Characterization of Physiologically Relevant Fatty Acids by Differential Scanning Calorimetry and Dielectric Thermal Analysis

摘要

Fatty acids are relevant to human life. The majority of biomaterials are comprisedrnof polyunsaturated fatty acids (PUFA); the PUFA are concentrated in the cell membranernand nervous tissue. Free fatty acids (FFA) are active metabolically and are precursors forrnprostaglandins. Fatty acid chemistry may be involved in inflammatory, neurological,rnmetabolic, neoplastic, immunological and cardiovascular diseases. The high distributionrnof fatty acids and associated pathologies warrant investigation of the physical propertiesrnof these critical acids (1-5). We have focused on the following physiologically relevantrnfatty acids for this study: stearic, oleic, arachidonic, linoleic, and linolenic. DifferentialrnScanning Calorimetry (DSC) of FFA was used to determine the transition temperaturesrnand heats of fusion and crystallization. It appears that the observed melt temperature ofrnthe unsaturated acids decreases with increasing double bond content, from one to fourrnsites of unsaturation. Another focus of this study is to evaluate the FFAs by DielectricrnThermal Analysis (DETA) as a function of temperature and frequency. The DETArnproperties of the air aged liquid FFAs indicate that the electrical conductivity andrncomplex permittivity can be correlated with the degree of unsaturation. The probablernconduction mechanism of the dipolar and oxidized "particles" follows the "PolaronrnTheory” or "Hopping Conduction Model” with the electron dense areas surrounding therndouble bonds as conduction pathways (6-9).