Application of photosynthesis to environmental and energy production problems

The highly efficient photoconversion ability of the photosynthetic molecular machinery is continuously spurring the assembly of artificial devices, using the photoconverting proteins for technological applications1. It is hence of paramount importance to have a robust, durable and versatile scaffold to be loaded with the integer and fully active photoconverter.In this communication, the photosynthetic reaction center (RC) from the bacterium R. sphaeroides is reconstituted in synthetic block co-polymer vesicles where it retains its functional activity. In particular amphiphilic symmetric block co-polymer, based on poly(2-methyloxazoline)-poly(dimethylsiloxane)-poly(2-methyl-oxazoline) (ABA) self-assemble in water2, forming the polymerosomes, i.e.structures resembling phospholipid liposomes but with an inherently higher stability.The protein loading of polymerosomes was obtained, for the first time, by using the so called micelle-to-vesicle transition (MVT) method3, a mild, highly biocompatible and well-established technique employed for membrane protein insertion in liposomes. ABA vesicles were characterized by TEM, AFM and DLS techniques. Interestingly, spectroscopic and enzymatic data, directly obtained from the embedded protein, indicate that the RC tends to place in the external portion of the ABA, i.e. the poly(2-methyloxazoline) facing the bulk solution and not, as expected, randomly oriented in the central poly(dimethylsiloxane) core. In these organic vesicles RCs shows, therefore, a much higher activity compared to the analogue vesicles formed by phospholipids4. The ABA scaffolding with an asymmetric distribution of RC can eventually be functionalized with opportune organic moieties to form supramolecular assemblies for the design of hybrid bio-organic photoconvertion devices.[1]F. Milano, R.R. Tangorra et al., Angew. Chem. Int. Ed., 51 (2012), 11019 - 11023[2]C. Nardin et al., Langmuir, 16 (2000) 1035-1041[3]F. Milano et al., Photosynth. Res., 100 (2009), 107-112[4]L. Nagy et al., Biochemistry, 43 (2004), 12913-12923