Experiments using what is believed to be the original atmospheric compounds do produce more than 100 kinds of simple organic compounds, and as such constitute nearly all the basic building blocks of living cells. Instead a drier surface such as that provided by clays and rock may have been more attractive. While attached, AA can act as a sort of catalyst for crystal growth. At the same time electric charges from clay elements such as iron and zinc can cause AA to link together to form polymers. Nineteen of the 20 AA have a central carbon atom surrounded by 4 chemical groups.
Clays attract and bind only the left-handed form which happens to be the type found in living cells.
However, a meteorite called Murchison was discovered which had mostly the L form of alanine. In other words, polymers have an intrinsic tendency to evolve into higher-order structures. One type of protobiont has been successfully recreated in the laboratory by Sidney W. Fox at the University of Miami. These are membrane-bound structures that are able to carry out some chemical reactions analogous to those found in living cells. Although not actually producing living cells this model offers a hypothesis on how cells could have evolved.