Chemical Character Research Articles

Phylogenetic analysis shows that Pyrenula (Pyrenulaceae) diversity is larger than expected: three new species and one new record discovered in China

The lichenised fungal genus Pyrenula is a very common crustose lichen element in tropical to subtropical forests, but little research has been done on this genus in China. We carried out an integrative taxonomic study on Pyrenula in China using morphological, anatomical, chemical characters, and molecular data (ITS, nuLSU, mtSSU). Three new species with muriform ascospores containing red oil when over-mature were found: Pyrenula submacularissp. nov., P. yunguiensissp. nov. and P. rufotetrasporasp. nov. Molecular data and TLC results of P. macularis and P. breutelii are for the first time reported and show that they are not synonyms. This is the first report of P. breutelii in China. Contrary to the previous reports of this genus, we found lichen substances in all the five species in this study, seemingly terpenoids. A key for the Pyrenula species reported in China is provided.

Effect of Different Chemical Pretreatments and Packaging Systems on Quality Characteristics of Fresh-Cut Pomegranate Arils (Punica granatum, L.)

Aims: Pomegranate (Punica granatum) is considered as challenging to consume due to its hard structure, hence used for fresh-cut production. Extending the shelf life of fresh-cut pomegranate arils would improve their marketability, transport efficiency, and reduce post-harvest losses. Study Design: Completely Randomized Design by using GRAPES (General R based Analysis Platform Empowered by Statistics). Place and Duration of Study: College of Agriculture, Kerala Agricultural University, February 2022-July 2024. Methodology: Pomegranate arils were extracted and treated with different pre-treatment solutions viz., 0.5% ascorbic acid, 0.5% citric acid, 1% calcium chloride and 1% calcium ascorbate for 4 minutes. The best pre-treatment solution was selected and arils were packaged in different packaging systems viz., shrink wrapping in 15µ polyolefin film, vacuum packaging in laminated pouches, MAP with N2 flushing in laminated pouches, aluminium tray wrapped with cling film and stored under two different storage conditions, after treating with 1% calcium ascorbate. Results: 1% calcium ascorbate was selected as the best pre-treatment solution and pre-treated arils kept in MAP with N2 flushing in laminated pouches stored under low temperature condition was found to be the best packaging and storage system. 1% calcium ascorbate treated arils in MAP with N2 flushing in laminated pouches stored under low temperature condition (10±5oC) had a shelf life of 6 days with superior physiological (PLW, percent leakage), chemical (acidity, vitamin C, phenol) and sensory characters (color, flavour, texture, appearance, taste and overall acceptability) as compared to control (2.00 days). Maximum vitamin C content of 23.02 mg 100g-1 and least phenol content of 214.16 mg 100g-1 were recorded on 6th day of storage. Conclusion: Pomegranate arils pre-treated with 1% calcium ascorbate for 4 minutes, kept in MAP with N2 flushing in laminated pouches stored under low temperature condition (10±5oC) can be considered as a protocol for shelf life extension of pomegranate arils.

Taxonomic studies on the lichenized fungi inhabiting bamboos and rattans of KFRI Peechi campus

A total of 17 lichen taxa inhabiting the bamboos and rattans of the Kerala Forest Research Institute, Peechi campus were enumerated. Out of these, sterile specimens of Cryptothecia, Pyxine, Tricharia, and some species of Porina and Strigula were identified up to generic level based on thallus morphology, anatomical and chemical characters. The study added eight species viz., Diorygma soozanum (Zahlbr.) M. Nakan. & Kashiw., Fellhanera bouteillei (Desm.) Vězda, Graphis pyrrhocheiloidesZahlbr., Gyalectidium cf. filicinum Müll. Arg., Herpothallon cinereum G. Thor, Porina tetramera (Malme) R. Sant., Puiggariella nemathora (Mont.) S.H. Jiang, Lücking & J.C. Wei, and Tricharia sp. as new distributional records to Kerala. The genera Fellhanera, Gyalectidium, Puiggariella, and Tricharia are reported for the first time in Kerala. Brief descriptions of the species new to Kerala are provided.

Selective removal of organic dyes via polymer inclusion membrane containing a perbenzylated β-cyclodextrin derivative

Organic dyes threaten aquatic ecosystems due to carcino/mutagenic properties, and their removal from wastewater is a crucial issue. The novel PIM (Polymer Inclusion Membrane) containing perbenzylated β-cyclodextrin (CD) derivative was designed as an effective material for the selective removal of organic dyes because the CD characterizes strong affinity to these compounds via inclusion complex formation. The PIM was obtained through standard solvent casting from CTA as a matrix, o-NPOE as a plasticizer, and perbenzylated β-CD as the carrier. The membrane transport was evaluated towards two different types of dyes, cationic (Methylene Blue) and anionic (Acid Orange 7), where the optimal concentration for dye removal was 50 and 75 mg/L, respectively. The efficiency of this process was around 83–90 % after 8 h, when the pH of the source/receiving phase induced the formation of non−/ionic forms of dyes, respectively. The optimal membrane composition based on mass ratio was 11.1:72.2:16.7 for CD:o-NPOE:CTA with a membrane thickness of 0.053 mm. The PIM was characterized by high selectivity dependent on both the pH of each phase used in the transport and the chemical character of the dyes. The molecular mechanism of the removal process was mostly based on the complex inclusion of dyes inside the CD cavity. The activation energies were 8.73 and 13.93 kJ/mol for MB and AO7, respectively. The dyes transport was limited by diffusion. This study provides information about novel PIM with an effective and selective carrier, the perbenzylated β-CD derivative, towards organic dyes.

Water holding capacity, aggregation, respiration, and chemical character of acid soil amended rice straw biochar enriched with different volumes of liquid extract (sap) of Kappapychus alvarezii

The quality of acidic soil is determined by organic C content produced from rice straw biochar in agriculture. In this context, liquid extract from Kappapychus alvarezii (K-sap) is used as a biochar enrichment agent. Therefore, this research aimed to (i) analyze the character of K-sap enriched rice straw biochar with different volumes, as well as (ii) evaluate the impact on soil water holding capacity, size class distribution, aggregate stability index, respiration rate, and acidic soil chemical characters. The treatment tested was the volume of K-sap kg-1 biochar, namely (i) without biochar, (ii) 0 mL, (iii) 500 mL, (iv) 1,000 mL, and (v) 1,500 mL. Each treatment was repeated three times and placed according to a randomized block design procedure. The area covered by K-sap, pore size, and amorphous degree increased while the pore volume of the biochar surface decreased. The addition of 1,000 mL of K-sap kg-1 biochar released a new peak number associated with the aliphatic and aromatic groups. The K-sap enriched biochar increased the proportion of soil aggregate size of 1-2 mm, water holding capacity, carbon storage, pH, total N, available P and K, exchangeable base cations as well as base saturation. Meanwhile, the concentration of Al3+ and H+ were decreased in the acidic soil solution. The results showed that the performance of rice straw biochar, K-sap volumes, soil chemical quality, water holding capacity, and ability to store carbon of the acidic soil was improved by adding K-sap volume.

Unlocking the Multi-Redox (Nb5+/Nb4+/Nb3+) Reactions in Nasicon- Nb2(PO4)3 Anode for Li- and Na-Ion Batteries

NASICON (Natrium Super-Ionic CONductor) type materials are known for their high structural, and thermal stability and superior sodium ion mobility which make this framework an efficient electrode material for Na-ion batteries.1 In recent times NASICON-type compounds have been widely explored as Li- and Na-ion cathodes and solid-state electrolytes but are largely ignored as anodes due to their lower capacities and higher intercalation voltages, which reduce the overall energy densities of Li- and Na-ion batteries (LIBs and SIBs). NASICON structure has a general molecular formula of NaxMM′(PO4)3, where two MO6 octahedra corners are shared with three PO4 tetrahedra along the c-direction resulting in the “lantern units” and each lantern unit joins six other lantern units, generating a large interstitial space that can accommodate up to four alkali cations per formula unit.2 In the NASICON family usually all members contain Na/Li ions in terms of synthesis and electrochemical/chemical oxidation routes must be employed to remove the Na from the parent compound.Herein, for the first time we will present a comprehensive study on the structural and electrochemical properties of the empty NASICON-type (contains no Li or Na ions in its pristine state) mixed valance Nb2(PO4)3 and its potential application as an anode in LIBs and SIBs. Due to the multi-redox activity of Nb, it is possible to attain high insertion capacity (~ 150 mAh g-1 for SIBs and ~ 170 for LIBs) and relatively lower voltages (1.8 V vs. Li+/Li0 and 1.4 V vs. Na+/Na0) compared to Ti or V-based NASICON anodes.3,4 Our in-situ XRD measurements revealed multiple-phase transformations during Li and Na intercalation with the formation of short-range ordered Li3Nb2(PO4)3 and triclinic (P-1)-Na3Nb2(PO4)3 at the end of discharge. The distinct electrochemical Li and Na intercalation behavior of the Nb2(PO4)3 anode can be ascribed to the relative differences in size, filling of crystallographic sites, and chemical characters of Li and Na ions. Our density functional theory calculations are also in agreement with the in-situ XRD measurements in predicting a stable Na3Nb2(PO4)3 composition in the Na-Nb2(PO4)3 pseudo-binary system. X-ray absorption spectroscopy confirms the participation of multi-redox Nb5+/Nb4+/Nb3+ couples. Although the micron-sized anode showed moderate storage capacities (~106 and 84 mAh g-1 for Li and Na cells, respectively) at 1C rate after 200 cycles, further optimization of electrode and electrolytes is expected to produce better performance. In the future, pairing Nb2(PO4)3 anode with suitable cathodes can enable high-energy density batteries.5

Caspofungin: Chemical characters, antifungal activities, and mechanism of actions

Caspofungin: Chemical characters, antifungal activities, and mechanism of actions

Atmospheric deposition of microplastics in an urban conglomerate near to the foothills of Indian Himalayas: Investigating the quantity, chemical character, possible sources and transport mechanisms

The global apprehension regarding the ubiquitous presence of microplastics (MPs) and their associated health risks underscore a significant challenge. However, our understanding on the occurrence and characteristics of this emerging class of pollutants in the different environmental compartments remains limited. For instance, despite housing approximately 20–25% of the global population, the evidence of the atmospheric MPs in Indian Subcontinent is exceedingly rare. Hence, we for the first-time present data on the depositional flux, chemical composition, morphological features of the atmospheric MPs collected from the foothills of Indian Himalayas. The total number of MPs for the collected samples ranged from 65 to 752 particles, with an average of 317 ± 171 particles count. The average flux of atmospheric MPs was 2256 ± 1221 particles/m2/day and varied significantly from 462 particles/m2/day to 5346 particles/m2/day. The highest deposition (5346 particles/m2/day) of atmospheric MPs was recorded during the 3rd week of sampling, coinciding with the Diwali festival. Based on the visual characteristics, we determined that the size of MPs ranged from 67 to 2320 μm, with a predominant presence of smaller particles (<1200 μm), primarily composed of fragments and films/sheets. Raman spectroscopy indicated that the analyzed MPs were mainly composed of 4 different polymer types, including PE (46.8 ± 7.2 %), PP (20.9 ± 7.4 %), PS (15.6 ± 3.8 %) and PET (16.7 ± 9.9 %). We further highlighted the extent to which climate variables control the deposition of atmospheric MPs in this urban conglomerate located in the foothills of Himalayas. Our Lagrangian parcel tracking approach showed that the greater frequencies are of local origin and clustered near to the studied region. We also speculate that atmospheric microplastics can be transported along the westerly winds. Though we did not observe any significant relation (p > 0.05) between meteorological parameters and the quantity of atmospheric MPs.

Digital Photoinduced Topographical Microsculpting of Hydrogels

AbstractHydrogels are soft materials widely used as a substrate or matrix for cell culture to mimic the physicochemical, structural, and mechanical properties of the cell's native microenvironment. Recently, a growing body of evidence has shown that substrate topography is a key determinant of cell behavior. These studies, however, mostly rely on the use of hard elastomeric materials, particularly as introducing topography in soft hydrogels is technically challenging, labor intensive, and often does not provide a flexible design space. Here, a new approach is presented that allows robust creation of topographies on hydrogels using a maskless and contactless UV‐sculpting approach. The sculpted topographies are highly programmable: the features can be designed using any digital drawing software, while the dimensions and resolution can be easily tuned via UV exposure dose or photoinitiator concentration. Microscale topographies (2–100 µm in size) can be created on a wide range of hydrogels with diverse chemical characters and mechanical properties (e.g., stiffness). As a proof of concept, this work shows that adherent cells on softer hydrogels align better to topographical cues than on stiffer hydrogels, underlining the importance of studying cell behavior in physiologically more relevant multi‐cue environments.

Ag decoration as a strategy to enhance the methanol and ethanol sensing on the biphenylene sheet

Efficient, miniaturized, and highly sensitive sensors to detect volatile organic compounds (VOCs) have become vital tools to minimize pulmonary diseases and other sicknesses. Therefore, the adsorption capabilities of methanol and ethanol were investigated on the recently synthesized biphenylene (BPN) monolayer using the Ag decoration. Although the pristine BPN has suitable VOCs adsorption, the lower adsorption strength and the small charge transfer affect the sensor performance. On the other hand, the Ag decoration increases the gas sensitivity, with moderate chemisorption values of –0.67eV and –0.83eV for methanol and ethanol, respectively, and transitory chemical bond character (neither ionic nor covalent) between Ag atoms and the –OH radical. In addition, significative work function changes (Δϕ > 0.23 eV), huge charge transfer, and rapid recovery times at room temperature, τ = 0.18s and τ = 87.9s for methanol and ethanol, respectively, indicate a great VOCs sensitivity. The feasibility of the Ag-BPN and Ag-BPN + VOCs systems by ab initio molecular dynamics (AIMDs) was analyzed, which confirms that both systems are stable at 500K. Therefore, the DFT calculations employed here can guide experimentalists in exploring new miniaturized sensor devices based on BPN.

Sp2-Iminosugar azobenzene O-glycosides: Light-sensitive glycosidase inhibitors with unprecedented tunability and switching factors

The conventional approach to developing light-sensitive glycosidase activity regulators, involving the combination of a glycomimetic moiety and a photoactive azobenzene module, results in conjugates with differences in glycosidase inhibitory activity between the interchangeable E and Z-isomers at the azo group that are generally below one-order of magnitude. In this study, we have exploited the chemical mimic character of sp2-iminosugars to access photoswitchable p- and o-azobenzene α-O-glycosides based on the gluco-configured representative ONJ. Notably, we achieved remarkably high switching factors for glycosidase inhibition, favoring either the E- or Z-isomer depending on the aglycone structure. Our data also indicate a correlation between the isomeric state of the azobenzene module and the selectivity towards α- and β-glucosidase isoenzymes. The most effective derivative reached over a 103-fold higher inhibitory potency towards human β-glucocerebrosidase in the Z as compared with the E isomeric form. This sharp contrast is compatible with ex-vivo activation and programmed self-deactivation at physiological temperatures, positioning it as a prime candidate for pharmacological chaperone therapy in Gaucher disease. Additionally, our results illustrate that chemical tailoring enables the engineering of photocommutators with the ability to toggle inhibition between α- and β-glucosidase enzymes in a reversible manner, thus expanding the versatility and potential therapeutic applications of this approach.

Sorption of Pt(II) on inactive biomass of Aspergillus Niger O-5 treated with cetyltrimethylammonium bromide

Platinum-group cytostatic have been found in natural waters due to the current inefficiency of wastewaters treatment plants. This study was aimed to the assessment of inactive biomass of Aspergillus niger O-5 treated with cetyltrimethylammonium bromide as sorbent for solid phase extraction of [PtCl4]2-complex from aqueous dissolutions for the subsequent development of new water treatment technologies. Maximum sorption capacity of 54 mg·g−1 was achieved at 25 °C under the following experimental conditions: pH of dissolution = 5, biomass mass = 10 mg, dissolution volume = 10 mL, Pt(II) mass = 0.5 mg and contact time = 30 min. The good fitting of the model of Ho and the increase of sorption capacity up to 102 mg·g−1 with temperature suggested the chemisorption as predominant mechanism. The mean free energy of adsorption was higher than 8 kJ·mol−1 for all temperatures, which also indicated the chemical character of the interaction. The absolute value of the standard molar Gibbs free energy of formation increased from 3.032 to 8.336 kJ· mol−1 with temperature signifying that the sorption was thermodynamically favored, occurred spontaneously and the degree of spontaneity increased with temperature. The positive value (32.3 kJ·mol−1) of the standard molar enthalpy qualified the sorption as an endothermic process, after which the adsorbent/sorbate system became more thermodynamically stable.

Isotope Hydrology and Hydrogeochemical Signatures in the Lake Malawi Basin: A Multi-Tracer Approach for Groundwater Resource Conceptualisation

Reliance on groundwater is outpacing natural replenishment, a growing imbalance that requires detailed and multi-faceted water resource understanding. This study integrated water-stable isotopes and hydrogeochemical species to examine hydrogeochemical processes during groundwater recharge and evolution in the Lake Malawi basin aquifer systems. The findings provide insights into groundwater source provenance, with non-evaporated modern precipitation dominating recharge inputs. Grouped hydrochemical facies exhibit five groundwater water types, prominently featuring Ca-Mg-HCO3. Modelled hydrogeochemical data underscore dominant silicate dissolution reactions with the likely precipitation of calcite and/or high-Mg dolomitic carbonate constrained by ion exchange. Isotope hydrology reinforces water resource system conceptualisation. Coupled isotopic-hydrogeochemical lines of evidence reveal a discernible spatial-seasonal inhomogeneity in groundwater chemical character, revealing a complex interplay of meteoric water input, evaporative effects, recharge processes, and mixing dynamics. Findings show that measurable nitrate across Malawi highlights a widespread human impact on groundwater quality and an urgent need for detailed modelling to predict future trends of nitrate in groundwater with respect to extensive fertiliser use and an ever-increasing number of pit latrines and septic systems arising from rapid population growth. This study not only refined the Lake Malawi basin aquifer systems conceptualisation but also provided isotopic evidence of groundwater and lake water mixing. This study sets a base for groundwater management and policy decisions in support of the Integrated Water Resources Management principles and Sustainable Development Goal 6 objectives for groundwater sustainability in the transboundary Lake Malawi basin.

A New Species and a New Record of Byssoid Arthoniaceae (Lichenized Ascomycota) from Southern China

This paper illustrates two species in the lichen-forming family Arthoniaceae from southern China, including a new species of Herpothallon, H. fibrosum L.L. Liu &amp; Lu L. Zhang and a new record of Cryptothecia, C. striata G. Thor for China. Herpothallon fibrosum has fluffy, cylindrical pseudoisidia, like a bundle of fiber, and psoromic acid and confluentic acid are present. Furthermore, the new record of Cryptothecia striata has been identified by morphological, anatomical, chemical, and molecular studies. The systematic position of the two species was clarified by the molecular sequence data from the small subunit of the mitochondrial ribosomal DNA (mtSSU). Detailed taxonomic descriptions, chemical characters, comparisons, and discussion of the characteristics of similar species are provided for the two species; the relationship between Cryptothecia and Herpothallon is also discussed here.

Effect of foliar application of micronutrients on yield attributes, yield and chemical characters of mango (Mangifera indica L.) cv. Amrapali

Effect of foliar application of micronutrients on yield attributes, yield and chemical characters of mango (Mangifera indica L.) cv. Amrapali

Collaborative optimization of de-NOx & NH4HSO4 decomposition over Cu-based LDO catalysts: Perspective from the acidic and redox properties

Low temperature de-NOx catalyst with excellent resistance to ammonium bisulfate (ABS) is of great practical significance. Study about the simultaneous optimization of de-NOx performance and ABS resistance by acidic and redox properties regulation is imperative. In this work, the influence of the acidic and redox properties to the de-NOx & ABS decomposition performance was investigated via three Cu-based LDO model catalysts with distinct surface chemical character. Test results indicated that the low temperature de-NOx performance of both the modified Cu2NiAl-LDO and Cu2CoAl-LDO catalysts was slightly improved, while their in situ ABS resistance behavior was remarkably different (Cu2CoAl-LDO > Cu3Al-LDO > Cu2NiAl-LDO). TPDC and TPSR test evidenced that the ABS thermal decomposition or its reactivity with NOx was facilitated over Cu2CoAl-LDO catalyst, but inhibited over Cu2NiAl-LDO catalyst. Characterizations revealed the Cu2CoAl-LDO catalyst with stronger redox property could contribute to ABS decomposition, while more weak acid sites on Cu2NiAl-LDO catalyst induced a negative effect for ABS decomposition. Our study might provide guidance on the rational design of de-NOx & anti-ABS catalysts for future studies.

Recent Advances in Gold Nanocluster-Based Biosensing and Therapy: A Review.

Gold nanoclusters (Au NCs) with bright emission and unique chemical reactivity characters have been widely applied for optical sensing and imaging. With a combination of surface modifications, effective therapeutic treatments of tumors are realized. In this review, we summarize the recently adopted biosensing and therapy events based on Au NCs. Homogeneous and fluorometric biosensing systems toward various targets, including ions, small molecules, reactive oxygen species, biomacromolecules, cancer cells, and bacteria, in vitro and in vivo, are presented by turn-off, turn-on, and ratiometric tactics. The therapy applications are concluded in three aspects: photodynamic therapy, photothermal therapy, and as a drug carrier. The basic mechanisms and performances of these systems are introduced. Finally, this review highlights the challenges and future trend of Au NC-based biosensing and therapy systems.

Two new species of the genus Lecidella (Lecanoraceae, Ascomycota) from maritime Antarctica, southern South America and North America

Abstract Two new species of the genus Lecidella, one with a North American-maritime Antarctic distribution and one with a so far exclusively southern South American-maritime Antarctic distribution, are described using molecular and morphological tools. Lecidella ayazii is a species growing on soil and also on mosses and has so far been found on the Antarctic Peninsula, as well as in the alpine areas of the La Sal Mountains, Utah, USA and in the Kivalliq Region (Nunavut) in the north of Canada, whereas L. drakensis occurs mainly on siliceous rocks, rarely on mosses, and has been recorded on both sides of the Drake Passage in southern Patagonia and the Antarctic Peninsula. Phylogenetic analysis of the nrITS sequence data shows that both species belong in the L. elaeochroma clade, each forming a highly supported and distinct group. Furthermore, they also differ in morphological and chemical characters from the species described so far in this clade. In addition, five further accessions were recorded from the maritime Antarctic, which were placed in the cosmopolitan and heterogeneous L. stigmatea clade, of which one could be assigned to the bipolar species L. siplei.

Comparative chemical characters of Ziziphi Spinosae Semen from geographical origins of China

Abstract Background Ziziphi Spinosae Semen (ZSS) contains a wide range of active components. Because existing methods cannot fully evaluate these components, a new quantitative method needs to be established for component characterization. Objective Ziziphi Spinosae Semen has gained increasing attention in recent years, primarily as a medicinal and edible plant. The content determination of ZSS is not specified in the Chinese Pharmacopeia (2020 edition). Environmental conditions in different production areas can influence the quality of ZSS. This study aims to identify ZSS collected from various geographical origins in China. Materials and methods High-performance liquid chromatography (HPLC) fingerprints were established using optimized HPLC-photo-diode array methods. Subsequently, similarity analysis and quantification of ZSS from different sources were conducted. Metabolites of ZSS were identified and evaluated using the UHPLC-Q Exactive HF Orbitrap MS system. Principal component analysis, hierarchical cluster analysis, and orthogonal partial least squares discriminant analysis were performed based on all peak areas. Results In this study, the components of ZSS against insomnia were screened through network pharmacology. As revealed by the results of protein-protein interaction network analysis, Gene Ontology analysis, and Kyoto Encyclopedia of Genes and Genomes pathway analysis, 14 core components, 10 core targets, and 25 pathways were identified. Thirty-four batches of ZSS fingerprints were established through the HPLC method, which identified 12 characteristic peaks, with 6 being qualitatively identified. An identification method for assessing differences in the chemical composition of ZSS from different origins was developed by using UHPLC-Q Exactive HF Orbitrap MS. Differential markers from various origins were screened and identified. Through multiple analyses such as principal component analysis and orthogonal partial least squares discriminant analysis, it was concluded that there were differences in ZSS metabolites from Hebei, Shandong, and Shaanxi provinces. Seventeen differential metabolites of different origins were identified. Conclusions This study confirmed that ZSS played a synergistic role in improving insomnia through multiple components, targets, and pathways. The content of all 5 components was high, except for jujuboside B. In addition, 6 compounds in ZSS extracts from different origins differed in content, indicating that different growth environments might impact the quality of ZSS.

The nature of the NO bond in amine oxides

AbstractDespite the ubiquitous presence of amine oxides in chemistry, there is no consensus about the nature of the NO bond in these compounds. In this work, we have used electron density analysis to investigate the nature of this bond in substituted amine oxides, R3NO, and have compared it with the nature of the NO bond in hydroxylamines, R2NOR, and model molecules that have well‐established chemical bond character. The results showed that the NO bond length and relative stability are proportional to the inductive effect of the substituents. Quantum chemical topology, natural bond orbitals (NBO), and natural resonance theory (NRT) analyses indicated that the NO bond is polar covalent in all the studied amine oxides, but the ionic contribution is different. NBO and NRT analyses revealed that molecules with more electronegative substituents have strongly delocalized NO and NR bonds, whereas molecules with electropositive substituents have localized bonds.