The sea surface microlayer (SSML) is often present at the ocean interface and provides a unique environment for chemical reactions to occur. One such reaction is the heterogeneous oxidation of the SSML components with ozone, which is hypothesized to be an important source of volatile compounds that may participate in marine aerosol formation and growth. To better understand this source, a biologically relevant model SSML is constructed using axenic Thalassiosira pseudonana cultures. This model SSML is shown to be reasonably reproducible for repeated experiments with a biological system and offers considerably more chemical and morphological complexities than single-molecule SSML representations for trying to understand the impact of marine biological processes on the atmosphere. Using proton transfer reaction mass spectrometry, this study demonstrates that C7–C10 gas-phase carbonyls arise from the oxidation of the model SSML with ozone. The ability of gas-phase products of ozone oxidation at the SSML to form aerosol particles was investigated with a scanning mobility particle sizer analyzer to determine the particle size and concentration of newly formed ultrafine aerosol particles. These particles are confirmed to be secondary organic aerosol (SOA) by analyzing their composition with an aerosol mass spectrometer, indicating that the source of the aerosol precursors is the organic material generated by the T. pseudonana cultures. The rates of SOA and carbonyl production are larger for 21 day-old cultures than for 7 day-old cultures, likely due to the release of the organic material from cell lysis in the older cultures. By demonstrating that the heterogeneous oxidation of the SSML forms SOA precursors that contribute to aerosol growth, this study emphasizes the importance of biological processes on the chemical reactions that can occur within the SSML.
Stimuli-responsive materials are exploited in biological, materials, and sensing applications. We introduce a new endogenous stimulus, biomacromolecule crowding, which we achieve by leveraging changes in thermoresponsive properties of polymers upon high concentrations of crowding agents. We prepare poly(2-oxazoline) amphiphiles that exhibit lower critical solution temperatures (LCST) in serum above physiological temperature. These amphiphiles stabilize oil-in-water nanoemulsions at temperatures below the LCST but are ineffective surfactants above the LCST, resulting in emulsion fusion. We find that the transformations observed upon heating nanoemulsions above their surfactant’s LCST can instead be induced at physiological temperatures through the addition of polymers and protein, rendering thermoresponsive materials “crowding responsive.” We demonstrate that the cytosol is a stimulus for nanoemulsions, with droplet fusion occurring upon injection into cells of living zebrafish embryos. This report sets the stage for classes of thermoresponsive materials to respond to macromolecule concentration rather than temperature changes.
Background: Peptide bonds are among the fundamental building blocks of life, polymerizing amino acids to form proteins that make up the structural components of living cells and regulate biochemical processes. The detection of glycine by NASA in comet Wild 2 in 2009 suggests the possibility of the formation of biomolecules in extraterrestrial environments through the interstellar medium. Detected in the dense molecular cloud Sagittarius B2, acetamide is the largest molecule containing a peptide bond and is hypothesized to be the precursor to all amino acids; as such, viability of its formation is of important biological relevance. Methods: Under a proposed mechanism of ammonia and ketene reactants, which have also been detected in dense molecular clouds in the ISM, the reaction pathway for the formation of acetamide was modelled using quantum chemical calculations in Gaussian16, using Austin-Frisch-Petersson functional with dispersion density functional theory at a 6-31G(d) basis set level of theory to optimize geometries and determine the thermodynamic properties for the reaction. Stability of the reactants, transition states, and products were examined to establish a reasonable mechanism. Conclusion: Product formation of acetamide was found to be highly exergonic and exothermic with a low energy barrier, suggesting a mechanism that is viable in the extreme density and temperature conditions found in ISM.
Sequence‐defined polymers can be programmed to self‐assemble into precise nanostructures for applications in biosensing, drug delivery, optics, and molecular computation. Inspired by the natural self‐assembly processes present in biological protein and DNA systems, sets of molecular design rules have emerged across materials classes as instructions to build a variety of tunable structures. This review highlights recent advances in self‐assembled sequence‐defined and sequence‐specific polymers across peptides, peptoids, DNA, and non‐biological synthetic materials, with a focus on synthesis, assembly processes and overall structure. Specifically, these self‐assembled structures are free‐floating, as such constructs can potentially serve as a platform for the aforementioned applications. Emphasis is placed on the molecular design of polymers that self‐assemble into zero‐dimensional, one‐dimensional, two‐dimensional, or three‐dimensional nanostructures. With the development of automated syntheses and increasing control over self‐assembly, future work may focus on emerging classes of compatible hybrid materials with exciting directions toward new architectures and applications.
Background: Many observational studies have found the presence of organic molecules in interstellar medium (ISM) via spectroscopy. NH2CONH2 (urea) was first detected in ISM in 2014. Containing two NH2 groups, urea is an important biological molecule in metabolism as a carrier for waste nitrogen. The discovery of urea in ISM suggests the possibility of the formation of other biomolecules which contain peptide bonds, such as proteins. This supports the origin of life theory proposing that these biomolecules were initially formed in space and later arrived to Earth. Methods: This study investigates two possible reaction pathways for the formation of protonated urea (ureaH+) in dense molecular clouds via molecules previously observed in the ISM, formamide (HCONH2) and protonated hydroxylamine (NH2OH2+). The thermodynamics and optimized geometries were calculated for the final steps of the formation of ureaH+ using Gaussian16 at the APFD/6-31G(d,p) level of theory and a transition state was confirmed. Results: The overall mechanism, as well as the studied proton rearrangement of an intermediate to ureaH+, were found to be exothermic and exergonic processes. Conclusion: From the calculations, the conditions of ISM provide an adequate environment for the formation of ureaH+ and urea.
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