Scientists detect key building blocks for RNA in a cloud in Milky Way
Some of the key building blocks of life — known as nitriles — have been detected by scientists at the heart of our Milky Way galaxy.
They were spotted 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 that nitriles are among the most abundant chemical families in the universe, lending support to the ‘RNA World’ theory of the origin of life.
This suggests life on Earth was originally based on RNA only, and DNA and protein enzymes evolved later.
RNA can fulfil both their functions: storing and copying information like DNA, and catalysing reactions like enzymes.
According to the ‘RNA World’ theory, nitriles and other building blocks for life needn’t necessarily all have arisen on Earth itself.
Discovery: Some of the key building blocks of life — known as nitriles — have been detected by scientists at the heart of our Milky Way galaxy. They were spotted in a molecular cloud of gas and dust (similar to this one pictured) by a team of international researchers
Experts said their discovery suggests that nitriles are among the most abundant chemical families in the universe, lending support to the ‘RNA World’ theory of the origin of life. This suggests that nitriles might have originated in space and ‘hitchhiked’ to the young Earth inside meteorites and comets (stock image)
LIFE ON EARTH MAY HAVE STARTED THANKS TO A MODIFIED VERSION OF MODERN-DAY RNA
Life on Earth may have started thanks to a modified version of modern-day DNA’s sister molecule, scientists believe.
DNA is the backbone of life and almost all of our planet depends on it but, on primordial Earth, a primitive version of its lesser-known sister – RNA – was the focal point for evolution, experts say.
RNA is structurally similar to DNA, except one of the four fundamental pieces, thymine, is substituted for uracil.
This changes the shape and structure of the molecule and researchers have long believed this chemical was vital to the development of Earth’s first lifeforms.
An accidental discovery by Harvard academics published in December 2018 found that a slightly different version of RNA may have been the key ingredient allowing life on Earth to blossom.
Scientists claim that a chemical called inosine may have been present in place of guanine, allowing for life to develop.
This slight change to the bases, known as a nucleotides, may provide the first known proof of the ‘RNA World Hypothesis’ – a theory which claims RNA was integral to primitive lifeforms – they say.
They might also have originated in space and ‘hitchhiked’ to the young Earth inside meteorites and comets during the ‘Late Heavy Bombardment’ period, between 4.1 and 3.8 billion years ago.
In support, nitriles and other precursor molecules for nucleotides, lipids, and amino acids have been found inside recent comets and meteors.
The question is, where in space could these molecules have come from?
Prime 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 around 100 K and is approximately three light years across, with a mass approximately one thousand times that of our Sun.
There’s no evidence that stars are currently forming inside G+0.693-0.027, although scientists suspect that it might evolve to become a stellar nursery in the future.
The team of experts detected a range of nitriles including cyanoallene, propargyl cyanide, cyanopropyne, and possibly cyanoformaldehyde and glycolonitrile, none of which had previously been found in the cloud, which is known as G+0.693-0.027.
Lead study author Dr Víctor M. Rivilla, a researcher at the Center for Astrobiology of the Spanish National Research Council, said: ‘Here we show that the chemistry that takes place in the interstellar medium is able to efficiently form multiple nitriles, which are key molecular precursors of the “RNA World” scenario.’
He added: ‘The chemical content of G+0.693-0.027 is similar to those of other star-forming regions in our galaxy, and also to that of solar system objects like comets.
‘This means that its study can give us important insights about the chemical ingredients that were available in the nebula that give rise to our planetary system.’
Researchers used the 100ft (30m)-wide IRAM telescope Granada, and the 130ft (40m)-wide Yebes telescope in Guadalajara.
The team of experts detected a range of nitriles including cyanoallene, propargyl cyanide, and cyanopropyne, which hadn’t yet been found in G+0.693-0.027, although they had been reported in 2019 in the TMC-1 dark cloud in the constellations 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 detected for the first time 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.
For DNA and RNA to form, two types of chemical building blocks – or nucleobases – are needed
Fellow study author Dr Miguel A Requena-Torres, a lecturer at Towson University in Maryland, said: ‘Thanks to our observations over the past few 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 in the centre of our galaxy, protostars of different masses, meteorites and comets, and also in the atmosphere of Titan, the largest moon of Saturn.’
Author Dr Izaskun Jiménez-Serra, also a researcher at the Center for Astrobiology of the Spanish National Research Council, said: ‘We have detected so far several simple precursors of ribonucleotides, the building blocks of RNA.
‘But there are still key missing molecules that are hard to detect.
‘For example, we know that the origin of life on Earth probably also required other molecules such as lipids, responsible for the formation of the first cells.
‘Therefore we should also focus on understanding how lipids could be formed from simpler precursors available in the interstellar medium.’
The study has been 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 found in the nucleus of all our cells that contains genetic information.
It is shaped like a double-helix and made 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 makes up the D in DNA.
This is a cyclic carbon-based chemical with five carbon atoms arranged as a pentagon.
At the second carbon atom there is an attached singular hydrogen atom in deoxyribose.
This can also have an additional oxygen attached as well.
In this case, the oxygenated chemical then forms what is simply known as ribose – the R in RNA.
The deoxy prefix literally means without oxygen.
Shape of RNA and DNA
RIbose can do almost everything deoxyribose can and also codes for genetic information in some cells and organisms.
When the oxygen is present it drastically alters how the chemicals bonds and sits alongside other molecules.
When oxygen is present – in RNA – it can take a variety of shapes.
When oxygen is not present in this specific location – in DNA – the molecule forms as the iconic double helix.
Uses of RNA
DNA is often broken down into RNA and read by the cells in order to translate and transcribe the genetic code in order to make proteins and other molecules essential for life.
RNA uses three of the same base pairs as DNA: Cytosine, Guanine, Adenine.
The othe base pair, Thymine, is swapped out in RNA for Uracil.
RNA is also often found in simpler organisms, such as bacteria.
It is often also a virus, with Hepatitis, flu and HIV all forms of RNA.
All animal cells use DNA, with one notable exception: the mitochondria.
Mitochondrian are the powerhouses of the cell and turn glucose into pyruvate and then into Adenosine triphosphate (ATP) via the Krebs cycle.
This process is all done in this one organelle in the cells and ATP is the universal form of energy and used throughout every aerobic organism.
In the mitochondria there is a small strand of RNA which is unique in the animal kingdom.
It is passed down from the mother exclusively (the father’s lives in the sperm but is dissolved during fertilisation) and allows humans to trace their maternal lineage back throughout time.