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  • Springer  (160)
  • 11
    Electronic Resource
    Electronic Resource
    Spectroscopic determination of cholinesterase activity and inhibition in sol-gel media (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1067-1070 
    Details
    ISSN: 1573-4846
    Keywords: cholinesterase ; sol-gel ; pesticide ; THA ; enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Biological activity of cholinesterases can be determined by optically monitoring the enzymatic reaction with indophenyl acetate, (N-4′-acetoxyphenyl)-4-quinone imine. At pH 8.0 cholinesterases hydrolyze this yellow dye to yield a blue reaction product. Cholinesterase inhibitors reduce the rate of this hydrolysis. Thus, by monitoring absorbance of the hydrolysis product at its maximum (630 nm) as a function of time, reaction rates of both cholinesterase activity and cholinesterase inhibition may be quantified spectroscopically. Using this technique, we measured the enzymatic activity of butyrylcholinesterase (BuChE) molecules encapsulated in tetramethyl orthosilicate (TMOS) silicate gel-glass prepared by hydrolysis and condensation. This activity is reduced, in a concentration-dependent manner, by the reversible cholinesterase inhibitors 1,5-bis(4-allyldimethyl-ammoniumphenyl) pentan 3-one dibromide (BADAPP) and 9-amino-1,2,3,4-tetrahydroacridine (THA; tacrine, Cognex). The gel-glasses are rigid, and compact, transparent and porous enough to allow reagents to diffuse in and out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436985
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  • 12
    Electronic Resource
    Electronic Resource
    Optical Properties and Dimer Formation in Copper Phthalocyanine-Doped Sol-Gel Matrices (1998)
    Springer
    Journal of sol gel science and technology 11 (1998), S. 241-250 
    Details
    ISSN: 1573-4846
    Keywords: copper phthalocyanine ; dimer ; monomer ; optical absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dimer formation in sol-gel matrices was studied using optical absorption spectroscopy of copper phthalocyanine tetrasulfonate dopants in silicate and aluminosilicate sol-gel matrices. Changes in the optical absorption spectra of dimers and monomers were correlated with various stages of the sol-gel process. Dimerization is strongly influenced by the chemistry of the pore liquid. The primary factors that control dimerization are the quantity of solvent remaining in the pores, pore solvent alcohol/water ratio, and presence of protons which can be either from the catalyst or from silanol groups on the silicate pore surfaces. Synthesis conditions which cause dye protonation invariably lead to dimerization during the latter stages of drying when the pore liquid becomes water-rich and there is a high dye concentration. These studies also identify chemical conditions which are able to avoid dye protonation and subsequently reduce dimer formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008602111839
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  • 13
    Electronic Resource
    Electronic Resource
    Allosteric Regulation of Enzymatic Reactions in a Transparent Inorganic Sol-Gel Material (1999)
    Springer
    Journal of sol gel science and technology 15 (1999), S. 57-62 
    Details
    ISSN: 1573-4846
    Keywords: glutamate dehydrogenase ; allosteric regulators ; sol-gel ; enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Glutamate dehydrogenase is encapsulated in a transparent porous silicate matrix by using sol-gel techniques. The inorganic polymer is formed around the enzyme (MW 〉 300,000 D). The enzyme is active in the material, catalyzes the reaction of L-glutamate to 2-oxoglutarate and follows Michaelis-Menten kinetics. The allosteric regulators ADP and GTP inhibit or activate the reaction; at pH 6, GTP acts as a strong activator and ADP acts as an inhibitor. This system involves a complex series of interactions; the co-enzyme NAD+ is required for catalysis, large-scale conformational changes accompany the binding of the substrate and coenzyme to the enzyme, the activators/inhibitors must bind to the enzyme to regulate the reactions, and the substrates and products must diffuse through the matrix to and from the binding site. The influence of the unique matrix on the complex enzymatic system is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008713014152
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  • 14
    Electronic Resource
    Electronic Resource
    In-situ fluorescence imaging of sol-gel thin film deposition (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 477-481 
    Details
    ISSN: 1573-4846
    Keywords: fluorescence probe ; luminescence ; thin film processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pyranine was used as a fluorescence probe to monitor the chemical evolution in-situ during thin film deposition by the dip coating process. The sensitivity of the pyranine luminescence to protonation/deprotonation effects was used to quantify changes in the water/alcohol ratio in real time within the depositing film as the substrate was withdrawn from the coating reservoir. The spatially resolved spectral results clearly showed that preferential evaporation of alcohol occurred with increasing distance from the reservoir and that the maximum water content reached rather high values near the drying line. Correlation of the luminescence results with the interference pattern of the drawn films allows the solvent composition in the film to be mapped as a function of film thickness. These experiments demonstrate for the first time that luminescent organic molecules may be applied to the processing science of sol-gel thin film deposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486294
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  • 15
    Electronic Resource
    Electronic Resource
    Encapsulation and reactivity of the enzyme oxalate oxidase in a sol-gel derived glass (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 827-829 
    Details
    ISSN: 1573-4846
    Keywords: biomaterials ; sensors ; enzyme ; biosensors ; spectroscopy in gels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The enzymes oxalate oxidase and peroxidase are encapsulated in stable, optically transparent, porous silica glass matrices synthesized under mild conditions using novel sol-gel synthetic techniques. The large enzymes are immobilized, but smaller molecules such as oxalate ions pass readily through the porous glass. Upon exposure to oxalate solutions, a colored glass is formed whose absorption spectrum and changes of absorbance with time are measured. The sensitivity of the response and the time-dependence of the response are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486359
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  • 16
    Electronic Resource
    Electronic Resource
    Biomolecular materials based on sol-gel encapsulated proteins (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 791-795 
    Details
    ISSN: 1573-4846
    Keywords: biomaterials ; proteins ; sensor ; spectroscopy in gels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The proteins copper-zinc superoxide dismutase (CuZnSOD), cytochrome c, myoglobin, hemoglobin, and bacterio-rhodopsin are encapsulated in stable, optically transparent, porous, silica glass matrices prepared by the sol-gel method such that the biomolecules retain their characteristic reactivities and spectroscopic properties. The resulting glasses allow transport of small molecules into and out of the glasses at reasonable rates but retain the protein molecules within their pores. The transparency of the glasses enables the chemical reactions of the immobilized proteins to be monitored by means of changes in their visible absorption spectra. Silica glasses containing the immobilized proteins have similar reactivities and spectroscopic properties to those found for the proteins in solution. The enzymes glucose oxidase and peroxidase were also encapsulated in transparent silica glass matrices. Upon exposure to glucose solutions, a colored glass is formed that can be used as the active element in a solid state optically based glucose sensor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486352
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  • 17
    Electronic Resource
    Electronic Resource
    Encapsulation of Proteins in Bulk and Thin Film Sol-Gel Matrices (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 629-634 
    Details
    ISSN: 1573-4846
    Keywords: protein encapsulation ; absorption spectroscopy ; thin films ; cytochrome c
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper considers the nature of the interactions between the sol-gel derived inorganic matrix and a specific biomolecule, cytochrome c. Optical absorption and impedance spectroscopies are used to characterize the influence of synthesis conditions on the protein's stability and conformation within the silica matrix. In some instances, encapsulation within the sol-gel matrix provides stabilization. For example, protein denaturation is reversible and aggregation is prevented. Moreover, the drying process does not negatively affect the protein; it is possible to regenerate the aged gel state by rehydration. The flexibility of the sol-gel process enables high quality cytochrome c-doped SiO2 thin films to be prepared. These films possess the characteristic reactivity and chemical function of cytochrome c in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018316108875
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  • 18
    Electronic Resource
    Electronic Resource
    Spectroscopic Determination of Cholinesterase Activity and Inhibition in Sol-Gel Media (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1067-1070 
    Details
    ISSN: 1573-4846
    Keywords: cholinesterase ; sol-gel ; pesticide ; THA ; enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Biological activity of cholinesterases can be determined by optically monitoring the enzymatic reaction with indophenyl acetate, (N-4′-acetoxyphenyl)-4-quinone imine. At pH 8.0 cholinesterases hydrolyze this yellow dye to yield a blue reaction product. Cholinesterase inhibitors reduce the rate of this hydrolysis. Thus, by monitoring absorbance of the hydrolysis product at its maximum (630 nm) as a function of time, reaction rates of both cholinesterase activity and cholinesterase inhibition may be quantified spectroscopically. Using this technique, we measured the enzymatic activity of butyrylcholinesterase (BuChE) molecules encapsulated in tetramethyl orthosilicate (TMOS) silicate gel-glass prepared by hydrolysis and condensation. This activity is reduced, in a concentration-dependent manner, by the reversible cholinesterase inhibitors 1,5-bis(4-allyldimethyl-ammoniumphenyl) pentan- 3-one dibromide (BADAPP) and 9-amino-1,2,3,4-tetrahydroacridine (THA; tacrine, Cognex). The gel-glasses are rigid and compact, transparent, and porous enough to allow reagents to diffuse in and out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018350828807
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  • 19
    Electronic Resource
    Electronic Resource
    On regular measures and Baire functions (1959)
    Springer
    Monatshefte für Mathematik 63 (1959), S. 19-23 
    Details
    ISSN: 1436-5081
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01328815
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  • 20
    Electronic Resource
    Electronic Resource
    Book reviews (1992)
    Springer
    Journal of economics 55 (1992), S. 221-244 
    Details
    ISSN: 1617-7134
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01227422
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