Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Effects of α-tocopherol and its acetate on the hydrolytic activity of phospholipase D in egg yolk phosphatidylcholine bilayers (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 598-603 
    Details
    ISSN: 1435-1536
    Keywords: Phospholipase D ; α-tocopherol ; α-tocopherol acetate ; egg yolk phosphatidylcholine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Effects of α-tocopherol (Toc) and α-tocopherol acetate (TocA) on the hydrolysis activity of phospholipase D (fromStreptomyces chromofuscus) were studied in small unilamellar vesicles (SUV) of egg yolk phosphatidylcholine (PC). Choline produced in the reaction was monitored by use of a choline oxidase — oxygen electrode. Addition of 18 mol% Toc into SUV (2 mM PC) brought about a twofold rate of choline production. On the other hand, the effect of 18 mol% TocA in SUV was very small. The apparent maximum velocity,V max(app), increased by addition of Toc in SUV. The apparent Michaelis constant,K m(app), was unchanged by addition of Toc and TocA in SUV. The Toc and TocA molecules did not have significant effects when PC was solubilized in the micelles of heptaethylene glycol dodecyl ether. The effects of Toc and TocA are, therefore, not due to specific ones on the enzyme itself, but rather upon the bilayer-organization of the substrate. Measurements of spreading pressure showed complete miscibility of PC and Toc, and limited mutual solubility of PC and TocA, suggesting stronger attractive interactions between Toc and PC than those between TocA and PC in the bilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653227
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Permeabilization and morphological changes in phosphatidylglycerol bilayers induced by an antimicrobial peptide, tachyplesin I (1993)
    Springer
    Colloid & polymer science 271 (1993), S. 901-908 
    Details
    ISSN: 1435-1536
    Keywords: Tachyplesin I ; lipid membrane ; permeability ; aggregation ; fusion ; micellization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Tachyplesin I, a broad-spectrum antimicrobial peptide fromTachypleus tridentatus has a basic (+7), amphiphilic, and cyclic β-sheet structure. We reported (Matsuzaki K. et al. (1991) Biochim. Biophys. Acta 1070:259–264) that 1) the action mechanism of tachyplesin I may be the permeabilization of bacterial membranes, 2) the peptide specifically permeabilizes acidic phospholipid bilayers, and 3) its Trp2 residue is located in the hydrophobic region near the surface of the bilayers. In this paper, we found that tachyplesin I dose-dependently induces not only the permeabilization but also aggregation/fusion and micellization of the phosphatidylglycerol large unilamellar vesicles (100 nm in diameter) either in the gel (L-α-dipalmitoylphosphatidyl-DL-glycerol (DPPG)) or liquid-crystalline (egg yolk L-α-phosphatidyl-DL-glycerol (egg PG)) phase, as revealed by light scattering and electron micrograph techniques. The solid DPPG vesicles were more susceptible to the peptide. At peptide to lipid molar ratios (P/L) of 1/500 to 1/200, interpeptide interactions formed a pore through which calcein, a fluorescent dye, can leak out of the vesicles. The pore lifetime was longer in the DPPG vesicles. Further addition of the peptide caused aggregation and/or fusion of the vesicles. At a charge-neutralizingP/L ratio of 1/7, the enlarged vesicles disintegrated into small spherical particles (10–20 nm in diameter). The mechanism for these morphological changes will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652773
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Incongruent dissolution of hydroxyapatite in the presence of phosphoserine (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 161-165 
    Details
    ISSN: 1435-1536
    Keywords: Hydroxyapatite ; phosphoserine ; incongruentdissolution ; adsorption ; ion-exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Concentrations of phosphate and calcium ions, liberated from the surface of hydroxyapatite (HAP) during the adsorption of phosphoserine (PSer), were determined at 30°C. HAP showed a marked incongruent dissolution behavior in the presence of PSer. That is, the concentration of phosphate ion in solution increases with the addition of PSer due to the ion-exchange between PSer and phosphate ion on HAP (molar ratio of the former to the latter=3∶2), whereas the concentration of calcium ion decreases with this release of phosphate ion, because the solubility product of HAP restricts the concentrations of both ions in solution (calculated values of — log (Ca2+)10 (PO 4 3− )6 (OH−)2 were 115.8±1.0). The affinity of PSer to HAP was highest at pH 5.8 where the PSer and the HAP surface had the opposite charges. This electrostatic attraction force between PSer and HAP was shielded to some extent by the addition of KCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00660306
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Activation and inhibition of lipoprotein lipase in mixed monolayers of medium or long chain-triglycerides and phospholipids (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 60-66 
    Details
    ISSN: 1435-1536
    Keywords: Key words Lipoprotein lipase ; inhibition ; phosphatidylcholine ; sphingomyelin ; triglyceride ; monolayer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  We evaluated the activation and inhibition effects of phosphatidylcholine (PC) and sphingomyelin (SM) on lipoprotein lipase (LPL) for medium or long chain-triglycerides (TG) in monolayers at the air/water interface. Monolayers of medium chain-TG, being in an expanded state at a surface pressure of 15 mN/m, showed low susceptibility to LPL in the subphase. Adding 50 mole% of PC or SM into these monolayers reduced the partial molecular area of the TG and enhanced the LPL activity. Monolayers of long chain-TG, being in a condensed state, showed high susceptibility of LPL either with or without PC. SM added to the long chain-TG monolayers, however, inhibited the LPL action. We investigated the interaction between TG and phospholipid on the basis of the collapse pressure-measurements of mixed monolayers. For medium chain-TG monolayers, PC and SM gave similar collapse pressure-composition profiles. Contrary to this, SM gave a markedly higher collapse pressure of long chain-TG than PC: SM stabilized the monolayer state of long chain-TG. These results suggested that I) orientation of the acyl chains of TG molecule in a monolayer is crucial for the LPL activity, and that II) strong interaction between SM and long chain-TG retards the substrate-transfer from the mixed monolayer to the catalytic pocket of LPL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050052
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Product-retardation and -activation of catalytic hydrolysis by phospholipase D in small unilamellar vesicles of egg yolk phosphatidylcholine (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 627-633 
    Details
    ISSN: 1435-1536
    Keywords: Key words Phospholipase D ; egg yolk phosphatidylcholine ; small unilamellar vesicles ; product-retardation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  We evaluated the hydrolysis of egg yolk phosphatidylcholine (PC) by phospholipase D from Streptomyces chromofuscus (PLD) in small unilamellar vesicles (SUV) in presence of 50 μM Ca2+. After initial choline production (hydrolysis of 1.5% of the PC at the outer leaflets of the vesicle bilayers), the hydrolysis was reduced to 5% of the initial velocity. The kinetic behavior in SUV of premixed PC and a low percentage of the hydrolysis product, phosphatidic acid (PA), was similar to that of PC SUV. The reduced velocity disappeared when the membrane structure was disintegrated by means of a nonionic surfactant. In the retardation phase, the partially hydrolyzed vesicles (postsubstrates) had much higher affinity for PLD than fresh PC SUV. These results indicated that small clusters of the product, PA, at the vesicle surface were responsible for the reduced velocity of hydrolysis. The initial velocity increased in a biphasic manner with the substrate concentration. At a PC concentration range up to 4 mM, the experimental data fit Michaelis–Menten kinetics. At concentrations above 6 mM, the velocity again markedly increased. Negatively charged mixed vesicles of PC and PA did not have such kinetics. Furthermore, adding PC SUV to the postsubstrates, where the fraction of free PLD was less than 0.05, induced steep choline production. These results showed that PLD bound to vesicles had higher activity than free PLD. We speculated that PLD bound to vesicles collided with and was directly transferred to PC SUV when the fraction of free PLD in aqueous medium was very small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050128
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Generation and electronic properties of lanthanide–cyclooctatetraene organometallic clusters in gas phase (1999)
    Springer
    The European physical journal 9 (1999), S. 283-287 
    Details
    ISSN: 1434-6079
    Keywords: PACS: 36.40.-c Atomic and molecular clusters – 36.40.Mr Spectroscopy and geometrical structure of clusters – 61.46.+w Clusters, nanoparticles, and nanocrystalline materials – 71.24.+q Electronic structure of clusters and nanoparticles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Organometallic clusters of lanthanide (Ln = Nd, Er, Eu, and Yb) and 1,3,5,7-cyclooctatetraene (C8H8) were produced by a combination of laser vaporization and molecular beam methods. In the mass spectra of [Ln n (C8H8) m ], compositions of m=n+1 were magic numbers. From mass spectrometry, photoionization spectroscopy, and photoelectron spectroscopy, we have concluded that these magic-numbered clusters take multiple-decker sandwich structures in which Ln atoms and C8H8 molecules are alternatedly piled up. These sandwich clusters are formed through ionic bonds composed of multiply charged cations [Ln k+  (k=2 and 3)] and multiply charged anions [C8H8 h-  (h=1, 1.5, and 2)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010926
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Prolonged release of drug from triacetyl-β-CyD complex for oral and rectal administration (1996)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 25 (1996), S. 181-184 
    Details
    ISSN: 1573-1111
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Triacetyl-β-cyclodextrin (TA-β-CyD), a hydrophobic cyclodextrin derivative, that is insoluble in water, was used to form a complex with flufenamic acid (FA). FA-TA-β-CyD complex formation was demonstrated by differential scanning calorimetry and powder X-ray diffractometry. The release rate of FA from the FA-TA-β-CyD complexes in phosphate buffer pH 6.8 was significantly retarded compared to that of FA from the FA and glucose mixture. When the FA-TA-β-CyD complexes were administered directly into the intraduodenal lumen, the plasma concentration of FA remained at a plateau level (10-18 μg/ml) for 6–8 h. An increased mean residence time of FA following FA-TA-β-CyD complexes administration was observed. These results indicate that TA-β-CyD may serve as a hydrophobic carrier in prolonged-release preparations of FA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01041565
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...