The fluorescence decay analysis of intramolecular two-state excited-state processes with added quencher is discussed in terms of compartments. The kinetics specifying the two excited-state species concentrations are derived. The fluorescence decay surface is expressed in terms of the system parameters, namely the rate constants and the spectroscopic parameters 81 and E l . 61 and T.1 are respectively the relative absorbance and the normalized spectral emission weighting factor of species 1. The report investigates the prerequisites for obtaining the unique set of system parameters. The results of this identifiability study indicate that the following conditions have to be satisfied in order to make an intramolecular two-state excited-state system with added quencher identifiable. First, the fluorescence decay surface must include at least one set of decay traces measured for a minimum of three different quencher concentrations at the same excitation/emission wavelength setting. One of the quencher concentrations used may be equal to zero. Second, the rate constants of quenching of the two excited species must be different. Third, at least one system parameter, which is not a rate constant of quenching, must be known. Under these conditions, four sets of system parameters are mathematically possible. If the known system parameter is a rate constant, decay traces of a suitable model compound measured at a minimum of two quencher concentrations must be included in the analysis in order to obtain the unique set of values for the rate constants. The unique set of (61,El) values can be recovered by including decay curves at a minimum of two quencher concentrations and at an additional excitation wavelength with a different or at another emission wavelength with a different El. If the known system parameter is a 81 value different from zero and unity, the fluorescence decay surface must include at least nine decay traces measured at four emission wavelengths with different E1 (corresponding to at least three quencher concentrations at the first emission wavelength and at least two quencher concentrations at the other three emission wavelengths), to uniquely determine the set of system parameters. If the known system parameter is a El value different from zero and one, at least four excitation wavelengths with different 61 are necessary to obtain the unique set of system parameters. The conclusions of the identifiability study are confirmed by the results from the global compartmental analysis of computer-generated fluorescence decay traces.

The crude product was purified by radial chromatography.Acknowledgment. K.R. thanks the University of Miami for a Maytag fellowship (1987)(1988)(1989)(1990). The initial phases of this work were supported by the National Science Foundation (Grant CHE-8210586) and the American Cancer Society (Grant F87-UM3). Continuing support has been provided by the National Institutes of Health (Grant GM-37985). The deuterium decoupled proton spectra were run at the Colorado State University Regional NMR Center, supported by the National Science Foundation (Grant CHE-8208821).Supplementary Material Available: Details of the preparation and physical and spectral data for compounds 1-5, 10, and 11 (14 pages). Ordering information is given on any current masthead page.

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Time-resolved fluorescence quenching measurements in micellar solutions of ionic surfactants, combined with the simultaneous recovery of decay parameters, demonstrate that the residence time of a quencher in the micelle can be varied by changing the electrostatic interaction between the micellar aggregate and the quencher or the hydrophobicity of the quencher, or by the addition of 1-butanol. When an alkylpyridiniitm chloride is used as a quencher with a cationic group, it always behaves as an immobile quencher in a solution of an anionic surfactant. However, it can, depending upon the length of the alkyl chain, behave as a mobile one in a solution of a cationic surfactant. In the latter case the migration of the quencher is due to the exchange of monomer quenchers among the micelles. The migration of strongly hydrophobic cationic quenchers is observed in sodium dodecyl sulfate solution upon addition of high concentrations of 1-butanol. Global analysis demonstrates that the exit rate constant of quenchers with different lengths of the alkyl chain is in this case identical. Furthermore, the quenching rate constant kq increases initially and then decreases upon the addition of 1-butanol. At a concentration of 1 M added 1-butanol the size of the aggregate becomes larger. Similar results are found in aqueous dodecyltrimethylammonium chloride/1-butanol mixed solutions. These results can be rationalized by the fragmentation-coagulation model of micellar systems. In this model the micelles exchange surfactant-butanol clusters containing the quencher and the excited probe.

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In eleven patients with uraemia on intermittent haemodialysis treatment, recombinant human erythropoietin (rHuEpo) was used at a dosage schedule of 100 IU/kg bodyweight thrice weekly. Erythrokinetic studies (blood volume, RBC survival and iron kinetics) were performed in nine cases before and after 6 months of treatment. The remaining two patients had only RBC and plasma volume determinations before and after treatment. Although total blood volume remained unchanged, RBC volume was increased in all cases. Red cell loss was not modified, and quantitative improvement of RBC production was noted in all cases. No qualitative defect of erythroid maturation or release was observed in the treated patients. In conclusion, rHuEpo treatment improves the anaemia of haemodialysis patients by normalising circulating RBC volume only through an increase in red cell production.

Während die Photodimerisierung der Furocumarine (I) in Übereinstimmung mit theoretischen Voraussagen ausgehend von einem angeregten Triplett‐Zustand zu den Dimeren (II) führt, sind die Verhältnisse bei der Photodimerisierung der Dihydrofurocumarine (III) komplizierter.

The hole transport properties of 5′-[4-[bis(4-ethylphenyl)amino]phenyl]-N,N,N′,N′-tetrakis(4-ethylphenyl)-[1,1′:3′,1′′-terphenyl]-4,4′′-diamine (pEFTP), an aromatic polyamine, have been studied extensively before. We report on the hole injection processes from metal electrodes, or redox solutions, into polymers molecularly doped with pEFTP. By use of the redox couple Fe 2+ /Fe 3+ at large fields, the injection of charges seems to be limiting the current density. At lower fields, competition between recombination and escape processes could be observed in the presence of the reduced form of the redox couple. The influence of the work function of the metals on the values of the dark currents suggests injection controlled currents characterized by almost exclusive hole transport.