Proteomic characterisation of hydrothermal redox damage

Redox proteomics analysis of hair shaft proteins upon hydrothermal and alkaline insult

OBJECTIVE

Human hair is regularly subjected to chemical and physical insults, such as heat, UV-irradiation and alkaline hair care products. These insults result in molecular modifications at the hair protein level that underpin mechanical and sensory property changes in the fibres. These changes can manifest itself in reduced hair quality and performance attributes observable to the consumer. In this work, changes in protein modification as a result of heat and alkaline treatments are determined.

METHODS

Redox proteomic profiling using high-resolution mass spectrometry was applied to map and evaluate amino acid residue modifications in human hair exposed to a combination of thermal treatments and alkali exposure with the aim to understand the underlying chemical processes.

RESULTS

Our results show that an increase in redox-related modifications is associated with exposure to higher levels of hydrothermal and alkaline insult. Post-translational modification profiling at the protein primary structural level delivered some further insights into the site-specificity of these modifications, with a clear increase in the number of cysteic acid modifications noticed in samples subjected to more extreme insults.

CONCLUSION

Pinpointing modification sides within proteins and the hair shaft proteome can be used as a basis for employing mitigation or repair strategies of hair protein damage caused by environmental or hair treatment-related insults.

The effects of blanching on composition and modification of proteins in navy beans (Phaseolus vulgaris)

Blanching is an important process in the preparation of navy beans (Phaseolus vulgaris L.) for canning. We here explore the effect of blanching which can profoundly affect protein composition and introduce protein-primary-level modifications. Amino acid analysis showed significantly decreased protein abundance (58.5%) in blanched beans compared to raw beans. Proteomic analyses revealed a decrease in high molecular weight isoforms of the major storage globulin proteins phaseolin (mean fold-change -3.7) and legumin (mean fold-change -2.5) and concomitant increase in their low molecular weight isoforms (mean fold-change 6.4 and 8.3, respectively). Blanched beans also had decreased abundance of lipoxygenase (mean fold-change -13.1), an enzyme responsible for product spoilage during storage. Increased lysinoalanine (up to 47%) and highly modified protein fragments were found in the processing waters, indicating heat- induced modifications. Correlating these molecular level changes thus provides a basis for evaluating how processing parameters can be modified to increase protein food quality.

Multi-parameter evaluation of the effect of processing conditions on meat protein modification

Evaluating the interconnecting effects of pH, temperature and time on food proteins is of relevance to food processing, and food functionality. Here we describe a matrix-based approach in which meat proteins were exposed to combinations of these parameters, selected to cover coordinates in a realistic processing space, and analyzed using redox proteomics. Regions within the matrix showing high levels of protein modification were evaluated for oxidative and other modifications. Both pH and temperature, independently, had a significant effect on the oxidative modifications mostly detected in myofibrillar proteins such as myosin and troponin and also collagen. Heat induced pyroglutamic acid formation was exclusively observed in the myofibrillar proteins. Potential interdependencies between pH, temperature and exposure time were evaluated using a 3-way analysis of variance (ANOVA) on protein modification levels to better understand how industry relevant process parameters influence protein quality and function.

Oxidative Modification of Trichocyte Keratins

Oxidation of keratin results in a range of deleterious effects, including discolouration and compromised physical and mechanical properties. Keratin oxidative degradation is driven by molecular-level events, with accumulation of modifications at the protein primary level resulting directly in changes to secondary, tertiary and quaternary structure, as well as eventually changes in the observable physical and chemical properties. Advances in proteomic analysis techniques provide an increasingly clearer insight into the cascade of molecular modification underpinning keratin oxidation and how this translates through to higher order changes in properties. This chapter summarises the effects of oxidation on keratin-based materials, the types of molecular modification associated with this, and advances in techniques and approaches for characterising this modification.

Proteomic Investigation of Protein Profile Changes and Amino Acid Residue Level Modification in Cooked Lamb Meat: The Effect of Boiling

Hydrothermal treatment (heating in water) is a common method of general food processing and preparation. For red-meat-based foods, boiling is common; however, how the molecular level effects of this treatment correlate to the overall food properties is not yet well-understood. The effects of differing boiling times on lamb meat and the resultant cooking water were here examined through proteomic evaluation. The longer boiling time was found to result in increased protein aggregation involving particularly proteins such as glyceraldehyde-3-phosphate dehydrogenase, as well as truncation in proteins such as in α-actinin-2. Heat-induced protein backbone cleavage was observed adjacent to aspartic acid and asparagine residues. Side-chain modifications of amino acid residues resulting from the heating, including oxidation of phenylalanine and formation of carboxyethyllysine, were characterized in the cooked samples. Actin and myoglobin bands from the cooked meat per se remained visible on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, even after significant cooking time. These proteins were also found to be the major source of observed heat-induced modifications. This study provides new insights into molecular-level modifications occurring in lamb meat proteins during boiling and a protein chemistry basis for better understanding the effect of this common treatment on the nutritional and functional properties of red-meat-based foods.

Digestion proteomics: tracking lactoferrin truncation and peptide release during simulated gastric digestion

Peptide release profiles from lactoferrin were tracked and characterised during simulated gastric digestion using a novel quantitative proteomic approach.