Some of life’s most important building blocks – known as nitriles – have been discovered by scientists at the heart of our Milky Way.
They were discovered in a molecular cloud of gas and dust by a team of international researchers using two telescopes in Spain.
Nitriles are important building blocks for RNA – a DNA-like nucleic acid present in all living cells.
Experts said their discovery suggests nitriles are among the most abundant chemical families in the universe, supporting the RNA World theory of the origin of life.
This suggests that life on Earth was originally based only on RNA, and DNA and protein enzymes evolved later.
RNA can perform both functions: store and copy information like DNA and catalyze reactions like enzymes.
According to the “RNA World” theory, nitriles and other building blocks of life do not necessarily all have to have originated on Earth itself.
Discovery: Some of life’s most important building blocks – known as nitriles – have been discovered by scientists at the heart of our Milky Way galaxy. They were discovered by a team of international researchers in a molecular cloud of gas and dust (similar to the one pictured here).
Experts said their discovery suggests nitriles are among the most abundant chemical families in the universe, supporting the RNA World theory of the origin of life. This suggests that nitriles may have originated in outer space and hitchhiked to young Earth in meteorites and comets (stock image).
LIFE ON EARTH MAY HAVE BEGUN THANKS TO A MODIFIED VERSION OF MODERN RNA
Life on Earth may have originated thanks to a modified version of modern DNA’s sister molecule, scientists believe.
DNA is the backbone of life and almost our entire planet depends on it, but on Primordial Earth a primitive version of its lesser known sister – RNA – was the focal point of evolution, experts say.
RNA is structurally similar to DNA except that uracil is replaced with one of the four basic parts, thymine.
This changes the shape and structure of the molecule, and researchers have long believed that this chemical was crucial in the evolution of Earth’s first life forms.
A chance discovery by Harvard academics, published in December 2018, found that a slightly different version of RNA may have been the key ingredient that allowed life to flourish on Earth.
Scientists claim that instead of guanine, a chemical called inosine may have been present, which allowed life to evolve.
This subtle change in bases known as nucleotides could provide the first known evidence for the “RNA World Hypothesis” — a theory claiming that RNA was an integral part of primitive life forms, they say.
They could also have originated in outer space and “hitched” in meteorites and comets to young Earth during the “late heavy bombardment” period 4.1 to 3.8 billion years ago.
In support, nitriles and other precursors to nucleotides, lipids, and amino acids have been found in recent comets and meteors.
The question is where in space these molecules could have come from.
Main candidates are molecular clouds, which are dense and cold regions of the interstellar medium and are suitable for the formation of complex molecules.
For example, the molecular cloud G+0.693-0.027 has a temperature of about 100 K, a diameter of about three light-years and a mass about a thousand times that of our Sun.
There is no evidence that stars are currently forming within G+0.693-0.027, although scientists suspect it may evolve into a stellar nursery in the future.
The team of experts discovered a range of nitriles, including cyanoallene, propargyl cyanide, cyanopropine and possibly cyanoformaldehyde and glycolonitrile, none of which had previously been found in the cloud known as G+0.693-0.027.
The lead author of the study, Dr. Víctor M. Rivilla, a researcher at the Spanish National Research Council’s Center for Astrobiology, said: “Here we show that the chemistry taking place in the interstellar medium is capable of efficiently forming multiple nitriles, which are the key molecular precursors of the ‘RNA World” scenarios.”
He added: “The chemical content of G+0.693-0.027 is similar to that of other star-forming regions in our galaxy and also to that of Solar System objects such as comets.
“This means that his study can give us important insights into the chemical components that were available in the nebula that gave rise to our planetary system.”
Researchers used the 100-foot (30 m) wide IRAM telescope in Granada and the 130-foot (40 m) wide Yebes telescope in Guadalajara.
The team of experts discovered a number of nitriles, including cyanoallene, propargyl cyanide and cyanopropine, which had not yet been found in G+0.693-0.027, although they had been reported in 2019 in the dark cloud TMC-1 in the constellation Taurus and Auriga, a molecular cloud with very different conditions than G+0.693-0.027.
The scientists also found possible evidence of cyanoformaldehyde and glycolonitrile.
Cyanoformaldehyde was first detected in the molecular clouds TMC-1 and Sgr B2 in the constellation Sagittarius and glycolonitrile in the sun-like protostar IRAS16293-2422 B in the constellation Ophiuchus.
Two types of chemical building blocks—or nucleobases—are needed for DNA and RNA to form
fellow student Dr. Miguel A. Requena-Torres, associate professor at Towson University in Maryland, said, “Thanks to our observations over the past several years, including the present results, we now know that nitriles are among the most abundant chemical families in the universe.
“We have found them in molecular clouds at the center of our galaxy, protostars of various masses, meteorites and comets, and also in the atmosphere of Titan, Saturn’s largest moon.”
The author Dr. Izaskun Jiménez-Serra, also a researcher at the Spanish National Research Council’s Center for Astrobiology, said: “We have so far discovered several simple precursors of ribonucleotides, the building blocks of RNA.
“But important molecules are still missing that are difficult to discover.
“For example, we know that other molecules such as lipids, which are responsible for the formation of the first cells, were probably also required for the emergence of life on Earth.
“Therefore, we should also focus on understanding how lipids might be formed from simpler precursors available in the interstellar medium.”
The study was published in the journal Frontiers.
DNA AND RNA EXPLAINED: THE MOLECULES THAT CONTAIN THE GENETIC INFORMATION FOR LIFE
DNA – deoxyribonucleic acid – is widely known as the molecule that resides at the nucleus of all our cells and contains genetic information.
It has the shape of a double helix and is made up of small sections called nucleotides.
Each nucleotide contains a nucleobase, a sugar, and a phosphate group.
The sugar component in this particular molecule is called deoxyribose and forms the D in DNA.
This is a carbon-based cyclic chemical with five carbon atoms arranged as a pentagon.
The second carbon atom in deoxyribose has an attached singular hydrogen atom.
Additional oxygen can also be connected to this.
In this case, the oxygenated chemical then forms what is known simply as ribose – the R in RNA.
That deoxy Prefix means literally without oxygen.
Form of RNA and DNA
RIbose can do almost everything deoxyribose can, and also encodes genetic information in some cells and organisms.
When the oxygen is present, it drastically changes how the chemicals combine and sit alongside other molecules.
When oxygen is present – in RNA – it can take different forms.
When there is no oxygen at that specific site – in the DNA – the molecule forms the iconic double helix.
Use of RNA
DNA is often broken down into RNA and read by cells to translate and transcribe the genetic code to make proteins and other vital molecules.
RNA uses three of the same base pairs as DNA: cytosine, guanine, adenine.
The other base pair, thymine, is exchanged for uracil in the RNA.
RNA is also often found in simpler organisms such as bacteria.
Often it is also a virus, in the case of hepatitis, influenza and HIV all forms of RNA.
All animal cells use DNA, with one notable exception: the mitochondria.
Mitochondria are the cell’s powerhouses, converting glucose into pyruvate and then into adenosine triphosphate (ATP) via the Krebs cycle.
This process all takes place in this one organelle in the cells and ATP is the universal form of energy and is used in every aerobic organism.
Inside the mitochondria is a small strand of RNA that is unique in the animal kingdom.
It is passed exclusively from the mother (the father lives in the sperm but is dissolved during fertilization) and allows people to trace their maternal lineage back through time.