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  • 1
    Electronic Resource
    Electronic Resource
    Advantages in using immobilized thermophilic β-glycosidase in nonisothermal bioreactors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 108-115 
    Details
    ISSN: 0006-3592
    Keywords: thermophilic β-glycosidase ; catalytic membranes ; nonisothermal bioreactors ; thermodialysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Catalytic membranes, obtained by immobilizing thermophilic β-glycosidase onto nylon supports, were used in a nonisothermal bioreactor to study the effect of temperature gradients on the rate of enzyme reaction. Two experimental approaches were carried out to explain the molecular mechanisms by which the temperature gradients affect enzyme activity. The results showed that the thermophilic enzyme behaved as the mesophilic β-galactosidase, exhibiting an activity increase which was linearly proportional to the transmembrane temperature difference. The efficiency of the system proposed was determined by calculating two constants, α and β, which represent respectively the percentage increase of enzyme activity when a temperature difference of 1°C or a temperature gradient of 1°C cm-1 were applied across the catalytic membrane. The increase of enzyme activity in nonisothermal bioreactors entailed a proportional reduction of production times. The advantages in using thermophilic enzymes immobilized in nonisothermal bioreactors are also discussed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:108-115, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular orbital analysis of the XPS spectra of PMDA-ODA polymide and its polyamic acid precursor (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 3325-3333 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The calculated carbon 1s (C1s) core energy-level positions of PMDA-ODA polymide and of its polyamic acid precursor are compared with the level positions inferred from XPS measurements. For the polyamic acid, calculation and experiment both yield a difference of approximately 1 eV between the carboxylic acid and the amide carbonyl C1s level positions. The difference in shape between the main C1s XPS peaks of the polyamic acid and polyimide is shown to be related to the difference in C1s core energy-level shifts of the carbon atoms composing the benzene ring adjacent to the amide or imide group. The planar imide or PMDA structure apparently yields larger core level shifts for these atoms. We have previously designated these atoms as “imide carbon atoms” (C-Im) to distinguish them from the aromatic carbon atoms (C-C) of the ODA part of the polymeric repeat unit. Comparison of the carbonyl XPS band intensities with the main peak intensities for the polyamic acid, as well as for the polyimide, suggests that there is a carbonyl deficiency at the surface of both of these materials.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080241216
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular orbital analysis of the XPS spectrum of a fluorine containing polyimide: PMDA-BDAF (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 1199-1205 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results of XPS measurements and molecular orbital calculations performed on the fluorine containing polyimide, PMDA-BDAF, are presented. The calculated carbon 1s (C1s) core energy level positions are compared with the level positions inferred from the XPS measurements. Within Koopman's approximation, the observed shape of the main XPS peak is consistent with the calculated distribution of C1s levels under this peak. Comparison of the magnitude of the carbonyl XPS peak intensity with the main peak intensity indicates a carbonyl C1s signal deficiency compared with that expected for “ideal bulk stoichiometry” i.e., for a polymer with no crosslinks or chain terminations. Comparison of data obtained from a grazing emission (surface sensitive) geometry with that obtained from a normal emission geometry, which probes more deeply into the bulk, indicates a signal enhancement of the C1s levels associated with carbon atoms of the CF3 groups as one nears the polymer surface. Such enhancement might be due to either actual differences in chemical composition, or to preferential structural ordering near the polymer surface.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260420
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  • 4
    Electronic Resource
    Electronic Resource
    Direct resolution, characterization, and stereospecific binding properties of an atropisomeric 1,4-benzodiazepine (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 495-505 
    Details
    ISSN: 0899-0042
    Keywords: stereoselective protein binding ; chiral HPLC ; circular dichroism ; stereoselective receptor binding ; HSA ; preparative HPLC ; atropisomeric benzodiazepine ; stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic resolution of 7-chloro-1,3-dihydro-1-(1,1-dimethylethyl)-5-(2-fluorophenyl)-2H-1,4-benzodiazepin-2-on (7), the 2′-fluoro, N1-tert-butyl analogue of diazepam, was attained on both analytical and preparative (mgs) scales, by using several chiral stationary phases (CSPs). The stereochemistry of this compound was characterized by means of 1H-NMR Nuclear Overhauser Effect (NOE) analysis. The single enantiomers of 7 were tested for their configuration and stereochemical stability by circular dichroism (CD), and their interaction with the central nervous system (CNS) benzodiazepine receptor was assayed, showing a significant difference in their binding affiities. Protein binding studies with human serum albumin (HSA, the main benzodiazepine carrier in human plasma) immobilized on a silica stationary phase revealed that HSA also preferentially binds one stereoisomer of 7. However, both on line CD detection and stereospecific interaction with other common drugs clearly demonstrated that the stereoselectivity of immobilized HSA for 7 is opposite to that for all the other studied benzodiazepines. In addition, HSA stereoselectivity for 7 is opposite to CNS receptor binding stereoselectivity for the same compound. Such HSA anomalous stereoselectivity for 7 was also confirmed in aqueous buffer solution by competitive displacement studies. Compared to other chiral 1,4-benzodiazepines, compound 7 thus shows several anomalous binding properties: HSA and the CNS receptor demonstrated opposite enantioselective discrimination; HSA has reversed enantioselectivity for compound 7; and HSA stereospecifically binds the low-affinity enantiomer. Chirality 9:495-505, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Optimization of short-column gas chromatography/electron ionization mass spectrometry conditions for the determination of underivatized anabolic steroids (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 420-430 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatographic/mass spectrometric method based on the use of short capillary gas chromatograph columns (3-5 m) and electron ionization mass spectrometry has been optimized and evaluated for the determination of underivatized anabolic steroids. The short-column gas chromatographic/mass spectrometric method was shown to result in short analysis times and to require minimal sample preparation, but suffered from some loss in sensitivity and chromatographic resolution compared with conventional gas chromatographic/mass spectrometric techniques for derivatized steroids. Therefore, short-column gas chromatographic conditions were optimized to maximize the sample transfer efficiency (sensitivity) from the gas chromatograph into the ion source of the mass spectrometer, while maintaining chromatographic integrity and minimizing thermal decomposition. Mass spectrometric conditions were optimized to maximize ionization efficiency with respect to the intensity of the molcular ion and degree of fragmentation such that positive identication of each steroid could be made based on the resulting mass spectra. Under optimized conditons, we have shown that underivatized anabolic steroids spiked into urine samples can be determined at low-nanogram levels using short-column chromatography/full-scan electron ionization mass spectrometry.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200210903
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  • 6
    Electronic Resource
    Electronic Resource
    Photoexcitations in linear trans-quinacridone (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 7 (1997), S. 35-38 
    Details
    ISSN: 1057-9257
    Keywords: photoluminescence ; time-resolved fast spectrocopy ; photoinduced absorption spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We have studied the photophysics of linear trans-quinacridone films by applying a variety of transient and continuous wave photomodulation techniques. Our experimental results demonstrate the ultrafast formation of excimer species which are responsible for the emission. The excimer decay kinetics seems to suggest a predominantly charge transfer character of these emitting species. This is consistent with the long-lived states which we detected on the millisecond time scale. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Photoexcitations in linear trans-quinacridone (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 7 (1997), S. 83-86 
    Details
    ISSN: 1057-9257
    Keywords: photoluminescence ; time-resolved fast spectrocopy ; photoinduced absorption spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We have studied the photophysics of linear trans-quinacridone films by applying a variety of transient and continuous wave photomodulation techniques. Our experimental results demonstrate the ultrafast formation of excimer species which are responsible for the emission. The excimer decay kinetics seems to suggest a predominantly charge transfer character of these emitting species. This is consistent with the long-lived states which we detected on the millisecond time scale. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Short-column gas chromatography/tandem mass spectrometry for the detection of underivatized anabolic steroids in urine (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 131-139 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Short-column (3.5 m) gas chromatography (GC)/tandem mass spectrometry (MS/MS) has been investigated for the detection of structurally related, underivatized anabolic steroids in urine. The approach described here demonstrates the ability to rapidly and qualitatively detect underivatized anabolic steroids in spiked urine matrices. In this approach, underivatized steroids are determined using a short-column GC separation, ionized by positive ion chemical ionization, and detected by selected reaction monitoring MS/MS. This approach permits positive identification of underivatized anabolic steroids based on retention time and the production of characteristic product ions. Preliminary detection limits studies in spiked urine samples showed quantitative results between 2 and 40 ng steroid per milliliter of urine. The potential advantages of this approach compared to present screening methods based on conventional (30 m) GC/MS are its rapidity and selectivity. Reliable qualitative identification can be performed with a short-column GC/MS/MS analysis of less than 6 min with a reduction in sample preparation time due to the elimination of the derivatization step.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200230303
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  • 9
    Electronic Resource
    Electronic Resource
    Thickness-direction thermal-expansion measurements (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 1329-1337 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermal expansivity in the thickness direction for three commercially synthesized and processed polyimide films, PMDA-ODA, BPDA-ODA, and BPDA-PDA, have been measured. The expansivity in the thickness direction is significantly higher than that in the in-plane direction. The observed anisotropy is explained by the orientation texture of the films. The differences in the expansivity is explained by the molecular conformation of the chain. The latter is calculated by energy minimization excluding the entropic effects. The conformation analysis reveals a helical-like conformation for ether-linkage-containing chains, which explains, which explains the higher expansivity in PMDA-ODA as opposed to BPDA-PDA. The possibility of helical conformation in PMDA-ODA and BPDA-ODA is novel. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460802
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  • 10
    Electronic Resource
    Electronic Resource
    Study of stability of recombinant plasmids during the continuous culture of Bacillus stearothermophilus NUB3621 in nonselective medium (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 507-514 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus stearothermophilus ; continuous culture ; plasmid stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The optimal culture conditions for Bacillus stearothermophilus NUB3621 (BGSC 9A5) in chemostat were studied. The results obtained showed that the optimal culture conditions in terms of biomass concentration and maximum growth rate were 65°C, pH 6.8 to 7.2. Dissolved oxygen became growth limiting at pO2 levels below 10%. Furthermore, this strain was transformed with three new hybrid vectors (pPAM2, pPCH2, or pPLY2) constructed by cloning in pRP9, a plasmid based on the thermophilic replicon, pBC1, and three heterologous genes: the α-amylase gene from Bacillus licheniformis, the cholesterol oxidase gene from Streptomyces sp., and the lipase gene from Pseudomonas fluorescens. The influence of several fermentative conditions on segregational and structural stability of the recombinant B. stearothermophilus NUB3621 transformants was studied.The parameters of plasmid loss, that is, rate of plasmid loss (R) and specific growth rate difference (δμ), were calculated. B. stearothermophilus NUB3621 carrying pRP9 showed great segregational stability in all the assayed conditions, exceeding more than 300 generations without significant plasmid loss, whereas NUB3621 carrying pPAM2, pPCH2, or pPLY2 exhibited relatively low plasmid stability. The segregational instability of the recombinant constructs increased by increasing the fermentation temperature, decreased by increasing the dilution rate, and was not affected by the level of dissolved oxygen. On the other hand, plasmid maintenance decreased in minimal medium if compared with the results obtained in complex medium. Restriction analyses carried out on cultures of NUB3621 carrying pRP9, pPAM2, pPCH2, or pPLY2, grown for 200 generations on nonselective media, revealed that all the clones tested contained the parental plasmids. These results indicate that the heterologous inserts did not affect the structural stability of the recombinant plasmids. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 507-514, 1997.
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