The mechanism of transfer of diglyceride between high density lipoproteins (HDL) was investigated with a pyrene-containing analogue whose fluorescent properties depend on the microscopic concentration in the lipoprotein. Transfer rates were first order, rapid (3.5s-1), and invariant over a 100-fold range of HDL concentration and over a 10-fold range of rac-1-oleyl-2-[4-(3-pyrenyl)butanoyl]glycerol concentrations. Similar behavior of the probe was observed with HDL3, although the rate was 40% slower. These results support a mechanism in which rate-limiting dissociation of the diglyceride analogue from one HDL particle into the aqueous phase precedes rapid diffusion and subsequent uptake by another such particle.

No abstract

No abstract

No abstract

Photochemically generated hot hydrogen atoms initiate reactions with simple molecular substrates including methane to produce organic alcohols, amines, acids, amino acids, and other compounds. The typical quantum yields for the formation of amino acids are 2 x 10(-5) to 4 x 10(-5). Hot hydrogen atoms may be important initiators of reactions in interstellar space and in planetary atmospheres.