Abstract
The biomolecular homochirality in living organisms has been investigated for decades, but its origin remains poorly understood. It has been shown that circular polarized light (CPL) and other energy sources are capable of inducing small enantiomeric excesses (ees) in some primary biomolecules, such as amino acids or sugars. Since the first findings of amino acids in carbonaceous meteorites, a scenario in which essential chiral biomolecules originate in space and are delivered by celestial bodies has arisen. Numerous studies have thus focused on their detection, identification, and enantiomeric excess calculations in extraterrestrial matrices. In this review we summarize the discoveries in amino acids, sugars, and organophosphorus compounds in meteorites, comets, and laboratory-simulated interstellar ices. Based on available analytical data, we also discuss their interactions with CPL in the ultraviolet (UV) and vacuum ultraviolet (VUV) regions, their abiotic chiral or achiral synthesis, and their enantiomeric distribution. Without doubt, further laboratory investigations and upcoming space missions are required to shed more light on our potential extraterrestrial molecular origins.
Highlights
carbon monoxide (CO) was Interstellar Ices found confirming the previous observations. They detected acetone, acetaldehyde and Laboratory interstellar ice chemistry has for a long time only been applied for the synthesis propionaldehyde; three carbonyl compounds able to undergo aldolic condensations leading to sugar and detection of amino acids, but recently aldehydes and sugars were found in such matrices as formation
As amino acids were the original stimuli for the search for chiral biomolecules in extraterrestrial matter, they have been extensively studied over the years
The solid understanding of the amino acid interactions with circular polarized light (CPL) and its consequences, along with the discovery of CPL in the universe, enabled the scientific community to evolve a plausible scenario where the pathways to biological homochirality was initiated in space
Summary
Life’s origin remains one of the most enigmatic and fascinating phenomena, requiring a thoughtful scientific explanation. As a matter of fact, CD represents the difference in the molar extinction coefficient (or more in absorption) at a given wavelength between both helicities of CPL by an enantiopure compound: This differential absorption between the two helicities of CPL results in unequal photolysis rates of two enantiomers when irradiated with either left- or right-handed CPL. Braun through same wavelength regions, giving rise to the possibility of inducing the same sign of ee in all irradiation of a racemic mixture of α-bromopropanoic acid ethyl ester in solution [24]. The expected of 13 C labelled racemic Ala were prepared and combined with improved analyses through the use of mirror effect between r- and l-CPL has been observed [28,29]; to ensure no experimental bias due to enantioselective multidimensional to aprepared time-of-flight mass spectrometer contamination, isotropic films gas of 13chromatography. Of reaction rates ξ ranging from 99.93% to 99.97% (Figure 1)
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