Mid-Infrared Spectroscopy for the Qualitative and Quantitative Analysis of the Wheat Proteome

TL;DR

Mid-infrared spectroscopy is shown to effectively analyze the protein structures and content in wheat, offering a new method for studying its proteome.

Contribution

The study demonstrates the use of ATR-MIR for analyzing wheat protein secondary structures and quantifying protein fractions.

Findings

Albumin and globulin fractions are primarily composed of α-helix structures.

MIR spectra of wheat protein fractions are significantly affected by sampling sites and variety.

Protein content quantification via the amide II band reveals significant differences across sampling sites.

Abstract

Wheat contributes
19% of protein in the global human diet. Mid-infrared
spectroscopy (MIR) combined with attenuated total reflection (ATR)
is an excellent analytical method for assessing the chemical composition
of complex biological samples. In contrast to established techniques
used for wheat protein analysis, we show that by using ATR-MIR the
protein secondary structures of different fractions can be studied.
We found that albumin and globulin fractions were primarily composed
of α-helix, with proportions of 57.8% and 45.9%, respectively.
Gliadins, meanwhile, contained 38.3% β-turn and 36.9% α-helix,
while glutenins predominantly exhibited 44.8% β-turn secondary
structures. In addition, we found that by using analysis of variance
(ANOVA) simultaneous component analysis (ASCA), the obtained MIR spectra
of the wheat protein fractions were significantly (p < 0.001) affected by the sampling sites and variety. Quantification
of the protein content of each sample through the amide II band also
revealed significant differences (p < 0.001) across
the sampling sites in the different protein fractions. The found concentration
range of protein fractions within the wheat samples were as follows:
1.7–3.6, 0.4–2.4, 4.0–5.4, and 0.8–4.8
g/100 g of albumins, globulins, gliadins, and glutenins, respectively.
In conclusion, this study shows that ATR-MIR has an immense potential
for wheat proteome analysis.

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