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Nano Letters Sep 2022The Seebeck effect of a molecular junction in a hopping regime or tunneling-to-hopping transition remains uncertain. This paper describes the Seebeck effect in molecular...
The Seebeck effect of a molecular junction in a hopping regime or tunneling-to-hopping transition remains uncertain. This paper describes the Seebeck effect in molecular epitaxy films (OPI where = 1-9) based on imine condensation between an aryl amine and aldehyde and investigates how the Seebeck coefficient (, μV/K) varies at the crossover region. The value of OPI linearly increased with increasing the molecular length (, nm), ranging from 7.2 to 38.0 μV/K. The increasing rate changed from 0.99 to 0.38 μV·K Å at = 3.4 nm (OPI). Combined experimental and theoretical studies indicated that such a change stems from a tunneling-to-hopping transition, and the small but detectable length-dependence of thermopower in the long molecules originates from the gradual reduction of the tunneling contribution to the broadening of molecular orbital energy level, rather than its relative position to the Fermi level. Our work helps to bridge the gap between bulk and nanoscale thermoelectric systems.
Topics: Aldehydes; Amines; Imines; Models, Theoretical
PubMed: 36067367
DOI: 10.1021/acs.nanolett.2c03083 -
Organic Letters Nov 2020The first total syntheses of (±)-melicolones A and B, which have a unique and densely functionalized framework derived from a rearranged prenylated acetophenone, were...
The first total syntheses of (±)-melicolones A and B, which have a unique and densely functionalized framework derived from a rearranged prenylated acetophenone, were accomplished in 12.3% combined overall yield. The concise and divergent synthesis of these two natural products, which were isolated in racemic form, was achieved in a longest linear sequence requiring only 9 steps (11 total steps) and 8 isolated intermediates using commercially available starting materials. This approach, which might enable access to all tetracyclic melicolones, features the highly regioselective (16:1) and diastereoselective (15:1) dipolar cycloaddition of a carbonyl ylide generated by the unusual cyclization of a rhodium carbene with the carbonyl oxygen atom of an aliphatic aldehyde. This cycloaddition proceeds with dominant steric control to give a highly functionalized oxabicycloheptane core. Stereoselective enolate alkylation led to a prenylated intermediate that underwent an intramolecular aldol reaction to give the penultimate tricyclic intermediate. Tandem epoxidation of the pendant prenyl group followed by a regioselective, acid-catalyzed cyclization delivered (±)-melicolones A and B.
Topics: Acetophenones; Aldehydes; Alkylation; Biological Products; Catalysis; Cyclization; Cycloaddition Reaction; Molecular Structure; Rhodium; Stereoisomerism
PubMed: 33136416
DOI: 10.1021/acs.orglett.0c03454 -
Nature Communications Mar 2021Volatile aldehydes are enriched in esophageal adenocarcinoma (EAC) patients' breath and could improve early diagnosis, however the mechanisms of their production are...
Volatile aldehydes are enriched in esophageal adenocarcinoma (EAC) patients' breath and could improve early diagnosis, however the mechanisms of their production are unknown. Here, we show that weak aldehyde detoxification characterizes EAC, which is sufficient to cause endogenous aldehyde accumulation in vitro. Two aldehyde groups are significantly enriched in EAC biopsies and adjacent tissue: (i) short-chain alkanals, and (ii) medium-chain alkanals, including decanal. The short-chain alkanals form DNA-adducts, which demonstrates genotoxicity and confirms inadequate detoxification. Metformin, a putative aldehyde scavenger, reduces this toxicity. Tissue and breath concentrations of the medium-chain alkanal decanal are correlated, and increased decanal is linked to reduced ALDH3A2 expression, TP53 deletion, and adverse clinical features. Thus, we present a model for increased exhaled aldehydes based on endogenous accumulation from reduced detoxification, which also causes therapeutically actionable genotoxicity. These results support EAC early diagnosis trials using exhaled aldehyde analysis.
Topics: Adenocarcinoma; Aldehyde Dehydrogenase; Aldehyde Oxidoreductases; Aldehydes; Biomarkers, Tumor; DNA Adducts; DNA Damage; Esophageal Neoplasms; Esophagus; Genes, p53; Humans; Metformin
PubMed: 33674602
DOI: 10.1038/s41467-021-21800-5 -
Molecules (Basel, Switzerland) Aug 2022Breath analysis provides great potential as a fast and non-invasive diagnostic tool for several diseases. Straight-chain aliphatic aldehydes were repeatedly detected in... (Review)
Review
Breath analysis provides great potential as a fast and non-invasive diagnostic tool for several diseases. Straight-chain aliphatic aldehydes were repeatedly detected in the breath of patients suffering from lung diseases using a variety of methods, such as mass spectrometry, ion mobility spectrometry, or electro-chemical sensors. Several studies found increased concentrations of exhaled aldehydes in patients suffering from lung cancer, inflammatory and infectious lung diseases, and mechanical lung injury. This article reviews the origin of exhaled straight-chain aliphatic aldehydes, available detection methods, and studies that found increased aldehyde exhalation in lung diseases.
Topics: Aldehydes; Biomarkers; Breath Tests; Exhalation; Humans; Lung Neoplasms; Volatile Organic Compounds
PubMed: 36014494
DOI: 10.3390/molecules27165258 -
Environmental Science. Processes &... Feb 2023Cooking emissions account for a major fraction of urban volatile organic compounds and organic aerosol. Aldehyde species, in particular, are important exposure hazards...
Cooking emissions account for a major fraction of urban volatile organic compounds and organic aerosol. Aldehyde species, in particular, are important exposure hazards in indoor residential and occupational environments, and precursors to particulate matter and ozone formation in outdoor air. Formation pathways of aldehydes from oils that lead to their emissions are not well understood. In this work, we investigate the underlying mechanisms involved in the formation of aldehydes from heated cooking oil emissions, through studying how antioxidants and oil composition modulate oxidation chemistry. Our results demonstrate that gaseous emissions are driven by radical-mediated autoxidation reactions in cooking oil, and the composition of cooking oils strongly influences the reaction mechanisms. Antioxidants have a dual effect on aldehyde emissions depending on the rates of radical propagation reactions. We propose a mechanistic framework that can be used to understand and predict cooking emissions under different cooking conditions. Our results highlight the need to understand the rates and mechanisms of autoxidation and other reactions in cooking oils in order to accurately predict the gas- and particle-phase emissions from food cooking in urban atmospheres.
Topics: Air Pollutants; Aldehydes; Oils; Particulate Matter; Cooking; Air Pollution, Indoor; Environmental Monitoring
PubMed: 35194622
DOI: 10.1039/d1em00532d -
MBio Aug 2023is a major human pathogen and the causative agent of tuberculosis disease. is able to persist in the face of host-derived antimicrobial molecules nitric oxide (NO) and...
is a major human pathogen and the causative agent of tuberculosis disease. is able to persist in the face of host-derived antimicrobial molecules nitric oxide (NO) and copper (Cu). However, with defective proteasome activity is highly sensitive to NO and Cu, making the proteasome an attractive target for drug development. Previous work linked NO susceptibility with the accumulation of -hydroxybenzaldehyde (HBA) in mutants with defective proteasomal degradation. In this study, we found that HBA accumulation was also responsible for Cu sensitivity in these strains. We showed that exogenous addition of HBA to wild-type cultures sensitized bacteria to Cu to a degree similar to that of a proteasomal degradation mutant. We determined that HBA reduced the production and function of critical Cu resistance proteins of the egulated n opper epressor (RicR) regulon. Furthermore, we extended these Cu-sensitizing effects to an aldehyde that may face within the macrophage. Collectively, this study is the first to mechanistically propose how aldehydes can render susceptible to an existing host defense and could support a broader role for aldehydes in controlling infections. IMPORTANCE is a leading cause of death by a single infectious agent, causing 1.5 million deaths annually. An effective vaccine for infections is currently lacking, and prior infection does not typically provide robust immunity to subsequent infections. Nonetheless, immunocompetent humans can control infections for decades. For these reasons, a clear understanding of how mammalian immunity inhibits mycobacterial growth is warranted. In this study, we show aldehydes can increase susceptibility to copper, an established antibacterial metal used by immune cells to control and other microbes. Given that activated macrophages produce increased amounts of aldehydes during infection, we propose host-derived aldehydes may help control bacterial infections, making aldehydes a previously unappreciated antimicrobial defense.
Topics: Animals; Humans; Mycobacterium tuberculosis; Copper; Aldehydes; Proteasome Endopeptidase Complex; Tuberculosis; Anti-Bacterial Agents; Mammals
PubMed: 37350636
DOI: 10.1128/mbio.00363-23 -
International Journal of Molecular... Feb 2022Aldehyde dehydrogenase 2 (ALDH2) has both dehydrogenase and esterase activity; its dehydrogenase activity is closely related to the metabolism of aldehydes produced... (Review)
Review
Aldehyde dehydrogenase 2 (ALDH2) has both dehydrogenase and esterase activity; its dehydrogenase activity is closely related to the metabolism of aldehydes produced under oxidative stress (OS). In this review, we recapitulate the enzyme activity of ALDH2 in combination with its protein structure, summarize and show the main mechanisms of ALDH2 participating in metabolism of aldehydes in vivo as comprehensively as possible; we also integrate the key regulatory mechanisms of ALDH2 participating in a variety of physiological and pathological processes related to OS, including tissue and organ fibrosis, apoptosis, aging, and nerve injury-related diseases. On this basis, the regulatory effects and application prospects of activators, inhibitors, and protein post-translational modifications (PTMs, such as phosphorylation, acetylation, S-nitrosylation, nitration, ubiquitination, and glycosylation) on ALDH2 are discussed and prospected. Herein, we aimed to lay a foundation for further research into the mechanism of ALDH2 in oxidative stress-related disease and provide a basis for better use of the ALDH2 function in research and the clinic.
Topics: Aldehyde Dehydrogenase; Aldehyde Dehydrogenase, Mitochondrial; Aldehydes; Apoptosis; Oxidative Stress; Protein Processing, Post-Translational
PubMed: 35269824
DOI: 10.3390/ijms23052682 -
Open Biology Apr 2022There are many reactive intermediates found in metabolic pathways. Could these potentially toxic molecules be exploited for an organism's benefit? We propose that during... (Review)
Review
There are many reactive intermediates found in metabolic pathways. Could these potentially toxic molecules be exploited for an organism's benefit? We propose that during certain microbial infections, the production of inherently reactive aldehydes by an infected host is a previously unappreciated innate immune defence mechanism. While there has been a significant focus on the effects of aldehydes on mammalian physiology, the idea that they might be exploited or purposefully induced to kill pathogens is new. Given that aldehydes are made as parts of metabolic programmes that accompany immune cell activation by the cytokine interferon-gamma (IFN-γ) during infections, we hypothesize that aldehydes are among the arsenal of IFN-γ-inducible effectors needed for pathogen control.
Topics: Aldehydes; Animals; Anti-Infective Agents; Cytokines; Interferon-gamma; Macrophages; Mammals; Nitric Oxide
PubMed: 35414258
DOI: 10.1098/rsob.220010 -
Food Research International (Ottawa,... Jun 2024The oxidation and degradation of fats lead to a decrease in the nutritional value of food and pose safety concerns. Saturated fatty acids also hold a significant...
The oxidation and degradation of fats lead to a decrease in the nutritional value of food and pose safety concerns. Saturated fatty acids also hold a significant position in the field of lipid oxidation. In this study, the oxidation products of methyl palmitate were investigated by using gas chromatography mass spectrometry (GC-MS). Seven monohydroperoxides and 72 secondary oxidation products were detected. Combined with density functional theory (DFT) calculations, the formation mechanisms of oxidation products can be summarized into four stages. The initial stage involved the formation of monohydroperoxides and alkanes, followed by the subsequent stage involving methyl x-oxo(hydroxy)hexadecanoates. The third stage involved the formation of methyl ketones, carboxylic acids, and aldehydes, while the final stage involved lactones. Meanwhile, methyl ketones were the most abundant oxidation product, approximately 25 times more abundant than aldehydes; the calculated results agreed well with the experimental results. The establishment of a comprehensive thermal oxidation mechanism for palmitic acid provided a new foundation for future lipid oxidation analyses.
Topics: Oxidation-Reduction; Gas Chromatography-Mass Spectrometry; Hot Temperature; Aldehydes; Palmitates; Palmitic Acid; Ketones; Carboxylic Acids
PubMed: 38729730
DOI: 10.1016/j.foodres.2024.114372 -
Journal of Inorganic Biochemistry Oct 2023Two oligonucleotide conjugates sharing the same sequence but incorporating a different 5'-terminal organometallic moiety were synthesized, by either direct mercuration...
Two oligonucleotide conjugates sharing the same sequence but incorporating a different 5'-terminal organometallic moiety were synthesized, by either direct mercuration in solution or oximation with an organomercury aldehyde on solid support. The potential of these conjugates to serve as new type of artificial ribonucleases was tested with a complementary 2´-O-methyl-RNA target sequence featuring a single cleavable RNA phosphodiester linkage. Both organomercury oligonucleotides greatly outperformed their metal-free counterparts as well as the previously reported small molecule organomercury RNA cleaving agent in catalytic activity, providing an important proof-of-concept. Compared to state-of-the-art metal-dependent artificial ribonucleases, however, the observed activity was modest.
Topics: Aldehydes; Oligonucleotides; RNA; Ribonucleases
PubMed: 37480764
DOI: 10.1016/j.jinorgbio.2023.112331