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Holt C, Carver JA. Invited review: Modeling milk stability. J Dairy Sci 2024; 107:5259-5279. [PMID: 38522835 DOI: 10.3168/jds.2024-24779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 02/15/2024] [Indexed: 03/26/2024]
Abstract
Novel insights into the stability of milk and milk products during storage and processing result from describing caseins near neutral pH as hydrophilic, intrinsically disordered, proteins. Casein solubility is strongly influenced by pH and multivalent ion binding. Solubility is high at a neutral pH or above, but decreases as the casein net charge approaches zero, allowing a condensed casein phase or gel to form, then increases at lower pH. Of particular importance for casein micelle stability near neutral pH is the proportion of free caseins in the micelle (i.e., caseins not bound directly to nanoclusters of calcium phosphate). Free caseins are more soluble and better able to act as molecular chaperones (to prevent casein and whey protein aggregation) than bound caseins. Some free caseins are highly phosphorylated and can also act as mineral chaperones to inhibit the growth of calcium phosphate phases and prevent mineralized deposits from forming on membranes or heat exchangers. Thus, casein micelle stability is reduced when free caseins bind to amyloid fibrils, destabilized whey proteins or calcium phosphate. The multivalent-binding model of the casein micelle quantitatively describes these and other factors affecting the stability of milk and milk protein products during manufacture and storage.
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Affiliation(s)
- C Holt
- School of Biomolecular Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
| | - J A Carver
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
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Wang J, Xie H, Dong Q, Liu J, Su J, An Y, Zeng B, Sun B, Liu J. The effect of arginine on inhibiting amyloid fibril derived from β-casein and the binding studies with multi-spectroscopic techniques. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 282:121681. [PMID: 35917615 DOI: 10.1016/j.saa.2022.121681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 07/22/2022] [Accepted: 07/24/2022] [Indexed: 06/15/2023]
Abstract
In general, β-casein is a stable molecular chaperone. However, the fact that amyloid fibrils derived from β-casein has been reported in some cases, which were usually associated with some malignant breast diseases. As an important amino acid, arginine not only exhibits the significance in casein synthesis in mammary gland, but also has great potentiality in inhibiting the amyloid fibril formation. Therefore, the influence of arginine on the amyloid fibrils formed by β-casein and further molecular mechanism were studied firstly with multi-spectroscopic techniques in the present work. The results of Thioflavin T determination, particle size analysis, transmission electron microscope observation showed that arginine not only inhibited the aggregation of β-casein at the growth stage, but also depolymerized the mature amyloid fibrils at the saturation stage. The further fluorescence experiment results demonstrated that the complex was formed between β-casein and arginine. Besides, there was one binding site and 0.48 nm binding distance. The thermodynamic parameters like ΔG0, ΔS0, ΔH0 were all negative, showing their binding reaction was spontaneous, and hydrogen bond and van der Waals force were the possibly chief intermolecular forces. Furthermore, the synchronous fluorescence spectra showing that the conformation of β-casein was affected and its tyrosine residues were gradually buried inside the protein. Our research would provide new insights into the treatments for the breast amyloidosis.
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Affiliation(s)
- Jia Wang
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China
| | - Hongliu Xie
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China
| | - Qinghai Dong
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China
| | - Jiayin Liu
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China
| | - Jun Su
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China
| | - Yang An
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China
| | - Baohua Zeng
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, PR China
| | - Bingxue Sun
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China
| | - Jihua Liu
- Department of Natural Product Chemistry, Pharmacy College, Jilin University, Changchun, PR China.
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