21 June 2010

Fuzzy logic of aging

The rejection of clear logic helped to study the aging of cellsAlexey Tymoshenko, GZT.RU
The journal PLoS Computational Biology published an article presenting a new model of cell aging (Andres Kriete, William J. Bosl, Glenn Booker, Rule-Based Cell Systems Model of Aging using Feedback Loop Motifs Mediated by Stress Responses).

Researchers from several medical and scientific centers in the USA, among which Harvard Medical School can be distinguished, have tried to solve one of the most difficult problems of modern biology with the help of fuzzy logic, a branch of mathematics that is an extension of ordinary mathematical logic.

As the authors of the work write in their article, it is extremely difficult to simulate a living cell because of the many parameters that describe its behavior. In the human genome, for example, there are about twenty thousand genes. Consequently, there can be at least the same number of different protein and RNA molecules inside the cell, hundreds of substances are involved in the processes of metabolism at the intracellular level, and the "body" of the cell itself is not a hollow ball at all.

Describing the behavior of a cell is a task as difficult as modeling the behavior of a city or a state, and scientists' troubles are not exhausted by a large number of different numerical values (concentrations of substances, their transfer rates, and so on). The number of experiments from which researchers know about the behavior of a real cell, although large, is not enough to complete the picture.

When clarity gets in the way

Ordinary logic (mathematical) assumes unambiguity of statements. In relation to biology and individual cells, this could mean that the cell model always adheres to the rules of the form "if there are more than a billion molecules around substance A and at the same time substance B, then division must begin."

But there is a problem with such accurate models: they do not always agree well with reality. The reason lies in the incompleteness of knowledge – scientists remain unaware of many of the rules by which the cell works. And only the so-called fuzzy logic makes it possible to obtain results of interest to researchers even with a lack of knowledge about the simulated system.

Instead of the binary opposition "hot-cold"
fuzzy logic devices allocate more states.

Fuzzy logic in technology does not involve the use of a binary "is-no" choice, but the attribution of the situation to one of the classes with rather blurred boundaries.

Changing different parameters,
describing the behavior of a cell in a model based on fuzzy logic.

What will it give?

Of course, the new model will not immediately produce a prescription for a life-prolonging medicine, and even more so it will not reveal the secret of immortality. Rather, it will prove to be a useful tool for biologists working on solving particular issues – studying the effect of free radicals on cells, looking for characteristic changes in certain diseases, and so on.

But do not underestimate the importance of models. Modeling for a scientist often turns out to be what makes it much faster to conduct research – currently, for example, with the help of supercomputers, a preliminary search for drugs is carried out or (if we ignore biology) testing prototypes of cars for safety in collisions. Instead of conducting tests on hundreds of animals or crashing one expensive car, you can simply run the program and look at the result.

Portal "Eternal youth" http://vechnayamolodost.ru21.06.2010

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