Novel Manifestations of Optical Activity

Many molecules possess shapes that distinguish them from their mirror images, much like a human hand. These handed, or chiral, molecules are of great importance in chemistry, biology, medicine and agriculture owing to their ubiquity and the vital roles that they play in biological function. Indeed, a remarkable and important consequence of the latter lies in the fact that the mirror-image forms, or enantiomers, of a chiral molecule can interact differently with living things. For example, one enantiomer of carvone is found in spearmint leaves whereas the opposite enantiomer is found in caraway seeds, thus being associated with different aromas; one enantiomer of methamphetamine is recognised as being a harmful narcotic whereas the opposite enantiomer is used as a decongestant. Means by which to probe and utilise molecular chirality are thus highly sought after, in both academic and industrial contexts.

One of the principal approaches available to us lies in the use of light that is itself chiral. Specifically, circularly polarised light, in which the electric and magnetic fields twist, like a corkscrew, in either a left- or a right-handed manner. Naturally, a chiral molecule interacts differently with these mirror-image forms of twisting light, much as a given human hand interacts differently with left- and right-handed gloves, and these differences enable us to explore and harness molecular chirality in various ways. More generally, differences in the response exhibited by matter, including chiral molecules, to left- and right-circularly polarised light comprise the subject of optical activity, applications of which are diverse and range from the study of the structures of viruses to the operation of liquid crystal displays. Molecular chirality and optical activity thus pervade science and technology.

Lying at the heart of my proposed Fellowship research is my observation that new types of light in which the electric and magnetic fields twist in unusual ways afford the possibility of improving our understanding of molecular chirality and our ability to utilise it and, more broadly, of significantly advancing the subject of optical activity and its applications. Following this observation, I will pioneer entirely new manifestations of optical activity in the translational degrees of freedom of molecules and atoms and in the rotational degrees of freedom of molecules, enable 'dormant' manifestations of optical activity in light scattering to be exploited, for the first time, and expand upon the understanding and applications of well-established manifestations of optical activity, including circular dichroism and optical rotation. New experimental techniques and technologies based upon my research could be employed to probe the laws of physics themselves in unprecedented ways; to measure enigmatic properties of light; to gain deeper understandings of the structures of molecules and atoms, their behaviour in chemical processes and their roles in biological function; to assist in the design and manufacture of new materials, cosmetics, foods, drugs and agrochemicals and much more besides.

My Fellowship will improve our understanding of molecular chirality and our ability to harness it and, more broadly, will see the subject of optical activity and its applications significantly advanced. Owing to the enormous importance of molecular chirality and optical activity in science and technology, it is difficult to overstate the potential for impact.

Anticipated outputs of my Fellowship research include: devices able to spatially separate the enantiomers of chiral molecules in a general manner using light for further applications; new and improved forms of spectroscopy with which to study the structures of molecules and atoms, their behaviour in chemical processes and their roles in biological function; advances in the design, manufacture and control of novel materials, including chiral metamaterials and liquid crystals. In addition to impacting academia as described in my 'Academic Beneficiaries' statement, my Fellowship thus stands to enhance the economic competitiveness of the UK and the health and quality of life of the general public, by servicing the many industries in which these outputs could find widespread adoption. Consider, for example:

The pharmaceutical industry
Chirality underpins biological function. Consequently, the enantiomers of a chiral molecule can interact differently with living things and, in particular, often function differently as drugs. One enantiomer of ethambutol, for example, is employed to treat tuberculosis whereas the opposite enantiomer causes blindness. Clearly, molecular chirality is vitally important in this context and, indeed, it is anticipated that nearly 95% of all pharmaceutical drugs will be chiral by 2020 [1]. Chirality and optical activity also impinge upon medical diagnostics. For example, small changes in protein level, detectable using circular dichroism, can indicate the presence of certain diseases.

The food industry
The enantiomers of a chiral molecule often taste and are metabolised differently. Sugar molecules, for example, are chiral and optical rotation is perhaps the principal means by which their concentrations are measured, with several successful UK-based companies currently manufacturing polarimeters for this purpose. Molecular chirality is also of great importance to agriculture itself, as many agrochemicals are chiral. One enantiomer of mecoprop, for example, functions as a herbicide whereas the opposite enantiomer is ineffective in this context.

The cosmetics industry
The enantiomers of a chiral molecule often smell different. One enantiomer of nootkatone, for example, smells of grapefruit whereas the opposite enantiomer smells woody. Molecular chirality is thus an important ingredient in the design and manufacture of perfumes.

The entertainment industry
Chirality and optical activity underly an abundance of high-end technologies. For example, the operation of the liquid crystal displays found in many calculators, televisions and computer screens utilises optical rotation. It has also been suggested that chiral molecular switches could form memory elements in future computers.

The global market for chiral technology, some 10-20% of which is based upon optical activity phenomena, is predicted to grow in value to £3bn by 2017, being driven largely by the increasing demands of the pharmaceutical and agrochemical industries [2]. Progress is hampered, however, by a lack of methods of general applicability and this is one of the areas in which my proposed Fellowship research shines.

[1] See, for example uk.finance.yahoo.com/news/chiral-technology-market-led-basf-000000637.html last accessed (27/01/2014)
[2] See, for example www.transparencymarketresearch.com/chiral-technology-market.html last accessed (27/01/2014)