Membrane dynamic alteration associated with the tumorigenicity of polyoma-transformed and revertant hamster cells

Activation of human lymphocytes by concanavalin A or purified protein derivative results in no alteration of fluorescence polarization of lipid probes although the electrophoretic mobility of the cells is changed

Upon stimulation with either concanavalin A or the tuberculin antigen, purified protein derivative, human peripheral blood lymphocytes, purified on Ficoll-Hypaque, did not exhibit a concomitant lipid fluidity alteration as measured by fluorescence polarization (P) of the lipid probe, 1,6-diphenyl-1,3-5-hexatriene (DPH). This result was independent of the incubation period, ranging from 10 min to 72 h. However, a general reduction in polarization value, from P = 0.287 (maintained for up to 2 h of incubation) to P = 0.225 after 20 h was observed for both experimental and control samples. Moreover, fluorescence polarization studies of the nonpenetrating modified DPH cationic lipid probe, 1-[4'-trimethylaminophenyl]-6-phenyl-1,3-5-hexatriene (TMA-DPH), also failed to show any change in lipid fluidity subsequent to a 1-3 h incubation of lymphocytes with concanavalin A. Cell electrophoretic mobility, however, was altered (mean cell mobility increased by 10-15%) in a fast response to stimulation and was observed within several hours of in vitro application of concanavalin A and purified protein derivative. This initial response disappeared with further incubation at 37 degrees C (greater than 3 h) and was followed by a decline of cellular mobility of the concanavalin A-exposed cells after 48 and 72 h of incubation. The unstimulated control cells did not change in mobility as a function of incubation time. The slow decline in mean cell mobility of the experimental cells is believed to be associated with blastogenesis. It is concluded that neither blastogenic transformation nor short term membrane alterations associated with human lymphocyte activation lead to lipid fluidity changes as measured in steady state by the fluorescence polarization of both DPH and TMA-DPH.

Fluorescent substrate analogue for adenosine deaminase: 3'-O-[5-(dimethylamino)naphthalene-1-sulfonyl]adenosine

The synthesis of the fluorescent derivative of adenosine, by reaction with 5-(dimethylamino)naphthalene-1-sulfonyl chloride in dry pyridine at low temperature, yielding 3'-O-[5-(dimethylamino)naphthalene-1-sulfonyl]adenosine (3'-O-dansyladenosine), is here described. 3'-O-Dansyladenosine is partially soluble in water (approximately 10(-4) M) and upon excitation at 325 nm exhibits maximum fluorescence emission at 516 +/- 22 nm (corrected) in buffered aqueous solution at pH 7.6 with a quantum yield of 0.21 and a lifetime of 11.8 +/- 0.2 ns. The fluorescence of 3'-O-dansyladenosine is sensitive to the polarity of its solvent: in pyridine, a quantum yield of 0.61 at the emission maximum of 435 nm was observed. 3'-O-Dansyladenosine is a reversible competitive inhibitor of adenosine deaminase with a moderate inhibitive dissociation constant K1 = (1.54 +/- 0.13) X 10(-5) M. The enzyme-substrate analogue association constant was determined by equilibrium dialysis to be K = (0.69 +/- 0.05) X 10(5) M-1, very close to KI-1. The hydrophobic nature of its binding site in adenosine deaminase is evident from the strong blue shift of the fluorescence emission maximum to 440 nm, the 4-fold increase in fluorescence quantum yield, and the longer lifetime of 15.8 +/- 0.2 ns; the tight, rigid nature of the complex is evident from its high fluorescence polarization value, 0.23. An 85% decrease in the fluorescence emission intensity of the adenosine deaminase-3'-O-dansyladenosine complex in the presence of adenosine indicates the selective binding to the enzyme active site. Correlation between the conformation of the probe, either when free in various solvents or when bound to the enzyme, and its fluorescence quantum yield is noted. 3'-O-Dansyladenosine is suitable for fluorescent labeling of adenosine deaminase in cell systems.