Scientists at The Skaggs Institute for Chemical Biology, a part of The Scripps Research Institute (TSRI), have published a paper in the current issue of Nature that suggests a possible answer to how one of the early steps necessary for the origins of life arose.

Principal Investigator M. Reza Ghadiri, Ph.D., Professor of Chemistry at TSRI, has created a biological polymer that can discriminate between two types of building blocks, taking those that are similar and building a copy of itself with them.

The research article, "A Chiroselective Peptide Replicator," is authored by Alan Saghatelian, Yohei Yokobayashi, Kathy Soltani, and M. Reza Ghadiri.

Information transfer is one of the most fundamental requirements for life. Human DNA, for instance, lives in cell nuclei, where it makes RNA and protein products that carry out the work of the cell, and (in the big picture) our bodies. Part of this work is replicating and dividing the DNA so that the cell can split into two new daughter cells. Life is defined by these replication processes.

What is also known is that all the DNA, RNA, and protein molecules in our bodies are all homochiral. That is, the L-amino acids from which proteins are made and the D-riboses from which DNA and RNA are made are all chiral molecules. They come in two non-superimposable mirror image forms, like your right and left hand. Our bodies can only use the L-form of amino acids (left-handed) and the D-form of ribose molecules (right-handed).

Since only the correct forms of these building blocks of life can be used, a natural question arises. How did the very first biological molecules assemble out of a presumed mixture of right and left-handed building blocks?

To answer this, Ghadiri and his colleagues asked if a molecule that was correctly composed of all right or all left-handed components could replicate itself. They used peptidesshort proteins of 32 amino acidsthat naturally fold into a long helix and stick to an
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Contact: Robin Goldsmith
rgoldsmi@scripps.edu
858-784-8134
Scripps Research Institute
13-Feb-2001