Design, Synthesis and Applications of Retinal-Based Molecular Machines

Abstract

Progress of mankind has always been related to the development and construction of new machines. In the last decades, science and technology have been involved in a race to increase the capacity of novel machines as well as in a progressive miniaturization of their parts. Further efforts to design and construct machines at the nanometer scale will lead to new and exciting applications in medicine, energy and materials. However, until now every attempt to build artificial systems at the molecular level with complex functions pales beside the Nature’s molecular machines at work. Myosin and kinesin enzymes responsible of muscle contraction, ATP synthase and cellular transport are all examples of Nature’s ability to provide living systems with complex machinery whose structures and detailed mechanisms we are just starting to unveil. Thus, by learning from Nature, we will be able to make use of the excellent properties refined by slow evolution. When we mimic Nature, we try to duplicate some of the features found in biological systems using synthetic analogues. Taking natural molecular machines as a starting point, we will try to design, synthesize and explore biomimetic artificial machines. Located at the interface between biology, physics and chemistry, the task of mimicking Nature’s results will need combined efforts from different disciplines and the use of every possible tool from theoretical calculations to advanced synthetic chemistry and structural characterization. In this chapter we will briefly review some of the better-known natural molecular machines as an inspiration for the design of biomimetic artificial machines. Specifically, the structure and function of the retinal molecular machine will be discussed. Taking the Nature’s work as a starting point, we will specify some of the requirements to build efficient molecular machines, such as controlling the motion at the molecular level and the energy supply. We will use these concepts to design a set of retinal-based biomimetic chemical switches. Comparison between the synthetic and biological structures allows to gather a better understanding of both systems together with some suggestions for further improvements. Some practical applications will also be presented together with an outlook for the near future.