We may have had several billion years under our belts to figure it out, but scientists today continue to be puzzled by how early cellular life on Earth first came to be.
And, more precisely, the chemical compounds which allowed it to happen.
Now it seems a new study might be able to provide some of the answers, after a team of chemists stumbled upon the ‘missing’ compound that could have been the catalyst for this epic journey to begin.
Researchers have long speculated that a chemical reaction called phosphorylation was a crucial step in the arrival of early life forms.
This is because in order for life to come into existence it needed a few simple ingredients – strands of nucleotides to store genetic information, chains of amino acids for cell function, and lipids to form cell walls and other structures.
These are just basic requirements of all biological structures.
Despite knowing this, scientists had never been able to find a phosphorylating chemical agent that would have plausibly been around at this time, in the right quantities, in the right place, to serve as the trigger.
But now researchers at the Scripps Research Institute have found one that could have played this central role: diamidophosphate (DAP).
Senior author Ramanarayanan Krishnamurthy and his colleagues have previously shown how DAP is able to generate a variety of simple sugars that are present in early life forms.
“That in turn would have allowed other chemistries that were not possible before, potentially leading to the first simple, cell-based living entities,” said Krishnamurthy.
“It reminds me of the fairy godmother in Cinderella, who waves a wand and poof, poof, poof, everything simple is transformed into something more complex and interesting,” he added.
It might have been able to do what early life forms required, but is there evidence that this compound even existed in this period?
Astronomers have found that this magical chemical compound would have indeed been around in the form of phosphorus-nitrogen compounds in the gas and dust of interstellar space.
And it continues to exist in humans today.
“DAP phosphorylates via the same phosphorus-nitrogen bond breakage and under the same conditions as protein kinases, which are ubiquitous in present-day life forms…it also closely resembles what is seen in the reactions at the heart of every cell’s metabolic cycle,” said Krishnamurthy.
Huenda ikawa tulikuwa na mabilioni ya miaka ya kugundua hilo, lakini wanasayansi leo wanaendelea kushangazwa na jinsi uhai wa chembe za kwanza ulivyotokea duniani. Na, kwa usahihi zaidi, misombo ya kemikali ambayo iliruhusu kutokea. Sasa inaonekana utafiti mpya unaweza kutoa baadhi ya majibu, baada ya timu ya wanakemia walijikwaa juu ya kiwanja "kikipo" ambayo inaweza kuwa kichocheo kwa safari hii ya kihistoria kuanza. Watafiti wamedokeza kwa muda mrefu kwamba mmenyuko wa kemikali unaoitwa phosphorylation ulikuwa hatua muhimu katika kuwasili kwa aina za maisha za mapema. Kwa sababu ili uhai uwepo, ulihitaji viungo vichache rahisi - nyuzi za nucleotidi ili kuhifadhi habari za urithi, minyororo ya asidi za amino ili kufanya kazi ya chembe, na lipidi ili kufanyiza kuta za chembe na miundo mingine. Hizi ni matakwa ya msingi tu ya miundo yote ya kibiolojia. Hata hivyo, wanasayansi hawajawahi kupata kemikali inayoweza kuchochea phosphorylation ambayo ingekuwa karibu wakati huo, kwa kiasi sahihi, mahali pazuri, ili kutumika kama kichocheo. Watafiti wa Scripps Research Institute wamegundua kwamba DAP (Dimethylphosphate) ni moja ya kemikali muhimu zaidi katika mfumo wa mwili. Mwandishi mwandamizi Ramanarayanan Krishnamurthy na wenzake wameonyesha hapo awali jinsi DAP inavyoweza kutengeneza sukari nyingi rahisi ambazo zipo katika aina za maisha za mapema. "Hiyo ingekuwa imeruhusu kemia nyingine ambazo hazikuwezekana hapo awali, uwezekano wa kuongoza kwa vitu vya kwanza rahisi, vya kuishi vinavyotegemea seli", alisema Krishnamurthy. "Inanikumbusha juu ya mama wa kifalme wa Cinderella, ambaye hupeperusha fimbo na poof, poof, poof, kila kitu rahisi hubadilishwa kuwa kitu tata na cha kuvutia zaidi", aliongeza. Inawezekana kwamba aliweza kufanya kile ambacho viumbe wa mapema walihitaji, lakini je, kuna uthibitisho kwamba kiwanja hicho kilikuwapo hata wakati huo? Wataalamu wa nyota wamegundua kwamba kemikali hiyo ya ajabu ilikuwa katika gesi na vumbi la anga ya kati ya nyota. Na inaendelea kuwepo katika wanadamu leo. "DAP hu phosphorylates kupitia kuvunjika kwa uhusiano wa phosphorus-nitrogen na chini ya hali sawa na kinases za protini, ambazo ziko kila mahali katika aina za maisha ya leo... pia zinafanana sana na kile kinachoonekana katika athari za moyo wa kila mzunguko wa kimetaboliki wa seli. """