Hasil untuk "Organic chemistry"

Andrés M Bran, Sam Cox, Oliver Schilter et al.

Large language models (LLMs) have shown strong performance in tasks across domains but struggle with chemistry-related problems. These models also lack access to external knowledge sources, limiting their usefulness in scientific applications. We introduce ChemCrow, an LLM chemistry agent designed to accomplish tasks across organic synthesis, drug discovery and materials design. By integrating 18 expert-designed tools and using GPT-4 as the LLM, ChemCrow augments the LLM performance in chemistry, and new capabilities emerge. Our agent autonomously planned and executed the syntheses of an insect repellent and three organocatalysts and guided the discovery of a novel chromophore. Our evaluation, including both LLM and expert assessments, demonstrates ChemCrow’s effectiveness in automating a diverse set of chemical tasks. Our work not only aids expert chemists and lowers barriers for non-experts but also fosters scientific advancement by bridging the gap between experimental and computational chemistry. Large language models can be queried to perform chain-of-thought reasoning on text descriptions of data or computational tools, which can enable flexible and autonomous workflows. Bran et al. developed ChemCrow, a GPT-4-based agent that has access to computational chemistry tools and a robotic chemistry platform, which can autonomously solve tasks for designing or synthesizing chemicals such as drugs or materials.

J. Kroll, J. Seinfeld

D. Monteith, J. Stoddard, C. Evans et al.

K. Tan, Samrat Ghosh, Zhiyong Wang et al.

L. Hammett

E. Anslyn, D. Dougherty

H. Zollinger

Z. Rappoport, Y. Apeloig

D. Barton, W. Ollis

I. Gutman, O. Polansky

Michael B. Smith, J. March

Hudson G. Roth, N. Romero, David A. Nicewicz

U. Wille

Claudio Hernández-Vera, Viviana V. Guzmán, Jérôme Pety et al.

(Abridged) Complex organic molecules (COMs) are considered essential precursors to prebiotic species. While COMs were once expected to be efficiently destroyed under UV-irradiated conditions, detections in photodissociation regions (PDRs) have challenged this view. However, the mechanisms by which UV radiation contributes to their formation are still uncertain. Here, we present moderately resolved maps of simple and complex organic molecules at the UV-illuminated edge of the Horsehead nebula, obtained by combining ALMA and IRAM 30m single-dish observations at $\sim 15^{\prime\prime}$ resolution. We analyze the spatial distribution of species such as C$^{17}$O, CH$_2$CO, CH$_3$CHO, HNCO, CH$_3$CN, and HC$_3$N. By incorporating previous C$^{17}$O and C$^{18}$O single-dish data as well as PdBI maps of H$_2$CO and CH$_3$OH, we derive profiles of gas density, temperature, thermal pressure, and column densities of the organic species as a function of distance from the UV source. Our results show that most organic species$-$particularly H$_2$CO, CH$_2$CO, CH$_3$CHO, HNCO, and CH$_3$CN$-$exhibit enhanced column densities at the UV-illuminated edge compared to cloud interiors, possibly indicating efficient dust-grain surface chemistry driven by the diffusion of atomic C and radicals produced via photodissociation of CO and CH$_3$OH, as supported by recent laboratory experiments. The exceptions, HC$_3$N and CH$_3$OH, can be attributed to inefficient formation on dust grains and ineffective non-thermal desorption into the gas phase, respectively. Additionally, contributions from gas-phase hydrocarbon photochemistry, possibly seeded by grain-surface products, cannot be ruled out. Further chemical modeling is needed to confirm the efficiency of these pathways for the studied species, which could have important implications for other cold, UV-irradiated environments such as protoplanetary disks.

Giuseppe De Giorgio, Pasquale D'Angelo, Giuseppe Tarabella et al.

In this article, we attempt to make a conceptual bridge between the research in biology, pre-biotic chemistry, biomimetics, and the tools used in organic bioelectronics in terms of materials and devices. The goal is discussing how materials and devices of organic bioelectronics can be exploited and used at the interface with biology, but also how, and at what extent, they can be adapted to mimicking nature-inspired properties, herein including unconventional computing strategies. The idea is to provide new hints and solid hypotheses for designing niche experiments that could benefit from a proper interaction, even at a basic communicative level, between materials science and biotechnology. The finale long-term vision goal being the vision of collecting experimental data that may help to made a step forward toward the implementation of the transition from inanimate objects to animated beings. The mathematical model canonically considered in this work is the Navier-Stokes-Nernst-Planck (NPNS) Model which is often used to model a charged continuum system such as the organic electrochemical transistors.

D. Navarro-Almaida, A. Taillard, A. Fuente et al.

Grain-surface chemistry plays a crucial role in the formation of molecules of astrobiological interest, including H$_{2}$S and complex organic molecules (COMs). They are commonly observed in the gas phase toward star-forming regions, but their detection in ices remains limited. Combining gas-phase observations with chemical modeling is therefore essential for advancing our understanding of their chemistry. In this paper we investigate the factors that promote or hinder molecular complexity combining gas-phase observations of CH$_{3}$OH, H$_{2}$S, OCS, N$_{2}$H$^{+}$, and C$^{18}$O with chemical modeling in two dense cores: Barnard-1b and IC348. We observed millimeter emission lines of CH$_{3}$OH, H$_{2}$S, OCS, N$_{2}$H$^{+}$, and C$^{18}$O along strips using the IRAM 30m and Yebes 40m telescopes. We used the gas-grain chemical model \texttt{Nautilus} to reproduce the observed abundance profiles adjusting parameters such as initial sulfur abundances and binding energies. H$_{2}$S, N$_{2}$H$^{+}$ and C$^{18}$O gas-phase abundances vary up to one order of magnitude towards the extinction peak. CH$_{3}$OH abundance remains quite uniform. These abundances can only be reproduced assuming a decreasing sulfur budget, which lowers H$_{2}$S and enhances CH$_{3}$OH abundances. Decreasing binding energies, which are expected in CO-rich apolar ices, are also required. The sulfur depletion required by H$_2$S is generally higher than that required by CH$_3$OH, suggesting unknown sulfur sinks. These findings highlight the intricate relationship between sulfur chemistry and COM formation, driven by the competition between sulfur and CO for hydrogen atoms. Our study emphasizes that the growth of CO ice and the progressive sequestration of hydrogen atoms by sulfur are critical in determining whether chemical complexity can develop, providing key insights into the early stages of star and planet formation.

Min Ye, Lifen Meng

This study used Houttuynia cordata as the precursor to prepare high fluorescence quantum yield carbon quantum dots (Hc-CQDs) by a simple hydrothermal method. The surface of the Hc-CQDs contained abundant functional groups, such as carboxyl, hydroxyl, and amino groups, which indicated the Hc-CQDs had good water solubility. On the basis of the excellent fluorescence characteristics of Hc-CQDs, a sensor was constructed to achieve high selectivity detection of Cr³⁺, and the detection limit of the Hc-CQDs was 49 μg/L. The sensor also exhibited strong anti-interference ability and excellent reproducibility, which was used for the determination of Cr³⁺ in environmental water samples, and its spiked recovery rate reached over 90%. Therefore, the Hc-CQDs had potential application in the analysis.

Fotios A. Lyssaios, Azucena González-Coloma, María Fe Andrés et al.

Endolichenic fungi represent an important ecological group of microorganisms that form associations with photobionts in the lichen thallus. These endofungi that live in and coevolve with lichens are known for synthesizing secondary metabolites with novel structures and diverse chemical skeletons making them an unexplored microbial community of great interest. As part of our search for new phytoprotectants, in this work, we studied the endolichenic fungus <i>Xylaria</i> sp. isolated from the lichen <i>Hypogymnia tubulosa</i>, which grows as an epiphyte on the bark of the endemic Canarian tree <i>Pinus canariensis</i>. From the extract of the liquid fermentation, we isolated two unreported piliformic derivatives, (+)-9-hydroxypiliformic acid (<b>1</b>) and (+)-8-hydroxypiliformic acid (<b>2</b>), along with four previously reported compounds, (+)-piliformic acid (<b>3</b>), hexylaconitic acid A anhydride (<b>4</b>), 2-hydroxyphenylacetic acid (<b>5</b>), and 4-hydroxyphenylacetic acid (<b>6</b>). Their structures were elucidated based on NMR and HRESIMS data. The extract and the isolated compounds were tested for their insect antifeedant (<i>Myzus persicae</i>, <i>Rhopalosiphum padi</i>, and <i>Spodoptera littoralis</i>), antifungal (<i>Alternaria alternata</i>, <i>Botrytis cinerea</i>, and <i>Fusarium oxysporum</i>), nematicidal (<i>Meloidogyne javanica</i>), and phytotoxic effects on mono- and dicotyledonous plant models (<i>Lolium perenne</i> and <i>Lactuca sativa</i>). Compounds <b>4</b>, <b>5</b>, and <b>6</b> were effective antifeedants against <i>M. persicae</i> and <b>4</b> was also active against <i>R. padi</i>. Moreover, <b>3</b> and <b>4</b> showed antifungal activity against <i>B. cinerea</i> and <b>4</b> was the only nematicidal. The extract had a strong phytotoxic effect on <i>L. sativa</i> and <i>L. perenne</i> growth, with compounds <b>3</b>, <b>4</b>, and <b>5</b> identified as the phytotoxic agents, while at low concentrations compounds <b>3</b> and <b>4</b> stimulated <i>L. sativa</i> root growth.

Ha L. Nguyen, F. Gándara, H. Furukawa et al.

Francisco Muñoz, Ziyad S. Haidar, Andreu Puigdollers et al.

The demand for novel tissue grafting and regenerative wound care biomaterials is growing as traditional options often fall short in biocompatibility, functional integration with human tissue, associated cost(s), and sustainability. Salmon aquaculture generates significant volumes of waste, offering a sustainable opportunity for biomaterial production, particularly in osteo-conduction/-induction, and de novo clinical/surgical bone regeneration. Henceforth, this study explores re-purposing salmon waste through a standardized pre-treatment process that minimizes the biological <i>waste</i> content, followed by a treatment stage to remove proteins, lipids, and other compounds, resulting in a mineral-rich substrate. Herein, we examined various methods—alkaline hydrolysis, calcination, and NaOH hydrolysis—to better identify and determine the most efficient and effective process for producing bio-functional nano-sized hydroxyapatite. Through comprehensive chemical, physical, and biological assessments, including Raman spectroscopy and X-ray diffraction, we also optimized the extraction process. Our modified and innovative alkaline hydrolysis–calcination method yielded salmon-derived hydroxyapatite with a highly crystalline structure, an optimal Ca/P ratio, and excellent biocompatibility. The attractive nano-scale cellular/tissular properties and favorable molecular characteristics, particularly well-suited for bone repair, are comparable to or even surpass those of synthetic, human, bovine, and porcine hydroxyapatite, positioning it as a promising candidate for use in tissue engineering, wound healing, and regenerative medicine indications.