Biotransformation of sulfamethoxazole by microalgae: Removal efficiency, pathways, and mechanisms

Recently, the biotransformation of sulfamethoxazole (SMX) by microalgae has attracted increasing interest. In particular, cytochrome P450 (CYP450) has been suggested to be the main enzymatic contributor to this biodegradation. However, the molecular evidence of CYP450 enzymes being involved in SMX biodegradation remains relatively unclear, hindering its applicability. Herein, the biodegradation of SMX by Chlorella sorokiniana (C. sorokiniana) was investigated, and comprehensively elucidated the reaction mechanism underlying CYP450-mediated SMX metabolism. C. sorokiniana was able to efficiently remove over 80% of SMX mainly through biodegradation, in which CYP450 enzymes responded substantially to metabolize SMX in cells. Additionally, screening of transformation products (TPs) revealed that N⁴-hydroxylation-SMX (TP270) was the main TP in the SMX biodegradation pathway of microalgae. Molecular dynamics (MD) simulation suggested that the aniline of SMX was the most prone to undergo metabolism, while density functional theory (DFT) indicated that SMX was metabolized by CYP450 enzymes through H-abstraction-OH-rebound reaction. Collectively, this work reveals key details of the hydroxylamine group of SMX, elucidates the SMX biodegradation pathway involving CYP450 in microalgae in detail, and accelerates the development of using microalgae-mediated CYP450 to eliminate antibiotics.

Gas-phase identification of (Z)-1,2-ethenediol, a key prebiotic intermediate in the formose reaction

Prebiotic sugars are thought to be formed on primitive Earth by the formose reaction. However, their formation is not fully understood and it is plausible that key intermediates could have formed in extraterrestrial environments and subsequently delivered on early Earth by cometary bodies. 1,2-Ethenediol, the enol form of glycolaldehyde, represents a highly reactive intermediate of the formose reaction and is likely detectable in the interstellar medium. Here, we report the identification and first characterization of (Z)-1,2-ethenediol by means of rotational spectroscopy. The title compound has been produced in the gas phase by flash vacuum pyrolysis of bis-exo-5-norbornene-2,3-diol at 750 °C, through a retro-Diels-Alder reaction. The spectral analysis was guided by high-level quantum-chemical calculations, which predicted spectroscopic parameters in very good agreement with the experiment. Our study provides accurate spectral data to be used for searches of (Z)-1,2-ethenediol in the interstellar space.

Pathways for the Formation of Formamide, a Prebiotic Biomonomer: Metal-Ions in Interstellar Gas-Phase Chemistry

The chemistry occurring in the interstellar medium (ISM) is an active area of contemporary research. New aspects of interstellar chemistry are getting unraveled regularly. In this context, the role of metal-ions in the chemistry occurring in the ISM is not well-studied so far. Herein, we highlight the role of metal-ions in interstellar chemistry. For this purpose, we choose the problem of gas-phase formamide formation in interstellar molecular clouds. Formamide is a key biomonomer and contains the simplest peptide [-(C═O)-NH-] linkage. With its two electronegative atoms ("O" and "N"), it provides an excellent platform to probe the role of the metal-ions. The metal-ions chosen are Na⁺, K⁺, Al⁺, Mg⁺, and Mg²⁺-all of them present in the ISM. The metal-ions are studied in three different forms as bare positively charged ions, as hydrated metal-ions co-ordinated with a molecule of water, and when the metal-ions are part of a neutral covalent molecule. With the aid of electronic structure calculations [CCSD(T) and DFT methods], we study different gas-phase pathways which result in the generation of interstellar formamide. Throughout our study, we find that metal-ions lower the barriers (with Mg⁺, Mg⁺⁺, and Al⁺ offering maximal stabilization of the transition states) and facilitate the reactions. The chemical factors influencing the reactions, how we consider the putative conditions in the ISM, the astrochemical implications of this study, and its connection with terrestrial prebiotic chemistry and refractory astrochemistry are subsequently presented. Based on our results, we also recommend the detection of two new closed-shell molecules, NH₂CH₂OH (aminomethanol) and CH₂NH₂⁺ (iminium ion), and two open-shell molecules, CONH₂ (carbamyl radical) and HCONH (an isomer of carbamyl radical), in the ISM.

A new multi-beam apparatus for the study of surface chemistry routes to formation of complex organic molecules in space

A multi-beam ultra-high vacuum apparatus is presented. In this article, we describe the design and construction of a new laboratory astrophysics experiment-VErs de NoUvelles Synthèses (VENUS)-that recreates the solid-state non-energetic formation conditions of complex organic molecules in dark clouds and circumstellar environments. The novel implementation of four operational differentially pumped beam lines will be used to determine the feasibility and the rates for the various reactions that contribute to formation of molecules containing more than six atoms. Data are collected by means of Fourier transform infrared spectroscopy and quadrupole mass spectrometry. The gold-coated sample holder reaches temperatures between 7 K and 400 K. The apparatus was carefully calibrated and the acquisition system was developed to ensure that experimental parameters are recorded as accurately as possible. A great effort has been made to have the beam lines converge toward the sample. Experiments have been developed to check the beam alignment using reacting systems of neutral species (NH₃ and H₂CO). Preliminary original results were obtained for the {NO + H} system, which shows that chemistry occurs only in the very first outer layer of the deposited species, that is, the chemical layer and the physical layer coincide. This article illustrates the characteristics, performance, and future potential of the new apparatus in view of the forthcoming launch of the James Webb Space Telescope. We show that VENUS will have a major impact through its contributions to surface science and astrochemistry.

Toward the RNA-World in the Interstellar Medium-Detection of Urea and Search of 2-Amino-oxazole and Simple Sugars

In the past decade, astrochemistry has witnessed an impressive increase in the number of detections of complex organic molecules. Some of these species are of prebiotic interest such as glycolaldehyde, the simplest sugar, or aminoacetonitrile, a possible precursor of glycine. Recently, we have reported the detection of two new nitrogen-bearing complex organics, glycolonitrile and Z-cyanomethanimine, known to be intermediate species in the formation process of ribonucleotides within theories of a primordial RNA-world for the origin of life. In this study, we present deep and high-sensitivity observations toward two of the most chemically rich sources in the galaxy: a giant molecular cloud in the center of the Milky Way (G + 0.693-0.027) and a proto-Sun (IRAS16293-2422 B). Our aim is to explore whether the key precursors considered to drive the primordial RNA-world chemistry are also found in space. Our high-sensitivity observations reveal that urea is present in G + 0.693-0.027 with an abundance of ∼5 × 10^-11. This is the first detection of this prebiotic species outside a star-forming region. Urea remains undetected toward the proto-Sun IRAS16293-2422 B (upper limit to its abundance of ≤2 × 10^-11). Other precursors of the RNA-world chemical scheme such as glycolaldehyde or cyanamide are abundant in space, but key prebiotic species such as 2-amino-oxazole, glyceraldehyde, or dihydroxyacetone are not detected in either source. Future more sensitive observations targeting the brightest transitions of these species will be needed to disentangle whether these large prebiotic organics are certainly present in space.