Pure phosphatides and the serodiagnosis of syphilis: relation of chemical structure to reactivity.

Several pure individual lecithins, all but one of which were synthetic, were used in cardiolipin antigens prepared for the VDRL microflocculation and Kolmer complement-fixation tests for syphilis.A number of compounds lacking one or more radicals of the lecithin molecule were used as substitutes for lecithin in an effort to determine reactive groupings.Several synthetic compounds related to cardiolipin, but simpler in structure, were tested as substitutes for it. Of these, certain fatty-acid derivatives of bis-(L-alpha-glyceryl)-phosphoric acid and of L-alpha-glycerophosphoric acid showed a limited reactivity in the VDRL and Kolmer tests.A number of weakly reactive antigens, in which both cardiolipin and lecithin had been replaced by synthetic compounds, were prepared for the VDRL test. The most reactive of these contained beta-(dioleoyl)-glycerophosphoric acid (sodium salt), dioleoyl lecithin and cholesterol.