Title:	Computational chemistry studies of light-driven rotary molecular motors and photosensory proteins
DNr:	SNIC 2014/1-359
Project Type:	SNIC Medium Compute
Principal Investigator:	Bo Durbeej <bo.durbeej@liu.se>
Affiliation:	Linköpings universitet
Duration:	2014-12-01 – 2015-12-01
Classification:	10407 10405 10603
Homepage:	http://www.liu.se/forskning/foass/bo-durbeej?l=en&sc=true
Keywords:

Abstract

This project, which is supported by Linköping University ("karriärkontrakt") and the Swedish Research Council, involves computational chemistry studies for improving the efficiency of synthetic light-driven rotary molecular motors, and for resolving a number of key issues concerning the mechanisms of photosensory proteins. Light-driven rotary molecular motors are molecules that can perform work by absorbing light energy and converting it to unidirectional rotary motion around a chemical bond. In this part of the project, we make use of quantum chemical methods to design motors exhibiting successively higher rotational frequencies, which is a key property for the use of these systems in nanotechnology. Furthermore, we also explore how the motors are best mounted on surfaces, which is another crucial step along the path toward full-fledged use of molecular motors as nanodevices. With respect to the SNAC Medium 2013 project upon which the present project builds, we will now also complement the quantum chemical calculations with classical and semi-classical excited-state molecular dynamics simulations performed with so-called surface hopping methods. This will enable us to estimate excited-state lifetimes and quantum yields, and thereby help provide a fuller picture of ways to accelerate the rotary motion of the motors. Present throughout all kingdoms of life, photosensory proteins like phytochromes regulate physiological processes in response to external light conditions. Although phytochromes were first detected more than fifty years ago, the basic chemical mechanisms underlying their biological functions remain poorly understood. This is largely a consequence of the fact that detailed structural data did not appear until 2005, when the first crystal structure of a phytochrome was reported. Together with a number of subsequent crystal structures, this pioneering effort provides guidance for ongoing experimental and computational work in the field. Using on the one hand so-called QM/MM methods that combine quantum and classical mechanics, and on the other surface-hopping excited-state molecular dynamics simulations, the project will establish how phytochromes are converted from an inactive state to a biologically active state. Furthermore, the project will uncover how phytochromes tune their light absorption to facilitate this conversion. These objectives offer great promise to fill long-standing gaps in the understanding of how phytochromes operate.