2D 1H NMR Spectroscopy Research Articles

Structure elucidation and biosynthesis gene cluster organization of the O-antigen of Escherichia coli O170

Enterotoxigenic Escherichia coli are causative agents of diarrhea in humans as well as animals, and E. coli O170 belongs to this virotype. Upon mild acid degradation of the lipopolysaccharide of E. coli O170, the branched O-polysaccharide chain was partially cleaved at β-d-glactofuranosidic linkages to give multiple products, including a linear tetrasaccharide and oligomers thereof. Studies of the acid degradation products and O-deacylated lipopolysaccharide by 1D and 2D 1H and 13C NMR spectroscopy enabled elucidation of the following O-polysaccharide structure: [Display omitted] Functions of genes in the O-antigen biosynthesis gene cluster were tentatively assigned and found to be in agreement with the O-polysaccharide structure.

A 1H NMR Study of Host/Guest Supramolecular Complexes of a Curcumin Analogue with β-Cyclodextrin and a β-Cyclodextrin-Conjugated Gemini Surfactant.

Host systems based on β-cyclodextrin (βCD) were employed as pharmaceutical carriers to encapsulate a poorly soluble drug, curcumin analogue (NC 2067), in order to increase its water solubility. βCD was chemically conjugated with an amphiphilic gemini surfactant with the ability to self-assemble and to form nanoscale supramolecular structures. The conjugated molecule, βCDgemini surfactant (βCDg), was shown to be a promising drug delivery agent. In this report, its physicochemical properties were assessed in aqueous solution using 1D and 2D 1H NMR spectroscopy. The results showed that the apolar hydrocarbon domain of the gemini surfactant was self-included within the βCD internal cavity. The host/guest complexes composed of native βCD or βCDg with NC 2067 were examined using 1D/2D ROESY NMR methods. The stoichiometry of βCD/NC 2067 complex was estimated using Job's method via 1H NMR spectroscopy. The binding geometry of NC 2067 within βCD was proposed using molecular docking and further supported by 1D and 2D ROESY NMR results. Addition of NC 2067 to βCDg revealed minimal changes to the overall structure of the βCDg system, in agreement with the formation of a βCDg/NC 2067 ternary complex.

Spectral and theoretical study of 2-methyl-3-{[(Z)-3-methyl-5-oxo-1-phenylpyrazol-4-ylidene)methyl]amino}quinazolin-4-one and its complexes with metal ions M(II)

2-Methyl-3-{[(Z)-3-methyl-5-oxo-1-phenylpyrazol-4-ylidene)methyl]amino}quinazolin-4-one was synthesized by condensation of 5-hydroxy-4-formyl-3-methyl-1-phenylpyrazole with N-amino-2-methylquinazolin-4-one and its structure and properties were studied by IR, 1H, 13C NMR, 2D 1H NMR (COSY) and electronic spectroscopy and mass-spectrometry. By the reaction of compound (III) with Cd(II), Zn(II), and Pb(II) acetates the intracomplex compounds of 1: 2 composition (metal: ligand) were obtained.

Effect of the alkyl chain length in 1-alkyl-3-methylimidazolium ionic liquids on inter-molecular interactions and rotational dynamics: A combined vibrational and NMR spectroscopic study

We have investigated the effect of increasing the alkyl chain length, n, in 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (CnC1ImTFSI) ionic liquids on both inter-molecular interactions and rotational dynamics. This has been addressed by combining 1D 1H and T1 relaxation NMR spectroscopy with vibrational spectroscopy, including both Raman and infrared. We find that the vibrational modes sensitive to inter-molecular interactions change only slightly with an increased alkyl chain length, with negligible changes for chains longer than the hexyl (n>6). This is nicely corroborated by 1H chemical shift changes, in particular of the aromatic protons. The 13C correlation times, τc, of the individual carbon atoms reveal that while the overall rotational mobility decreases with n, different dynamical properties are observed with the polar domains becoming the most dynamic and the imidazolium ring and its closest chain segment the most rigid. We conclude that the formation of segregated nano-domains in CnC1ImTFSI is accompanied by the formation of nano-dynamical heterogeneities, which can explain why classical theories fail to describe the dependence on n of macroscopically observed properties.

Structure and genetics of the O-antigen of Escherichia coli O169 related to the O-antigen of Shigella boydii type 6

The O-polysaccharide (O-antigen) of Escherichia coli O169 was studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the branched hexasaccharide repeating unit was established: [Display omitted] The O-polysaccharide of E. coli O169 differs from that of Shigella boydii type 6 only in the presence of a side-chain glucose residue. A comparison of the O-antigen biosynthesis gene clusters between the galF to gnd genes in the genomes of the two bacteria revealed their close relationship. The glycosyltransferase gene responsible for the formation of the β-d-Glcp-(1→6)-α-d-Galp linkage in the O-antigen was identified in the gene cluster.

Generalized adaptive intelligent binning of multiway data

NMR metabolic fingerprinting methods almost exclusively rely upon the use of one-dimensional (1D) 1H NMR data to gain insights into chemical differences between two or more experimental classes. While 1D 1H NMR spectroscopy is a powerful, highly informative technique that can rapidly and nondestructively report details of complex metabolite mixtures, it suffers from significant signal overlap that hinders interpretation and quantification of individual analytes. Two-dimensional (2D) NMR methods that report heteronuclear connectivities can reduce spectral overlap, but their use in metabolic fingerprinting studies is limited. We describe a generalization of Adaptive Intelligent binning that enables its use on multidimensional datasets, allowing the direct use of nD NMR spectroscopic data in bilinear factorizations such as principal component analysis (PCA) and partial least squares (PLS).

Structure of the O-polysaccharide of Escherichia coli O87

The following structure of the O-polysaccharide of Escherichia coli HS1/2 serving as a primary receptor for bacteriophage DT57-12 was elucidated by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy: [Display omitted] This structure is shared by E. coli O87 type strain. Putatively assigned functions of genes in the O-antigen gene cluster of E. coli O87 are consistent with the O-polysaccharide structure established.

Structure of fructans from three strains of Cronobacter dublinensis

Partially O-acetylated fructan was isolated by phenol—water extraction of cells of Cronobacter dublinensis G2732 followed by anion-exchange chromatography on DEAE-Toyopearl 650M. Structure of the isolated fructan was established by 2D 1H and 13C NMR spectroscopy. The same fructan but lacking O-acetyl groups was isolated from two other C. dublinensis strains, G3947 and G4061. Genes for the fructan biosynthesis were not found at the typical Cronobacter O-antigen gene cluster located between the conserved genes galF and gnd and are evidently located elsewhere on the chromosome.

Structure and gene cluster of the O-antigen of Escherichia coli O140

An acidic O-polysaccharide (O-antigen) was isolated from the lipopolysaccharide of Escherichia coli O140 and studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the branched hexasaccharide repeating unit was established: ▪The O-antigen gene cluster of E. coli O140 was sequenced. The gene functions were tentatively assigned by a comparison with sequences in the available databases and found to be in full agreement with the E. coli O140 polysaccharide structure.

Structure of the O-polysaccharide of the lipopolysaccharide of Pseudomonas chlororaphis subsp. aureofaciens UCM B-306

Structure of the O-specific polysaccharide from Pseudomonas chlororaphis subsp. aureofaciens UCM B-306 was elucidated by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The polysaccharide is built up of trisaccharide repeats containing d-rhamnose, 2,4-diacetamido-2,4,6-trideoxy-d-glucose (d-QuiNAc4NAc), and 2-acetamido-2-deoxy-d-galacturonic acid (d-GalNAcA), which is amidated in ∼40% repeats. It was suggested that the O-polysaccharide has a blockwise structure, which can be presented as follows:-[→3)-α-d-Rhap-(1→4)-α-d-GalpNAcA-(1→3)-α-d-QuipNAc4NAc-(1-]n→ and -[→3)-α-d-Rhap-(1→4)-α-d-GalpNAcAN-(1→3)-α-d-QuipNAc4NAc-(1-]m→, where GalNAcAN indicates 2-acetamido-2-deoxy-d-galacturonamide, n:m=∼3:2.

Synergetic skin targeting effect of hydroxypropyl-β-cyclodextrin combined with microemulsion for ketoconazole

The objective was to develop a ternary skin targeting system for ketoconazole (KET) using a combined strategy of microemulsion (ME) and cyclodextrin (HP-β-CD), i.e., KET-CD-ME, which exploits both virtues of cyclodextrin complex and ME to obtain the synergetic effect. KET-CD-ME was formulated using Labrafil M 1944 CS as oil phase, Solutol HS 15 as surfactant, Transcutol P as cosurfactant, and HP-β-CD solution as aqueous phase. The formulation of KET-CD-ME was optimized and the optimal formulation was characterized in terms of particle size, size distribution, pH value, and viscosity. Long term stability experiment showed that HP-β-CD could increase the physical stability of ternary system and KET chemical stability. Percutaneous permeation of KET from KET-CD-ME in vitro through rat skin was investigated in comparison with KET microemulsion (KET-ME), KET HP-β-CD inclusion solution (KET-CD), KET aqueous suspension, and commercial KET cream; the results showed that the combination of ME with HP-β-CD exhibited significantly synergistic effect on KET deposition within the skin (29.38±1.79μg/cm2) and a slightly synergistic effect on KET penetration through the skin (11.3μg/cm2/h). The enhancement of the combination on skin deposition was further visualized by confocal laser scanning microscope (CLSM). In vitro sensitivity against Candida parapsilosis test indicated that KET-CD-ME enhanced KET antifungal activity mainly owing to the solubilization of HP-β-CD on KET in the ternary system. Moreover, the interactions between HP-β-CD and KET in the ternary system were elucidated through microScale thermophoresis (MST) and 2D 1H NMR spectroscopy. The profiles from MST confirmed the host–guest interactions of HP-β-CD with KET in the ternary system and a deep insight into the interactions between KET and HP-β-CD were obtained by means of 2D 1H NMR spectroscopy. The results indicate that the ternary system of ME combination with HP-β-CD may be a promising approach for skin targeting delivery of KET.

Structures and gene clusters of the closely related O-antigens of Escherichia coli O46 and O134, both containing d-glucuronoyl-d-allothreonine

The O-polysaccharides (O-antigens) were isolated by mild acid degradation of the lipopolysaccharide (LPS) of Escherichia coli O46 and O134. The structures of their linear tetrasaccharide repeating units were established by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy: ▪.where d-aThr indicates d-allothreonine and R indicates O-acetyl substitution (∼70% on aThr and∼15% on GalNAc) in E. coli O46 whereas the O-acetylation is absent in E. coli O134. Functions of genes in the essentially identical O-antigen gene clusters of E. coli O46 and O134 were tentatively assigned by a comparison with sequences in available databases and found to be in agreement with the O-polysaccharide structures established.

Structure elucidation of the capsular polysaccharide of Acinetobacter baumannii AB5075 having the KL25 capsule biosynthesis locus

Capsular polysaccharide was isolated by the phenol–water extraction of Acinetobacter baumannii AB5075 and studied by 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the linear trisaccharide repeating unit was established:→3)-β-d-ManpNAcA-(1→4)-β-d-ManpNAcA-(1→3)-α-d-QuipNAc4NR-(1→where R indicates (S)-3-hydroxybutanoyl or acetyl in the ratio∼2.5:1. The genes in the polysaccharide biosynthesis locus designated KL25 are appropriate to the established CPS structure.

Structure of a new pseudaminic acid-containing capsular polysaccharide of Acinetobacter baumannii LUH5550 having the KL42 capsule biosynthesis locus

The capsular polysaccharide from Acinetobacter baumannii LUH5550 was studied by 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the branched trisaccharide repeating unit was established:▪where Pse5Ac7RHb indicates 5-acetamido-3,5,7,9-tetradeoxy-7-[(R)-3-hydroxybutanoylamino]-l-glycero-l-manno-non-2-ulosonic acid. The genes in the capsule biosynthesis locus designated KL42 are consistent with the structure established.

Study on Dendrobium officinale O-acetyl-glucomannan (Dendronan®): Part V. Fractionation and structural heterogeneity of different fractions

In this study, we used gradient ethanol precipitation method to fractionate Dendrobium officinale O-acetyl-glucomannan sample (DOP) and obtained four major fractions. All of them were O-acetyl glucomannans but with different Man/Glc ratio, molecular weight, and intrinsic viscosity. A method based on 1D 1H NMR spectroscopy was developed to calculate the degree of substitution of O-acetyl group and to evaluate the percentage of O-2 and O-3 position occupied by acetyl groups. It was observed that as ethanol concentration increased, the collected fractions tended to contain more O-acetyl groups. There were more acetyl groups attached to O-2 position than to O-3 position, but as ethanol concentration increased, the difference between O-2 and O-3 substitution tended to decrease. Furthermore, we extensively hydrolyzed the four major fractions using mannanase and cellulose into oligosaccahrides. These oligosaccharides were subjected to MALDI-tof-MS analysis. Results showed that glucomannan fragments rich in O-acetyl groups were highly resistant to cellulase and mannanase hydrolysis. The four fractions varied in the distribution pattern of oligosaccharides produced by enzymatic hydrolysis. In conclusion, all the four fractions were different in detailed structural features, although they shared the same major structure as 2,3-O-acetyl-glucomannan.

Synthesis, structure, and properties of the product formed in the reaction of ortho-diphenylphosphinobenzaldehyde and N-tosyl-1,2-phenylenediamine

Interaction of ortho-diphenylphosphinobenzaldehyde with N-tosyl-1,2-phenylenediamine afforded the product of intramolecular Wittig reaction, N-{2-[2-(Diphenylphosphoryl)benzylamino]phenyl}-4-methylbenzenesulfonamide. Its structure was established on the basis of IR, 1H NMR, 13C NMR, and 2D 1H NMR (COSY) spectroscopy. Reaction mechanism was studied by means of quantum chemistry DFT method. Complexforming property of the obtained diphenylphosphine oxide was investigated.

Temperature sensitive supramolecular self assembly of per-6-PEO-β-cyclodextrin and α,ω-di-(adamantylethyl)poly(N-isopropylacrylamide) in water.

The host/guest interactions in water of a star polymer consisting of a β-cyclodextrin (β-CD) core bearing six poly(ethylene oxide) arms linked to the C6 positions of β-CD (β-CD-PEO7, Mn 5000 g mol(-1)) and α,ω-di-(adamantylethyl)poly(N-isopropylacrylamide) (Ad-PNIPAM-12K, Mn 12,000 g mol(-1)) were studied by 1D and 2D (1)H and (13)C NMR spectroscopy, isothermal calorimetry (ITC), and light scattering (LS). In cold water (T < 26 °C) supramolecular "dumbbell" assemblies, consisting of PNIPAM chains with β-CD/Ad inclusion complexes at each end, formed viaβ-CD-insertion of the terminal Ads through the β-CD secondary face. Light scattering, microcalorimetry (DSC), and DOSY NMR studies indicated that mixed aqueous solutions of β-CD-PEO7 and Ad-PNIPAM-12K undergo a reversible heat-induced phase transition at ∼32 °C, accompanied by a release of a fraction of the Ad-bound β-CD-PEO7 into bulk solution and the formation of aggregated Ad-PNIPAM-12K stabilized by a β-CD-PEO7 shell.

Structure of the capsular polysaccharide of Acinetobacter baumannii 1053 having the KL91 capsule biosynthesis gene locus

Acinetobacter baumannii 1053 is the type strain for the maintenance of specific bacteriophage AP22, which infects a fairly broad range of A. baumannii strains circulating in Russian clinics and hospitals. A capsular polysaccharide (CPS) was isolated from cells of strain 1053 and studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the linear trisaccharide repeating unit was established: [Display omitted] where ManNAcA and FucNAc indicate 2-acetamido-2-deoxymannuronic acid and 2-acetamido-2,6-dideoxygalactose, respectively. A polysaccharide having the same repeating unit but a shorter chain was isolated by the phenol–water extraction of bacterial cells. Sequencing of the CPS biosynthesis gene locus showed that A. baumannii 1053 belongs to a new group designated KL91. The gene functions assigned putatively by a comparison with available databases were in agreement with the CPS structure established.

Structural and genetic studies of the O-antigen of Escherichia coli O163

An acidic O-polysaccharide (O-antigen) of Escherichia coli O163 was obtained by mild acid hydrolysis of the lipopolysaccharide and studied by sugar analysis and Smith degradation along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the linear tetrasaccharide repeating unit was established, which is unique among known structures of bacterial polysaccharides: [Display omitted] Functions of genes in the O-antigen gene cluster of E. coli O163 were tentatively assigned by comparison with sequences in the available databases and found to be in agreement with the O-polysaccharide structure. Relationships between O-antigen structures and gene clusters of E. coli O163 and Salmonella enterica O41 are discussed.

Structure of the O-specific polysaccharides from planktonic and biofilm cultures of Pseudomonas chlororaphis 449

O-Specific polysaccharides were obtained from the lipopolysaccharides isolated from the planktonic and biofilm cultures of Pseudomonas chlororaphis 449 and studied by composition analysis and 1D and 2D 1H and 13C NMR spectroscopy. The following structure was established: [Display omitted] where the degree of non-stoichiometric 6-O-acetylation of GalNAc is ∼60% in the planktonic form or ∼10% in biofilm.