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Introduction:
The utilization and availability of protein depended on the types of protein and their specific susceptibility to enzymatic hydrolysis (inhibitory activities) in the gastrointestinal tract and was also highly associated with protein molecular structures and profiles. Studying internal protein structure leaded to an understanding of the components that make up a whole protein. An understanding of the molecular structure of the whole protein was often vital to understanding its digestive behavior and nutritive value in animals. Protein secondary structures include main α-helix and β-sheet, and small amount of β-turn and random coil. The protein structure profiles (such as percentage of these secondary structures and their ratios) highly influence protein quality, nutrient utilization, availability and digestive behavior in both animal and human. Mainly because protein structure affects access to gastrointestinal digestive enzymes, which results in affecting protein values and protein availability. However, studies on protein internal structures at molecular and cellular levels in relation to nutritive value and digestive behaviors of protein in animals are extremely rarely.
Advanced Synchrotron-based Bioanalytical Technique
Advanced synchrotron radiation-based bioanalytical technique has been developed as a rapid, direct, non-destructive, bioanalytical technique. This technique takes advantage of synchrotron light brightness (million times brighter than sun light) and small effective source size and is capable of exploring protein structural make-up within microstructures of a biological tissue without destruction of inherent structures at ultra-spatial resolutions. To day there has been very little application of novel advanced technique to the study of “pure” protein inherent structure at a cellular level in feeds.
Feed Protein Research Updated
In this article, a novel approach was introduced to show the potential of the newly developed, advanced synchrotron-based analytical technology, which can be used to localize relatively “pure” protein in feed tissue and relatively reveal protein inherent structure and protein molecular chemical make-up within intact tissue at cellular and subcellular levels. Several complex protein structure analytical techniques, Gaussian and Lorentzian multi-component peak modeling, univariate and multivariate analysis, principal component analysis (PCA), and hierarchical cluster analysis (CLA), are employed to relatively reveal features of protein inherent structure and distinguish protein inherent structure differences between varieties/species and between treatments (processing, heat-treatments) in feeds. By using a multi-peak modeling procedure, relative estimates for feed protein secondary structure analysis can be made for comparison purpose in relation to protein value and nutrient availability. By using the PCA and CLA analyses, the feed protein molecular structure can be qualitatively separate one group from another. In a recent study, “Effect of Heat Processing on Protein Secondary Structures (α-Helix and β-Sheet) at a Cellular Level and Protein Fractions in Relation to Rumen Degradation Behaviors of Protein: A Novel Approach”, the results showed that with synchrotron-based technique it was revealed that the secondary structure of protein differed between the raw and roasted golden flaxseeds in terms of percentage and ratio of α-helix and β-sheet within cellular dimension. The roasting reduced percentage of α-helix, increased percentage of β-sheet and reduced α-helix to β-sheet ratio in the golden flaxseeds, which indicated that a negative effect of the roasting on protein values, utilization and bioavailability. These results were proved by the CNCPS in situ degradation data which also revealed that the roasting increased protein bound to lignin, and Maillard reaction protein (which are poorly used by animals) and increased indigestible and undegradable protein. The further research is needed to determine sensitivities of protein inherent structure to various heat processing and quantify the relationship between protein structures and nutrient availability and digestive behavior of various protein sources. Information will be valuable as a guide to maintain protein quality and predict digestive behaviors and nutrient availability. Through heat processing, the manipulation can be done to obtain information on optimal processing conditions of protein as intestinal protein source to achieve target values for potential high net absorbable protein in the small intestine. In another study, “Shining Light on the Differences in Molecular Structural Chemical Make-up and the Cause of Distinct Degradation Behavior between Malting- and Feed-Type Barley”, the items assessed included:
1) molecular structural differences in protein amide I to II intensities and their ratio within cellular dimensions;
2) molecular structural differences in protein secondary structure profile and their ratios;
3) molecular structural differences in carbohydrate component peak profile. The results indicated that it is mostly likely the protein molecular structure (make-up) that may play a major role to cause different degradation kinetics between the two varieties of barleys (not carbohydrate molecular structure).
Conclusions
It is believed that with the advanced synchrotron-based technology, it provides a new approach for protein structure research in feed at ultra-spatial resolutions in relation to protein quality and nutrient availability, it provides better insight in the mechanisms involved and the intrinsic protein molecular structural changes occurring upon processing and makes a significant step and an important contribution to research in examining the molecular structure (chemical make-up) of plant, feed and seeds.
