Nucleic acid segregation and compartmentalization were likely essential functions that primitive compartment systems resolved during evolution. Recently, polyester microdroplets generated from dehydration synthesis of various α-hydroxy acids (αHA) were suggested as potential primitive compartments. Some of these droplets can differentially segregate and compartmentalize organic dyes, proteins, and nucleic acids. However, the previously studied polyester microdroplets included limited αHA chemical diversity, which may not reflect the chemical diversity available in the primitive Earth environment. Here, we increased the chemical diversity of polyester microdroplet systems by combinatorially adding an αHA monomer with a basic side chain, 4-amino-2-hydroxybutyric acid (4a2h), which was incorporated with different ratios of other αHAs containing uncharged side chains to form combinatorial heteropolyesters via dehydration synthesis. Incorporation of 4a2h in the polymers resulted in the assembly of some polyester microdroplets able to segregate fluorescent RNA or potentially acquire intrinsic fluorescent character, suggesting that minor modifications of polyester composition can significantly impact the functional properties of primitive compartments. This study suggests one process by which primitive chemical systems can increase diversity of compartment "phenotype" through simple modifications in their chemical composition.
One-pot synthesis of sugar-functionalized oligomeric caprolactone was carried out by lipase-catalyzed esterification of ε-caprolactone (ECL) with methyl-d-glucopyranoside (MGP) followed by the elongation of functionalized oligomer chain. Functionalization was performed in a custom-fabricated glass reactor equipped with Rushton turbine impeller and controlled temperature at 60 °C using tert-butanol as reaction medium. The overall reaction steps include MGP esterification of ECL monomer and its subsequent elongation by free 6-hydroxyhexanoate monomer units. A ping-pong bi-bi mechanism without ternary complex was proposed for esterification of ECL and MGP with apparent values of kinetic constant, namely maximal velocity (Vmax ), Michaelis constant for MGP (KmMGP ), and Michaelis constant for ECL (KmECL ) at 3.848 × 10-3 M H-1 , 8.189 × 10-2 M, and 6.050 M, respectively. Chain propagation step of MGP-functionalized ECL oligomer exhibits the properties of living polymerization mechanism. Linear relationship between conversion (%) and number average molecular weight, Mn (g mol-1 ), of functionalized oligomer was observed. Synthesized functionalized oligomer showed narrow range of molecular weight from 1,400 to 1,600 g mol-1 with more than 90% conversion achieved. Structural analysis confirmed the presence of covalent bond between the hydroxyl group in MGP with carboxyl end group of ECL oligomer.
Compartmentalization was likely essential for primitive chemical systems during the emergence of life, both for preventing leakage of important components, i.e., genetic materials, and for enhancing chemical reactions. Although life as we know it uses lipid bilayer-based compartments, the diversity of prebiotic chemistry may have enabled primitive living systems to start from other types of boundary systems. Here, we demonstrate membraneless compartmentalization based on prebiotically available organic compounds, α-hydroxy acids (αHAs), which are generally coproduced along with α-amino acids in prebiotic settings. Facile polymerization of αHAs provides a model pathway for the assembly of combinatorially diverse primitive compartments on early Earth. We characterized membraneless microdroplets generated from homo- and heteropolyesters synthesized from drying solutions of αHAs endowed with various side chains. These compartments can preferentially and differentially segregate and compartmentalize fluorescent dyes and fluorescently tagged RNA, providing readily available compartments that could have facilitated chemical evolution by protecting, exchanging, and encapsulating primitive components. Protein function within and RNA function in the presence of certain droplets is also preserved, suggesting the potential relevance of such droplets to various origins of life models. As a lipid amphiphile can also assemble around certain droplets, this further shows the droplets' potential compatibility with and scaffolding ability for nascent biomolecular systems that could have coexisted in complex chemical systems. These model compartments could have been more accessible in a "messy" prebiotic environment, enabling the localization of a variety of protometabolic and replication processes that could be subjected to further chemical evolution before the advent of the Last Universal Common Ancestor.
The stability of refined, bleached, and deodorized palm olein (RBDPO) was studied under controlled heating conditions. RBDPO was heated continuously for 24 h at 160, 170, and 180 °C, with oil sampled at four hour intervals. Thermo-oxidative alterations were measured through various parameters, such as monomeric oxidized triacylglycerols (oxTAG), total polar compounds (TPC), polymerized triacylglycerols (PTG), oxidative stability, and fatty acid composition. After 24 h of heating, the TPC and triacylglycerol oligomers showed a linear increase with heating time at all heating temperatures. At the end of the heating study, more epoxy acids were formed than keto and hydroxy acids. Moreover, caprylic acid, which was not present in fresh oil, was formed in significant amounts. The increase in oxTAG was strongly correlated with the increase in the p-anisidine value and total oxidation value. The decreases in diacylglycerol and free fatty acids were strongly correlated with an increase in PTG.