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  • 1
    Electronic Resource
    Electronic Resource
    Heat Stable Langmuir-Blodgett Film of Glutathione-S-Transferase (1995)
    s.l. : American Chemical Society
    Langmuir 11 (1995), S. 2719-2725 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00007a062
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  • 2
    Electronic Resource
    Electronic Resource
    A new instrument for the simultaneous determination of pH and redox potential (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4341-4346 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A significant upgrading of a recently introduced biosensor system, called potentiometric alternating biosensor is presented. The transducer consists of a light-addressable silicon chip, which provides regions properly modified and functionalized to yield sensitivity to either pH or redox potentials. The computer controlled system drives an array of light sources, allowing two-dimensional signal acquisition and processing. The system can provide multiparameter information related to the local modifications made on the sensing surface of the transducer. This work presents a detailed description of the measuring principles and the spatial resolution obtainable with the system. In addition, the complete circuit design is presented, both for signal conditioning, and for the bidimensional matrix addressing. A typical experiment for selective measurements is presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145325
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  • 3
    Electronic Resource
    Electronic Resource
    A simple method for preparing calibration standards for the three working axes of scanning probe microscope piezo scanners (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 748-751 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method for preparing samples suitable for calibrating scanning probe microscopes (SPM) and for eliminating any distortions in images is described. Samples consist of polystyrene particles organized in monolayers and bilayers with hexagonal-ordered domains. The monolayer is not uniform, but is characterized by areas without particles. These discontinuities allow the measurement of the thickness of the monolayer in order to calibrate the z axes, while the lattice constant of the domains can be used as a calibration standard for the x and y axes. The nondeformability of the particles after the deposition on the substrate has been studied by an optical microscope, equipped for interferometric measurements, scanning force microscopy, and scanning tunneling microscopy. The use of these standards directly as substrates for samples is proposed to correct the distortions in the SPM images. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146803
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  • 4
    Electronic Resource
    Electronic Resource
    High order DNA structure as inferred by optical fluorimetry and scanning calorimetry (1997)
    Springer
    Molecular biology reports 24 (1997), S. 235-246 
    Details
    ISSN: 1573-4978
    Keywords: calorimetry ; chromatin-DNA ; fluorescence ; optical microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract New quantitative insights on the native high order chromatin-DNA structure existing within interphase nuclei are obtained by monitoring the effects of two common well-characterized fixatives, glutaraldehyde and ethanol/acetic acid mixture, at the level of the intranuclear DNA distribution and structures. Reproducible distinct levels of DNA fluorescence intensity and their intranuclear distribution are apparent in unfixed and fixed thymocytes by using DAPI and quantitative optical microscopy based on a charge coupled device. The fluorescent histograms correlated with the calorimetric thermograms on the very same thymocytes fixed and unfixed, establish an unequivocal baseline for the different levels of structural organization of the chromatin within the intact nucleus; namely their number, DNA packing ratio and fiber diameter. A systematic comparison among all the numerous models, being so far proposed for the quinternary and quaternary levels of DNA folding, to identifies the rope or ribbon-like and the chromonema as the ones that best fit with the in situ distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006861801216
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  • 5
    Electronic Resource
    Electronic Resource
    X-ray small angle scattering study of chromatin as a function of fiber length (1998)
    Springer
    Molecular biology reports 25 (1998), S. 73-86 
    Details
    ISSN: 1573-4978
    Keywords: calf thymus chromatin ; chromatin high order structure ; fiber length ; X-ray small angle scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This work investigates the structure of native calf thymus chromatin as a function of fiber length and isolation procedures by using X-ray small angle scattering technique. Two methods of chromatin isolation have been compared in order to better understand the differences reported by various authors in terms of chromatin high order structure. In addition to these experimental results the effects of shearing have also been studied. In order to explain the differences among these chromatin preparations we built several models of chromatin fibers (represented as a chain of spherical subunits) assuming increasing level of condensation at increasing salt concentrations. For all these fiber models the corresponding theoretical X-ray scattering curves have been calculated and these results have been used to explain the influence of fiber length on the scattering profiles of chromatin. The comparison between experimental and theoretical curves confirms that the high molecular weight chromatin-DNA prepared by hypotonic swelling of nuclei (without enzymatic digestion) displays a partially folded structure even at low ionic strength, whereas the low molecular weight chromatin-DNA prepared by a brief nuclease digestion appears very weakly folded at the same ionic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006838708493
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of polyamines on higher-order folding of in situ chromatin (1998)
    Springer
    Molecular biology reports 25 (1998), S. 237-244 
    Details
    ISSN: 1573-4978
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Modifications of the higher-order chromatin structure induced by polyamines have been quantitatively investigated in situ through a non-invasive biophysical approach using Differential Scanning Calorimetry and Quantitative Fluorescence Microscopy. Calorimetric and intensitometric profiles have been acquired for samples of native thymocytes, alternatively suspended in buffers, with or without natural polyamines (spermine and spermidine). The results here reported show that the structure and distribution of nuclear chromatin in situ considerably change upon the ionic composition of the environment. A quantitative analysis of this data and a comparison with previous results obtained from isolated chromatin fibers was carried out. Finally, an inverse relationship between chromatin condensation and nuclear volume was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006937212430
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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.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of histone acetylation on chromatin structure (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 466-475 
    Details
    ISSN: 0730-2312
    Keywords: histone acetylation ; chromatin structure ; circular dichroism ; ethidium bromide intercalation ; differential scanning calorimetry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The effect of histone acetylation was monitored on CHO chromatin structure, following the addition of 7 mM Na-butyrate to the cell culture medium. The properties of both control and hyperacetylated chromatins and nuclei were investigated by circular dichroism, ethidium bromide intercalation, differential scanning calorimetry, and affinity chromatography. Our results are compatible with modest but significant alterations in the various levels of chromatin organization, as a result of the charge neutralization of some lysine residues within the N-terminal region of the histonic octamer. Namely, large statistically significant differences do exist in the heat capacity thermograms of native nuclei, where unfolding into single nucleofilament of the highly packed native chromatin superfiber appears associated with acetylation; at the same time CD, EB, and affinity chromatography point to modest but consistent differences in the compactness of isolated nucleosomes and polynucleosomes. J. Cell. Biochem. 64:466-475. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
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    A new instrument for the simultaneous determination of pH and redox potential (1995)
    American Institute of Physics
    Details
    Publication Date: 1995-08-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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  • 10
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    Role of Protein Unfolding in Monolayer Formation on Air−Water Interface (1996)
    American Chemical Society
    Details
    Publication Date: 1996-01-01
    Print ISSN: 0743-7463
    Electronic ISSN: 1520-5827
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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