It might be a bad idea to mix detergents with chromosomes. But new research published in the journal Nature reports how a protein that has surfactant-like properties coats our chromosomes to protect them from other cellular material. 

Our chromosomes are enclosed inside the nucleus by a nuclear membrane. When cells are dividing, the nuclear membrane breaks apart until the chromosomes are allotted to each daughter cell, then rebuilt again. Hence, there is a time our chromosomes are exposed to cellular material that is normally kept outside the nucleus (also called cytoplasm). But how the chromosomes are kept clean until the nuclear membrane is rebuilt is not clear.

Scientists found that a protein called Ki-67 has surfactant-like properties – similar to detergents – and sticks to the chromosomes as they start to segregate. Surfactants (or surface-acting-agents) are double-faced molecules that have a water-friendly and an oil-friendly side. This makes them efficient carriers or protectors. 

While usually surfactants are made by a combination of fats and water-loving particles, Ki-67 is likely the first protein known to act as a surfactant molecule. 

The researchers estimate that ~210 molecules of Ki-67 stick to each per square micrometer of the chromosomes. They stick head-first, keeping their tails facing out to prevent any cytoplasmic material from reaching the chromosomes. Then, when the chromosomes are divvied up and the nuclear membrane is about to be re-built, the Ki-67 molecules help keep the chromosomes clustered together.