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  • 1
    Electronic Resource
    Electronic Resource
    A frequency deconvolution procedure using a conjugate gradient minimization method with suitable constraints (1994)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 409-421 
    Details
    ISSN: 0886-9383
    Keywords: Deconvolution ; FT-IR spectroscopy ; Protein conformations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a variety of spectroscopic techniques the fundamental problem exists of determination of the individual spectral components, intrinsically overlapped in the measured spectrum. This is a typical deconvolution problem and several methods and techniques have been proposed for its solution in the technical literature, but suggestions of new approaches are still of interest. A new deconvolution procedure is presented here based on the use of the conjugate gradient minimization algorithm with the addition of sutiable constraints directly obtained by the application to the measured spectrum of the second-derivative operator or more sophisticated resolution enhancement procedures. Since in the examined case deconvolution essentially requires the minimization of a non-convex function, the use of such constraints is extremely important to supply suitable input parameters to the conjugate gradient algorithm to avoid obtaining minimum points which have no physical meaning. In our case each spectral compoent used for deconvolution has been assumed to have a Gaussian analytical definition fully identified by three parameters (amplitude, central frequency, spectral bandwidth), so that the input values required to start the deconvolution process are the number M of Gaussian components and 3M suitable initial approximations of the parameters above. It is shown that all this information can be obtained from the measured data. The deconvolution procedure was implemented by a FORTRAN Microsoft Version 5.1 program and experimental results relative to spectroscopic data obtained by FT-IR analysis of human serum albumin are reported. The results are discussed and compared with data obtained by the use of other techniques.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180080606
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  • 2
    Electronic Resource
    Electronic Resource
    On the nature of intermolecular interactions in polymer blends. Use of model compounds as a tool for investigating polymer-polymer miscibility (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 34 (1994), S. 1-6 
    Details
    ISSN: 0959-8103
    Keywords: polymer blends ; miscibility ; functionalized polyolefins ; model compounds ; FTIR ; 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: An FTIR study has been performed on two low molecular weight model compounds of diethylmaleate functionalized polyethylene, ethyl 3-carbethoxy-4-propylheptanoate (EPH) and ethyl 3-carbethoxy-4-hexyldecanoate (EHD), recording spectra in different solvents (heptane, tetrahydrofuran, carbon tetrachloride, chloroform) and in the presence of a presumable PVC model, 2-chlorobutane (2CB). These different systems allowed the observation of some correlations between spectroscopic data and chemical composition of solutions and functionalized polyethylene/PVC blends, supporting the hypothesis of specific hydrogen bond type interactions between the carboxylic oxygen of the functionalized polyethylene and the methinic hydrogens of PVC.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210340101
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational study of isotactic poly[(S)-5-methyl-1-heptene] and poly[(S)-2-methylbutyl vinyl ether] by IR spectroscopy (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 1251-1259 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared (IR) investigation of structurally analogous optically active polymers such as poly[(S)-5-methyl-1-heptene (1)] and poly[(S)-2-methylbutyl vinyl ether (2)] was carried out in the solid state, in the molten state, and in solution. Vibrational data are in accordance with the existence of helical conformations in solution and in the molten state for both polymers, confirming the previous suggestions based on optical rotation measurements. In particular, an accurate examination of the spectral region between 850 and 700 cm-1, where characteristic absorptions of the sec-butyl group occur, enables us to assign the medium intensity band at 827 cm-1 (present in both polymers in the solid state) to the GTTG-T conformation of the side chains.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.180150710
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular interactions in the poly(vinyl chloride)-di-n-butylphthalate system determined by infrared spectroscopy (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 1187-1192 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared studies of the poly(vinyl chloride) (PVC)/di-n-butylphthalate (DBP) system are reported. Spectra of DBP in different solvents seem to be indicative of the ability of DBP to interact with PVC chains in the same way as with polyesters and of competitive interactions between DBP molecules and DBP with PVC. Plots of the width at half-height of the carbonyl stretching vibration, measured at 25 and at -180°C, as a function of composition, show a sudden change of slope at about 60% PVC concentration by weight, indicating that above this polymer composition interaction between DBP and PVC dominates that between DBP molecules. This change corresponds to a “singularity” observed in the dependence of the glass transition temperature on composition.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180230610
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of the secondary structure of isomeric forms of human serum albumin by a particular frequency deconvolution procedure applied to fourier transform IR analysis (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 639-653 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new deconvolution procedure was applied to the analysis of Fourier transform in spectra of human serum albumin secondary structure in the native state and in states denatured by heat and acid treatment. The deconvolution method is based on the use of the Conjugate Gradient Minimization Algorithm, with the addition of suitable constraints directly obtained by the application to the measured spectrum of the second derivative operator. This method computes central band frequency, bandwidth, and amplitude of the different spectral components of conformation-sensitive amide bands. In the specific case, it was applied to analysis of the amide I band, and the quantitative determination of the different secondary structures (α-helix, β-sheet, β-turns, and random) was attempted for all the samples examined.The precision of the quantitative determination depends on the amounts of these structures present in the protein. The coefficient of variation is 〈10% for values of amide I component 〉15%. The accuracy was tested by comparing, by means of linear regression, the results obtained for human serum albumin, hemoglobin, α-chymotrypsin, and cytochrome c, using our method, with those obtained by x-ray crystallography and CD; the results obtained by other vibrational spectroscopic approaches were also compared. The fit standard error between x-ray and ir secondary structure values estimated by our method is 2.5% for α-helix, 7.16% for β structures, and 5.1% for other structures (turns and random coils).Quantitative results are given for the secondary structures (α-helix, turns, and β-strands) present in the native state (turns and β-strands up to now unknown in aqueous solution), together with the percentages of these structures and additional ones (random coils and β-sheets) formed during denaturization. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of secondary structure of normal fibrin from human peripheral blood (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 545-553 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The secondary structure of human fibrin from normal donors and from bovine and suilline plasma was studied by Fourier transform ir spectroscopy and a quantitative analysis of its secondary structure was suggested. For this purpose, a previously experimented spectrum deconvolution procedure based on the use of the Conjugate Gradient Minimisation Algorithm with the addition of suitable constraints was applied to the analysis of conformation-sensitive amide bands. This procedure was applied to amide I and III analysis of bovine and suilline fibrin, obtained industrially, and to amide III analysis of human fibrin clots. The analysis of both amide I and III in the first case was useful in order to test the reliability of the method. We found bovine, suilline, and human fibrin to contain about 30% α-helix (amide I and III components at 1653 cm-1, and 1312 and 1284 cm-1, respectively), 40% β-sheets (amide I and III components at 1625 and 1231 cm-1, respectively) and 30% turns (amide I and III components at 1696, 1680, 1675 cm-1, and 1249 cm-1, respectively). The precision of the quantitative determination depends on the amount of these structures in the protein. Particularly, the coefficient of variation is 〈 10% for percentage values of amide I and III components 〉 15 and 5%, respectively. The good agreement of our quantitative data, obtained separately by amide I and amide III analysis, and consistent with a previous fibrinogen (from commercial sources) study that reports only information about fibrin β-sheet content obtained by factor analysis, leads us to believe that the amounts of secondary structures found (α-helix, β-sheets, and turns) are accurate. © 1997 John Wiley & Sons, Inc. Biopoly 41: 545-553, 1997.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Qualitative and quantitative analysis of the secondary structure of cytochrome C Langmuir-Blodgett films (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 227-237 
    Details
    ISSN: 0006-3525
    Keywords: fourier transform ir spectroscopy ; protein conformations ; cytochrome C ; Langmuir-Blodgett film ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A qualitative and quantitative analysis of the conformation of Langmuir-Blodgett (LB) dried films of cytochrome C on silicon wafers was performed by Fourier transform ir (FTIR) spectroscopy. A deconvolution procedure was applied to the amide I band analysis, in order to determine the percentage of the different secondary structures. Qualitative analysis was performed by examining difference spectra.Films obtained by spreading protein solutions at pH 7.4 and 1, dried at 25 and 100°C, on silicon wafers were also examined in order to detect spectral components associated with denatured protein domains, and to compare them with cytochrome C LB films.FTIR spectroscopy showed that the following important changes characterise LB film spectra: (a) the α-helix component is higher (its percentage is 57 and 54%) than the one estimated in dried film obtained by spreading the solutions at pH 7.4 on a silicon substrate (43%), (b) there is an increase in the intensity of bands attributed to protonated carboxy group bands, involved and not involved in the formation of hydrogen bonds, and a decrease in those attributed to deprotonated carboxy groups, (c) the intensity of several bands attributed to aromatic amino acids and aliphatic chains increases, and (d) bands due to O(SINGLEBOND)H stretching vibrations of crystallization water are present.These conformational changes could be induced by protein-protein interaction caused by the close packing of molecules that occurs during LB film formation; it cannot be excluded that they may be accompanied by partial changes in the tertiary structure of the protein. A preferential orientation of protein molecules in LB films is also a possibility. © 1997 John Wiley & Sons, Inc. Biopoly 42: 227-237, 1997
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Vibrational analysis of functionalized polyolefins/poly(vinylchloride) blends (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 9-14 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Polyolefins functionalized with diethylmaleate were mixed with poly(vinylchloride) (PVC) in different compositions. Intermolecular interactions involving the carbonyl groups of the side chains of the functionalized polyolefins and methine hydrogens of PVC were investigated by means of infrared spectroscopy. The major flexibility of the ester groups attached to the backbone chains, with respect to polyesters, seems to increase the capability of such groups to interact with groups of more polar polymers, thus allowing prediction of easier miscibility, which however also depends on the starting polyolefin structure and function-alization degree.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260105
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  • 9
    Electronic Resource
    Electronic Resource
    Infrared study of phase transitions in thermotropic liquid crystal polyestersPresented in part at the VII AIM National Meeting, Galzignano, Italy, September, 1985, preprint, p. 149. (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 25-37 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three samples of semiflexible thermotropic liquid-crystalline polyesters based on mesogenic aromatic triads and a decamethylene spacer have been investigated by IR spectroscopy at various temperatures between room temperature and 290°C. The crystal-to-liquid crystal (either nematic or smectic) phase transition was accompanied by fairly strong spectral variations, whereas slight, but significant, changes in the IR profiles were detected at the liquid crystal-to-isotropic transition. By comparing the results obtained with the spectral behavior recorded for corresponding structural analogs of low molar mass, it was possible to attribute the spectral variations observed in the polymer samples to a decrease in intermolecular interactions rather than to conformational changes. The thermal transitions indicated by IR spectra were in good agreement with the analogous data obtained by calorimetric or optical microscopy techniques.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090270102
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  • 10
    Electronic Resource
    Electronic Resource
    FTIR-microspectroscopy and DSC studies of poly(vinylidene fluoride) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 41 (1996), S. 35-41 
    Details
    ISSN: 0959-8103
    Keywords: fourier transform-infrared microspectroscopy (FTIR-M) ; DSC ; poly(vinylidene fluoride) ; polymorphism ; 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: Poly(vinylidene fluoride) (PVDF) samples, obtained by casting from tetrahydrofuran solutions and submitted to various thermal treatments, have been examined by Fourier transform-infrared microspectroscopy (FTIR-M) and differential scanning calorimetry (DSC). This kind of analysis allowed us to examine microdomains of samples with different morphological characteristics and to obtain an indication of the polymorphism of PVDF. In some cases the simultaneous presence of two or three forms has been evidenced thanks to the comparison of FTIR-M spectra and DSC traces. Vibrational spectra of single crystalline forms can be recorded by FTIR-M on phase homogeneous microdomains.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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