A sensitive quantitative analysis of abiotically synthesized short homopeptides using ultraperformance liquid chromatography and time-of-flight mass spectrometry

In the origins of life field understanding the abiotic polymerization of simple organic monomers (e.g., amino acids) into larger biomolecules (e.g., oligopeptides), remains a seminal challenge. Recently, preliminary observations showed a limited set of peptides formed in the presence of the plausible prebiotic phosphorylating agent, diamidophosphate (DAP), highlighting the need for an analytical tool to critically evaluate the ability of DAP to induce oligomerization of simple organics under aqueous conditions. However, performing accurate and precise, targeted analyses of short oligopeptides remains a distinct challenge in the analytical chemistry field. Here, we developed a new technique to detect and quantitate amino acids and their homopeptides in a single run using ultraperformance liquid chromatography-fluorescence detection/time of flight mass spectrometry. Over an 8-minute retention time window, 18 target analytes were identified and quantitated, 16 of which were chromatographically separated at, or near baseline resolution. Compound identity was confirmed by accurate mass analysis using a 10 ppm mass tolerance window. This method featured limits of detection < 5 nM (< 1 fmol on column) and limits of quantitation (LOQs) <15 nM (< 3 fmol on column). The LODs and LOQs were upwards of ∼28x and ∼788x lower, respectively, than previous methods for the same analytes, highlighting the quantifiable advantages of this new method. Both detectors provided good quantitative linearity (R2 > 0.985) for all analytes spanning concentration ranges ∼3 - 4 orders of magnitude. We performed a series of laboratory experiments to investigate DAP-mediated oligomerization of amino acids and peptides and analyzed experimental products with the new method. DAP readily polymerized amino acids and peptides under a range of simulated environmental conditions. This research underscores the potential of DAP to have generated oligopeptides on the primordial Earth, enhancing prebiotic chemical diversity and complexity at or near the origin of life.

Quantitative Analysis of Glycine Oligomerization by Ion-Pair Chromatography

This paper describes a method for the quantitative analysis of mixtures of glycine and its oligomers by ion-pair high-performance liquid chromatography (IP-HPLC), with a particular focus on applications in origins-of-life research. We demonstrate the identification of glycine oligomers (Gly _n ) up to 14 residues long-the approximate detectable limit of their solubility in water-and measurement of the concentration of these species in the product mixture of an oligomerization reaction. The molar response factors for higher oligomers of glycine-which are impractical to obtain as pure samples-are extrapolated from direct analysis of pure standards of n = 3-6, which established a clear linear trend. We compare and contrast our method to those in previous reports with respect to accuracy and practicality. While the data reported here are specific to the analysis of oligomers of glycine, the approach should be applicable to the design of methods for the analysis of oligomerization of other amino acids.

Effects of pressure on the structure and lattice dynamics of α-glycine: a combined experimental and theoretical study

This concomitant experimental and theoretical study provides a definitive EOS for α-glycine up to the record pressure of 50 GPa.

Behavior of intermolecular interactions in α-glycine under high pressure

Pressure-response on the crystal structure of deuterated α-glycine was investigated at room temperature, using powder and single-crystal X-ray diffraction, and powder neutron diffraction measurements under high pressure. No phase change was observed up to 8.7 GPa, although anisotropy of the lattice compressibility was found. No significant changes in the compressibility and the intramolecular distance between non-deuterated α-glycine and deuterated α-glycine were observed. Neutron diffraction measurements indicated the distance of the intermolecular D⋯O bond along with the c-axis increased with compression up to 6.4 GPa. The distance of another D⋯O bond along with the a-axis decreased with increasing pressure and became the shortest intermolecular hydrogen bond above 3 GPa. In contrast, the lengths of the bifurcated N-D⋯O and C-D⋯O hydrogen bonds, which are formed between the layers of the α-glycine molecules along the b-axis, decreased significantly with increasing pressure. The decrease of the intermolecular distances resulted in the largest compressibility of the b-axis, compared to the other two axes. The Hirshfeld analysis suggested that the reduction of the void region size, rather than shrinkage of the strong N-D⋯O hydrogen bonds, occurred with compression.

Temperature-induced oligomerization of polycyclic aromatic hydrocarbons at ambient and high pressures

Temperature-induced oligomerization of polycyclic aromatic hydrocarbons (PAHs) was found at 500–773 K and ambient and high (3.5 GPa) pressures. The most intensive oligomerization at 1 bar and 3.5 GPa occurs at 740–823 K. PAH carbonization at high pressure is the final stage of oligomerization and occurs as a result of sequential oligomerization and polymerization of the starting material, caused by overlapping of π-orbitals, a decrease of intermolecular distances, and finally the dehydrogenation and polycondensation of benzene rings. Being important for building blocks of life, PAHs and their oligomers can be formed in the interior of the terrestrial planets with radii less than 2270 km.

Formation of Diastereoisomeric Piperazine-2,5-dione from DL-Alanine in the Presence of Olivine and Water

DL-Alanine (Ala) was heated with/without powdered olivine and water at 120 °C for 8 days to investigate the formation of the diastereoisomers of piperazine-2,5-dione (diketopiperazine, DKP). When only DL-Ala was heated with a small amount of water, 3.0 % of DL-Ala changed to cis- and trans-DKP after 8 days. DKPs were not detected after heating when no water was added. The presence of a small amount of water is important factor controlling peptide production rates under thermal conditions. When DL-Ala was heated with olivine powder for 8 days, the yields of cis- and trans-DKP were 6.8 and 4.9 %, respectively. The high yield of cis-DKP compared with trans-DKP was attributed to greater thermal stability of cis-DKP. After heating for 8 days, the diastereoisomeric excess of cis-DKP without olivine was 7.3 %, whereas a much higher value of 16.3 % was obtained in the presence of olivine. Taken together, these results show that olivine is not only an efficient catalyst for the formation of DKPs but that it also play a significant role in determining the diastereoisomer selectivity of these cyclic dipeptides.