Mechanisms of light energy harvesting in dendrimers and hyperbranched polymers

Since their earliest synthesis, much interest has arisen in the use of dendritic and structurally allied forms of polymer for light energy harvesting, especially as organic adjuncts for solar energy devices. With the facility to accommodate a proliferation of antenna chromophores, such materials can capture and channel light energy with a high degree of efficiency, each polymer unit potentially delivering the energy of one photon-or more, when optical nonlinearity is involved. To ensure the highest efficiency of operation, it is essential to understand the processes responsible for photon capture and channelling of the resulting electronic excitation. Highlighting the latest theoretical advances, this paper reviews the principal mechanisms, which prove to involve a complex interplay of structural, spectroscopic and electrodynamic properties. Designing materials with the capacity to capture and control light energy facilitates applications that now extend from solar energy to medical photonics. © 2011 by the authors; licensee MDPI, Basel, Switzerland

Synthetic CO2-fixation enzyme cascades immobilized on self-assembled nanostructures that enhance CO2/O2 selectivity of RubisCO

Abstract Background With increasing concerns over global warming and depletion of fossil-fuel reserves, it is attractive to develop innovative strategies to assimilate CO2, a greenhouse gas, into usable organic carbon. Cell-free systems can be designed to operate as catalytic platforms with enzymes that offer exceptional selectivity and efficiency, without the need to support ancillary reactions of metabolic pathways operating in intact cells. Such systems are yet to be exploited for applications involving CO2 utilization and subsequent conversion to valuable products, including biofuels. The Calvin–Benson–Bassham (CBB) cycle and the enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) play a pivotal role in global CO2 fixation. Results We hereby demonstrate the co-assembly of two RubisCO-associated multienzyme cascades with self-assembled synthetic amphiphilic peptide nanostructures. The immobilized enzyme cascades sequentially convert either ribose-5-phosphate (R-5-P) or glucose, a simpler substrate, to ribulose 1,5-bisphosphate (RuBP), the acceptor for incoming CO2 in the carboxylation reaction catalyzed by RubisCO. Protection from proteolytic degradation was observed in nanostructures associated with the small dimeric form of RubisCO and ancillary enzymes. Furthermore, nanostructures associated with a larger variant of RubisCO resulted in a significant enhancement of the enzyme’s selectivity towards CO2, without adversely affecting the catalytic activity. Conclusions The ability to assemble a cascade of enzymes for CO2 capture using self-assembling nanostructure scaffolds with functional enhancements show promise for potentially engineering entire pathways (with RubisCO or other CO2-fixing enzymes) to redirect carbon from industrial effluents into useful bioproducts