DNA helix shows the best use of space

How small is a piece of string? Or, to be precise, into how small a box can you put a piece of string? It might seem trivial but scientists say it is important in predicting the shape of DNA and proteins. Their latest answer is that nature's method is the most efficient.

How small is a piece of string? Or, to be precise, into how small a box can you put a piece of string? It might seem trivial but scientists say it is important in predicting the shape of DNA and proteins. Their latest answer is that nature's method is the most efficient.

The question of how best to use a limited space to pack objects fascinates researchers. In the biological world this often involves coils and strings of molecules rather than individual ball-like atoms.

An international team led by Professor Amos Maritan has shown that the best way to wind a coil depends on its thickness and how easily it can "bend" around a curve. The work is reported today in the journal Nature.

For coils that can be bent more tightly, they found that the famous double helix - as used in DNA - is the most efficient. Past physical measurements, show DNA is just 4 per cent below the "bendiness" limit.

The findings could also affectscientific thinking about how some protein-based diseases, notably Creutzfeldt-Jakob disease (CJD) and mad cow disease, or BSE, develop.