Heteronuclear Multiple Bond Correlation Spectroscopy Research Articles

Isosakuranetin-5-O-rutinoside: A New Flavanone with Antidepressant Activity Isolated from Salvia elegans Vahl.

Ursolic acid (1) and a new flavanone, 5-O-(6-rhamnosylglucoside)-7-hydroxy-4'-methoxyflavanone (2), were isolated from the leaves of Salvia elegans Vahl. These natural products displayed antidepressant activity in mice as determined by means of a forced swimming test (FST) evaluation. Structural elucidation was carried out by chemical derivatization (acetylation) and spectroscopic analyses, such as 1H- and 13C-NMR and two-dimensional (2-D) COSY, heteronuclear multiple quantum coherence (HMQC), and heteronuclear multiple-bond correlation (HMBC) spectroscopy experiments.

Characterization of an Antibiotic Produced by Bacillus subtilis JW-1 that Suppresses Ralstonia solanacearum

Bacillus subtilis JW-1 was isolated from rhizosphere soil as a potential biocontrol agent of bacterial wilt caused by Ralstonia solanacearum. Seed treatment followed by a soil drench application with this strain resulted in >80% reduction in bacterial wilt disease compared with that in the untreated control under greenhouse conditions. The antibacterial compound produced by strain JW-1 was purified by bioactivity-guided fractionation. Based on mass spectroscopy and nuclear magnetic resonance spectral data ((1)H, (13)C, (1)H-(1)H correlation spectroscopies, rotating frame nuclear Overhauser effect spectroscopy, and heteronuclear multiple-bond correlation spectroscopy), the structure of this compound was elucidated as a cyclic lipopeptide composed of a heptapeptide (Gln-Leu-Leu-Val-Asp-Leu-Leu) bonded to a β-hydroxy-iso-hexadecanoic acid arranged in a lactone ring system.

Phlomiside: A new steroid from Phlomis bracteosa

A new steroid named Phlomiside (1) has been isolated from the whole plant including roots from the ethylacetate fraction of Phlomis bracteosa along with four known compounds namely β-amyrin (2), β-sitosterol (3), stigmasterol (4) and oleanolic acid (5). The structure assignments are based primarily on two-dimensional (2D)-NMR techniques including correlation spectroscopy (COSY), heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC) and nuclear overhauser effect spectroscopy (NOESY) experiments.

Multidimensional NMR characterization of perfluorinated monomer and its precursors

Perfluorinated monomer (perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolane), its precursor (perfluoro-2,4,5-trimethyl-1,3-dioxolane-2-carboxylic acid), as well as their hydrocarbon precursor (methyl 2,4,5-trimethyl-1,3-dioxolane-2-carboxylate), were prepared and studied by 1D- and advanced 2D NMR techniques. For both perfluorinated compounds, the structures of their possible isomers were proven by 2D NMR spectroscopy. Due to the large 19F spectral window, this study used selective versions of the correlation spectroscopy (COSY) and nuclear Overhauser effect spectroscopy (NOESY) experiments to provide better resolution and sensitivity. In addition, a new variation of the gradient heteronuclear single quantum coherence spectroscopy (gHSQC) sequence was successful for observing two-bond 19F13C correlations. Compared with the gradient heteronuclear multiple bond correlation spectroscopy (gHMBC) spectrum, the 2JFC gHSQC spectrum is greatly simplified due to the absence of splittings caused by multi-quantum coherence. Quantitative 1H or 19F 1D NMR was used to confirm the resonance assignments and to calculate the ratio of isomers. The configurational compositions of perfluorinated compounds and their hydrocarbon precursor support the idea that fluorination by elemental fluorine is a free radical process.

Investigation of Cation Degradation in Anion Exchange Membranes Using Multi-Dimensional NMR Spectroscopy

Low temperature anion exchange polymer electrolyte membrane (AEM) based fuel cells and electrolyzers have been successfully shown to convert hydrogen and oxygen to electricity (and vice-versa) with high efficiencies and energy densities with non-precious group metals. However, a significant challenge to realizing these technologies is the poor alkaline stability of the AEMs. In this work, we present the results of our multi-faceted approach to better understand AEM degradation in alkaline media. Several two-dimensional (2D) NMR techniques were applied to comprehensively elucidate cation degradation in polysulfone-based AEMs exposed to alkaline solutions. The 2D NMR tools utilized were: a) homonuclear correlation spectroscopy (COSY), b) 1H-X (X = 13C or 31P) heteronuclear multiple quantum correlation spectroscopy (HMQC), and c) 1H-13C heteronuclear multiple bond correlation spectroscopy (HMBC). Analysis of the 2D NMR spectra enabled precise identification of the degradation products for several different cation chemistries (quaternary ammonium, imidazolium, and phosphonium types). The observation of multiple degradation products highlighted the fact that the cation groups degraded through fundamentally different mechanisms. A clear understanding of the degradation mechanism is a critical requirement in the process of selecting or designing alternate cation chemistries for alkaline resilient AEMs.

Antiinflammatory and Antioxidant Flavonoids and Phenols from Cardiospermum halicacabum (倒地鈴 Dào Dì Líng)

Seventeen compounds, quercetin-3-O-α-l-rhamnoside (1), kaempferol-3-O-α-l-rhamnoside (2), apigenin-7-O-β-d-glucuronide (3), apigenin 7-O-β-d-glucuronide methyl ester (4), apigenin 7-O-β-d-glucuronide ethyl ester (5), chrysoeriol (6), apigenin (7), kaempferol (8), luteolin (9), quercetin (10), methyl 3,4-dihydroxybenzoate (11), p-coumaric acid (12), 4-hydroxybenzoic acid (13), hydroquinone (14), protocathehuic acid (15), gallic acid (16), and indole-3-carboxylic acid (17), were isolated from the ethanol extract of Taiwanese Cardiospermum halicabum. All chemical structures were determined by physical and extensive spectroscopic analyses such as 1H Nuclear Magnetic Resonance spectroscopy (NMR), 13C NMR, 1H-1H Correlation spectroscopy (1H-1H COSY), Heteronuclear Multiple Quantum Coherence spectroscopy (HMQC), Heteronuclear Multiple-bond Correlation spectroscopy (HMBC), and Nuclear Overhauser Effect spectroscopy (NOESY), as well as comparison with literature values. Furthermore, the High-Performance Liquid Chromatography-Photodiode Array Detector (HPLC-DAD) fingerprint profile was established for the determination of major constituents in the EtOAc extract and retention times of the isolated compounds. All isolated compounds were also evaluated for antiinflammatory and antioxidant activities.

Antiinflammatory and Antioxidant Flavonoids and Phenols from Cardiospermum halicacabum ( Dào Dì Líng).

Seventeen compounds, quercetin-3-O-α-l-rhamnoside (1), kaempferol-3-O-α-L-rhamnoside (2), apigenin-7-O-β-D-glucuronide (3), apigenin 7-O-β-D-glucuronide methyl ester (4), apigenin 7-O-β-D-glucuronide ethyl ester (5), chrysoeriol (6), apigenin (7), kaempferol (8), luteolin (9), quercetin (10), methyl 3,4-dihydroxybenzoate (11), p-coumaric acid (12), 4-hydroxybenzoic acid (13), hydroquinone (14), protocathehuic acid (15), gallic acid (16), and indole-3-carboxylic acid (17), were isolated from the ethanol extract of Taiwanese Cardiospermum halicabum. All chemical structures were determined by physical and extensive spectroscopic analyses such as 1 H Nuclear Magnetic Resonance spectroscopy (NMR), 13C NMR, 1H-1H Correlation spectroscopy (1H-1H COSY), Heteronuclear Multiple Quantum Coherence spectroscopy (HMQC), Heteronuclear Multiple-bond Correlation spectroscopy (HMBC), and Nuclear Overhauser Effect spectroscopy (NOESY), as well as comparison with literature values. Furthermore, the High-Performance Liquid Chromatography- Photodiode Array Detector (HPLC-DAD) fingerprint profile was established for the determination of major constituents in the EtOAc extract and retention times of the isolated compounds. All isolated compounds were also evaluated for antiinflammatory and antioxidant activities.

Complete NMR assignment of a sulfonated aromatic block copolymer via heteronuclear single-quantum correlation, heteronuclear multiple-bond correlation and heteronuclear single-quantum correlation total correlation spectroscopy

A sulfonated aromatic block copolymer (SABC), consisting of hydrophobic and hydrophilic blocks, was analyzed by heteronuclear single-quantum correlation (HSQC), heteronuclear multiple-bond correlation (HMBC) and HSQC total correlation spectroscopy (HSQC–TOCSY). Because of its complicated chemical structure with five different phenylene rings, 12 types of 1H signals and 24 types of 13C signals were observed in a narrow chemical shift range (7.0–8.0 p.p.m. for 1H and 118–162 p.p.m. for 13C). To improve the 1H signal separation, the temperature conditions for the 1H nuclear magnetic resonance (NMR) experiments were optimized. Moreover, 1H and 13C NMR signal assignments for the hydrophobic blocks were performed using HSQC and HMBC, with reference to the assignments of a model oligomer. For the hydrophilic blocks, furthermore, HSQC–TOCSY techniques were applied. As a result of these studies, complete 1H and 13C NMR signal assignments were made for the SABC. The ion-exchange capacity (IEC) and the copolymerization composition were calculated using the 1H NMR assignments for the SABC, and the IEC value obtained in this way was consistent with that obtained via titration. A sulfonated aromatic block copolymer (SABC), consisting of hydrophobic and hydrophilic blocks, was analyzed by 2D NMR techniques of HSQC, HMBC and HSQC–TOCSY. Because of its complicated chemical structure with five different phenylene rings, 12 types of 1H signals and 24 types of 13C signals were observed in a narrow chemical shift range (7.0–8.0 p.p.m. for 1H and 118–162 p.p.m. for 13C). As a result of these studies, complete 1H and 13C NMR signal assignment of SABC was performed.

STRUCTURAL CHARACTERIZATION AND ANTI-GLYCATION ACTIVITYIN VITROOF A WATER-SOLUBLE POLYSACCHARIDE FROMDENDROBIUM HUOSHANENSE

A water-soluble polysaccharide with anti-glycation activity, designated as DHP-W2, was isolated and purified from the fresh stems of Dendrobium huoshanense. DHP-W2 mainly consisted of glucose, xylose, galactose and trace of galacturonic acid, and its average molecular weight was approximately 73 kDa. Methylation analysis and one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy, including 1H-NMR, 13C-NMR, 1H-1H correlation spectroscopy, heteronuclear single quantum correlation spectroscopy and heteronuclear multiple-bond correlation spectroscopy, revealed that the repeating units of DHP-W2 had a backbone consisting of 1,6-linked β-D-Glcp, 1,4-linked β-D-Glcp and 1,4,6-linked β-D-Glcp with branches at O-4/6. Sugar residues of branches were 1,2,4-linked α-D-Xylp, 1,4-linked α-D-Xylp, 1-linked α-D-Xylp, 1-linked α-D-Galp and 1-linked α-D-GalpA. Preliminary experiment in vitro indicated that DHP-W2 had an anti-glycation activity with dose- and time-dependent effects. PRACTICAL APPLICATIONS Because of potential biological and pharmacological functions, polysaccharides from edible and medicinal plants have gained special attention in the food industry. Dendrobium huoshanense C. Z. Tang and S. J. Cheng, 1984, which is a well-known edible and medicinal plant belonging to Orchidaceae family, has been used as a tonic to prevent cataractogenesis, throat inflammation and chronic superficial gastritis for centuries in China. This paper reports the structure features of a homogeneous polysaccharide obtained from D. huoshanense and its anti-glycation activity by a combination of chemical, instrumental and biochemical analysis approaches, including gas chromatography–mass spectrometry (GC-MS), methylation analysis, Fourier transform infrared, one- and two-dimensional nuclear magnetic resonance spectroscopy, and fluorescence spectrophotometry. The paper's purpose was to provide structural information not only for further elucidation of the relationship between structure and function but also for better understanding of pharmacological mechanism of D. huoshanense polysaccharides. It can be expected to develop the functions of the polysaccharides from D. huoshanense in food industries.

Structural Determination of a Key Exopolysaccharide in Mixed Culture Aerobic Sludge Granules Using NMR Spectroscopy

Nuclear magnetic resonance (NMR) techniques were used to elucidate the structure of an exopolysaccharide material previously revealed to be important in formation of aerobic granules. The 1D NMR spectral data acquired showed that this gel-forming polysaccharide was a major component of granular EPS, while 1D and 2D NMR spectra showed it consisted of eight sugar residues. These were assigned as α-galactose, α-rhamnose, 2-acetoamido-2-deoxy-α-galactopyranuronic acid, β-mannose, β-galactose, β-glucuronate, β-glucosamine, and N-acetyl β-galactosamine. With the exception of 2-acetoamido-2-deoxy-α-galactopyranuronic acid, a highly unusual sugar, their presence was confirmed with high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Carbon and proton shifts were assigned for each sugar. Heteronuclear multiple bond correlation (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY) were used to identify linkage sites between individual sugar residues. This gel-forming exopolysaccharide appeared to be a highly complex single heteropolysaccharide with a repeat sequence of α-galactose, β-mannose, β-glucosamine, N-acetyl-β-galactosamine, and 2-acetoamido-2-deoxy-α-galactopyranuronic acid. It has a disaccharide branch of β-galactose and β-glucuronic acid attached to 2-acetoamido-2-deoxy-α-galactopyranuronic acid and an α-rhamnose branch attached to α-galactose.

Hexa-, hepta- and nonaprenylhydroquinones isolated from marine sponges Sarcotragus muscarum and Ircinia fasciculata inhibit NF-k B signalling in H4IIE cells

Abstract Objectives Marine organisms have proven to be a rich source of potent pharmacologically active compounds. Three polyprenyl-1,4-hydroquinone derivates (hexaprenyl-1,4-hydroquinone, heptaprenyl-1,4-hydroquinone and nonaprenyl-1,4-hydroquinone) were isolated from the Zoobenthos-inhabiting sponges Sarcotragus muscarum and Ircinia fasciculata from the Eastern Mediterranean Sea (phylum: Porifera; class: Demospongiae). Methods Hexa-, hepta- and nonaprenylhydroquinone were identified by 1H-NMR, H,H-COSY, heteronuclear multiple bond correlation, FAB-MS and UV spectroscopy. The effects of the compounds on cell viability was determined using the MTT assay; anti-oxidative potential was measured using the Trolox equivalent antioxidative capacity assay. Inhibition of nuclear factor-k B activity was detected by secreted alkaline phosphatase assay. Activity against an array of protein kinases was determined in 96-well FlashPlates. Key findings All compounds had prominent antioxidative activity, comparable to that of the synthetic vitamin E derivate Trolox. Hexaprenylhydroquinone showed the greatest cytotoxicity in H4IIE hepatoma cells (EC50 2.5 μM). All three compounds inhibited NF-k B signalling in this cell line, with heptaprenylhydroquinone being the most active. Screening of 23 kinases involved in signal transduction pathways (cell proliferation, survival, angiogenesis and metastasis) showed that hexaprenylhydroquinone and heptaprenylhydroquinone inhibited the activity of the epidermal growth factor receptor (IC50 1.6 and 1.4 μg/ml, respectively), and heptaprenylhydroquinone also inhibited the activity of other kinases (Src tyrosine kinase, vascular endothelial growth factor receptor 3 and insulin-like growth factor 1 receptor). Conclusions The prenylated hydroquinones isolated from the marine sponges S. muscarum and I. fasciculata showed cytotoxic and antioxidative activities and inhibited NF-k B signalling in H4IIE hepatoma cells and protein kinases. These findings may result in the generation of new lead substances in cancer therapy.

Simultaneous C7- and N1-prenylation of cyclo-l-Trp-l-Trp catalyzed by a prenyltransferase from Aspergillus oryzae

A putative prenyltransferase gene cTrpPT was amplified from Aspergillus oryzae DSM1147, cloned into pQE70 and overexpressed in Escherichia coli. The overproduced His(6)-CTrpPT was purified to near homogeneity and incubated with L-tryptophan or tryptophan-containing cyclic dipeptides in the presence of dimethylallyl diphosphate. The formation of the enzyme products was monitored with HPLC. It was shown that CTrpPT differed clearly from other known indole prenyltransferases in several aspects. This enzyme showed higher substrate specificity towards aromatic substrates, but lower regioselectivity regarding the prenylation position than other indole prenyltransferases. Cyclo-L-Trp-L-Trp was much better accepted than other cyclic dipeptides tested in this study. In comparison to other indole prenyltransferases with one dominant enzyme product, at least two product peaks were detected in the reaction mixtures of CTrpPT. (1)H- and (13)C-NMR analyses, including long-range (1)H-(13)C connectivities in Heteronuclear Multiple-Bond Correlation (HMBC) and Nuclear Overhauser Effect Spectroscopy (NOESY), proved the structures of the enzyme products as C7- and N1-prenylated derivatives with a ratio of 1:1.2 using cyclo-L-Trp-L-Trp as substrate. The K(M) values were determined at about 2.5 mM for dimethylallyl diphosphate and 0.3 mM for cyclo-L-Trp-L-Trp with a turnover number of 0.33 s(-1).

Hexa-, hepta- and nonaprenylhydroquinones isolated from marine sponges <I>Sarcotragus muscarum</I> and <I>Ircinia fasciculata</I> inhibit NF-<I>κ</I>B signalling in H4IIE cells

Marine organisms have proven to be a rich source of potent pharmacologically active compounds. Three polyprenyl-1,4-hydroquinone derivates (hexaprenyl-1,4-hydroquinone, heptaprenyl-1,4-hydroquinone and nonaprenyl-1,4-hydroquinone) were isolated from the Zoobenthos-inhabiting sponges Sarcotragus muscarum and Ircinia fasciculata from the Eastern Mediterranean Sea (phylum: Porifera; class: Demospongiae). Hexa-, hepta- and nonaprenylhydroquinone were identified by (1)H-NMR, H,H-COSY, heteronuclear multiple bond correlation, FAB-MS and UV spectroscopy. The effects of the compounds on cell viability was determined using the MTT assay; anti-oxidative potential was measured using the Trolox equivalent antioxidative capacity assay. Inhibition of nuclear factor-kappaB activity was detected by secreted alkaline phosphatase assay. Activity against an array of protein kinases was determined in 96-well FlashPlates. All compounds had prominent antioxidative activity, comparable to that of the synthetic vitamin E derivate Trolox. Hexaprenylhydroquinone showed the greatest cytotoxicity in H4IIE hepatoma cells (EC50 2.5 muM). All three compounds inhibited NF-kappaB signalling in this cell line, with heptaprenylhydroquinone being the most active. Screening of 23 kinases involved in signal transduction pathways (cell proliferation, survival, angiogenesis and metastasis) showed that hexaprenylhydroquinone and heptaprenylhydroquinone inhibited the activity of the epidermal growth factor receptor (IC50 1.6 and 1.4 mug/ml, respectively), and heptaprenylhydroquinone also inhibited the activity of other kinases (Src tyrosine kinase, vascular endothelial growth factor receptor 3 and insulin-like growth factor 1 receptor). The prenylated hydroquinones isolated from the marine sponges S. muscarum and I. fasciculata showed cytotoxic and antioxidative activities and inhibited NF-kappaB signalling in H4IIE hepatoma cells and protein kinases. These findings may result in the generation of new lead substances in cancer therapy.

Organometallic Osmium(II) and Ruthenium(II) Biphenyl Sandwich Complexes: X‐ray Crystal Structures and 187Os NMR Spectroscopic Studies in Solution

AbstractWe report the synthesis of the ruthenium(II) and osmium(II) organometallic sandwich complexes [Ru(η6‐bip)2](OTf)2 (1) and [Os(η6‐bip)2](OTf)2 (2) containing biphenyl (bip) as the arene ligand, and the X‐ray crystal structures of 1·MeOH and 2. The unit cell of the osmium complex contains molecules in which the unbound phenyl ring of the biphenyl ligands exists in both staggered and eclipsed configurations, whereas for the ruthenium complex the rings are only eclipsed. Both crystal structures possess CH/π and π–π stacking interactions. 187Os (nuclear spin 1/2, natural abundance of 1.64 %) has a very low gyromagnetic ratio and is one of the most insensitive nuclei in the periodic table. We show that inverse NMR spectroscopic detection by the use of 1H/187Os heteronuclear multiple bond correlation (HMBC) spectroscopy allows the ready observation of the 187Os resonance of complex 2 via couplings to arene ring protons. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Classification of Italian Honeys by 2D HR-NMR

The importance of honey has been recently increased because of its nutrient and therapeutic effects, but the adulteration of honey in terms of botanical origin has increased, too. The floral origin of honeys is usually determined using melisso-palynological analysis and organoleptic characteristics, but the application of these techniques requires some expertise. A number of papers have confirmed the possibility of characterizing honey samples by selected chemical parameters. In this study high-resolution nuclear magnetic resonance (HR-NMR) and multivariate statistical analysis methods were used to identify and classify honeys of five different floral sources. The 71 honey samples (robinia, chestnut, citrus, eucalyptus, polyfloral) were analyzed by HR-NMR using both 1H NMR and heteronuclear multiple bond correlation spectroscopy (HMBC). Spectral data were analyzed by application of unsupervised and supervised pattern recognition and multivariate statistical techniques such as principal component analysis (PCA) and general discriminant analysis (GDA). The use of 1H-(13)C HMBC coupled with appropriate statistical analysis seems to be an efficient technique for the classification of honeys.

Positive Identification of the Principal Component of a White Powder as Scopolamine by Quantitative One‐Dimensional and Two‐Dimensional NMR Techniques

An unidentified white powder collected as evidence in an intelligence investigation was characterized exclusively by nuclear magnetic resonance (NMR) analysis. A small fraction of the powder dissolved in D2O was subjected to a series of one- and two-dimensional techniques which were used to elucidate the molecular structure of the powder's major component and positively identify it as the scopolamine biotoxin. Quantitative one-dimensional experiments identified individual proton and carbon atom sites, and conventional 14N spectroscopy detected a single nitrogen atom site. Heteronuclear single quantum coherence data correlated all protons to their directly bonded carbon atom, and together with the quantitative spectra, were used to determine the number of protons directly bonded to each carbon atom. The presence of a methyl, carboxyl, and a benzyl group was also identified from these data. Correlation spectroscopy detected a three proton and a nine proton JH,H network, representing a CH2CH moiety and seven carbon atom ring, respectively. These five elements were assembled into an almost complete molecular structure by using long-range, J-coupled, 1H-13C pairs detected by heteronuclear multiple bond correlation (HMBC) spectroscopy and 1H-1H dipolar-coupled pairs found from nuclear Overhauser effect spectroscopy (NOESY) data. Additional oxygen atom sites were inferred from 1H-13C correlation intensities in the HMBC spectra along with 1H and 13C chemical shift values, or directly from NOESY correlations. Only a single oxygen atom site could not be inferred from NMR data, but its presence was inferred from comparisons to target analyte structures to complete the structure of the scopolamine molecule. To confirm these results, an ethanol/H2O solution of the powder was analyzed by direct infusion into an ion trap mass spectrometer. A prominent base signal was observed at m/z 304.1 amu, corresponding to the protonated molecular ion of scopolamine. Subsequently, the ion was selected and subjected to collision-induced dissociation, producing characteristic major MS/MS fragments at m/z 138.1 and 156.1. Comparisons of 1H and 13C chemical shift values and JH,H values measured from our NMR data were found to agree very favorably with previously reported values for scopolamine in D2O.

Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2D NMR spectroscopy

Carboxyl groups are abundant in natural organic molecules (NOM) and play a major role in their reactivity. The structural environments of carboxyl groups in IHSS soil and river humic samples were investigated using 2D NMR (heteronuclear and homonuclear correlation) spectroscopy. Based on the 1H– 13C heteronuclear multiple-bond correlation (HMBC) spectroscopy results, the carboxyl environments in NOM were categorized as Type I (unsubstituted and alkyl-substituted aliphatic/alicyclic), Type II (functionalized carbon substituted), Type IIIa, b (heteroatom and olefin substituted), and Type IVa, b (5-membered heterocyclic aromatic and 6-membered aromatic). The most intense signal in the HMBC spectra comes from the Type I carboxyl groups, including the 2 J CH and 3 J CH couplings of unsubstituted aliphatic and alicyclic acids, though this spectral region also includes the 3 J CH couplings of Type II and III structures. Type II and III carboxyls have small but detectable 2 J CH correlations in all NOM samples except for the Suwannee River humic acid. Signals from carboxyls bonded to 5-membered aromatic heterocyclic fragments (Type IVa) are observed in the soil HA and Suwannee River FA, while correlations to 6-membered aromatics (Type IVb) are only observed in Suwannee River HA. In general, aromatic carboxylic acids may be present at concentrations lower than previously imagined in these samples. Vibrational spectroscopy results for these NOM samples, described in an accompanying paper [Hay M. B. and Myneni S. C. B. (2007) Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1: Infrared spectroscopy. Geochim. Cosmochim. Acta (in press)], suggest that Type II and Type III carboxylic acids with α substituents (e.g., –OH, –OR, or –CO 2H) constitute the majority of carboxyl structures in all humic substances examined. Furoic and salicylic acid structures (Type IV) are also feasible fragments, albeit as minor constituents. The vibrational spectroscopy results also suggest that much of the “Type I” signal observed in the HMBC spectrum is due to carboxylic acid esters and possibly α-substituted alicyclic acids.

Comprehensive Sequence Distribution Analysis of Butyl methacrylate-Acrylonitrile Copolymers by Two-dimensional NMR Spectroscopy

The acrylonitrile-butyl methacrylate (A/B) copolymers were synthesized by solution polymerization utilizing 2,2′-azobisisobutyronitrile (AIBN) as free radical initiator. Reactivity ratios were assessed by Kelen-Tudos and non-linear error in variable method and were found to be rA=0.37±0.03, rB=1.44±0.16 (KT) and rA=0.36, rB=1.40 (RREVM) respectively which confirmed that butyl methacrylate monomer is more reactive than acrylonitirile towards propagating chain during radical polymerization. 2D HSQC spectroscopy in conjugation with TOCSY afforded explicit information about compositional and configurational sequences. Methine and β-methylene regions revealed compositional sensitivity up to pentad and tetrad level respectively with meso and racemic configurations. TOCSY demonstrated the coupling between the methine protons of A centered triad and pentad units with β-methylene protons of various tetrads. Heteronuclear multiple-bond correlation (HMBC) spectroscopy has been employed to study carbon (carbonyl/nitrile)-proton coupling. The carbonyl and nitrile carbons expressed compositional sensitivity up to the triad level.

Phosphorus–nitrogen compounds: Synthesis and spectral investigations on new spiro-cyclic phosphazene derivatives

The condensation reaction of { N-[(2-hydroxyphenylmethyl)amino]-4,6-dimethylpyridine} ( 2), which is a reduction product of 1, with trimer N 3P 3Cl 6 affords partially a substituted spiro-cyclic phosphazene derivative ( 3). The fully substituted phosphazenes ( 4 and 5) have also been obtained from the reactions of 3 with the excess of pyrrolidine and morpholine. The characterizations and spectral investigations of these compounds have been made by elemental analyses, FTIR, 1H-, 13C-, 31P NMR, correlation spectroscopy (COSY), heteronuclear chemical shift correlation (HETCOR), heteronuclear multiple-bond correlation (HMBC) and mass spectroscopy (MS). The salient features of spectral data of these compounds have been discussed.

Separation and characterization of alkyl phenol formaldehyde resins demulsifier by adsorption chromatography, gel permeation chromatography, infrared spectrometry and nuclear magnetic resonance spectroscopy

This paper deals with the separation and characterization of alkyl phenol formaldehyde resins demulsifier by infrared spectrometry and nuclear magnetic resonance spectroscopy after separation of the different surfactants and low molecular additives by adsorption chromatography. Firstly, the types of surfactants are identified by methylene blue chloride–chloroform test method and the elemental analysis such as Ca, K, Mg, Na, P, S and N. Then, the different surfactants and low molecular components are separated by adsorption chromatography after parts of low molecular components are dried in an oven, and the molecular weight distribution is measured by gel permeation chromatography also. Finally, the separated surfactants are determined by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR) spectroscopy. The distortionless enhancement by polarization transfer (DEPT), H, C correlated spectroscopy (H, C–COSY), H, H correlated spectroscopy (H, H–COSY) and heteronuclear multiple-bond correlation (HMBC) spectroscopy are applied to determine the molecular structures.