Variation of 1,6-Diphenyl-1,3,5-Hexatriene Lifetime Distributions in Differentiating Proerythroblasts. A Multifrequency Phase and Modulation Fluorometry Study
During the cell differentiation process structural and functional properties peculiar to the mature, specialized cell are acquired. Although the molecular basis of the process are still largely unknown, the appearance of specific structural membrane components (Seiser, 1973; Fukuda et al., 1981) leaded to investigations on the cell membranes involvement in differentiation. Moreover, the modulation of the activity of some membrane enzyme during physiological processes could be achieved by structural and dynamical modification of the membrane matrix (Kimelberg, 1977). Since the heterogeneity of cell membranes composition many efforts have been devoted to the detection and quantitation of different coexisting lipid phases (Klausner et al., 1980; Karnowsky, 1979; Parasassi et al., 1984). The fluorescence lifetime of l,6-diphenyl-1,3,5-hexatriene (DPH) shows marked values differences when inserted in phospholipid vesicles of different phases. Characteristic lifetime values have been determined for the pure gel and liquid-crystalline phase of the vesicles, and the quantitation of the phospholipid physical state has been possible also in the case of coexisting different phases (Parasassi et al., 1984). Nevertheless, this approach gave ambiguous results when applied to cell membranes. In the case of natural samples a separation of the membrane matrix between the gel and the liquid-crystalline phase could represent an oversimplification because of the heterogeneity of the sample and the multiplicity of environments and conformations of the fluorophore.
KeywordsK562 Cell Fluorescence Lifetime Membrane Matrix Lifetime Distribution Phospholipid Vesicle
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