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. 2020 Dec;49(8):799-808.
doi: 10.1007/s00249-020-01475-4. Epub 2020 Nov 13.

Probing the effect of aroma compounds on the hydrodynamic properties of mucin glycoproteins

Affiliations

Probing the effect of aroma compounds on the hydrodynamic properties of mucin glycoproteins

Vlad Dinu et al. Eur Biophys J. 2020 Dec.

Abstract

Aroma compounds are diverse low molecular weight organic molecules responsible for the flavour of food, medicines or cosmetics. Natural and artificial aroma compounds are manufactured and used by the industry to enhance the flavour and fragrance of products. While the low concentrations of aroma compounds present in food may leave no effect on the structural integrity of the mucosa, the effect of concentrated aroma volatiles is not well understood. At high concentrations, like those found in some flavoured products such as e-cigarettes, some aroma compounds are suggested to elicit a certain degree of change in the mucin glycoprotein network, depending on their functional group. These effects are particularly associated with carbonyl compounds such as aldehydes and ketones, but also phenols which may interact with mucin and other glycoproteins through other interaction mechanisms. This study demonstrates the formation of such interactions in vitro through the use of molecular hydrodynamics. Sedimentation velocity studies reveal that the strength of the carbonyl compound interaction is influenced by compound hydrophobicity, in which the more reactive short chain compounds show the largest increase in mucin-aroma sedimentation coefficients. By contrast, the presence of groups that increases the steric hindrance of the carbonyl group, such as ketones, produced a milder effect. The interaction effects were further demonstrated for hexanal using size exclusion chromatography light scattering (SEC-MALS) and intrinsic viscosity. In addition, phenolic aroma compounds were identified to reduce the sedimentation coefficient of mucin, which is consistent with interactions in the non-glycosylated mucin region.

Keywords: Aldehydes; Aroma; Hydrodynamics; Interactions; Mucin; Phenols.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Sedimentation velocity, g(s) analysis showing the sedimentation coefficient distributions of bovine submaxillary mucin (1.0 mg/mL) and the effect of aldehydes and ketones (1.0 mg/mL); and bottom: plot of hydrophobicity, logP against % change in mucin complexation as determined by the area under the normalised sedimentation coefficient curve. Rotor speed: 30,000 rpm (90,000 g), 20.0 ºC
Fig. 2
Fig. 2
SEC-MALS results showing the light scattering (LS) elution profile of BSM, hexanal and the result of their interaction. Insert shows the summary for the hydrodynamic parameters for the main peaks, such as the apparent weight average molar mass (Mw) and radius of gyration (Rg)
Fig. 3
Fig. 3
Solomon–Ciuta intrinsic viscosity [η]sc analysis showing the quantitative effect of hexanal addition to bovine submaxillary mucin (1.0 mg/mL) in 0.1 M phosphate buffer saline. The polynomial fit is based on six data points derived from the separate hexanal/BSM mixtures
Fig. 4
Fig. 4
Sedimentation velocity, g(s) analysis showing the sedimentation coefficient distributions of BSM (0.5 g/mL) and the result of its interactions with different phenol volatile compounds (0.5 mg/mL). Rotor speed: 30,000 rpm (90,000 g), 20.0 ºC
Fig. 5
Fig. 5
Suggested effects on mucin–mucin interactions in solution: a Polysdisperse, random coil model of mucin in solution showing its multimeric assembly containing the glycosylated “bottlebrush” polypeptide backbone and the non-glycosylated “naked” protein region; b A proposed representation of the effect of chaotropic compounds on the solution structure of mucins; c Proposed representation of the effects of compounds causing mucin aggregation
Fig. 6
Fig. 6
Raw data showing the changes in fringe concentration and residuals plots for BSM, BSM/aroma compounds mixtures and hexanal control, plotted using the GUSSI extension in SEDFIT (Brautigam 2015)
Fig. 7
Fig. 7
Sedimentation coefficient distribution of hexanal control (1.0 mg/mL) in 0.1 M PBS pH 7. Rotor speed: 30,000 rpm (90,000 g), 20.0 ºC
Fig. 8
Fig. 8
Raman spectra of BSM (c = 10 mg/mL) with and without p-cresol. The mucin/p-cresol sample was dialysed against a 14 kDa membrane prior to Raman analysis to remove excess p-cresol. Performed in 0.1 M PBS pH 7 at 20.0 °C. Adapted from (Dinu et al. 2019a)

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