Protein secondary structures (α-helix and β-sheet) at a cellular level and protein fractions in relation to rumen degradation behaviours of protein: a new approach

Abstract

Studying the secondary structure of proteins leads to an understanding of the components that make up a whole protein, and such an understanding of the structure of the whole protein is often vital to understanding its digestive behaviour and nutritive value in animals. The main protein secondary structures are the a-helix and b-sheet. The percentage of these two structures in protein secondary structures influences protein nutritive value, quality and digestive behaviour. A high percentage of b-sheet structure may partly cause a low access to gastrointestinal digestive enzymes, which results in a low protein value. The objectives of the present study were to use advanced synchrotron-based Fourier transform IR (S-FTIR) microspectroscopy as a new approach to reveal the molecular chemistry of the protein secondary structures of feed tissues affected by heat-processing within intact tissue at a cellular level, and to quantify protein secondary structures using multicomponent peak modelling Gaussian and Lorentzian methods, in relation to protein digestive behaviours and nutritive value in the rumen, which was determined using the Cornell Net Carbohydrate Protein System. The synchrotron-based molecular chemistry research experiment was performed at the National Synchrotron Light Source at Brookhaven National Laboratory, US Department of Energy. The results showed that, with S-FTIR microspectroscopy, the molecular chemistry, ultrastructural chemical make-up and nutritive characteristics could be revealed at a high ultraspatial resolution (,10 mm). S-FTIR microspectroscopy revealed that the secondary structure of protein differed between raw and roasted golden flaxseeds in terms of the percentages and ratio of a-helixes and b-sheets in the mid-IR range at the cellular level. By using multicomponent peak modelling, the results show that the roasting reduced (P,0·05) the percentage of a-helixes (from 47·1 % to 36·1 %: S-FTIR absorption intensity), increased the percentage of b-sheets (from 37·2 % to 49·8 %: S-FTIR absorption intensity) and reduced the a-helix to b-sheet ratio (from 0·3 to 0·7) in the golden flaxseeds, which indicated a negative effect of the roasting on protein values, utilisation and bioavailability. These results were proved by the Cornell Net Carbohydrate Protein System in situ animal trial, which also revealed that roasting increased the amount of protein bound to lignin, and well as of the Maillard reaction protein (both of which are poorly used by ruminants), and increased the level of indigestible and undegradable protein in ruminants. The present results demonstrate the potential of highly spatially resolved synchrotron-based infrared microspectroscopy to locate 'pure' protein in feed tissues, and reveal protein secondary structures and digestive behaviour, making a significant step forward in and an important contribution to protein nutritional research. Further study is needed to determine the sensitivities of protein secondary structures to various heat-processing conditions, and to quantify t...

In silico Designing of Protein Rich in Large Neutral Amino Acids Using Bovine αs1 Casein for Treatment of Phenylketonuria

“…A total of 63 different protein models were designed using different template sequence including bovine αs1 casein to enrich LNAA contents (except Phe). Furthermore, a high percentage of β-sheets may cause hindrance to gastrointestinal digestive enzymes that result in low protein value and less protein availability [16]. Therefore, the designed protein should have α-helical structures and coils, without any β-sheets.…”

“…The designing was based on the binary patterning using Polar (P) and Non-polar (N) amino acids [15]. A high percentage of β-sheets may cause low access to gastrointestinal digestive enzymes resulting in low protein value and low protein bioavailability [16]. Understanding the structure of whole protein is important to know the digestive behavior, nutritive value, utilization and availability in animals [17].…”

Effect of protein secondary structures in mixed feedstuff detected by Fourier transform infrared spectroscopy on ruminal protein degradation kinetics

“…Until the nineties, the quality of FTIR increased gradually to reach extremely good signal-to-noise ratios (Goormaghtigh et al 2009). It was found that the newly advanced synchrotron technology (S-FTIR) as a rapid, direct, non-invasive, and non-destructive bio-analysis technique ( Wetzel et al 1998;Yu 2005a) could be used to reveal protein structures of feedstuff tissues affected by heat processing ( Yu 2005a;Doiron et al 2009) and investigate the relationship between protein molecular structures and protein degradation kinetics and nutritive value in the rumen ( Yu 2005b;Yu and Nuez-Ortin 2010). S-FTIR has more advantages than globar-sourced FTIR.…”

Identification of hydrated and dehydrated lipids and protein secondary structures in seeds of cotton (Gossypium hirsutum) lines Diwas Kumar Silwal

“…Activities such as heating and roasting have been reported [14] to increase the percentage of -sheets in cellular level. This protein structure is un-degradable and un-digestible, which lowers the feed value and its access to gastrointestinal digestive enzymes in ruminants [24]. Thus, CS-B progeny lines higher in -sheets may not be desirable as feedstock development choice.…”