This review covers two important techniques, high resolution nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS), used to characterize food products and detect possible ...adulteration of wine, fruit juices, and olive oil, all important products of the Mediterranean Basin. Emphasis is placed on the complementary use of SNIF-NMR (site-specific natural isotopic fractionation nuclear magnetic resonance) and IRMS (isotope-ratio mass spectrometry) in association with chemometric methods for detecting the adulteration.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Lipopolysaccharide (LPS) induced Gram-negative sepsis and septic shock remain lethal in up to 60 % of cases, and LPS antagonists that neutralize its endotoxic action are the subject of intensive ...research. In the last decade peptidic antagonists have become increasingly important in providing leads for treatment of LPS-mediated diseases. In this review an overview of the sources, functions and structures of antiseptic and antibacterial peptides that interact with LPS is presented.
In order to confirm that tert-butyl ester protection at the isoglutaminyl residue prevents the base-catalyzed iso-glutamine = glutamine rearrangement in title compounds, ...6-0-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-N-acetylmura-moyl-L-alanyl-D-glutamine (7) was synthesized from α-benzyl glycoside of 6-0-(2-acetamido-3,4,6-tri-0-acetyl-2-deoxy-β-D-glucopyranosyl)-N-acetylmuramic acid (2) and Z-L-Ala-D-Glu(NH
2
)OBu
t
via its α-tert-butyl ester 5.
1
H and
13
C NMR measurements were carried out with regioisomeric β-GlcNAc-(1-→6)-MurNAc-L-Ala-D-glutamine and -isoglutamine derivatives; the presented data show differences that enable distinction between the sugar-peptide regioisomers.
Trans-octahydro-2H-1,4-benzoxazin-3-one and its 2-alkyl derivatives can be conveniently prepared from trans-2-azidocyclohexanol and corresponding α-haloacids.
Glycerol, which functions as an osmoregulator in the early stages of Aspergillus niger growth, slowly diffuses out of the cells and possibly into the mitochondria. Since mitochondrial nicotine ...adenine dinucleotide phosphate (NADP+)-specific isocitrate dehydrogenase is inhibited by glycerol, citrate starts to accumulate in the cells. At physiological pH values citric acid dissociates and affects the intercellular and extracellular pH. By the phosphorus-31-nuclear magnetic resonance technique a drop in intracellular pH from 7.1 to about 6.5 has been detected, which might significantly influence metabolic rates. In vitro tests showed that the highest concentration of glycerol was found in the medium at about the same time as the change in morphology. This could account for the inhibition of mitochondrial nicotine adenine dinucleotide phosphate (NADP+)-specific isocitrate dehydrogenase (ICDH) and cause the initiation of citric acid accumulation (Legisa and Mattey 1986a). The present paper attempts to elucidate the initiation of this accumulation.
Cationic antibacterial peptides are potentially therapeutic in the treatment of sepsis, because of their amalgamated antibacterial and lipopolysaccharide-binding activities. We prepared acyl ...analogues of the peptide fragment of human lactoferrin, which originally had weak antibacterial activity. It was found that 12 carbon units constitute the optimal acyl chain length, enhancing the antibacterial activity and binding of lipopolysaccharide by up to two orders of magnitude. Lactoferrin-based lipopeptides approached the activity of polymyxin B, a lipopeptide of natural origin, but were also active against Gram-positive bacteria.
In our work, the capacity of 1D and 2D
1
H
and
13
C
homo and heteronuclear nuclear magnetic resonance (NMR) experiments were examined for the characterization of amino acids and anthocyanins, the ...“minor” but important compounds of wine. The compositions of amino acids and anthocyanins influence the flavour of wines and their composition could be used to differentiate wines according to the vine variety, geographical origin and year of production. Anthocyanins are also the major components responsible for the red wine color and they have a wide range of biochemical and pharmacological effects such as antimicrobial and antioxidant activities.
We use the signal intensities in 1D
1
H
NMR spectra in the chemometric analysis of white wines from Slovenia. The use of signals of seven amino acids gives a good separation of wines according to the vine variety, while adding also the signal intensities of glycerol, butylene glycol and succinic acid, the separation of wines between the Coastal and continental part of Slovenia was achieved.
By using 1D and 2D NMR experiments the reliable assignment of
1
H
and
13
C
resonances of anthocyanins, peonidine 3-glucoside, petunidine 3-glucoside, cyanidine 3-glucoside, delphinidine 3-glucoside and malvidine 3-glucoside in CD
3OD was established, which will serve as a tool for the identification of a particular fraction in liquid chromatographic analysis.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The cyclic decapeptides polymyxin B (PmB) and E (PmE) (mo-K‘TK‘-cyclo-K‘K‘XLK‘K‘T; mo, methyl octanoate; K‘, diaminobutyric acid; X, d-Phe (PmB) or d-Leu (PmE)) display antimicrobial and ...lipopolysaccharide (LPS) antagonistic activities. We have investigated the conformational behavior of PmB and PmE in water solution, free and bound to LPS, by homonuclear NMR and molecular modeling methods. The free peptides exist in equilibria of fast exchanging conformations with local preferences for a distorted type II‘ β-turn from residues 5−8, and/or a γ-turn in residue 10. These two motifs are not present in the bound conformation of the peptides. The latter is amphiphilic separating the two hydrophobic residues in the cycle from the positively charged diaminobutyric acid side chains by an envelope-like fold of the cycle. The bound conformation is used for the derivation of a model of the PmB−lipid A complex based on electrostatic interactions and reduction of hydrophobic area. The proposed mode of binding breaks up the supramolecular structure of LPS connected with its toxicity. The model should contribute to the understanding of entropy-driven PmB−lipid A binding at the molecular level and assist the design of inhibitors of endotoxic activity.
PDF
