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  • 1
    Electronic Resource
    Electronic Resource
    Maximum likelihood method for the analysis of time-resolved fluorescence decay curves (1991)
    Springer
    European biophysics journal 20 (1991), S. 247-262 
    Details
    ISSN: 1432-1017
    Keywords: Maximum likelihood ; Fluorescence decay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The usefulness of fluorescence techniques for the study of macromolecular structure and dynamics depends on the accuracy and sensitivity of the methods used for data analysis. Many methods for data analysis have been proposed and used, but little attention has been paid to the maximum likelihood method, generally known as the most powerful statistical method for parameter estimation. In this paper we study the properties and behavior of maximum likelihood estimates by using simulated fluorescence intensity decay data. We show that the maximum likelihood method provides generally more accurate estimates of lifetimes and fractions than does the standard least-squares approach especially when the lifetime ratios between individual components are small. Three novelties to the field of fluorescence decay analysis are also introduced and studied in this paper: a) discretization of the convolution integral based on the generalized integral mean value theorem: b) the likelihood ratio test as a tool to determine the number of exponential decay components in a given decay profile; and c) separability and detectability indices which provide measures on how accurately, a particular decay component can be detected. Based on the experience gained from this and from our previous study of the Padé-Laplace method, we make some recommendations on how the complex problem of deconvolution and parameter estimation of multiexponential functions might be approached in an experimental setting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00450560
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Tumor growthin vivo and as multicellular spheroids compared by mathematical models (1994)
    Springer
    Bulletin of mathematical biology 56 (1994), S. 617-631 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In vivo volume growth of two murine tumor cell lines was compared by mathematical modeling to their volume growth as multicellular spheroids. Fourteen deterministic mathematical models were studied. For one cell line, spheroid growth could be described by a model simpler than needed for description of growthin vivo. A model that explicitly included the stimulatory role for cell-cell interactions in regulation of growth was always superior to a model that did not include such a role. The von Bertalanffy model and the logistic model could not fit the data; this result contradicted some previous literature and was found to depend on the applied least squares fitting method. By the use of a particularly designed mathematical method, qualitative differences were discriminated from quantitative differences in growth dynamics of the same cells cultivated in two different three-dimensional systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460714
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Rate transition and regulatory coupling in endocytosis of interferon-α and tumor necrosis factor-α in human epithelial tumor cells (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 48 (1992), S. 203-214 
    Details
    ISSN: 0730-2312
    Keywords: endocytosis ; regulatory coupling ; kinetic models ; nested models ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The time-dependent concentrations of interferon-α and tumor necrosis factor-α associated with the membrane and internalized by cells contain information on the kinetics of endocytosis and their cellular processing. This information can be reduced quantitatively by application of the respective compartmental models. In our studies of human epithelial tumor cells interacting with human interferon-α and human tumor necrosis factor -α, we accounted only for actual endocytosis and elimination of the tracer from cells by a novel method sensitive to changes in the rate of endocytosis, to the delay in tracer elimination, and to the nonlinear regulatory coupling between endocytosis and the internalized ligand. Data reduced by this method resulted in best-fit parameter values statistically superior to values obtained by previous methods (Bajzer et al., 1989). The results indicate a change with time in the rate of endocytosis of tumor necrosis factor-α and the inhibition of endocytosis by the endocytosed ligand-receptor complex. We conclude that sorting and processing of interferon-α and tumor necrosis factor -α are restricted by the type of both the receptor and the cell.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240480211
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    Paper (German National Licenses)
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