Do you need a protein for efficient photochemistry?

Some of the most essential processes in nature and for todays society and economy rely on the efficient interaction between light and matter. They range from photolithography used to create processors for todays computing needs to fundamental processes in nature, such as photosynthesis and vision. The latter exhibit a level of reactivity and speed that researchers have struggled for decades to recreate and understand in the laboratory. A case in point is the primary event in vision, the cis-trans isomerisation of the retinal chromophore in the visual pigment rhodopsin. This reaction is superbly fast and efficient when taking place inside the protein. 11-cis retinal in solution, however, reacts very slowly and inefficiently.
The goal of our research is to unravel the source of the additional reactivity inside the protein. We have recently demonstrated for the first time, that a very minor chemical change to the retinal molecule can induce dynamics in solution that are comparable to those found in an evolution-optimised protein environment. The goal now is to systematically map the photochemical consequences of a series of potentially influential modifications to the molecule. The ultimate aim of this work is not only to reproduce the reactivity found in nature, but, more importantly, use the lessons learned in the design process to establish fundamental rules for what makes a light-induced process efficient and how it can be tuned rationally. These results will find applications in exactly those types of processes that have motivated the work in the first place: conversion of light into chemical energy for future alternative energy applications and the development of perfectly controllable molecular switches.

There are a number of possible beneficiaries to this research.
The primary focus of the work is to understand a complex phenomena related to the conversion of light into energy, but new methods will be developed during our work.

The methods that will be developed during our work relate to improving the synthesis of retinal derivatives. These molecules are used extensively by vision researchers, who will benefit directly from improved access to important materials. In the long term, clinical scientists, and ultimately those with vision problems may benefit. Retinal derivates are also used clinically to treat a number of skin conditions and some cancers, and are under investigation for the treatment of other cancers. Medicinal chemists, the pharmaceutical industry, and ultimately some patients may benefit from some of our methodology work.

The main aim of the research is to understand what controls the speed, efficiency and selectivity of photochemical processes. There is tremendous academic, industrial, governmental and public interest in developing efficient light harvesting devices. Scientific advances in our understanding of the relationship between structure and its interaction with light will be of great benefit to other academics working in this broad and important area. Scientists working on new photoreceptors will benefit from an increased theoretical understanding and the demonstration of a methodological, multidisciplinary approach toward solving these important problems. Scientists working on vision research could benefit in the same way.

The long term benefits from understanding how to achieve efficent conversion of light into energy are potentially huge for the economy of the UK. One of the most important challenges facing society today is tacking the ever-increasing need for energy without relying of fossil fuels. Understanding bacteriorhodopsin based photosynthesis and how this system harnesses the suns energy could have implications in terms of quality of life and health. Advances in our understanding brought forward by basic research could potentially lead to energy independence, which would remove potential sources of conflict at various levels.

Besides energy, this research could lead to advanced communications systems. The lessons learned on how to control speed and selectivity in receptors could be applied in the future as the basis of new customised light-based devices.

In biology molecular machines are extensively used to accomplish a huge number of complex and intricate functions, while current man-made systems are still primitive. Rhodopsin and bacteriorhodopsin are in fact devices triggered by the switching mechanism of the olefin isomerisation reaction, and in principle, this could be the basis of synthetic systems capable of complex functions. Insights from this work could lead to the development of new tools of high potential importance to a number of areas. The recent developments in using cis-trans switches to control ion channel flow and neural activity has tremendous potential, and our work will aid the design of new molecular switches.