Collagen is a mammal ’s favorite protein , more used in the body than any other . It seems dinosaurs appreciated it too , as traces have been found in some fossils , but only now have chemists worked out how the commonly fragile molecule could survive for so long .
A few decades ago , collagen was most famous for being injected into hoi polloi ’s peel to make them take care young . It already had many other applications by then , such as being heated to make gel for sweets and jellies and as a casing for sausages . Long before that , collagen mucilage were in use at least8,000 age ago . Today it is the trendy linear in a lot of foods , but it also make up a substantial portion of our bodies .
We do n’t wait to regain collagen in fossils more than a few thousand years old , however , because it is held together by peptide adhesion that get broken when wet . However , a fewremarkable dinosaur fossilsstill have intact collagen , include one specimen of aLufengosaurusdated to the early Jurassic,195 million years ago .
A dinosaur with a schematic of the carbonyl groups, showing the bonds between carbon atoms in some and oxygens in others that keep water out.Image Credit: ACS Central Science CC-By-4.0
That ’s astonishing for a protein that at room temperature ordinarily loses half its bonds every 500 age . New research attributes this survival to an program of thePauli elision principle , which you may recall from high shoal chemistry .
In the normal row of result , water breaks collagen ’s peptide bonds through hydrolysis , even whenbacteria do n’t get at it . Dry condition can reach out its lifespan – that glue sample number from the desert around the Dead Sea – but everywhere has wet periods since the Mesozoic .
scientist from MIT seek to explain the collagen sample ’ survival and found carbonyl chemical group interactions seem to be responsible . “ We provide evidence that that fundamental interaction prevents weewee from attacking the peptide Bond and cleaving them . That just fly in the face of what happens with a normal peptide bond , ” senior author Professor Ron Raines say in astatement .
The essential bonds within collagen are between carbon and nitrogen particle in neighboring amino acid . Taking advantage of its capacity to imprint four hamper , the carbon paper atom allocates two to an O atom to form a carbonyl group , leaving an negatron free to bind .
What had not previously been recognize is when these carbonyl groups can bond to each other they make a water - resistant link . This is where Pauli ’s principle comes in . Pauli realized particle ca n’t have more than one electron with a special twist in an orbital . The carbonyl - carbonyl bail effectively max out the usable orbitals , leaving nowhere for the electrons from water to get in to initiate crack-up .
Raines ’ team produced two proteins with collagen - like composition in forms capable of turning into each other . They named one cis and the other trans ( the term were common in chemistry before being caught in a culture war ) . The cis form let on down on photograph to water , but the collagen - similar trans form resists , thanks to its fill orbitals .
“ A peptide bond is either cis or trans , and we can convert the cis to trans proportion . By doing that , we can mimic the instinctive state of collagen or create an unprotected peptide bond . And we saw that when it was unprotected , it was not long for the world , ” Raines said .
For whatever reason the collagen in a 68 - million - year - oldT. rexand a 195 - million - year - oldLufengosaurus(among others ) must have been mostly trans , allowing it to subsist until we could study it .
Similar bonds have been regard in other protein , but in those causa , while the Julian Bond may suffer , the remainder of the proteins get destroyed by hydrolysis . “ Collagen is all threefold helices , from one goal to the other , ” Raines sound out . “ There ’s no weak connexion , and that ’s why I think it has survived . ”
There ’s a intellect dinosaurs and mammals alike make such widespread usage of collagen , both in our finger cymbals and in the ligaments that touch base them , and in humans ’ fount , our skin . “ Collagen is the scaffold that holds us together , ” Raines said . “ What induce the collagen protein so stable , and such a good choice for this scaffold , is that unlike most proteins , it ’s fibrous . ”
Moreover , our bones and ligament are expose to H2O - based liquids like blood . Without a way to resist hydrolysis , the more permanent parts of our bodies would ask to be always rebuilt , so collagen plays a full of life function in our longevity .
The study is capable access inACS Central Science .
