Transcription and the Pitch Angle of DNA

TL;DR

This paper explores the geometric relationship between the pitch angle of B-DNA and its ability to undergo transcription, proposing that a smaller pitch angle than the zero-twist angle facilitates the process.

Contribution

It introduces a geometric criterion based on the pitch angle being less than the zero-twist angle for DNA transcription to occur.

Findings

The estimated pitch angle of B-DNA is approximately 38 degrees.

The zero-twist angle for B-DNA is about 41.8 degrees.

Empirical data supports the geometric criterion for transcription.

Abstract

The question of the value of the pitch angle of DNA is visited from the perspective of a geometrical analysis of transcription. It is suggested that for transcription to be possible, the pitch angle of B-DNA must be smaller than the angle of zero-twist. At the zero-twist angle the double helix is maximally rotated and its strain-twist coupling vanishes. A numerical estimate of the pitch angle for B-DNA based on differential geometry is compared with numbers obtained from existing empirical data. The crystallographic studies shows that the pitch angle is approximately 38 deg., less than the corresponding zero-twist angle of 41.8 deg., which is consistent with the suggested principle for transcription.