Aromatic Carboxyl Research Articles

Understanding CO adsorption in MOFs combining atomic simulations and machine learning

This study introduces a computational method integrating molecular simulations and machine learning (ML) to assess the CO adsorption capacities of synthesized and hypothetical metal–organic frameworks (MOFs) at various pressures. After extracting structural, chemical, and energy-based features of the synthesized and hypothetical MOFs (hMOFs), we conducted molecular simulations to compute CO adsorption in synthesized MOFs and used these simulation results to train ML models for predicting CO adsorption in hMOFs. Results showed that CO uptakes of synthesized MOFs and hMOFs are between 0.02–2.28 mol/kg and 0.45–3.06 mol/kg, respectively, at 1 bar, 298 K. At low pressures (0.1 and 1 bar), Henry’s constant of CO is the most dominant feature, whereas structural properties such as surface area and porosity are more influential for determining the CO uptakes of MOFs at high pressure (10 bar). Structural and chemical analyses revealed that MOFs with narrow pores (4.4–7.3 Å), aromatic ring-containing linkers and carboxylic acid groups, along with metal nodes such as Co, Zn, Ni achieve high CO uptakes at 1 bar. Our approach evaluated the CO uptakes of ~ 100,000 MOFs, the most extensive and diverse set studied for CO capture thus far, as a robust alternative to computationally demanding molecular simulations and iterative experiments.

Molecular characteristics of dissolved organic matter regulate the binding and migration of tungsten in porous media

Tungsten (W) is an emerging contaminant that poses potential risks to both the environment and human health. While dissolved organic matter (DOM) can significantly influence the W's environmental behavior in natural aquifers, the mechanisms by which DOM's molecular structure and functional group diversity impact W binding and migration remain unclear. Using molecular weight-fractionated soil and sediment DOM (<1 kDa, 1–100 kDa, and 100 kDa–0.45 μm), this study systematically investigated the relationship between DOM molecular characteristics and tungstate (WO42−) binding properties using multiple spectroscopic methods, including FTIR, fluorescence spectroscopy and XPS. The migration behavior of WO42− in porous media was also investigated through quartz sand column experiments. Results revealed that approximately 75 % of W was controlled by DOM, with over 50 % binding to low molecular weight DOM (<1 kDa). Tungsten bound to medium-high molecular weight DOM (1–100 kDa, >100 kDa) showed a greater propensity for retention, with the >100 kDa fractions demonstrating stronger selective binding to W, exhibiting distribution coefficients (Kmd) of 6.11 L/g and 10.69 L/g, respectively. Further analysis indicated that W primarily binds with aromatic rings, phenolic hydroxyls, polysaccharides, and carboxyl groups in DOM, potentially affecting DOM structural stability and consequently influencing W migration characteristics. Free W migration in quartz sand was primarily controlled by Langmuir monolayer adsorption, leading to local enrichment (Da = 6.83, Rd = 86.98). When bound to DOM, W's migration ability significantly increased (Rd = 8–10), with adsorption shifting to a Freundlich multilayer model, primarily controlled by convective transport (Npe = 27–62> > 1.96), while adsorption effects weakened (Da ≈ 1). This study, for the first time, systematically reveals the regulatory mechanisms of DOM molecular characteristics on tungsten's environmental behavior. It offers crucial parameter support for constructing tungsten migration models and provides important guidance for tungsten pollution risk assessment and remediation strategies.

Integrated computational analysis, in vitro, in vivo investigation on Myristica fragrans Houtt. essential oils for potential anti rheumatic activities

Rheumatoid arthritis (RA) is an inflammation associated autoimmune disorder that is prevalent worldwide. Occurrence of severe side effects with current therapeutic regimens is major concern these days. We investigated Myristica fragrans mace and seed for management of inflammation and RA. Oils were extracted and analyzed using ATR-FTIR conforming occurrence of the aromatic amine, phenolic, and carboxylic acid groups mostly found in terpenoids. Most of tested compounds exhibited compliance with drug likeness, bioavailability and ADMET set parameters of safety. Molecular docking analysis showed interaction (-0.6 ΔG (kJ mol-1) of Myristicin with 4F5S. A significant antioxidant activity with DPPH, H2O2 and FRAP assays was observed in case of essential oil. Essential oil part also presented a significant protective effect during heat induced hemolysis (66 ± 1.0 %), BSA denaturation assay (61 ± 1.4 %) and higher levels of proteinase inhibition (70 ± 1.4 %). Acute antiflammatory model in rat presented a significant decrease in inflammation with essential oil. It was concluded that Myrictica fragrans essential oil possess significant (p < 0.005) anti-inflammatory potential that can play a key role in management of RA.

Fabrication of Adsorbent Using Nano-Sized Lignocellulosic Biochar Coated on Luffa Aegyptiaca Sponge to Remove Heavy Metal Chromium VI

Eliminating heavy metal Cr (VI) in liquids is challenging. Developing adsorbents using sustainable, cheap, and biodegradable materials is still a concern. Therefore, this study aims to synthesize a heavy metal adsorbent by transforming forest residue into nano-sized lignocellulose biochar. This nano-sized lignocellulosic biochar, with the assistance of chitosan and alginate, was coated onto the Luffa aegyptiaca sponge surface to complete the structure of the proposed heavy metal adsorbent. This adsorbent is easy to apply in adsorbing heavy metals, is durable, and can be reused. The adsorbent products were characterized to observe the functional groups by Fourier Transform Infrared (FTIR) and surface morphology by Scanning Electron Microscopy (SEM). The adsorbents were also experimented with contact times of 120 and 1200 minutes in the adsorption process. The decrease in heavy metal concentration was analyzed by Atomic Absorption Spectroscopy (AAS). Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX) observed the adsorbent surface that has absorbed heavy metal ions. FTIR characterization of surface functional groups showed the presence of hydrogen, aliphatic C-H group, C=C aromatic ring, carboxyl groups, and carbonate ion, capable of binding heavy metal Cr (VI). The morphology of the adsorbent coated on luffa showed that the adsorbent was well attached. The results of the adsorption process showed a decrease in Cr (VI) concentration, with adsorption efficiency reaching 94% for 1200 min and adsorption capacity of 0.36 mg/g. SEM-EDX results validated the attachment of Cr (VI) heavy metal ions to the adsorbent surface.

Biomolecular interactions between the antibacterial ceftolozane and the human inflammatory disease target ADAM17: a drug repurposing study

Inhibition of a disintegrin and metalloproteinase-17 (ADAM17), a metzincin, is proposed as a novel therapeutic strategy to suppress overproduction of the proinflammatory cytokine TNF-α in rheumatoid arthritis and inflammatory bowel disease. Existing ADAM17 inhibitors generate toxic metabolites in-vivo or haven’t progressed in clinical trials. Previous studies suggest that ligands which bind to ADAM17 active site by interacting with the Zn ion and L-shaped hydrophobic S1’- and S3’-pockets and forming favorable hydrogen bonds could act as potential ADAM17 inhibitors. Here, we investigated whether the FDA-approved anti-bacterial drug ceftolozane, a cephalosporin containing aromatic groups and carboxyl groups as probable zinc binding groups (ZBGs), forms non-covalent interactions resulting in its binding in the active site of ADAM17. In this study, the density functional theory (DFT), molecular docking and molecular dynamics calculations with the catalytic chain of ADAM17 show that carboxyl group of ceftolozane acts as moderate ZBG, and its extended geometry forms hydrogen bonds and hydrophobic interactions resulting in a binding affinity comparable to the co-crystallized known ADAM17 inhibitor. The favorable binding interactions identified here suggest the potential of ceftolozane to modulate ADAM17 activity in inflammatory diseases. ADAM17 cleaves and releases epidermal growth factor (EGF) ligands from the cell surface. The shed EGF ligands then bind to the EGF receptors to drive embryonic development. Therefore, our findings also suggest that use of ceftolozane during pregnancy may inhibit ADAM17-mediated shedding of EGF and thus increase the risk of birth defects in humans. Communicated by Ramaswamy H. Sarma

Changes in Molecular Structure of Humic Substances in Cambisols under Agricultural Use

Soil organic matter stability and transformation affected by agriculture is a global problem of great concern. This study aimed to reveal structural changes in humic molecules under conventional soil tillage in Cambisols of the Transbaikal area. Humic acids were isolated from the humus horizons of native and arable variants of Eutric Cambisol Cryic (gleyic, humic, loamic) from the forest steppe, and Haplic Cambisol (arenic, humic, protocalcic) from the steppe zone. The changes in the humic substances’ quality were evaluated by means of an elemental analysis and 13C nuclear magnetic resonance spectroscopy. The results indicate that different agronomic management affected the changes in the composition and molecular structure of humic acids. Soil tillage induced an increase in the carbon content, the proportion of aromatic compounds and carboxyl groups and the depletion in nitrogen. As measured by 13C NMR spectroscopy, the intensity of these changes was determined by soil properties and the hydrothermal regime. Organic matter from Eutric Cambisol Cryic was suggested as providing significant environmental resistance to the agricultural impact due to the optimization of the water regime and a loamy texture. Prolonged ploughing of sandy Haplic Cambisol under the arid conditions promoted deep changes in the humic substances’ composition and chemical structure.

AdenPredictor: accurate prediction of the adenylation domain specificity of nonribosomal peptide biosynthetic gene clusters in microbial genomes.

Microbial natural products represent a major source of bioactive compounds for drug discovery. Among these molecules, nonribosomal peptides (NRPs) represent a diverse class that include antibiotics, immunosuppressants, anticancer agents, toxins, siderophores, pigments, and cytostatics. The discovery of novel NRPs remains a laborious process because many NRPs consist of nonstandard amino acids that are assembled by nonribosomal peptide synthetases (NRPSs). Adenylation domains (A-domains) in NRPSs are responsible for selection and activation of monomers appearing in NRPs. During the past decade, several support vector machine-based algorithms have been developed for predicting the specificity of the monomers present in NRPs. These algorithms utilize physiochemical features of the amino acids present in the A-domains of NRPSs. In this article, we benchmarked the performance of various machine learning algorithms and features for predicting specificities of NRPSs and we showed that the extra trees model paired with one-hot encoding features outperforms the existing approaches. Moreover, we show that unsupervised clustering of 453 560 A-domains reveals many clusters that correspond to potentially novel amino acids. While it is challenging to predict the chemical structure of these amino acids, we developed novel techniques to predict their various properties, including polarity, hydrophobicity, charge, and presence of aromatic rings, carboxyl, and hydroxyl groups.

Influence of Acid Reagents on Oil Sediment Formation

The formation of oil sediment in highly paraffinic oil in the presence of carboxylic and naphthenic acids was studied. The influence of the concentration and composition of acids on the process of sediment inhibition and the concentrations of paraffins, resins, and asphaltenes in sediments was demonstrated. In the composition of sediments obtained from oil with the addition of acidic reagents, the amount of light n-alkanes increased and the fraction of higher molecular weight hydrocarbons decreased. The concentrations of aliphatic fragments and carboxyl groups in the resins of sediments obtained with the addition of acidic reagents decreased, and the aromaticity coefficient increased. Asphaltenes in the sediment were characterized by a decrease in the concentrations of aromatic structures and carboxyl groups.

Green synthesis of silver nanoparticles using banana peel extract and application on banana preservation

AbstractThis study aimed to develop an environmentally friendly silver nanoparticles (AgNPs) using banana peel extract as reducing and capping agent. AgNPs obtained were characterized via Fourier‐transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Preservation of banana blocks coated with sodium carboxymethyl cellulose (Na‐CMC) and Na‐CMC incorporated with AgNPs (Na‐CMC + AgNPs) for 5 days were also conducted. Besides the AgO, which has been identified in FTIR analysis, AgNPs synthesized using banana peel extract exhibited aromatic nitro compound, carboxyl, and hydroxyl groups as well. SEM image showed AgNPs in agglomeration caused by drying process. Banana blocks coated with Na‐CMC + AgNPs showed better preservation as no molds growth were observed throughout the 5 days storage. Meanwhile, banana blocks coated with only Na‐CMC showed molds started to grow on the 3rd day. This preliminary study evidenced that Na‐CMC incorporated with AgNPs could prolong shelf life of banana against mold growth.

The structural model of coal is studied by quantum chemistry calculation and separation of coal liquefied oil group components

This study amis to study the coal structure model by quantum chemistry calculations and the separation of coal liquefied oil group components. Ultimate analysis, Proximate analysis, and maceral analysis, along with Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance carbon spectroscopy (13C CP/MAS NMR) were used to develop the Jinjitan coal structural model. Molecular structures bond order was determined through the use of quantum chemical calculations.The most difficult bonds to break, according to our investigations, were those between aromatic structures and carboxyl or carbonyl groups. An autoclave liquefaction experiment and a group component separation experiment were conducted in an effort to further confirm the structural information and gain a deeper grasp of the characteristics of coal liquefaction oil. The gas chromatography-mass spectrometry (GC–MS) indicated that polycyclic aromatics, due to their greater molecular weight, exhibited peaks with a longer retention duration. As well, quantum chemistry calculations revealed the structure of the small molecule after the broken bond, which wasverified in the aromatic and saturated hydrocarbons after the separation of coal liquefied oil group components.

Computational prediction for the metabolism of human UDP-glucuronosyltransferase 1A1 substrates

UDP-glucuronosyltransferase (UGT) 1A1, one of the most important isoforms in UGTs superfamily, has attracted increasing concerns for its special role in the clearance and detoxification of endogenous and exogenous substances. To avoid the clinical drug-drug interactions, it is of great importance to have the knowledge of the metabolic profile of UGT1A1 substrates early. Herein, we purposed to establish machine learning models to predict the metabolic propeties of UGT1A1 substrates. On the basis of the literature-derived substrates database of UGT1A1, automatic metabolism prediction models for the aromatic hydroxyl (ArOH) and carboxyl (COOH) groups were developed with eight machine learning methods, among which, three methods, i.e. Random Forest, Random Subspace and J48, illustrated the best performance either for the aromatic hydroxyl and the carboxyl model. The models illustrated good robustness when they were evaluated with functions like “Precision”, “Recall”, “F-Measure”, “AUC”, “MCC”, etc. Nice accuracy was observed for the aromatic hydroxyl and carboxyl model of these methods, whose AUCs ranged from 0.901 to 0.997. Additionally, the ArOH model was applied to predict the UGT1A1-mediated metabolism of an external set. Two new unknown substrates, cytochrome P450 (CYPs)-mediated metabolites of gefitinib, were predicted and identified, which were validated by in vitro assays. In summary, this study provides a reliable and robust strategy to predict UGT1A1 metabolites, which will be helpful either in rational-optimization of drug metabolism or in avoiding drug-drug interactions in clinic.

Distribution of Molecular Weight of Humic Substances Isolated from Soils of Tallgrass Temperate Rainforests (Chernevaya Taiga)

The boreal forests of Russia are one of the largest forest areas on the planet. As a result of climate change, the rate of carbon sequestration and stabilization of organic matter are important indicators of environmental conservation. To understand mechanisms of stabilization and the structure of soil organic carbon, the molecular-weight (MW) distribution of humic acids (HAs) in soils of the central deciduous-forest zone of boreal forests (Chernevaya taiga, transitional ecotone forest, coniferous forest) was studied. Analysis of the MW distribution of HAs was conducted using size-exclusion chromatography. This approach allowed us to obtain the distribution of high-, medium-, and low-molecular fractions of HAs. It has been revealed that the content of the low-MW fraction prevails over the content of the medium- and high-MW fractions of HAs, which indicates the process of stabilization in soil organic matter. The accumulation of low-molecular-weight fraction occurs with the aromaticity increase in HAs, which indicates that HAs with a relatively high proportion of aromatic fragments have smaller hydrodynamic radius and a lower MW. It has been statistically substantiated that the low-molecular-weight fraction correlates with the content of aromatic compounds and carboxyl structural fragments of HAs, which indicates the resistance of the soil organic matter of Chernevaya taiga to biodegradation.

Synthesis of Cyclic Peptides in SPPS with Npb-OH Photolabile Protecting Group.

Significant efforts have been made in recent years to identify more environmentally benign and safe alternatives to side-chain protection and deprotection in solid-phase peptide synthesis (SPPS). Several protecting groups have been endorsed as suitable candidates, but finding a greener protecting group in SPPS has been challenging. Here, based on the 2-(o-nitrophenyl) propan-1-ol (Npp-OH) photolabile protecting group, a structural modification was carried out to synthesize a series of derivatives. Through experimental verification, we found that 3-(o-Nitrophenyl) butan-2-ol (Npb-OH) had a high photo-release rate, high tolerance to the key conditions of Fmoc-SPPS (20% piperidine DMF alkaline solution, and pure TFA acidic solution), and applicability as a carboxyl-protective group in aliphatic and aromatic carboxyl groups. Finally, Npb-OH was successfully applied to the synthesis of head–tail cyclic peptides and side-chain–tail cyclic peptides. Moreover, we found that Npb-OH could effectively resist diketopiperazines (DKP). The α-H of Npb-OH was found to be necessary for its photosensitivity in comparison to 3-(o-Nitrophenyl)but-3-en-2-ol (Npbe-OH) during photolysis-rate verification.

Crystal structures of lanthanide terephthalate tetrahydrate, R2(C8H4O4)3(H2O)4, R = La–Er

The crystal structures of 11 lanthanide terephthalate tetrahydrates have been refined using laboratory X-ray powder diffraction data and optimized using density functional techniques. The lattice parameters and R–O bonds exhibit expected trends based on the cation size. The R–O bond distances in the Rietveld-refined structures are similar. However, in the density functional theory (DFT)-optimized structures, the bond distances break into two distinct groups, longer and shorter R–O bonds. This indicates that the bond distance restraints imposed upon the refined structures may have a greater impact than is expected from their weights. The aromatic carboxyl groups were not completely planar, but it is known that the carboxyl groups can rotate to accommodate hydrogen bonding and coordination to the metal. Both water molecules coordinated to the lanthanides act as hydrogen bond donors, but only one of the three unique carboxyl groups acts as an acceptor.

Humus substances in the swamp ecosystems of taiga zone of Western Siberia

Eutrophic peatlands with a predominantly humate type of humus is dominated according to content of hydrophobic humus substances accumulated in the solid phase of peat. Oligotrophic peatlands with fulvate type of humus are characterized by minimal storages. Mesotrophic peatlands occupy a transitional position, both in terms of storage and in terms of the humus type – humate-fulvate. Hydrophilic components of the water phase are characterized by fulvate humus, regardless of the type of peatland, but differ in the proportion of the contribution of humus substances in the amphiphilic system of swamp ecosystems. It is the highest in the thickness of the oligotrophic peatland almost 31%, slightly lower in the mesotrophic – 25% and much less in the eutrophic – 6%. Structural features of macromolecules of humic acids of swamp waters of various genesis are determined. The humic acids of mesotrophic waters are adjacent to the group of reduced compounds, they are more enriched with aromatic structures and carboxyl groups in relation to oligotrophic waters. The humic acids of oligotrophic waters belong to a group of oxygenated compounds, have low enrichment of nitrogen, contain more methoxyl carbon and carbohydrates (polysaccharides). These structural features are caused by geochemistry of waters feeding the peatlands and specific mechanisms of humic acids synthesis on the swamps of different genesis. The volume of dissolved organic carbon stock from wetland ecosystems through system of taiga rivers of left bank of Middle Ob is 805 kt per year.

Миколиз древесины, его продукты и их использование. IV. Компонентный состав микологически разрушенной древесины

The article is devoted to the study of the component composition of mycologically destroyed wood. As a result of wood mycolysis under the action of wood-destroying fungi enzymes, so-called «rot» is formed with a chemical composition different from healthy wood. It is noted that the «brown rot» of wood is enriched with lignin components of wood and «white rot» with carbohydrate components of wood. The results of analyses of ligno-carbohydrate complexes of spruce wood «brown rot», birch wood «white rot» and a group study of low-molecular compounds isolated by extraction methods with various solvents are presented. It is noted that the content of lignin in the sample of «brown rot» wood is four times higher than in the sample of «white rot». It is shown that birch wood with «white rot» is significantly enriched with cellulose. The chemical nature of some groups of extractive substances has been revealed. In the extracts of mycologically destroyed wood, substances of phenolic, alcoholic and quinone nature were found. The presence of derivatives of aromatic and aliphatic carbonyl and carboxyl compounds is noted. Among the products of mycolysis, carbohydrates, flavanoids and terpenoids have been identified. Based on the analysis, an assumption is made that mycologically destroyed wood contains a wide range of phenolic and carbohydrate compounds contained both in the original wood and in the spores and hyphae of wood-destroying fungi themselves. The idea is substantiated that the study of extractive substances of mycologically destroyed wood makes it possible to predict possible directions of the prospective use of this raw material for obtaining target products. This article is the fourth in the cycle «Wood mycolysis, its products and their use», the previous ones were published in the journal «Forestry Bulletin», 2020, v. 24, no. 2, 6; v. 25, no. 1.

Structural activity comparison of abutilon indicum and synthetic NSAIDs by using spectroscopy and chromatography techniques

The present study was performed to find out the structural similarity of hydroalcoholic extract of abutilon indicum and standard non-steroidal anti-inflammatory drugs (NSAIDs) using various analytical and chromatography techniques. The characterization was performed by fourier transform infrared spectrophotometer (FTIR), UV–Vis spectrophotometer, thin layer chromatography (TLC), and reverse-phase high phase liquid chromatography (RP-HPLC). Paracetamol and aceclofenac were used as standard NSAIDs. The FTIR peaks obtained for abutilon indicum were at wavenumber 2933.81, 2359.61, 1459.90, 762.73, 1640.09, 1559.74, and 3253.75 cm−1 confirms the presence of aromatic acid, hydroxyl group, and carboxylic groups. In addition, the UV–Vis profile showed peaks at 274 nm and 244.5 nm for abutilon indicum in methanol and sodium hydroxide respectively. Further, the TLC method showed the retention factor (Rf) values at 0.38 and 0.36 for abutilon indicum which were almost similar to Rf values of paracetamol and aceclofenac. The peak and retention time from RP-HPLC for abutilon indicum showed the values at 3.640 and 2.603 that were in accordance with standard NSAIDs. Thus, this study can give an insight that abutilon indicum does contain structures similar to paracetamol and aceclofenac which are responsible for their analgesic activity.

Evaluation of characteristics and microbial community of anaerobic granular sludge under microplastics and aromatic carboxylic acids exposure

The influences of polyether sulfone (PES) microplastics and different structures aromatic carboxylic acids such as benzoic acid (BA), phthalic acid (PA), hemimellitic acid (HA), and 1-naphthoic acid (1-NA) on the performances and characteristics of anaerobic granular sludge as well as the microbial community were investigated. The chemical oxygen demand (COD) removal efficiency was the highest in the experimental group with 40 mg/L BA, reaching 90.1%. The inhibitory effect of aromatic carboxylic acids addition on the 2,3,5-triphenyltetrazolium chloride (TTC) activity was more obvious than that on 2-para (iodo-phenyl)-3(nitrophenyl)-5(phenyl) tetrazolium chloride (INT) activity. Compared with the control group (only 0.5 g/L PES microplastics, 60.6 mg TF·g TSS·h−1), the inhibition effect of TTC activity was 32.5 mg TF·g TSS·h−1 and 44.3 mg TF·g TSS·h−1 in the 40 mg/L HA and 40 mg/L 1-NA experimental groups, respectively. When aromatic carboxylic acids were added, the activities of acetate kinase and coenzyme F420 in the anaerobic granular sludge decreased. The excitation-emission matrix (EEM) fluorescence spectra indicated that loosely bound extracellular polymeric substances (LB-EPS) began to decay. After the addition of different aromatic carboxylic acids, the CC and CH functional groups of the anaerobic granular sludge increased, suggesting that aromatic carboxylic acids migrated to the surface of anaerobic granular sludge, such a transfer would lead to changes in anaerobic granular sludge performance. High-throughput sequencing technology showed that the dominant microbial communities in the anaerobic granular sludge were Proteobacteria, Methanothrix, and Methanomicrobia. After the addition of aromatic carboxylic acids, the relative abundances of Proteobacteria, Methanobacterium, and Methanospirillum increased. In the presence of PES, 1-NA had the most serious toxicity to the anaerobic granular sludge.

Temperature induced supramolecular structural transition and as a host cavity to capture the guest molecules

The two-dimensional (2D) molecular self-assembled arrangements at the liquid–solid interface are dominated by many parameters such as the molecular structure and the environment of adsorbed molecules. In this study, the impact of temperature on the self-assembled structures of tetrathiafulvalene derivatives TTF-C6, which contains two aromatic carboxyl groups and two alkyl side chains, was investigated by scanning tunneling microscopy (STM) technique. Experimental result reveals that the compacted linear structures of TTF-C6 can be transformed into the cavity structures by increasing the HOPG substrate temperature. The cavity structures can serve as template system to capture different guest molecules such as coronene (COR) and C60. However, the proportion of two guest molecules in the host cavities is different. The corresponding density functional theory (DFT) calculations were carried out to verify the experimental results. Such temperature-induced structural transitions are used to adjust the packing density of molecule and capture different guest molecule.

Molecular Speciation of Size Fractionated Particulate Water-Soluble Organic Carbon by Two-Dimensional Nuclear Magnetic Resonance (NMR) Spectroscopy.

Particulate matter is associated with increased morbidity and mortality; its effects depend on particle size and chemical content. It is important to understand the composition and resultant toxicological profile of particulate organic compounds, the largest and most complex fraction of particulate matter. The objective of the study was to delineate the nuclear magnetic resonance (NMR) spectral fingerprint of the biologically relevant water-soluble organic carbon (WSOC) fraction of size fractionated urban aerosol. A combination of one and two-dimensional NMR spectroscopy methods was used. The size distribution of particle mass, water-soluble extract, non-exchangeable organic hydrogen functional types and specific biomarkers such as levoglucosan, methane sulfonate, ammonium and saccharides indicated the contribution of fresh and aged wood burning emissions, anthropogenic and biogenic secondary aerosol for fine particles as well as primary traffic exhausts and pollen for large particles. Humic-like macromolecules in the fine particle size range included branched carbon structures containing aromatic, olefinic, keto and nitrile groups and terminal carboxylic and hydroxyl groups such as terpenoid-like polycarboxylic acids and polyols. Our study show that 2D-NMR spectroscopy can be applied to study the chemical composition of size fractionated aerosols.