PubMed · 1202687
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V N Karnaukhov, A M Shamarov, V A Iashin, V I Kulakov. 1975. [Inverted microspectrofluorimeter].. https://pubmed.ncbi.nlm.nih.gov/1202687/
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Novel anionic gemini surfactants, 1,2-bis(N-beta-carboxypropanoyl-N-alkylamino)ethane (2CnenAm; n is hydrocarbon chain length of 6, 8, 10, 12, or 14), with two hydrocarbon chains, two carboxylate groups, and two amide groups, were synthesized by three-step reactions. Their solution properties were characterized by equilibrium and dynamic surface tension, steady-state fluorescence spectroscopy of pyrene, and dynamic light-scattering techniques. The surface tension measurements of 2CnenAm give low critical micelle concentrations (cmc), great efficiency in lowering the surface tension, and strong adsorption at air/water interface. Gemini surfactants behave normally with the logarithm of cmc decrease linearly with the chain length. In addition, adsorption and micellization behavior of 2CnenAm was estimated by parameter of pC20, cmc/C20, and standard free energy (DeltaG(0)mic and DeltaG(0)ads); they are significantly influenced by hydrocarbon chain length, and the adsorption is promoted more than the micellization as chain length becomes longer. The results of dynamic light-scattering and fluorescence quenching indicate that small micelles of 2CnenAm are observed at the concentrations above the cmc, and further large particles are also seen. Further, from the dynamic surface tension measurements, it is found that the shorter hydrocarbon chain length of 2CnenAm, the faster the rate of decrease of surface tension.
There are two fluorescence peaks at 350 and 700 nm for tryptophane in pH 7.43 Tris buffer solution, as the excited wavelength is at 296 nm. The fluorescence peak at 700 nm is a nonlinear 1/2 fraction frequency fluorescence peak for tryptophane. The fluorescence intensities of 350 and 700 nm peaks are proportional to tryptophane concentration in the range of 0-1 x 10(-5) mol.L-1. The half width of (delta lambda)350 for 350 nm and (delta lambda)700 for 700 nm peak decreases slowly with tryptophane concentration. And the F700 nm/F350 nm and (delta lambda)700/(delta lambda)350 are constant. The two peaks have similar fluorescence behavior. An energy level principle for fraction frequency fluorescence and resonance principle of fraction frequency have been proposed, and applied to explaining the fraction frequency fluorescence of tryptopane.
Overlap of multiple states or multiple species in a chemical system often creates a congested fluorescence spectrum that is difficult to interpret. The resolution of component spectra is essential for the understanding of the structure and dynamics of such multicomponent systems. In this paper, two-dimensional fluorescence correlation spectroscopy (2D FCS) is presented for the dissection of component spectra using the time correlation function. In 2D FCS, the time response of fluorescence intensity is collected at various wavelengths upon an external perturbation. The time correlation function is evaluated between wavelengths. A two-dimensional fluorescence correlation spectrum, or a plot of the correlation intensity as a function of two wavelength axes, resolves the overall spectrum into component spectra. The characteristics of the two-dimensional time correlation function are demonstrated in the frequency domain fluorescence spectroscopy in which the sinusoidally modulated excitation provides the external perturbation. Using 2D FCS, fine vibronic structures of the component fluorescence emission spectra were completely resolved from a strongly overlapped one-dimensional mixture spectrum. The existence of multiple microenvironments of a probe molecule in a biological system is evidenced by nonzero asynchronous correlation intensities. The corresponding spectra are retrieved from correlation analysis. Unlike traditional resolution methods in fluorescence spectroscopy based on statistical fitting of fluorescence decays, 2D FCS can resolve species whose fluorescence decays are linked by the rate constants in chemical reactions and species displaying multiexponential decay kinetics.