical limit from κ matches observed rates remarkably well. The T7 helicase at 130 bp/s is ~76% of this limit - close to our coupling constant (5/24 ≈ 21% loss expected).
DNA helicase is not unique. Across biology, hexameric ring motors appear again and again. The geometry that makes helicase work makes ALL rotary motors work.
DNA helicase unwinding the double helix - the molecular motor in action
| Motor | Function | Ring Size | Rotation Rate |
|---|---|---|---|
| DNA Helicase | Unwind DNA | Hexamer (6) | ~167 Hz |
| F₁-ATPase | ATP synthesis | Hexamer (α₃β₃) | ~130 Hz |
| Bacterial Flagellum | Cell propulsion | Ring motor | ~300 Hz |
| Viral Portal | DNA packaging | Dodecamer (12) | Variable |
| AAA+ ATPases | Protein unfolding | Hexamer (6) | Variable |
60° sectors = equilateral triangular symmetry. Maximum stability with minimum components.
Six points of contact distribute mechanical load evenly around the ring.
6 steps ≈ 60% of a DNA turn. Efficient for tracking helical substrates.
Standard protein domain sizes fit 6x around a functional pore.
F₁-ATPase is the rotary motor portion of ATP synthase - the enzyme that produces most of the ATP in cells. It is the smallest known rotary motor.
~10 nm
Nanoscale
~130 Hz
7,800 RPM
~100%
Near perfect
The motor rotates in 120° steps (3 per revolution) as it synthesizes ATP. Each step corresponds to one ATP molecule. The geometry is inescapable.
Bacteria swim using rotating flagella powered by molecular motors embedded in their cell membrane. These motors can spin at up to 300 Hz (18,000 RPM).
The flagellar motor is more complex than helicase - it has multiple ring components - but the fundamental principle is the same: rotary motion powered by sequential conformational changes around a ring.
Across all these motors, we see similar efficiency limits:
This ~20% "loss" appears in:
The geometry sets the limit. The motors approach it but cannot exceed it.
Explore the geometric relationships yourself. All calculations derive from the fundamental constant κ = 2π/180.
| Constant | Value | Expression |
|---|---|---|
| κ | 0.0349066... | 2π/180 |
| κ_shadow (1/κ) | 28.6478897... | 180/2π |
| σ | 0.3125 | 5/16 |
| cos(BC) | 0.6667... | 2/3 |
| coupling | 0.2083... | 5/24 |