The structural basis of biological systems -- on the structures of transfer RNA and DNA and on some biological...

Tetrahelix polynucleotide structure is important in biological systems. Though it is disputed there is firm evidence that transfer RNA has a tetrahelix structure and has the form of a simple cylinder. There is overwhelming chemical, biochemical and sequence evidence and the structure satisfies the constraints of the unit cell lattice. Tetrahelix structure also occurs in DNA and appears to be the most stable form and in many cases the naturally occurring form under physiological conditions. The consequences of tetrahelix structure clarify some longstanding problems such as the physical basis of supertwisting and of compact structure.