Of Montmorillonite and Men

by Gabrielle DeMarco on April 19, 2012

Decades ago, Rensselaer chemist James Ferris created long chains of RNA molecules in the lab using simple clay materials and basic organic molecules as a catalyst. The discovery helped launch a theory on how life on Earth may have arisen so many years ago – a theory that still stands strong today.

Many astrobiologists support the theory that life first arose as RNA-based instead of DNA-based. The theory, known widely as the RNA World Hypothesis, is a highly plausible pathway to life because RNA, like DNA, can store genetic information and catalyze many of the chemical reactions required to maintain cellular life. Though well supported, the theory still lacks some important pieces of evidence. Most critically, scientists are trying to prove what the actual process was that caused the giant leap from the proverbial “primordial soup” to the formation of RNA.

In Ferris’ well-known theory, a simply clay material likely to be found on the surface of Earth around the time of life’s formation called montmorillonite served as a catalyst for the formation of RNA. He supported this theory in the landmark paper in the journal Nature when he grew chains of RNA molecules as long as 50 molecules at near room temperature. It was an exceptional feat of chemistry that still resonates today.

This week, nearly 50 years after Ferris joined Rensselaer, several of his mentees, colleagues, and collaborators are coming together to honor his sustained legacy in origins of life research. The group is dedicating a session at this year’s Astrobiology Science Conference to Ferris and his work. The conference is the largest gathering of astrobiology scientists in the world.

And despite his long career and legacy in the field, Ferris and his long-time colleagues within his laboratory here at Rensselaer continue to regularly publish new research on the origins of life and the possibilities of the humble montmorillonite.

For example, Ferris and his research partners recently published new findings in both Biochemical and Biophysical Research Communications and Origin of Life and Evolution of Biospheres that further support the theory of montmorillonite as a sparkplug for life. They found that as the chains of RNA formed by montmorillonite grow longer in length, they also become more specifically organized.

One of the main issues with all existing theories on the origins of life has to do with the basic arrangement of our molecules. Molecules can either be chiral or achiral. Chiral objects are mirror images of one another. The most common example of chiral objects is human hands. As anyone who has only mismatched gloves can tell you, you can’t stack a left-handed glove on a right-handed glove and have them match up (those darn thumbs). Achiral molecules are exact copies of one another in their mirror image (think of two beach balls).

What in the world does this have to do with the origins of life? Well, life is homochiral. This means that life is comprised of molecules of the same chiral arrangement. So if two chiral molecules are mirror images of one another (right- and left-handed if you will); two homochiral molecules are exact copies of one another in the same right- or left-handed arrangement. In other words, the molecules that make up our proteins, RNA, DNA and other vital components are either right- or left-“handed”. And so, our RNA and DNA is made up of only right-handed molecules. Any significant deviations from this arrangement and we would no longer have the classic double helix structure. Try stacking a bunch of right-handed gloves on top of one another and then throwing in the occasional left-handed one. The structure would be wonky and unsound. More evidence is pointing to the fact that homochirality of our molecules proceeded life. Thus, any theory on the origins of life worth its salt must account for the jump from a jumble of mismatched molecules to a neat homochiral combination. So how on Earth or Mars or even Gliese 581-g did life become homochiral?

The problem with uncovering our homochiral roots is that the precursors to life are actually a little too easy to grow in the lab. Sort of creepy to think about, but the equipment and processes of the modern chemistry laboratory can make easy work of creating organic molecules. But, recreating homochiral molecules has been very hard for research to do in the lab without resorting to the use of harsh chemicals or processes that weren’t present on the early Earth and therefore aren’t likely natural pathways to life.

In their most recent studies of montmorillonite, Ferris and his team discovered that as chains of RNA were formed, the longer they grew the more homochiral they became. And it wasn’t a tiny increase. Homochirality increased from 64 to 97 percent. This means that something about the clay may be causing the molecules to sort themselves into the correct formation as they grow without harsh chemicals or high temperatures. The work continues to support the theory Ferris has long supported and provides an important framework of knowledge on the potential chemical origins of each of us.