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Equation 1 · Part 2 · Structure from Sequence: What Protein Folding Prediction Did and Did Not Settle

Symbol nu^L-1

Nconf=ν L−1.N_{\mathrm{conf}} = \nu^{\,L-1}.
ν L−1\nu^{\,L-1}

What this part means

nuLu^L-1 is one of the signed contributions combined to compute the quantity on the left.

Its job in the formula

nuLu^L-1 is one of the signed contributions combined to compute the quantity on the left.

The passage around this formula

The standard framing of why search cannot be the mechanism is combinatorial. Treat each residue as having some small number of accessible backbone conformations, and the number of chain configurations is exponential in length: Nconf=ν L−1N_{\mathrm{conf}} = \nu^{\,L-1}. Take a modest three states per residue and a hundred-residue chain. The arithmetic gives 3^{100} ≈\approx 5.2 ×\times 10^{47} configurations; sampling one every 10^{-13} seconds would take about 5 ×\times 10^{34} seconds, on the order of 10^{27} years. Real proteins of that size fold in microseconds to seconds. The gap is not a factor to be tightened by better bookkeeping; it is dozens of orders of magnitude.

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An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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Sources cited in the article section

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