The spin-lattice (T1) and spin-spin (T2) relaxation times of protons on linoleic acid (LA), arachidonic acid (AA), and DHA in CDCl3 solutions and aqueous micelles were measured. Protons at hydrophobic sites on DHA and AA in micelles had a longer T2 than those on LA, whereas little difference was found for proton relaxation times among fatty acids in CDCl3 solutions. DHA molecules in micelles were thus more flexible than LA in micelles.
By means of surface tension measurement (Wilhelmy method), micellization and adsorbed film formation were investigated for three combinations of mixed surfactant systems: a typical anionic surfactant, sodium dodecylsulfate (SDS) was combined with three nonionic surfactants used as membrane-protein solubilizers, n-alkyl (octyl, nonyl and decyl)-N-methylglucamides (MEGA-8, MEGA-9 and MEGA-10, respectively) in water at 30°C. The data of surface tension (γ) versus logarithmic total molality of both single and mixed surfactant systems (mt) plots as a function of mole fraction of surfactant 2 (2 corresponds to MEGA-n’s), X2, enabled us to determine critical micellization concentration (CMC), minimum surface tension at CMC (γCMC), surface excess (Γt), mean surface area occupied by a molecule (Am) and parameters related to synergism in surface activity such as pC20 and CMC/C20. Based on the regular solution theory, the relation of compositions of the singly dispersed phase (X2) and the composition of the adsorbed film phase (Z2) were estimated, and then the interaction parameters in micelles (ωR) and in adsorbed film (ωA) were also calculated. Both the CMC-X2 and CMC-Y2 curves were found for all combinations to show a negative deviation from ideal mixing, and even the curve of mt (bulk phase concentration) versus Z2 produced a prominent negative ωA. A marked synergism in surface tension reduction was observed for these MEGA-n’s mixtures with SDS; the extent of the synergism increased in the order of MEGA-8, -9 and -10. A positive synergism was observed, even from the partial molecular area (PMA) and the minimum free energy at surface G(S)min= (γCMC·Am·L) where, L is the Avogdro’s number.
For assessment of the physiological significance of 9-methyl-4-trans,8-trans-sphingadienine (9-methyl base) in cerebroside-accumulating yeast, determination was made of the content and chemical compositions of cerebrosides in Kluyveromyces lactis and the results were compared for growth temperatures at 15°C, 25°C and 35°C. Compared with the culture prepared at the optimal growth temperature (25°C), greater time was required to reach the stationary phase of cells grown at 15°C. A reduction in cell weight was noted at 35°C. Cerebroside content in cells cultured at 15°C was significantly less than at 25°C or 35°C. Also, the ratio of cerebroside to phosphorus in the total lipid fraction at 15°C was less than at 25°C. In the 15°C culture, the 9-methyl base, the most predominant fungal cerebroside sphingoid base, increased beyond that in the 25°C preparation, though was essentially the same as at 35°C. K. lactis is thus shown to modulate not only the content but sphingoid base composition of cerebrosides in response to temperature. Fatty acid compositions in all cerebrosides examined were the same. These and the results from a previous study (J. Oleo Sci., Vol. 51, 741-747, 2002) provide basis for assuming 9-methyl branched chain in yeast cerebroside molecules to be essential for maintaining sufficient membrane fluidity for a low temperature environment.
We applied a continuous 13CO2 breath test to examination of the effects of n-3 polyunsaturated fatty acid (PUFA) insufficiency on fatty acid β-oxidation. Fischer rats were divided into two groups, and were reared on two different regimens of diet for multiple successive generations. One diet was adequate with respect to n-3 PUFA and the other was insufficient in n-3 PUFA. Rats (the F18 generation) were given [U-13C]docosahexaenoic acid or [U-13C]palmitic acid by intravenous injection, and expired 13CO2 was continuously measured using a mass spectrometer. Fatty acid oxidation was evaluated by two parameters, the half-life of 13CO2 in the breath and cumulative 13CO2 recovery from the labeled fatty acids. When [U-13C] docosahexaenoic acid was administered, cumulative 13CO2 recovery was 40% lower in the n-3 PUFA-insufficient diet group than in the n-3 PUFA-adequate diet group. The half-life appeared to be the same for the two diet groups. In the case of [U-13C]palmitic acid, neither the half-life nor cumulative 13CO2 recovery significantly differed between the two diet groups. These results suggest that overall β-oxidation of DHA in a whole-body system is decreased under n-3 PUFA insufficiency. Our finding shows that the 13CO2 breath test can be used to assess n-3 PUFA insufficiency. The test provides a useful and invasive method for evaluation of fatty acid β-oxidation.
Fluorinated silane coupling agents with a benzene ring as a spacer, CnF2n + 1-C6H4-SiX3 (n = 4, 6 and 8; X = Cl, OCH3 and NCO), were synthesized and their properties were examined to improve the surface modifying properties of the conventional fluorinated silane coupling agents. The silane coupling agents with a chloro- and methoxy-type hydrolytic groups were synthesized by the reactions of tetrachlorosilane and tetramethoxysilane with the intermediate, Rf-C6H4-MgBr, obtained through the Grignard reaction of the product of the reaction between p-dibromobenzene and perfluoroalkyl iodide in the presence of copper powder. The isocyanato-type silane coupling agents were obtained by allowing the chloro-type coupling agents synthesized to react with silver cyanate. All of the silane coupling agents thus synthesized were colorless transparent liquids. Evaluations were made on the glass surface modified with each of the coupling agents in terms of water contact angle, thermal stability, oxidation resistance, and acid resistance. The coupling agents had the properties similar to those of the conventional fluorinated silane coupling agents with the exception of thermal stability, showing that the newly synthesized agents were thermally stable up to about 300°C.
The synthesis and carbon-13 NMR longitudinal relaxation times (T1) studies on the calixarene-substituted porphyrin dimers possessing conformational fluctuation were carried out for the first time. The T1 values were measured under proton-noise-decoupling conditions by the inversion-recovery technique. The T1 values for a calixarene bridged porphyrin dimer 1 decrease with the increase in the solvent polarity. This implies that the T1 values reflect the diffusion rate. As to a motion of the phenol unit, there are two different motions for phenol units in 1 and 2: a seesaw motion around a C-2 to C-2’ axis (A) and a rotational motion around a C-1 to C-4 axis (B). The T1 values indicate that in 1 motion (B) is predominant over motion (A). This shows that motion (A) is specifically suppressed because of the hydrogen-bonding interactions in 1.