Sep 17, 2026 07:09 PM
(This post was last modified: Sep 17, 2026 07:13 PM by C C.)
https://www.sciencealert.com/scientists-...uman-blood
EXCERPTS: If you think you know what DNA looks like, there may be a surprise hiding in your blood. DNA instantly brings to mind its famous double helix. But genetic material does not always remain in that familiar form. Some pieces can fold into compact, four-stranded structures.
These unusual shapes have previously been seen inside cells. Now scientists say they have caught them folded in human blood plasma. So why is DNA in our blood at all?
As cells throughout the body die, they leave behind small fragments of DNA. These enter the bloodstream like pieces of a torn message, carrying clues about what is happening inside us.
Until now, scientists have concentrated on reading the message: its genetic letters, the length of each fragment, and where in the genome it came from. A new preprint study suggests that how the message is folded could matter too. Researchers detected four-stranded structures called G-quadruplexes, or G4s, in genetic material captured directly from human plasma.
"Our study provides, to our knowledge, the first direct biochemical evidence that folded G-quadruplex structures are present in nucleic acids captured directly from human plasma," University of Cologne molecular biologist Robert Hänsel-Hertsch told ScienceAlert.
[...] But the discovery opened another mystery. Although the investigation began with ultrashort DNA, the experiment could not reveal whether the detected G4s were made from DNA or RNA. RNA can fold into the same four-stranded shape, and the detectors recognize the structure rather than the molecule underneath it.
Hänsel-Hertsch described this as "a real limitation". One next step will be to treat the captured material with enzymes that destroy either DNA or RNA before testing it again. Sequencing the folded molecules could then reveal their identity and genomic origin.
Scientists also do not know which tissues released them, or whether the structures folded inside cells or only after entering the bloodstream. So what might they tell us about health?
G4s often occur in parts of the genome involved in controlling genes, and elevated G4 levels have been observed in several tumor types. This raises the possibility that G4s circulating in blood could one day provide information about cancer that cannot be found by reading DNA sequences alone. But this is not a new cancer test.
The study was designed to establish that folded G4s are present in plasma, not to compare people with cancer against healthy participants. Before considering any diagnostic application, researchers must identify the molecules and measure them in carefully characterized groups of patients and healthy volunteers.
Only then will they know whether illness changes the number, origin, or pattern of these folded structures in a useful way. (MORE - missing details)
EXCERPTS: If you think you know what DNA looks like, there may be a surprise hiding in your blood. DNA instantly brings to mind its famous double helix. But genetic material does not always remain in that familiar form. Some pieces can fold into compact, four-stranded structures.
These unusual shapes have previously been seen inside cells. Now scientists say they have caught them folded in human blood plasma. So why is DNA in our blood at all?
As cells throughout the body die, they leave behind small fragments of DNA. These enter the bloodstream like pieces of a torn message, carrying clues about what is happening inside us.
Until now, scientists have concentrated on reading the message: its genetic letters, the length of each fragment, and where in the genome it came from. A new preprint study suggests that how the message is folded could matter too. Researchers detected four-stranded structures called G-quadruplexes, or G4s, in genetic material captured directly from human plasma.
"Our study provides, to our knowledge, the first direct biochemical evidence that folded G-quadruplex structures are present in nucleic acids captured directly from human plasma," University of Cologne molecular biologist Robert Hänsel-Hertsch told ScienceAlert.
[...] But the discovery opened another mystery. Although the investigation began with ultrashort DNA, the experiment could not reveal whether the detected G4s were made from DNA or RNA. RNA can fold into the same four-stranded shape, and the detectors recognize the structure rather than the molecule underneath it.
Hänsel-Hertsch described this as "a real limitation". One next step will be to treat the captured material with enzymes that destroy either DNA or RNA before testing it again. Sequencing the folded molecules could then reveal their identity and genomic origin.
Scientists also do not know which tissues released them, or whether the structures folded inside cells or only after entering the bloodstream. So what might they tell us about health?
G4s often occur in parts of the genome involved in controlling genes, and elevated G4 levels have been observed in several tumor types. This raises the possibility that G4s circulating in blood could one day provide information about cancer that cannot be found by reading DNA sequences alone. But this is not a new cancer test.
The study was designed to establish that folded G4s are present in plasma, not to compare people with cancer against healthy participants. Before considering any diagnostic application, researchers must identify the molecules and measure them in carefully characterized groups of patients and healthy volunteers.
Only then will they know whether illness changes the number, origin, or pattern of these folded structures in a useful way. (MORE - missing details)