Boreskov

PL‐8MOLECULAR COLONIES AS A PRE‐CELLULAR FORMOF COMPARTMENTALIZATIONChetverin A.B.Institute of Protein Research of the Russian Academy of Sciences,Pushchino, Moscow Region, 142290 RussiaThe need for compartmentalizationThe main feature of a cell which distinguishes it from a mere aliquot of a biochemicalsolution is that the cell must be capable of evolution. However, evolution cannot occurwithout compartmentalization, some kind of segregation of the cell from its environment[1‐ 3]. It looks tempting to consider liposomes as a pre‐cellular form ofcompartmentalization of biochemical reactions. Liposomes are capable of spontaneousproliferation by incorporating new lipid micelles or molecules followed by breaking downinto smaller vesicles. Moreover, it was shown that if a liposome was loaded with RNA, NTPs,and a replicase, the liposome division was coupled with RNA replication [4], which isreminiscent of cell division. However, in using liposomes as cell analogs there are a lot of yetunresolved problems, of which the most serious is that lipid membrane is hardly permeableto hydrophilic low molecular weight compounds, such as nucleotides or their precursorsneeded for the synthesis of biopolymers, which had to enter the cell from the environment.Even passive diffusion of such compounds is very slow, with the half time required fortransmembrane equilibration exceeding 10 h [5]. This makes the rate of intra‐liposomesynthesis of nucleic acids unacceptably low even at the extra‐liposome concentration ofnucleotide substrates as high as 5 mM, which can hardly be expected of the ‘primordialsoup’.Molecular colonies as an alternative to liposomesAnother form of compartmentalization of biochemical reactions could be molecularcolonies that formed when RNA or DNA are amplified in a porous solid medium [6]. Thesynthesized copies remain nearby the parental template, and make up a spherical cluster ofmolecules which resemble a cell. The principal difference from the cell is that it is notenveloped with a lipid membrane. Nevertheless, compartmentalization is achieved here, asthe colony is separated from the surrounding medium. It was shown that all basicbiochemical reactions needed for reproduction and functioning of a living cell, such as RNA18