PubMed · 6944900
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L Forsten. 1981-04-15. [Current data on composites].. https://pubmed.ncbi.nlm.nih.gov/6944900/
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Absorption spectra of the isolated D1/D2/cytochrome b-559 complex have been measured in the temperature range 80-300 K. All spectra were analyzed in terms of a linear combination of Gaussian bands and the thermal broadening data interpreted in terms of a model in which the spectrum of each pigment site is broadened by (a) a homogeneous component due to linear electron-phonon coupling to a low-frequency protein vibration and (b) an inhomogeneous component associated with stochastic fluctuations at each pigment site. In order to obtain a numerically adequate description of the absorption spectra, a minimum number of five sub-bands is required. Further refinement of this sub-band description was achieved by taking into account published data from hole burning and absorption difference spectroscopy. In this way, both a six sub-band description and a seven sub-band description were generated. In arriving at the seven sub-band description, the original five sub-band wavelength positions were essentially unchanged. Thermal broadening analysis of the seven sub-band description yielded data which displayed the closest correspondence with the literature observations. The wavelength positions of the sub-bands were near 661, 667, 670, and 675 nm, with two bands near 680 and 684 nm. The two almost isoenergetic sub-bands near 680 nm, identified as P680 and pheophytin, have optical reorganization energies around 40 and 16 cm-1, respectively. All other sub-bands, identified as accessory pigments, have optical reorganization energies close to 16 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)
The mechanisms governing the interaction of mixtures of sodium dodecyl sulfate (SDS) and nonylphenol oxyethylenated with 10 mol of ethylene oxide (NP(EO)10) with phosphatidylcholine liposomes were investigated. Permeability alterations were detected as a change in 5(6)-carboxyfluorescein (CF) released from the interior of vesicles and bilayer solubilization as a decrease in the static light scattered by liposome suspensions. Three parameters were described as the effective surfactant/lipid molar ratios (Re) at which the surfactant system (a) resulted in 50% of CF release (Re50%CF), (b) saturated the liposomes (ReSAT), and (c) led to a complete solubilization of these structures (ReSOL). From these parameters the corresponding surfactant partition coefficients (K50%CF, KSAT, and KSOL) were determined. Despite the fact that Re increased as the mole fraction of the SDS rose (XSDS), the K parameters showed maximum values at XSDS 0.6 and 0.2 for K50%CF and KSAT, respectively, the KSOL reaching the highest value in the absence of SDS XSDS = 0). Thus, the higher the surfactant contribution in surfactant/lipid system, the lower the XSDS at which the maximum bilayer/water partitioning of mixed surfactant systems added took place. The free surfactant concentrations SW were lower than the mixed surfactant CMCs at subsolubilizing level, whereas it remained similar to these values during saturation and solubilization of bilayers in all cases.
Micellar colloids are distinguished from other colloids by their association-dissociation equilibrium in solution between monomers, counter-ions and micelles. According to classical thermodynamics, the standard Gibbs energy of formation of micelles at fixed temperature and pressure can be related to the critical micelle concentration. This relation is different for two models which are widely used to describe micelle formation, namely the Phase Separation and the Mass Action Models. These approaches and the assumptions upon which they are based are analysed in this paper. We show that the two models can be generalised to include surfactant salts having different stoichiometries.