Humans have long sought to add flavour to their food, with high-value spices being one of the main drivers of early international trade. However, the development of industrial food processing in the 19th century led to the growth of the flavour industry, which now supplies both natural and synthesised flavour compounds. While there is no evidence that approved flavourings cause harm at the levels found in food, we have now reached a point where they are used in large quantities in non-food products, such as e-cigarettes and vaping mixes. Previous research has shown that flavour compounds can bind to proteins, focusing on how that affects flavouring. In work recently published in Food Chemistry, researchers from the University of Nottingham investigated, using a model system, whether the flavour compounds we ingest could affect the structure and shape of human proteins. Their results show that the flavouring methyl anthranilate (MA) spontaneously binds to bovine serum albumin (BSA) and sets the foundation for future research on flavour-protein interactions.
The study aimed to investigate the effect of flavour compounds on the shape and structure of endogenous proteins (i.e. proteins that might be found within a consumer), using a simple model system. The researchers chose the widely studied protein bovine BSA and methyl anthranilate (MA), a naturally occurring flavour compound. Producing an intense and fruity grape aroma, MA is widely used in drinks, candies, and vaping mixtures.
The team combined lab techniques - sedimentation velocity, analytical ultracentrifugation, size exclusion chromatography and fluorescence spectroscopy - with Small Angle X-ray Scattering (SAXS) at Diamond's B21 beamline to discover if MA binds to BSA and whether that binding caused changes to the protein's shape or structure.
Dr Vlad Dinu is the lead author on the paper. He said:
Size exclusion chromatography uses a column filled with different sizes of pores to separate macromolecules based on their size. It's a very sensitive technique that enabled us to distinguish between single protein molecules, proteins bound to the flavour compound, and any instances where the proteins had aggregated into dimers or trimers. That meant we could use SAXS to see what was happening to the shape and structure of the proteins. In this case, I dropped off the samples, and the beamline staff conducted the experiments for us, as COVID-19 regulations were in place.
Dr Dinu continued;
The results from Diamond were crucial in establishing that MA does bind to BSA. The results from all of the techniques we used agreed that these two molecules can definitely bind together, and that there could be a resulting change in the asymmetry or shape of the protein. We used complementary molecular modelling and dynamics simulations to suggest possible binding sites on the protein, but more work would be needed to confirm that.
We know that flavour compounds bind to proteins in the human body - that's how our flavour and aroma receptors work. When the flavour binds to a flavour receptor, that's how we smell and taste. This study shows that flavour compounds can also affect protein structure, and the next question to answer is whether that affects protein function. Could the flavour compounds we ingest or inhale affect proteins in our respiratory or gastrointestinal systems?
There are over nine thousand aroma compounds, and many more aroma precursors, arising from food processing, digestion, and bacterial activity. We know that some of these volatile compounds can affect bacterial responses in plants, fungi, and animals. However, we know very little about their role in the human gut ecosystem. This work helps to set the foundation for future research on flavour-protein interactions and offers new opportunities for understanding the effects of small compounds on protein structure.
Principal Beamline Scientist for B21, Nathan Cowieson, comments;
The B21 beamline team worked hard throughout the COVID-19 lockdown period scaling up opportunities for automated data collection and remote access and measuring samples relevant to the pandemic, as well as other research areas. Its great to see our work during that period contributing to this kind of innovative discovery. We continue to offer mail-in data collection for liquid samples measured directly or via our inline chromatography system as well as solid or viscous samples.
To find out more about the B21 beamline or discuss potential applications, please contact Principal Beamline Scientist Nathan Cowieson: firstname.lastname@example.org.
Dinu V et al. Flavour compounds affect protein structure: The effect of methyl anthranilate on bovine serum albumin conformation. Food Chemistry 388 (2022): 133013. DOI:10.1016/j.foodchem.2022.133013.
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