Trans-Membrane Electron Transfer (TM-ETR) promoted by Membrane-Associated Photocatalytic Minerals

A. G. BRACAMONTE; PROF. NITA SAHAI

Congreso; SCOL 2014; 2014

SCOL 2014

The aim of this project is to develop a model system which represents transmembrane energy transduction in a protocell, where a photocatalytic mineral associated with the membrane plays the role of a ?prebiotic enzyme.? In modern cells, TM-ETR is achieved by enzymes embedded within the phospholipid membrane. We propose that photocatalytic minerals, such as CdS or FeS, may have initiated electron transfer across the membrane. Sulfide minerals are proposed because they were likely common on early Earth under the low atomspheric O2 partial pressure .[1] TM-ETR has been achieved previously using an intramembrane polyaromatic hydrocarbon, which played the role of transmembrane electron-shuttle.[2] We believe that many pathways could have lead to TM-ETR, including minerals as prebiotic enzymes in TM-ETR. The model protocell was constructed here as follows: (1) vesicle membrane composed of single chain amphiphiles, decanoic acid (DA) and decanol (DOH); (2) Oxidant, methyl viologen (MV2+), which changes from colorless to blue when reduced to MV+.; (c) reductant, methanol (CH3OH); (4) transmembrane electron shuttler Napthopyrene (Npth); and (5) photocatalytic minerals, TiO2, FeS and CdS, associated with the membrane. Preliminary results showed that TiO2 promoted the TM-ETR reaction. Ambiguous results were seen with FeS, no ETR was observed for CdS. Attempts are currently underway to repeat the experiments in an O2-free atmosphere.