ESI HRMS Research Articles

Acyclic Diaminocarbene Platinum(IV) Complexes Synthesized by the Oxidative Addition of MeI and I<sub>2</sub>

The oxidative addition of methyl iodide or molecular iodine to the bis(С,N-chelate) deprotonated diaminocarbene platinum(II) complexes [Pt{C(N(H)Ar)(NC(N(H)Ph)N(Ph)}2] (Ar = C6H3-2,6-Me2 (Xyl), C6H2-2,4,6-Me3 (Mes), and C6H4-4-Me (pTol)) affords the corresponding platinum(IV) derivatives in a yield of 89–99%. The addition of CF3CO2H is accompanied by the protonation of the nitrogen atoms of the diaminocarbene fragment to form the cationic complexes [[PtI(X)-{C(N(H)Ar)(NC(N(H)Ph)N(Ph)}2]CF3CO2H (X = Me, I). The structures of the compounds are determined by elemental analysis; high resolution mass spectrometry with electrospray ionization (ESI HRMS); IR spectroscopy; 1H, 13C{1H}, 19F{1H}, and 195Pt{1H} NMR spectroscopy; 2D NMR spectroscopy (1H,1Н COSY, 1H,1Н NOESY, 1H,13C HSQC, 1H,13C HMBC, 1H,15N HSQC, 1H,15N HMBC), and X-ray diffraction (XRD) and thermogravimetric analyses. The synthesized platinum(IV) complexes are thermally stable to 200–260°C and are electroneutral molecules with the octahedral coordination sphere formed by two deprotonated diaminocarbene C,N-chelate substituents and iodine and methyl or two iodine atoms localized in the apical positions.

Synthesis, characterization, anticancer activity, molecular docking and DFT calculation of 3-acetylcoumarin thiosemicarbazones and Schiff’s bases

The new thiosemicarbazones (3a-d) of 3-acetylumbelliferone and Schiff’s bases (4a-b) of 3-acetylcoumarin were synthesized, characterized by elemental analysis, UV–Vis, FT-IR, NMR, and ESI-HR MS, and evaluated for their anticancer potency against the human breast cancer (MCF-7) cell line. All the tested compounds exhibited good to moderate anticancer efficacy in a dose-dependent manner. The synthesized compounds exhibited potent preferential inhibition effects against the MCF-7 cell line, with IC50 range of 147.8–505.1 µg/mL. The most potent compound, (E)-N-(1-(7-hydroxy-2-oxo-2H-chromen-3-yl) ethylidine)-2,6-dimethylmorpholine-4-carbothiohydrazide (3c), showed significant cytotoxicity with an IC50 value of 147.8 µg/mL against the tested cell line. It showed a higher proportion of cells in G1 (37.21 %) and S (26.86 %) phases and a lower proportion of cells in G2 phase (26.37 %), with respect to control. Molecular docking of all the synthesized compounds with target proteins VEGFR2 and EGFR demonstrated their significant binding affinity and interactions with key residues compared to the reference drug (erlotinib). DFT-based analysis showed that all the compounds have effective reactivity due to the low band gap energy of HOMO and LUMO relative to the reference drug, erlotinib (4.26 eV). The reactivity-related quantum mechanical parameters η, S, χ, μ, and ω indicated that these compounds have a high efficacy towards the target enzymes VEGFR2 and EGFR. All of the synthesized compounds had drug-like action, according to ADMET predictions.

New secondary metabolites produced by an engineered strain Streptomyces sp. XZQH13OEΔastC

Two previously undescribed alkaloids (1–2), five known alkaloids (3–7) and five cyclodipeptides (8–12) were obtained from an ansatrienin-producing mutant strain Streptomyces sp. XZQH13OEΔ astC. Their structures were elucidated by analysis of the 1D, 2D NMR and ESI HRMS data and by comparison with the reported data. The antibacterial activities of compounds 1–12 were evaluated.

Distribution, chemical, and molecular composition of high and low molecular weight humic-like substances in ambient aerosols

Abstract. Humic-like substances (HULIS) encompass a continuum of molecular weight (MW) ranges, yet our understanding of how HULIS characteristics vary with MW is still limited and not well established. In this study, a combination of ultrafiltration and solid-phase extraction protocols was employed to fractionate the high MW (HMW; > 1 kDa) and low MW (LMW; < 1 kDa) HULIS fractions from ambient aerosols collected during summer and winter at a rural site. Subsequently, comprehensive characterization using total organic carbon, high-performance size exclusion chromatography (HPSEC), UV-visible (UV-vis) and fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), and negative electrospray ionization high-resolution mass spectrometry (ESI–HRMS) were conducted. The results revealed that HMW HULIS were dominated by larger-sized chromophores, substantially constituting a higher fraction of total organic carbon and UV absorption at 254 nm than LMW HULIS. While both HMW and LMW HULIS shared similar fluorophore types and functional groups, the former exhibited higher levels of humification and a greater presence of polar functional groups (e.g., −COOH; > C=O). HRMS analysis further unveiled that molecular formulas within HMW HULIS generally featured smaller sizes but higher degrees of unsaturation and aromaticity compared to those within LMW HULIS fractions. This observation suggests the possibility of small molecules assembling to form the HMW HULIS through intermolecular weak forces. Moreover, HMW HULIS contained a higher proportion of CHON but fewer CHO compounds than LMW HULIS. In both HMW and LMW HULIS, the unique molecular formulas were primarily characterized by lignin-like species, yet the former displayed a prevalence of N-enriched and highly aromatic species. Additionally, HMW HULIS contained more unique lipid-like compounds, while LMW HULIS exhibited a distinct presence of tannin-like compounds. These findings provide valuable insights into the distribution, optical properties, and molecular-level characteristics of HULIS in atmospheric aerosols, thereby advancing our understanding of their sources, composition, and environmental implications.

Chemometric Analysis Combined with GC × GC-FID and ESI HR-MS to Evaluate Ultralow-Sulfur Diesel Stability.

Diesel has been the most employed fuel in highway and nonhighway transportation systems. Many studies over the past years have attempted to classify diesel as a stable or unstable composition since this fuel can still degrade during storage or thermal oxidative processes. Products generated because of such degradation are the reason for the formation of soluble gums and insoluble organic particulates, which in turn cause a negative influence on engine performance. This work reports a detailed composition of nonpolar and polar compounds in many ultralow-sulfur diesel (ULSD) samples by comprehensive two-dimensional gas chromatography with a flame ionization detector (GC × GC-FID) and electrospray ionization high-resolution mass spectrometry (ESI HR-MS). In addition, chemometric approaches were applied for ULSD storage stability investigation. GC × GC-FID experiments achieved the nonpolar chemical characterization for the ULSD samples, including all main hydrocarbon classes: paraffins, mono- and dinaphthenics and olefins, and aromatics. The GC × GC-FID data combined with principal component analysis (PCA) described that the separation of the samples' concerning storage stability was mainly due to the contents of mono- and diaromatic compounds in the unstable ULSD samples. Moreover, PCA was also applied to the ESI (±) data set, and the results highlight the presence of compounds belonging to O class (natural antioxidants), which decrease the rate of oxygen consumption in the fuel, characterizing it as stable composition. The basic nitrogen compounds are mostly present in the stable ULSD samples indicating that they did not affect the stability of the fuel. On the other hand, the HC classes presented pronounced abundance among unstable ULSD samples suggesting that the fuel degradation may go through the oxidation of hydrocarbons and the formation of Ox compounds as byproducts. Furthermore, MS/MS experiments point to the formation of CcHhNnOo-like precursor species, which can react with each other and lead to the formation of gums and insoluble sediments in the fuel. In summary, the results express the potential of using the GC × GC-FID and ESI (±) Orbitrap MS techniques as valuable tools for diesel stability evaluations.

Determination of Umifenovir and Its Metabolites by High-Performance Liquid Chromatography with Combined Mass Spectrometric Detection

An approach to the highly sensitive and selective determination of the bromine-containing antiviral drug umifenovir (Arbidol) and its metabolites in natural and waste water, activated sludge, and bottom sediments by chromatography-mass spectrometry based on a combination of two techniques– inductively coupled plasma mass spectrometry (ICP MS) and electrospray ionization high-resolution mass spectrometry (ESI HRMS) is developed. Reversed-phase chromatographic separation and detection based on ESI HRMS provide the reliable detection and identification of analytes in complex matrices, while the use of ICP-MS with 79Br signal detection makes it possible to exclude matrix effects and use a single analytical standard for quantitative analysis. The use of solid-phase extraction and pressurized liquid extraction as sample preparation methods made it possible to achieve limits of detection at a level of 0.2 ng/L and 2 µg/kg for liquid and solid samples, respectively. The developed approach was successfully tested in the analysis of real samples. It is shown that the concentrations of analytes in urban wastewaters are in the range 4.4–260 ng/L. The highest concentration (up to 3.7 mg/kg) is characteristic of activated sludge, which acts as an effective sorbent for umifenovir and its transformation products.

Development of tissue paper-based chemosensor and demonstration for the selective detection of Cu2+ and Hg2+ ions.

Heavy metals emanate from natural and man-made sources, such as agricultural chemicals including fertilisers and pesticides, medical waste, and chemicals released from industries. Detection and monitoring toxic metal ions is one of the challenges confronting scientists in biological, environmental, and chemical systems. This study describes the design and synthesis of a new imidazole-based fluorescent and colourimetric chemosensor (DPICDT) for highly selective sensing of Hg2+ and Cu2+ ions in aqueous acetonitrile medium. The probe was synthesised by coupling benzil and substituted aldehyde using ethanolic ammonium acetate. The structure of DPICDT was confirmed via IR spectra, NMR, and HR-MS spectra. The DPICDT probe displayed a rapid naked-eye response towards Cu2+ ions from colourless to red-purple and significant fluorescence quenching response towards Hg2+ over other competitive metal ions in both solution and solid support. The binding modes of DPICDT with Cu2+ and Hg2+ ions were found to be at a 1 : 1 ratio as determined using Job plot, ESI HR-MS, and the sensing mechanism was evolved by 1H NMR titrations, HR-MS spectra, and DFT calculations. The lower detection limit was 15.1 nM for Cu2+, eventually far less than the World Health Organization guideline for drinking water (Cu2+ - 31.5 μM) and 1.17 μM for Hg2+ (permissible concentration 2 ppb). Promisingly, the tissue paper-based DPICDT test strips and silica-supported DPICDT were developed and demonstrated for on-site application without resorting to expensive instruments.

Second Generation Self‐Assembling Dendrimer Combining Supramolecular and Dynamic Covalent Chemistry

AbstractA monodisperse second generation self‐assembled dendrimer has been obtained combining supramolecular chemistry and dynamic covalent chemistry as orthogonal binding moieties. A branching unit 18 and a core 5 were connected via a heteroleptic terpyridine zinc complex exploiting the sterical hindrance of mesitylene units in the 6,6’’‐position of one of the terpyridines as the distinction between the ligands. Solubility problems could be solved by introduction of an ethylhexyl ether. The final sphere of the dendrimer was connected via imines, hydrazones and oximes, whereby the oxime made from O‐methylhydroxylamine (22) led to a complete turnover of all aldehyde functions. Furthermore, no amine signal was left and also no signals for a diffusion constant of the hydroxylamine 22 were observed. The successful formation of the dendrimers was analyzed by 1H NMR and DOSY NMR spectroscopy. Furthermore both, the first and second generation dendrimers could be detected by ESI HRMS.

Protective effects of E Se tea extracts against alcoholic fatty liver disease induced by high fat/alcohol diet: In vivo biological evaluation and molecular docking study

Background: With the development of economy and increased workload, chronic a high-fat/alcohol diet intake may lead to alcoholic fatty liver disease (AFLD), which is considered as a crucial health problem worldwide. E Se tea is produced of the leaves and leaf buds of Malus toringoides (Rehd.) Hughes in Tibet and has human health benefits with anti-hyperglycemia, hypertension, and hyperlipidemia effects. Purpose: The objective of this work was to investigate the protective effect of aqueous-ethanol and hot-water extracts of E Se tea against chronic high-fat/alcohol diet induced AFLD rats. Methods: Firstly, to determine the chemical profiling of E Se tea extracts, UHPLC–ESI–HRMS analysis was conducted. Secondly, Sprague-Dawley male rats were used to establish the AFLD animal model by feeding with high-fat/alcohol diet. The animals were treated with E Se tea extracts for 12 weeks. Serum parameters were determined, histologic sections were prepared, and activities of enzymes related to inflammatory response and lipid metabolism imbalance were analyzed. The underlying mechanisms of E Se tea extracts alleviating AFLD were analyzed by immunofluorescence staining and Western blotting analysis. Lastly, key targets of 11-MT against AFLD were verified through molecular docking. Results: In this study, seven main compounds were confirmed or tentatively identified in E Se tea extracts by UHPLC–ESI–HRMS. The results revealed that both the extracts could reverse histopathological steatotic alternation of the liver and reduced the activity of liver damage markers (ALT, AST). E Se tea extracts mitigated oxidative stress by inhibiting CYP2E1 protein and lipid peroxidation parameters (MDA), but enhancing the endogenous antioxidants (CAT, GSH, SOD). Moreover, E Se tea extracts ameliorated inflammation by restraining the activation of NF-κB, consequently releasing the expression of proinflammatory cytokines (TNF-α, IL-6, IL-1β, COX-2 and iNOS). Subsequently, E Se tea extracts reduced hepatocyte apoptosis by increasing capase-9, caspase-3 and Bax protein expression but decreasing Bcl-2 protein expression. Furthermore, E Se tea extracts improved metabolism imbalance by stimulating AMPK/SREBP1/FAS and PPAR-α/CPT1 signaling pathway by regulating lipid metabolism parameters (TC, TG, HDL-C, LHD-C). Furthermore, molecular docking results indicated that 7 chemical constituents of E Se tea extracts had strong docking affinity with 4 key target proteins (AMPK, PPAR-α, NF-кB and Caspase-9). Conclusion: E Se tea ameliorated AFLD through ameliorating inflammatory response, apoptosis, and lipid metabolism imbalance.

Switchable Aromaticity of Phthalocyanine via Reversible Nucleophilic Aromatic Addition to an Electron-Deficient Phosphorus(V) Complex.

Reversible nucleophilic addition to a phthalocyanine core was observed for the first time for the electron-deficient cationic phosphorus(V) complex [PcP(OMe)2]+, whose reaction with KOH afforded a highly distorted nonaromatic adduct bearing an OH group at one of the α-pyrrolic carbon atoms. This adduct was characterized by single-crystal X-ray diffraction, ESI HRMS, and NMR, and UV-vis spectroscopy, together with quantum-chemical modeling. The acidic treatment of this adduct restored aromaticity and recovered the starting cationic complex. The reversible aromaticity breakage resulted in dramatic changes in the photophysical properties of the studied complex, which could pave the way to novel switchable Pc-based compounds and materials.

2-Hydroxy-3-(4-oxy(2,2,6,6-tetramethylpiperidin-1-oxyl)butoxy)benzaldehyde

Salen-type complexes with transition metals and corresponding polymers attract great scientific interest due to their high electrochemical properties and potential for use as part of next generation organic energy storage devices. Because of their good conductivity but relatively low capacity, energy-intensive additives such as quinones or TEMPO fragments can significantly enhance the capacitive characteristics of the electrode materials. Herein, we report a preparation of precursor for a modified Salen-type complex, the substituted 2,3-Dihydroxybenzaldehyde by butoxy linkers with TEMPO fragment using alkylation reaction. The resulting product was characterized by the 1H and 13C, COSY, HMBC, HSQC nuclear magnetic resonance (NMR), ESI–high resolution mass spectrometry (ESI–HRMS), and Fourier-transform infrared spectroscopy (FTIR). The reported approach opens the way for easy modification of Salen-type complexes in order to increase their specific characteristics.

2,6-Bis((benzoyl-R)amino)pyridine (R = H, 4-Me, and 4-NMe2) Derivatives for the Removal of Cu(II), Ni(II), Co(II), and Zn(II) Ions from Aqueous Solutions in Classic Solvent Extraction and a Membrane Extraction.

In this paper, the application of new substituted 2,6-bis((benzoyl-R)amino)pyridine (R = H, 4-Me, and 4-NMe2) derivatives for the recovery of copper(II), nickel(II), cobalt(II), and zinc(II) ions from aqueous solutions was described. The structures of the synthesized compounds were confirmed by nuclear magnetic resonance spectroscopy (NMR), electrospray ionization high-resolution mass spectrometry (ESI HRMS), and tandem mass spectrometry methods (HCD MS/MS). Three different derivatives of 2,6-bis((benzoyl-R)amino)pyridine were used as carriers in membrane processes and as extractants in classic solvent extraction. In each case, the single derivative recovery was carried out on a model solution that contained only one type of metal ions. Spectrophotometry studies were performed to determine the stability constants of the complexes formed by the synthesized species with analyzed metals ions. The results obtained indicate that the synthesized compounds form stable complexes with Cu(II), Ni(II), Co(II), and Zn(II) ions and can be used in both types of studied recovery processes. However, the effectiveness of the synthesized compounds in the recovery of metal ions depends both on the structure of compounds and properties of metals as well as on their concentration.

Deconvolution of post- and pre-salt petroleum sources in southeastern offshore Brazilian basins

The Campos, Santos and Espírito Santo Basins are part of the southeastern offshore Brazilian basins (SEOBB) where pre-salt reserves are located. This represents the most important oil province in Brazil. Constant growth in the discoveries and production of the country’s oil reserves has shown the importance of the pre-salt discoveries; thus, proper oil constituent characterization at the molecular level is needed for this type of petroleum. Six oils, collected in pre- and post-salt reservoirs from SEOBB, were evaluated using GC-FID, GC–MS, GC-C-IRMS, GC × GC-TOFMS, and ESI(±)-Orbitrap HRMS. The biomarker parameters obtained indicated a lacustrine input for all the oils, except for the TAB-4G post-salt oil. All the oils reached the peak of the oil generation window, except the TAB-4G oil, which reached the late stage. The carbon isotope profiles suggested a lacustrine depositional environment for the organic matter (OM) with δ13C isotopic amplitudes ranging from 3.2‰ to 6.9‰. The profile of the TAB-4G oil suggested a contribution from terrestrial OM. This work is one of the first to apply ESI(±)-Orbitrap HRMS for geochemical characterization. In both (±) ionization modes, the data showed that the oils had high percentages of Nx classes, especially N1 compounds, strengthening the interpretation of a lacustrine origin for the OM. ESI(-) HRMS showed that the TAB-4G oil contained a high relative percentage of Ox classes, especially O1 with 8–16 double bond equivalents (DBE) species, suggesting a marine contribution. The combination of the conventional geochemical approach with advanced chromatographic and mass spectrometric techniques allowed for a comprehensive molecular characterization of the post- and pre-salt oils, contributing to a better understanding of the prolific SEOBB petroleum systems.

Specification of the nitrogen functional group in a hydrotreated petroleum molecule using hydrogen/deuterium exchange electrospray ionization high-resolution mass spectrometry.

Hydrotreatment is extensively used for the production of clean fuel. Attaining an understanding of the structural conversion of the nitrogen species during hydrotreatment is very challenging due to the compositional complexity and the absence of a proper characterization method. In the presented work, we coupled hydrogen/deuterium exchange (HDX) with positive-ion electrospray ionization high-resolution mass spectrometry ((+) ESI HR MS) to investigate the difference between the composition of the nitrogen-containing species and the functional groups before and after hydrotreatment. The solvent and additive were optimized for HDX (+) ESI HRMS through systematic evaluations on model nitrogen-containing compounds. We found that adding deuterated water (D2O) and deuterated formic acid (DCOOD) significantly increased the degree of HDX and thus facilitated the identification of nitrogen functional groups. After application to the hydrotreated petroleum samples, the compositional variation of intermediate amine compounds during the heavy petroleum hydrotreatment process was clearly revealed.

Characterization of lacosamide metabolites by UHPLC–ESI–HRMS method

In this study, the in vitro phase I metabolism of lacosamide was characterized with the use of ultra-high-performance liquid chromatography combined with high-resolution mass spectrometry (quadrupole time-of-flight). The use of two metabolism simulation techniques (photocatalysis and human liver microsomes) allowed the characterization of a polar metabolite of parent compound, not yet described. The experiment with the participation of HLM gave the ability to describe the full liver metabolic pathway of lacosamide. It has been proven that this molecule undergoes deacetylation, demethylation, and during liver tissue metabolism. Photocatalysis with the use of a TiO2 catalyst was proved to be a complementary technique in mimicking in vitro drug metabolism.

Crystallomycin revisited after 60 years: aspartocins B and C.

The study of an archived sample of crystallomycin complex using HPLC, ESI HRMS, and 2D NMR showed that two major components of the antibiotic, compounds 1 and 2, are lipopeptides having the same peptide core, Asp1-cyclo(Dab2-Pip3-MeAsp4-Asp5-Gly6-Asp7-Gly8-Dab9-Val10-Pro11-), N-acylated either with Δ3-iso-tetradecenoyl or Δ3-anteiso-pentadecenoyl that are identical to aspartocins C and B, respectively. According to the 2D NMR study, compound 2 in DMSO solution exists as a mixture of four conformers. The producing strain was identified as Streptomyces griseorubens. Compounds 1 and 2 have considerable Ca2+-dependent activity against Gram-positive bacteria including five MRSA strains.

Mechanistic Study of Copper-Catalyzed C-H Hydroxylation/C-S Coupling by ESI-HR MS and DFT Calculations.

The reaction mechanism of Cu-catalyzed C-H hydroxylation/C-S coupling was studied using electrospray ionization high resolution mass spectrometry (ESI-HR MS) and density functional theory calculations (DFT). Notably, a series of CuI and CuIII complexes were observed as key intermediates and identified using ESI-HR MS. Furthermore, a catalyst cycle involving proton abstraction/oxidative addition/reductive elimination was proposed. This study is important and valuable with respect to C-H functionalization.

Copper 5,10,15,20-Tetrakis-(3,4-dibenzyloxyphenyl)porphyrin

The copper complex of 5,10,15,20-tetrakis-(3,4-dibenzyloxyphenyl)porphyrin (CuTDBOPP) was synthesized and characterized with electronic absorption spectroscopy and ESI high-resolution spectrometry. In the electronic spectrum, there was a shift in the Soret band from 424 nm to 420 nm that indicated that the insertion of the metal ion was successful. Additionally, the number of Q bands decreased from four peaks to a single peak at 541 nm. The molar absorptivity of the Soret and Q band are 3.4 × 105 cm−1·M−1 and 1.8 × 105 cm−1·M−1, respectively. The ESI HRMS was in excellent agreement with simulated isotopic distribution spectra. CuTDBOPP was incorporated into a series of Gratzel cells where the open current voltage was recorded.

Synthesis, Spectroscopic Characterization and X-ray Structure Analysis of 6-(2,5-Dichlorothiophen-3-yl)-2-methoxy-4-(4-methoxyphenyl)pyridine-3-carbonitrile

The title compound was prepared by the condensation of an equimolar mixture of 1-(2,5-dichlorothiophen-3-yl)-3-(4-methoxyphenyl)prop-2-en-1-one, malononitrile and sodium hydroxide. The molecular structure was fully characterized using different spectroscopic methods. Mass ESI–HRMS measurements were performed. The HRESIMS analysis revealed the molecular formula, C18H12Cl2N2O2SNa, with [M + Na]+ and [M + Na + 2]+ and [M + Na + 4]+ isotopic clusters characteristic for a dichlorinated compound. The compound was also thoroughly characterized by 1H, 13C, NMR spectra and 2D NMR spectra (COSY, HSQC and HMBC). The molecular structure was confirmed by X-ray single crystal analysis. The new compound crystallizes in the orthorhombic, Pbcn space group with unit cell dimensions: a = 31.901(7) A, b = 15.412(4) A, c = 7.3655(14) A, V = 3621.3(13) A3 and Z = 8. In the title compound, the central pyridine ring carries four substituents, a thiophene ring, a methoxyphenyl ring, a carbonitrile group and a methoxy group. The dihedral angles between the planes of the pyridine ring, the thiophene ring and the methoxyphenyl ring are 36.66 and 40.18°, respectively. Intermolecular C–H···O/N, π···π and anion···π [Cl···π] interactions are found in the crystal structure. All interactions consolidate a three dimensional network. Synthesis, characterization, crystal, molecular structure, and crystal supramolecularity of 6-(2,5-dichlorothiophen-3-yl)-2-methoxy-4-(4-methoxyphenyl)pyridine-3-carbonitrile are reported.

Structure of the β-l-fucopyranosyl phosphate-containing O-specific polysaccharide of Escherichia coli O84

Fine structure of the O-polysaccharide chain of the lipopolysaccharide (O-antigen) defines the serospecificity of bacterial cells, which is the basis for O-serotyping of medically and agriculturally important gram-negative bacteria including Escherichia coli. In order to obtain the O-polysaccharide for structural analysis, the lipopolysaccharide was isolated from cells of E. coli O84a by phenol/water extraction and degraded with mild acid. However, the O-polysaccharide was cleaved at a highly acid-labile β-l-fucopyranosyl phosphate (β-l-Fucp-1-P) linkage to give mainly a pentasaccharide that corresponded to the O-polysaccharide repeat. Therefore, the lipopolysaccharide and the pentasaccharide as well as their O-deacylated derivatives were studied using sugar analysis, NMR spectroscopy, and (for oligosaccharides) ESI HR MS, and the O84-polysaccharide structure was established. The O-polysaccharide is distinguished by the presence of β-l-Fucp-1-P and randomly di-O-acetylated 6-deoxy-d-talose, which are found for the first time in natural carbohydrates. The gene cluster for the O84-antigen biosynthesis was analysed and its content was found to be consistent with the O-polysaccharide structure.