Abstract
The partition ratios of radioactive fatty acids between n-heptane and a physiological buffer at 37 degrees C were measured. The fatty acids included the saturated acids with an even number of carbons from 10 to 18 and the unsaturated acids oleic, linoleic, and linolenic. In addition, the partition ratios of decanoate, myristate, and palmitate were determined over a wide pH range. Any single plot of partition ratio vs. aqueous concentration of an acid gave a nearly straight line, a finding consistent with very little association in the aqueous phase. In the case of the acids with 16 and 18 carbon atoms, however, comparison of the constants calculated from these plots with the assumption of no aqueous phase association revealed several inconsistencies. These inconsistencies cannot be resolved completely by assuming the existence of fatty acid association in the aqueous solution. We believe that at least some of the deviations are due to the presence of trace quantities of radioactive impurities in the labeled fatty acids. For example, purification of a sample of supposedly pure [1-(14)C]myristate by a series of solvent extractions increased the partition ratio by a factor of 1.5. Although all of the observations cannot be explained by this interpretation, we believe that our studies suggest that there is no appreciable association of fatty acids under the usual physiological conditions.
Highlights
The partition ratios of radioactive fatty acids between n-heptane and a physiological buffer at 37°C were measured
T h e partition of long-chain fatty acids between n-heptane and a n aqueous phosphate buffer was measured by Goodman [1, 2] in conjunction with his studies on fatty acid binding to serum albumin
T h e model employed by Goodman for the analysis of these data assumed the existence of fatty acid dimerization in the heptane phase but no association in the aqueous phase
Summary
Heptane (50 ml) containing the radioactive compound was extracted with an equal volume of 0.01 N HzS04 followed by extraction with an equal volume of 0.05 M NazHP04, pH 7.0 This final step was repeated five times in order to ensure removal of short-chain fatty acid impurities. Aliquots of the heptane and the aqueous phases from each flask were added to 15 ml of a toluene-Triton X-100 80:20 (v/v) scintillator solution containing 0.55% 2,5-diphenyloxazole and 0.01%. The partition ratio (P.R.) is defined as the ratio of concentration of all fatty acid in the organic phase (12,t)o that in the aqueous phase (Cw).It is well established that in organic solvents dimerization of carboxylic acids occurs. If we assume that the hydration of the fatty acids in the organic phase is due to interaction between the water molecules and the carboxyl groups, the hydration constants K1 and K2 should be independent of chain length. Surements with the Mechrolab osmometer that indicate that the vapor pressure of heptane in equilibrium with decanoic acid solutions as concentrated as 0.4 M can be adequately explained solely on the basis of dimer formation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
