Professor Hans Westerhoff's hypothesis of fragility in biological networks is gradually picking up steam. Science News covered it today and I described it as part of a feature on systems biology at the start of the month for the IET's Engineering & Technology.
Westerhoff's approach is deceptively simple. If you look at all the chemical kinetics model for a cell, you can calculate how robust each reaction by analysing the change in production of a target compound based on how much you reduce the amount of enzyme that supports that step. If you cut enzyme concentration by 1 per cent and the production of chemical barely budges, it's robust.
There is no principle of conservation of robustness in a cell: some simply are better at producing material than others. However, if you invert the numbers and call them the fragility of the step, they always add up to one. In a sense, fragility is always conserved. That provides drug designers with a new set of non-obvious targets. In cancers, for example, many drugs try to hit the effects of an oncogene. But the pathways controlled by those genes are often strengthened in a cancer, so they are actually poor targets. Better to look at a precursor that may have a weak link.
