ENHANCED VESICLE ASSEMBLY RATE AT THE MINERAL/WATER INTERFACE

Vesicles formed by single-chain fatty acids in aqueous conditions may approximate primitive cells available on early Earth prior to life's origins. The rate that these protocell membranes assemble is known to increase in the presence of mineral surfaces (Hanczyc et al., 2007). However, no additional study has determined how the mineral surface structure or chemistry specifically contributes to this rate enhancement. We investigated the vesicle assembly rate of decanoic acid at pH ~ 7 in the presence of a wide array of well-characterized rock-forming minerals and Archean rocks. We observed that all rock and mineral surfaces increased the initial vesicle assembly rate of decanoic acid. The initial vesicle assembly rate was dependent on the mineral loading, surface area, and surface charge as determined by the isoelectric point of the mineral surface. It is possible that both net positive and net negative minerals increase the assembly rate of vesicles by adsorbing and concentrating fatty acids at locally-positive or neutral surface sites. In this concentrated aqueous environment, it is more probable that fatty acids would spontaneously form vesicles at pH ~ 7. The rocks and minerals we investigated in this study were likely present in a variety of geological settings on early Earth. It is possible, therefore, that mineral surfaces at many prebiotic geochemical settings may have enhanced primitive cell assembly.

Hanczyc M. M., Mansy, S. S. and Szostak, J. W. (2007) Mineral directed membrane assembly. Orig. Life Evol. Biosph., 37, 67-82.