About the Project
- Acquire diverse skills set centred on understanding of the ‘Biophysics of Life’ by working with Life Scientists and Chemists at Warwick University
- Unravel the energy transfer mechanisms occurring in Garden Cress Sprout (a member of the Brassicaceae family), specifically within light absorbing molecules (eg sinapoyl malate) used as antioxidants and solar protection in the cosmeceutical industry
- Develop a better appreciation of when to harvest Garden Cress Sprout for its light absorbers, ultimately benefitting the environment in terms of using less natural resources (eg water) and growth additives
Ultraviolet radiation that reaches the Earth’s surface has extensive impact on the biosphere [1,2]. Of particular interest is the high energy component of solar UV radiation spectrum, the UV-B (280-315 nm) and shorter wavelengths of the UV-A spectrum (<340 nm) termed, henceforth, UV-radiation (UVR). In plants, UVR acts as a signal transducer for numerous processes including immune response, plant morphology and the phenylpropanoid pathway [2,3]. Deleterious effects of UVR exposure to organisms are widely known, for example, reduction of photosynthesis, growth inhibition and susceptibility to pathogens [4,5]. As such, plants synthesize and deposit UVR-absorbing compounds in epidermal tissue via the phenylpropanoid pathway to protect against too much UVR [2,3]
Specifically, studies of gene mutations in the plant Arabidopsis thaliana, a member of the Brassicaceae family, have found that the phenylpropanoid pathway could be disrupted such that the concentration of sinapate esters present in the epidermal layers of the plant are reduced, rendering the plant hypersensitive to UVR exposure [6-11]. Such experiments point towards sinapate esters as being the likely class of UVR screening molecules used by Brassicaceae plants. Sinapate esters are a derivative of sinapic acid, and closely related to sinapoyl malate which has been the dominant ester-constituent deposited in the upper epidermis of Arabidopsis plant leaves [7,8,11].
We have recently proposed that solar protection of sinapate esters is driven by a molecular isomerisation [12-14]; the esters absorb UVR and, through a molecular twist, they convert potentially damaging absorbed UVR into vibrational motion (or heat). Having transferred this heat energy to the surrounding environment, the esters are then ready to reabsorb further UVR and hence provide the plant with the necessary solar protection. However, intriguing questions arise including: (1) what is the composition of these ester-species during the growth cycle of the plant; and (2) how do their composition vary with geographic location of the plant?
In this PhD proposal, our aim is to address these questions. We will specifically focus on another member of the Brassicaceae family, that of the Garden Cress Sprout. We will determine the composition of these esters (in the form of ‘extracts’) during the Garden Cress Sprout growth cycle and establish how geographic location (eg northern vs southern parts of UK) impacts this composition. Importantly, we will use state of the art analytical techniques based on laser spectroscopy to determine their solar protection mechanisms in as close to their natural environment as possible. Our insight could impact which stage of the growth cycle one harvests the plant for these extracts, which are finding widespread use, for example, in the cosmeceutical industries as antioxidants and SPF boosters.
Multiple aqueous extraction of Garden Cress Sprouts will be carried out to obtain the UV-active ingredients. This will then be followed by standard HPLC and LCMS to ascertain the relative amounts of esters (and other light absorbers) in the extract. This will be repeated for different Garden Cress Sprouts obtained at different points along growth season and geographic location.
Transient absorption spectroscopy  will be used to track energy-flow in extracts following absorption of UV-radiation. This technique is crucial in enabling us to build molecular-movies of energy flow across 10-15–10-3 seconds. Initially, the samples will be solution-based (dissolved in polar and nonpolar solvents). However, our plan is to develop this technique such that we deposit these samples on (and within) model waxy cuticles to mimic the natural environment these extracts reside. Further characterisation will be done using steady-state techniques (UV/Vis/FTIR).
Training and skills
The student will be trained to perform a diverse range of experiments, primarily based at the University of Warwick. The student will benefit from exposure to a number of experimental techniques at Warwick (HPLC, LCMS, extraction/encapsulation, laser experiments, steady-state UV/Vis and FTIR spectroscopy) and Mibelle where the student will be given a tour of the facilities Figure 1: Schematic illustrating the front line defence to UVR exposure of the ester sinapoyl malate centred on quality control. Mibelle Group Biochemistry also has expertise in science communication with specific training provided and opportunities to contribute towards social media channels and engage with media outlets.
Partners and collaboration (including CASE)
This project will be a partnership between the School of Life Sciences and the Chemistry Department at Warwick and Mibelle Group Biochemistry. Additionally, the project will benefit from the international networks from both partners. For example, Stavros (Warwick co-supervisor) leads an EU consortium that strives to develop ‘photon-to-molecule heaters’ (BoostCrop); these heaters protect plants from cold-snaps. The current proposal centres around understanding energy transfer mechanisms and will therefore be of great interest to researchers within BoostCrop (and vice versa). Mibelle Group Biochemistry are involved in a number of international collaborations with industrial partners. These collaborations will provide an ideal platform for dissemination of the results from this project.
 Paul, N.D., Gwynn-Jones, D. (2003). ‘Ecological roles of solar UV radiation: towards an integrated approach’, Trends Ecol. Evol., 18, p48.
 Caldwell, M.M., Bornman, J.F. Ballare, C.L., Flint, S.D., Kulandaivelu, G. (2007) ‘Terrestrial ecosystems, increased solar ultraviolet radiation, and interactions with other climate change factors’, Photochem. Photobiol. Sci., 6, p252.
 Jenkins, G.I. (2009) ‘Signal transduction in responses to UV-B radiation’, Annu. Rev. Plant Biol., 60, p407.
 Tevini, M., Teramura, A.H. (1989) ‘UV-B effects on terrestrial plants’, Photochem. Photobiol., 50, p479.
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 Li, J., Ou-Lee, T.-M., Raba, R., Amundson, R.G., Last, R.L. (1993) ‘Arabidopsis flavonoid mutants are hypersensitive to UV-B irradiation’, Plant Cell, 5, p171.
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 Baker, L.A., Horbury, M.D., Greenough, S.E., Allais, F., Habershon, S., Stavros V.G.(2016) ‘Ultrafast photoprotecting sunscreens in natural plants’, J. Phys. Chem. Lett., 7, p 56.
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