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Biomedical subjects

K Arnold

Publications and source records attributed to K Arnold.

At least 73 records · Page 4Linked to original sources
PubMed1999

Cartilage degradation by hyaluronate lyase and chondroitin ABC lyase: a MALDI-TOF mass spectrometric study.

Matrix-assisted laser desorption ionization and time-of-flight mass spectrometry (MALDI-TOF MS) has been used to investigate degradation products of two selected polysaccharides of cartilage (chondroitin sulfate and hyaluronic acid). Testicular hyaluronate lyase and chondroitin ABC lyase were used for enzymic digestion of both polysaccharides as well as of cartilage specimens. Polysaccharide solutions and cartilage supernatants were assayed by positive and negative MALDI-TOF MS. Especially chondroitin ABC lyase produced high amounts of digestion products (unsaturated di- and tetrasaccharides) from polysaccharides as well as from cartilage, clearly monitored by MALDI-TOF MS. It is concluded that MALDI-TOF MS provides a precise and fast tool for the determination of oligosaccharides since no previous derivatization is required.

Animals↗
PubMed1999

Molecular dynamics of a tetrasaccharide subunit of chondroitin 4-sulfate in water.

Molecular dynamics (MD) simulations on a tetrasaccharide subunit of chondroitin 4-sulfate (CS4) in aqueous solution were carried out to study its interactions with water. Pair distribution functions and diffusion coefficients were calculated from a 4 ns trajectory and the hydration of different molecular groups was analysed. The average values of the interglycosidic torsion angles found in the simulations are phi 13 = -10 degrees, psi 13 = -85 degrees and phi 13 = 80 degrees, psi 13 = 90 degrees for the beta-(1-->3) linkage, and phi 14 = -10 degrees, psi 14 = -70 degrees for the beta-(1-->4) linkage. Hydrophobic patches formed by sugar ring CH groups were found. The diffusion coefficients of the water molecules vary from 1.4 x 10(-9) to 2.3 x 10(-9) m2 s-1 depending on the distances between the water molecules and the atoms of the CS4 molecule and the type of CS4 atoms, respectively. Reorientation correlation times of the water molecules in the vicinity of different CS4 atoms were estimated to be about 1 ps at a polymer concentration of 4 wt.% CS4. The number of hydrogen bonds between the water molecules and the acceptor atoms of CS4 was determined to be about 20 per disaccharide unit, indicating a higher hydration ability of chondroitin sulfate in comparison with non-sulfated oligosaccharides. Substructures, where water molecules are involved in hydrogen bonds to different sugar rings, were found, which may be important for the stabilisation of the secondary structure of the CS4 molecule.

Carbohydrate Conformation↗
PubMed1999

Lipid analysis by matrix-assisted laser desorption and ionization mass spectrometry: A methodological approach.

Whereas matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has gained high importance in the field of protein analysis, surprisingly few studies were published about the use of MALDI for lipid analysis. Lipids, however, are well-suited for MALDI since all experiments can be performed in a sole organic phase and, thus, extremely homogeneous matrix/analyte mixtures are formed. We report here for the first time the application of MALDI-TOF-MS for the analysis of diacylglycerols, phosphatidylcholines, and (poly)phosphoinositides. It is shown that in a matrix of 2,5-dihydroxybenzoic acid the molecular ions (M + 1) of phosphatidylcholines as well as the corresponding adducts of different phosphoinositides are easily detected even in complex mixtures, and thus, detailed data on the fatty acid composition are provided. In contrast, diacylglycerols are mainly detected as the corresponding sodium or potassium adducts, but not as the protonated forms. Fragmentation reactions of fatty acids on the double bonds and on the polar lipid head group are observed to a minor extent in the spectra of all investigated lipids. Generally, choline derivatives are most sensitive toward further fragmentation reactions. Due to its very high sensitivity (up to picomolar concentrations) MALDI-TOF-MS can be used for the direct investigation of biologically relevant lipid mixtures occurring, e.g. , in cell membranes. The analysis of the lipid composition of neutrophilic granulocytes is given as a representative example for future applications.

Diglycerides↗
PubMed1999

Self-diffusion of water in cartilage and cartilage components as studied by pulsed field gradient NMR.

Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) was used to investigate the self-diffusion behavior of water molecules in cartilage, polymeric cartilage components, and different model polymers. The short-time self-diffusion coefficients (diffusion time delta approximately/= 13 msec) are found to decrease steadily with decreasing water content. This holds equally well for cartilage and cartilage components. The short-time diffusion coefficients are subjected to a rather nonspecific obstruction effect and mainly depend on the water content of the sample. The long-time diffusion coefficients in cartilage (delta approximately/= 500 msec), however, reflect structural properties of this tissue. Measurements with varying observation times as well as experiments involving enzymatic treatment of articular cartilage suggest that the collagenous network in cartilage is likely to be responsible for the observed restricted diffusion.

Animals↗
PubMed1999

Investigation of phospholipid area compression induced by calcium-mediated dextran sulfate interaction.

The association of anionic polyelectrolytes such as dextran sulfate (DS) to zwitterionic phospholipid surfaces via Ca(2+) bridges results in a perturbation of lipid packing at physiologically relevant Ca(2+) concentrations. Lipid area compression was investigated in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) multilamellar bilayer dispersions by (2)H-NMR and in monolayer studies. Binding of DS to DMPC surfaces via Ca(2+) results in denser lipid packing, as indicated by higher lipid chain order. DMPC order parameters are homogeneously increased throughout the lipid bilayer. Higher order translates into more extended hydrocarbon chains and decreased average lipid area per molecule. Area compression is reported as a function of DS concentration and molecular weight. Altering the NaCl and Ca(2+) concentrations modified electrostatic interactions between DS and phospholipid. A maximal area reduction of DeltaA = 2.7 A(2) per DMPC molecule is observed. The lipid main-phase transition temperature increases upon formation of DMPC/Ca(2+)/DS-complexes. Lipid area compression after addition of DS and Ca(2+) to the subphase was also observed in monolayer experiments. A decrease in surface tension of up to 3.5 mN/m at constant molecular area was observed. DS binds to the lipid headgroups by formation of Ca(2+) bridges without penetrating the hydrophobic region. We suggest that area compression is the result of an attractive electrostatic interaction between neighboring lipid molecules induced by high local Ca(2+) concentration due to the presence of DS. X-ray diffraction experiments demonstrate that DS binding to apposing bilayers reduces bilayer separation. We speculate that DS binding alters the phase state of low-density lipoproteins that associate with polyelectrolytes of the arterial connective tissue in the early stages of arteriosclerosis.

Arteriosclerosis↗