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Chen R, Song Y, Wang Z, Ji H, Du Z, Ma Q, Yang Y, Liu X, Li N, Sun Y. Developments in small-angle X-ray scattering (SAXS) for characterizing the structure of surfactant-macromolecule interactions and their complex. Int J Biol Macromol 2023; 251:126288. [PMID: 37582436 DOI: 10.1016/j.ijbiomac.2023.126288] [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: 04/19/2023] [Revised: 08/08/2023] [Accepted: 08/09/2023] [Indexed: 08/17/2023]
Abstract
The surfactant-macromolecule interactions (SMI) are one of the most critical topics for scientific research and industrial application. Small-angle X-ray scattering (SAXS) is a powerful tool for comprehensively studying the structural and conformational features of macromolecules at a size ranging from Angstroms to hundreds of nanometers with a time-resolve in milliseconds scale. The SAXS integrative techniques have emerged for comprehensively analyzing the SMI and the structure of their complex in solution. Here, the various types of emerging interactions of surfactant with macromolecules, such as protein, lipid, nuclear acid, polysaccharide and virus, etc. have been systematically reviewed. Additionally, the principle of SAXS and theoretical models of SAXS for describing the structure of SMI as well as their complex has been summarized. Moreover, the recent developments in the applications of SAXS for charactering the structure of SMI have been also highlighted. Prospectively, the capacity to complement artificial intelligence (AI) in the structure prediction of biological macromolecules and the high-throughput bioinformatics sequencing data make SAXS integrative structural techniques expected to be the primary methodology for illuminating the self-assembling dynamics and nanoscale structure of SMI. As advances in the field continue, we look forward to proliferating uses of SAXS based upon its abilities to robustly produce mechanistic insights for biology and medicine.
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Affiliation(s)
- Ruixin Chen
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Yang Song
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Zhichun Wang
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Hang Ji
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Zhongyao Du
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Qingwen Ma
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Ying Yang
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Xingxun Liu
- College of Food Science and Engineering, Nanjing University of Finance and Economics, Nanjing, Jiangsu, China
| | - Na Li
- National Facility for Protein Science in Shanghai, Shanghai Advanced Research Institute, CAS, Shanghai, China.
| | - Yang Sun
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China.
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Du Z, Xu N, Yang Y, Li G, Tai Z, Li N, Sun Y. Study on internal structure of casein micelles in reconstituted skim milk powder. Int J Biol Macromol 2022; 224:437-452. [DOI: 10.1016/j.ijbiomac.2022.10.135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 10/09/2022] [Accepted: 10/15/2022] [Indexed: 11/05/2022]
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3
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Sun Y, Tai Z, Yan T, Dai Y, Hemar Y, Li N. Unveiling the structure of the primary caseinate particle using small-angle X-ray scattering and simulation methodologies. Food Res Int 2021; 149:110653. [PMID: 34600655 DOI: 10.1016/j.foodres.2021.110653] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 08/11/2021] [Accepted: 08/17/2021] [Indexed: 11/27/2022]
Abstract
The low-resolution structure of casein (CN) clusters in sodium caseinate (NaCas) solution and its conformational dynamics were obtained by size-exclusion chromatography (SEC), analytical ultracentrifugation (AUC), small-angle X-ray scattering (SAXS), and molecular dynamics (MD) simulations. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and native PAGE revealed that the casein clusters consisted predominantly of α- and β-CN complexes, and a trace amount of κ-CN. The AUC analysis indicated that the casein clusters were composed of 34.6% of casein monomers, 19.2%, 20.4%, and 25.8% of complexes with molar weight (Mw) of ~50.3, ~70.6, and ~133 kDa, respectively. The volume fractions of components in casein clusters were quantified as 64.3% of αs1-β-αs2-CN, 22.3% of αs1-CN, 8.5% of αs2-CN, and 4.4% of αs1-αs2-CN, respectively. The ensemble optimization method (EOM) gave a fitting result where αs1-β-αs2-CN species coexisted in ~35.3% under compact conformation and ~64.7% in elongated conformation in solution. The three-dimensional structures of αs1-β-αs2-CN from EOM showed a good overlay on the casein clusters ab initio model obtained from DAMMIN and DAMMIX program. MD simulations revealed that αs1-β-αs2-CN underwent a conformational change from the elongated state into the compact state within the initial 200 ns of simulations. The addition of nonionic surfactants affected little the backbone-to-backbone interactions in the formation of the casein clusters. We propose that αs1-CN, β-CN, αs2-CN, and κ-CN associated in consecutive steps into casein clusters, and a trace of κ-CN may be located at the surface of the assemblies limiting the growth of casein aggregates.
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Affiliation(s)
- Yang Sun
- College of Vocational and Technical Education, Yunnan Normal University, Yieryi Avenue, No. 298, 650092 Kunming, Yunnan, People's Republic of China.
| | - Zhonghong Tai
- College of Vocational and Technical Education, Yunnan Normal University, Yieryi Avenue, No. 298, 650092 Kunming, Yunnan, People's Republic of China
| | - Tingting Yan
- College of Vocational and Technical Education, Yunnan Normal University, Yieryi Avenue, No. 298, 650092 Kunming, Yunnan, People's Republic of China
| | - Yiqi Dai
- College of Vocational and Technical Education, Yunnan Normal University, Yieryi Avenue, No. 298, 650092 Kunming, Yunnan, People's Republic of China
| | - Yacine Hemar
- Catalyst Tec Limited., 16 Beatrice Tinsley Cresecnt, Rosedale 0632, Auckland, New Zealand; International Joint Research Laboratory for Functional Dairy Protein Ingredients, U.S.-China, People's Republic of China
| | - Na Li
- National Facility for Protein Science in Shanghai, Zhangjiang Lab, Shanghai Advanced Research Institute, CAS, No.333, Haike Road, Shanghai, Shanghai 201210, People's Republic of China.
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Hemar Y, Banjar W, Otter D, Yang Z. Viscosity, size, structural and interfacial properties of sodium caseinate obtained from A2 milk. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Yesiltas B, Torkkeli M, Almásy L, Dudás Z, García-Moreno PJ, Sørensen ADM, Jacobsen C, Knaapila M. Small-Angle Neutron Scattering Study of High Fat Fish Oil-In-Water Emulsion Stabilized with Sodium Caseinate and Phosphatidylcholine. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:2300-2306. [PMID: 32068398 DOI: 10.1021/acs.langmuir.9b03269] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report on small-angle neutron scattering (SANS) investigations of separate phase domains in high fat (70%) oil-in-water emulsions emulsified with the combination of sodium caseinate (CAS) and phosphatidylcholine (PC). The emulsion as a whole was studied by contrast variation to identify scattering components dominated by individual emulsifiers. The emulsion was subsequently separated into the aqueous phase and the oil-rich droplet phase, which were characterized separately. Emulsions produced with 1.05% (w/w) CAS and PC fraction which varies between 1.75% (w/w) and 0.35% (w/w) provided droplets between 10 and 19 μm in surface weighted mean in 70% fish oil-in-water emulsions. At least two-third of the overall CAS is associated with the interface, while the rest remains with the aqueous phase. Six percent of PC formed a monolayer in the interface, while the rest of the PC remains in the droplet phase in the form of multilayers. When the separated components were resuspended, the resuspended emulsion showed similar characteristics compared to the original emulsion in terms of droplet size distribution and neutron scattering. Instead, CAS in the aqueous phase separated from the emulsion shows aggregation not present in the corresponding CAS-in-D2O system.
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Affiliation(s)
- Betül Yesiltas
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Mika Torkkeli
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - László Almásy
- Neutron Spectroscopy Department, Centre for Energy Research, 1121 Budapest, Hungary
| | - Zoltán Dudás
- Neutron Spectroscopy Department, Centre for Energy Research, 1121 Budapest, Hungary
| | - Pedro J García-Moreno
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Department of Chemical Engineering, University of Granada, 18003 Granada, Spain
| | - Ann-Dorit M Sørensen
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Charlotte Jacobsen
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Matti Knaapila
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
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Peyronel F, Marangoni AG, Pink DA. Using the USAXS technique to reveal the fat globule and casein micelle structures of bovine dairy products. Food Res Int 2019; 129:108846. [PMID: 32036933 DOI: 10.1016/j.foodres.2019.108846] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 11/15/2019] [Accepted: 11/18/2019] [Indexed: 11/26/2022]
Abstract
Cows' milk is a commodity used worldwide to make many dairy products. We have used the ultra small angle X-ray scattering (USAXS) technique to reveal the fat globule and casein micelle structures of some dairy products. USAXS covers the q-range 5 × 10-4 Å-1 < q < 10-1 Å-1, thereby allowing the study of micron-scale structures present in those dairy products. We measured the USAXS intensity, Iq, as a function of the scattering vector magnitude, q, for samples of skim milk, non-homogenized whole milk, homogenized whole milk, half and half and heavy cream, at two temperatures, 7 °C and 45 °C. The data collected from the scattering experiments were fitted using the Unified fit model run under the IRENA software from the Advanced Photon Source, Argonne National Laboratory (Illinois, USA). The fittings were carried out when the data were plotted as log[I(q)] vs log[q]. We observed a combination of linear regions (LRs) and knees. Two parameters of interest were obtained from the fittings, a radius of gyration, Rg, and a Porod exponent, P. Unified fit allowed us to fit up to four structural levels. One of the knees was centered at q ≈ 8 × 10-3 Å-1 for all samples measured at 7 °C, but vanished at 45 °C. Two LRs were identified as being either due to casein micelles (CMs) or to fat globules (FGs). The porod exponent obtained from these LRs allowed us to describe the surface morphology of CMs and FGs. Two of the Rg values gave a rough estimate of the FGs and CMs sizes. FGs were identified for samples of homogenized whole milk, half and half and heavy cream in the q-region 2 × 10-4 < q < 8 × 10-4 Å-1. We found that, in the absence of chymosin, or changes in pH, CaCl2 concentration or temperature changes, skim milk and non-homogenized whole milk displayed a Porod exponent that indicated a behavior characteristic of aggregation. Using computer simulations, we found that, seemingly, bovine CMs spontaneously formed approximately 1-dimensional aggregates possibly analogous to swollen randomly branched polymers.
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Affiliation(s)
| | | | - David A Pink
- Physics Department, St. Francis Xavier University, Antigonish, NS, Canada; Food Science Department, University of Guelph, Guelph, ON, Canada
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7
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Yesiltas B, Torkkeli M, Almásy L, Dudás Z, Wacha AF, Dalgliesh R, García-Moreno PJ, Sørensen ADM, Jacobsen C, Knaapila M. Interfacial structure of 70% fish oil-in-water emulsions stabilized with combinations of sodium caseinate and phosphatidylcholine. J Colloid Interface Sci 2019; 554:183-190. [PMID: 31299546 DOI: 10.1016/j.jcis.2019.06.103] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 06/20/2019] [Accepted: 06/30/2019] [Indexed: 11/28/2022]
Abstract
We report on the structural evaluation of high fat fish oil-in-water emulsions emulsified with sodium caseinate (CAS) and phosphatidylcholine (PC). The microemulsions contained 70% (w/w) fish oil with 1.05-1.4% (w/w) CAS and 0.4-1.75% (w/w) PC and were studied by the combination of light scattering together with small-angle X-ray and neutron scattering (SAXS/SANS). Aqueous CAS forms aggregates having a denser core of about 100 kDa and less dense shell about 400 kDa with the hard sphere diameter of 20.4 nm. PC appears as multilayers whose coherence length spans from 40 to 100 nm. PC monolayer separates oil and water phases. Moreover, 80% CAS particles are loosely bound to the interface but are not forming continuous coverage. The distance between aggregated CAS particles in microemulsion is increased compared to CAS aggregates in pure CAS-in-water system. PC multilayers become larger in the presence of oil-water interface compared to the pure PC mixtures. Bilayers become larger with increasing PC concentration. This study forms a structural base for the combination of CAS and PC emulsifiers forming a well-defined thin and dense PC layer together with thick but less dense CAS layer, which is assumed to explain its better oxidative stability compared to single emulsifiers.
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Affiliation(s)
- Betül Yesiltas
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
| | - Mika Torkkeli
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
| | - László Almásy
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, 1525 Budapest, Hungary; State Key Laboratory of Environment-Friendly Energy Materials, Southwest University of Science and Technology, Mianyang 621010, China
| | - Zoltán Dudás
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, 1525 Budapest, Hungary
| | - András Ferenc Wacha
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences Hungarian Academy of Sciences, 1525 Budapest, Hungary
| | - Robert Dalgliesh
- Rutherford Appleton Laboratory, ISIS Facility, Chilton OX11 0QX, UK
| | - Pedro J García-Moreno
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Ann-Dorit M Sørensen
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Charlotte Jacobsen
- Division of Food Technology, National Food Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
| | - Matti Knaapila
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
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8
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Sun Y, Zhang J, Wang H, Wang T, Cheng H, Yu B, Oliveira CL. Sulfate dodecyl sodium-induced stability of a model intrinsically disordered protein, bovine casein. Food Hydrocoll 2018. [DOI: 10.1016/j.foodhyd.2018.03.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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9
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Lu Y, McMahon D, Metzger L, Kommineni A, Vollmer A. Solubilization of rehydrated frozen highly concentrated micellar casein for use in liquid food applications. J Dairy Sci 2015; 98:5917-30. [DOI: 10.3168/jds.2015-9482] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 05/02/2015] [Indexed: 11/19/2022]
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10
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Peixoto PDS, Bouchoux A, Huet S, Madec MN, Thomas D, Floury J, Gésan-Guiziou G. Diffusion and partitioning of macromolecules in casein microgels: evidence for size-dependent attractive interactions in a dense protein system. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:1755-1765. [PMID: 25604622 DOI: 10.1021/la503657u] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Understanding the mechanisms that determine the diffusion and interaction of macromolecules (such as proteins and polysaccharides) that disperse through dense media is an important fundamental issue in the development of innovative technological and medical applications. In the current work, the partitioning and diffusion of macromolecules of different sizes (from 4 to 10 nm in diameter) and shapes (linear or spherical) within dispersions of casein micelles (a protein microgel) is studied. The coefficients for diffusion and partition are measured using FRAP (fluorescence recovery after photobleaching) and analyzed with respect to the structural characteristics of the microgel determined by the use of TEM (transmission electron microscopy) tomography. The results show that the casein microgel displays a nonspecific attractive interaction for all macromolecules studied. When the macromolecular probes are spherical, this affinity is clearly size-dependent, with stronger attraction for the larger probes. The current data show that electrostatic effects cannot account for such an attraction. Rather, nonspecific hydration molecular forces appear to explain these results. These findings show how weak nonspecific forces affect the diffusion and partitioning of proteins and polysaccharides in a dense protein environment. These results could be useful to better understand the mechanisms of diffusion and partitioning in other media such as cells and tissues. Furthermore, there arises the possibility of using the casein micelle as a size-selective molecular device.
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Affiliation(s)
- Paulo D S Peixoto
- INRA , UMR1253 Science et Technologie du Lait et de l'Œuf, 65 rue de Saint Brieuc, 35000 Rennes, France
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11
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Apparent voluminosity of casein micelles determined by rheometry. J Colloid Interface Sci 2012; 386:174-80. [DOI: 10.1016/j.jcis.2012.07.075] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 07/10/2012] [Accepted: 07/11/2012] [Indexed: 11/22/2022]
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12
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Bouchoux A, Gésan-Guiziou G, Pérez J, Cabane B. How to squeeze a sponge: casein micelles under osmotic stress, a SAXS study. Biophys J 2011; 99:3754-62. [PMID: 21112300 DOI: 10.1016/j.bpj.2010.10.019] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/24/2010] [Accepted: 10/08/2010] [Indexed: 11/18/2022] Open
Abstract
By combining the osmotic stress technique with small-angle x-ray scattering measurements, we followed the structural response of the casein micelle to an overall increase in concentration. When the aqueous phase that separates the micelles is extracted, they behave as polydisperse repelling spheres and their internal structure is not affected. When they are compressed, the micelles lose water and shrink to a smaller volume. Our results indicate that this compression is nonaffine, i.e., some parts of the micelle collapse, whereas other parts resist deformation. We suggest that this behavior is consistent with a spongelike casein micelle having a triple hierarchical structure. The lowest level of the structure consists of the CaP nanoclusters that serve as anchors for the casein molecules. The intermediate level consists of 10- to 40-nm hard regions that resist compression and contain the nanoclusters. Those regions are connected and/or partially merged with each other, thus forming a continuous and porous material. The third level of structure is the casein micelle itself, with an average size of 100 nm. In our view, such a structure is consistent with the observation of 10- to 20-nm casein particles in the Golgi vesicles of lactating cells: upon aggregation, those particles would rearrange, fuse, and/or swell to form the spongelike micelle.
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Affiliation(s)
- Antoine Bouchoux
- INRA, UMR1253 Science et Technologie du Lait et de l'Œuf, F-35042 Rennes, France.
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Le Feunteun S, Mariette F. PFG−NMR Techniques Provide a New Tool for Continuous Investigation of the Evolution of the Casein Gel Microstructure after Renneting. Macromolecules 2008. [DOI: 10.1021/ma702246m] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Steven Le Feunteun
- Cemagref, Food Process Engineering Research Unit, CS 64426, 17 avenue de Cucillé, 35044 Rennes, Cedex, France
| | - François Mariette
- Cemagref, Food Process Engineering Research Unit, CS 64426, 17 avenue de Cucillé, 35044 Rennes, Cedex, France
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Le Feunteun S, Mariette F. Impact of casein gel microstructure on self-diffusion coefficient of molecular probes measured by 1H PFG-NMR. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2007; 55:10764-10772. [PMID: 18047279 DOI: 10.1021/jf071982v] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The translational dynamics of poly(ethylene glycol) (PEG) polymers with molecular weights (Mw) varying from 6x10(2) to 5x10(5) were investigated by pulsed field gradient NMR in casein suspensions and in gels induced by acidification, enzyme action, and a combination of both. For molecules with Mw<or=1020, the diffusion was only dependent on the casein concentration whatever the molecular weight of the probe or the sample studied. However, for PEG with Mw>or=8000, there was strong dependence of diffusion on PEG size and on the casein network structure as revealed by scanning electron microscopy images. The diffusion coefficients of the two largest PEGs were increased after coagulation by amounts that depended on the internal structure of the gel. In addition, the 527,000 g/mol PEG was found to deviate from Gaussian diffusion behavior to greater or lesser extents according to the casein concentration and the sample microstructure. The results are discussed in terms of network rearrangements.
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16
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Mozersky SM. Calculation of Particle Mass from Sedimentation Field-Flow Fractionation Data: The Buoyancy Factor. SEP SCI TECHNOL 2006. [DOI: 10.1080/01496399208029221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Samuel M. Mozersky
- a AGRICULTURAL RESEARCH SERVICE, EASTERN REGIONAL RESEARCH CENTER, UNITED STATES DEPARTMENT OF AGRICULTURE , 600 E. MERMAID LANE, PHILADELPHIA , PENNSYLVANIA , 19118
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17
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Casein micelle structure: What can be learned from milk synthesis and structural biology? Curr Opin Colloid Interface Sci 2006. [DOI: 10.1016/j.cocis.2005.11.005] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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18
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Colsenet R, Soderman O, Mariette F. Effect of Casein Concentration in Suspensions and Gels on Poly(ethylene glycol)s NMR Self-Diffusion Measurements. Macromolecules 2005. [DOI: 10.1021/ma051294h] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Roxane Colsenet
- Process Engineering Technology Research Unit, Cemagref, CS 64426, 17 avenue de Cucillé, 35044 Rennes, Cedex, France, and Physical Chemistry 1, Chemical Center, University of Lund, P.O. Box 124, S-22100 Lund, Sweden
| | - Olle Soderman
- Process Engineering Technology Research Unit, Cemagref, CS 64426, 17 avenue de Cucillé, 35044 Rennes, Cedex, France, and Physical Chemistry 1, Chemical Center, University of Lund, P.O. Box 124, S-22100 Lund, Sweden
| | - François Mariette
- Process Engineering Technology Research Unit, Cemagref, CS 64426, 17 avenue de Cucillé, 35044 Rennes, Cedex, France, and Physical Chemistry 1, Chemical Center, University of Lund, P.O. Box 124, S-22100 Lund, Sweden
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Panouillé M, Benyahia L, Durand D, Nicolai T. Dynamic mechanical properties of suspensions of micellar casein particles. J Colloid Interface Sci 2005; 287:468-75. [PMID: 15925612 DOI: 10.1016/j.jcis.2005.02.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Revised: 02/01/2005] [Accepted: 02/02/2005] [Indexed: 11/28/2022]
Abstract
Small micellar casein particles, so-called submicelles, were obtained by removing colloidal calcium phosphate from native casein by adding sodium polyphosphate. Aqueous submicelle suspensions were characterized using light scattering and rheology as a function of concentration and temperature. The casein submicelles behave like soft spheres that jam at a critical concentration (C(c)) of about 100 g L(-1). The viscosity does not diverge at C(c), but increases sharply, similarly to that of multiarm star polymers. C(c) increases weakly with increasing temperature, which leads to a strong decrease of the viscosity close to and above C(c). Concentrated submicelle suspensions show strong shear-thinning above a critical shear rate and the shear stress becomes independent of the shear rate. The critical shear rates at different temperatures and concentrations are inversely proportional to the zero-shear viscosity. At much higher shear rates, the shear stress fluctuates strongly in time indicating inhomogeneous flow. The frequency dependence of casein submicelle suspensions is characterized by elastic behavior at high frequencies (concentrations) and viscous behavior at low frequencies (concentrations).
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Affiliation(s)
- Maud Panouillé
- Polymères, Colloïdes, Interfaces, UMR CNRS, Université du Maine, 72085 Le Mans cedex 9, France
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Panouillé M, Durand D, Nicolai T, Larquet E, Boisset N. Aggregation and gelation of micellar casein particles. J Colloid Interface Sci 2005; 287:85-93. [PMID: 15914152 DOI: 10.1016/j.jcis.2005.02.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Revised: 02/01/2005] [Accepted: 02/02/2005] [Indexed: 11/19/2022]
Abstract
Micellar casein particles (submicelles) are formed by removing calcium phosphate from native casein. The submicelles aggregate and eventually form a gel with a rate that increases strongly with increasing temperature and casein concentration. At low casein concentrations the gel is very weak and collapses under its own weight so that a precipitate is formed. The structure of the aggregates is studied using light scattering and cryo-electron microscopy. It is found that the aggregates have a self-similar structure with fractal dimension 2. The viscoelastic properties of the gel are studied by frequency scans of the loss and storage moduli during the gelation process. The bonds between the submicelles probably involve calcium phosphate complexes.
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Affiliation(s)
- Maud Panouillé
- Polymères, Colloïdes, Interfaces, UMR-CNRS, Université du Maine, 72085 Le Mans cedex 9, France
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Guyomarc'h F, Law AJR, Dalgleish DG. Formation of soluble and micelle-bound protein aggregates in heated milk. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2003; 51:4652-4660. [PMID: 14705892 DOI: 10.1021/jf0211783] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The formation of heat-induced aggregates of kappa-casein and denatured whey proteins was investigated in milk-based dairy mixtures containing casein micelles and serum proteins in different ratios. Both soluble and micelle-bound aggregates were isolated from the mixtures heated at 95 degrees C for 10 min, using size exclusion chromatography. Quantitative analysis of the protein composition of the aggregates by reverse phase high-performance liquid chromatography strongly suggested that primary aggregates of beta-lactoglobulin and alpha-lactalbumin in a 3 to 1 ratio were involved as well as kappa-casein, and alpha(s2)-casein in micellar aggregates. The results gave evidence that heat-induced dissociation of micellar kappa-casein was implicated in the formation of the soluble aggregates and indicated that a significant amount of kappa-casein was left unreacted after heating. The average size of the aggregates was 3.5-5.5 million Da, depending on the available kappa-casein or the casein:whey protein ratio in the mixtures. The size and density of these aggregates relative to those of casein micelles were discussed.
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Mariette F, Topgaard D, Jönsson B, Soderman O. 1H NMR diffusometry study of water in casein dispersions and gels. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2002; 50:4295-4302. [PMID: 12105961 DOI: 10.1021/jf0115948] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The self-diffusion coefficients of water in casein solutions and gels were measured using a pulsed-gradient spin-echo nuclear magnetic resonance technique (PGSE NMR). The dependence of the self-diffusion coefficient of water on the concentration and structure of casein is reported. The results were analyzed using a cell model. It was found that the water self-diffusion coefficient is insensitive to the structure of the casein in solution or in a gelled state. The influence of casein concentration on the water self-diffusion coefficient could be explained by obstruction from the casein molecule. Assuming a simple model with two water regions, each characterized by a specific water concentration and value of the water diffusion coefficient, the water mobility reduction induced by the casein can be rationalized.
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Affiliation(s)
- François Mariette
- Cemagref, UR Technologie des Equipements Agro-alimentaires, CS 64426, 17 Avenue de Cucillé, 35044 Rennes, Cedex, France.
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24
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Bak M, Rasmussen LK, Petersen TE, Nielsen NC. Colloidal calcium phosphates in casein micelles studied by slow-speed-spinning 31P magic angle spinning solid-state nuclear magnetic resonance. J Dairy Sci 2001; 84:1310-9. [PMID: 11417687 DOI: 10.3168/jds.s0022-0302(01)70160-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The composition of bovine casein micelles was analyzed by 31P magic angle spinning solid-state nuclear magnetic resonance spectroscopy. By looking at isotropic and anisotropic 31P chemical shift parameters, resonance line shapes, the combination of single-pulse and 1H to 31P cross-polarization spectra, and comparison with spectra for various model compounds combined with multiple-component simulation and iterative fitting procedures, we were able to identify and quantify a variety of inorganic and organic phosphates in the micelles. These include phosphates from mobile and immobile inorganic hydroxyapatite-type phosphates as well as phosphates from kappa-casein and the Ca2+-binding phosphoserines from alphas1-, alphas2-, and beta-casein. This information is discussed in relation to previous knowledge and various models for the colloid formation.
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Affiliation(s)
- M Bak
- Department of Molecular and Structural Biology Science Park, University of Aarhus, Denmark
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25
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Lopez C, Lesieur P, Keller G, Ollivon M. Thermal and Structural Behavior of Milk Fat. J Colloid Interface Sci 2000; 229:62-71. [PMID: 10942542 DOI: 10.1006/jcis.2000.6988] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The thermal and structural properties of unstable varieties of triacylglycerols (TGs) crystallizing in milk fat globules of cream are examined in the range -8- +50 degrees C using a new instrument allowing simultaneously time-resolved synchrotron X-ray diffraction at both wide and small angles as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC). Small angle X-ray diffraction shows that the unstable alpha form first formed by cream quenching to -8 degrees C corresponds in fact to two different lamellar phases corresponding to 2L (47 Å) and 3L (70.4 Å) arrangements of TGs. The bilayered structure is very unstable since it disappears during the course of a 20-min isothermal conditioning at -8 degrees C. On fast heating, the crystalline evolution of cream TGs demonstrates the monotropic character of their polymorphism. The structural and thermal behaviors of cream which are compared to that of its anhydrous milk fat isolated from the cream (C. Lopez et al., J. Dairy Sci., submitted) show that the crystallization occurring in emulsion droplets is similar to bulk. However, the comparison of XRD peak widths indicates that the TG crystallization is more disordered in emulsion. This disorder is attributed to the constraints due to the interface curvature in emulsion droplets. Copyright 2000 Academic Press.
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Affiliation(s)
- C Lopez
- Equipe Physico-Chimie des Systèmes Polyphasés, UMR 8612 du CNRS, 5 rue J.B. Clément, Châtenay-Malabry, 92296, France
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26
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Curley DM, Kumosinski TF, Unruh JJ, Farrell HM. Changes in the secondary structure of bovine casein by Fourier transform infrared spectroscopy: effects of calcium and temperature. J Dairy Sci 1998; 81:3154-62. [PMID: 9891263 DOI: 10.3168/jds.s0022-0302(98)75881-3] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Bovine casein submicelles and reformed micelles, produced by addition of Ca2+, were examined by Fourier transform infrared spectroscopy at 15 and 37 degrees C in aqueous salt solutions of K+ and Na+. Previous measurements of caseins, made in D2O and in the solid form, can now be made in a more realistic environment of H2O. When analyzed in detail, data obtained by Fourier transform infrared spectroscopy have the potential to show subtle changes in secondary structural elements that are associated with changes in protein environment. Electrostatic binding of Ca2+ to casein resulted in a redistribution of the components of the infrared spectra. Addition of Ca2+ in salt solutions of K+ and Na+ led to apparent decreases in large loop or helical structures at 37 degrees C with concomitant increases in the percentage of structures having greater bond energy, such as turns and extended helical structures. At 15 degrees C, Na+ and K+ have differential effects on the Ca(2+)-casein complexes. All of these observations are in accordance with the important role of serine phosphate side chains as sites for Ca2+ binding in caseins and the swelling of the casein structure upon incorporation into reformed micelles at 37 degrees C. This new open, hydrated structure is buttressed by a change in backbone as evidenced by a shift in absorbance to higher wave numbers (greater bond energies) as colloidal micelles are reformed.
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Affiliation(s)
- D M Curley
- USDA, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, PA 19038, USA
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28
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Rasmussen LK, Sørensen ES, Petersen TE, Nielsen NC, Thomsen JK. Characterization of phosphate sites in native ovine, caprine, and bovine casein micelles and their caseinomacropeptides: a solid-state phosphorus-31 nuclear magnetic resonance and sequence and mass spectrometric study. J Dairy Sci 1997; 80:607-14. [PMID: 9149956 DOI: 10.3168/jds.s0022-0302(97)75977-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The phosphate sites in native ovine, caprine, and bovine casein micelles have been analyzed using sequence analysis, mass spectrometric analysis, and solid-state 31P nuclear magnetic resonance spectroscopy. Using a combination of S-ethylcysteine derivatization, sequence analysis, and mass spectrometric analysis, the phosphorylation sites of ovine (SerP151 and SerP168), caprine (SerP151 and SerP168), and bovine (SerP149) caseinomacropeptides have been localized. Various solid-state 31P methods using magic angle spinning have been applied to ascertain the local structure and dynamics of the phosphorylated serine residues and the inorganic calcium phosphates within the micelles. Contributions from the phosphorylated serine residues of kappa-CN, located in the C-terminal portion of the molecule, to the mobile constituents of the micelles were assigned by comparison with 31P nuclear magnetic resonance spectra of purified caseinomacropeptides from the various species in the dissolved state. Comparison of the 31P magic angle spinning nuclear magnetic resonance spectra of ovine, caprine, and bovine casein micelles indicates that the micelles from these species are very similar but not identical.
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Affiliation(s)
- L K Rasmussen
- Protein Chemistry Laboratory, University of Aarhus, Denmark
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29
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Thomsen JK, Jakobsen HJ, Nielsen NC, Petersen TE, Rasmussen LK. Solid-state magic-angle spinning 31P-NMR studies of native casein micelles. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 230:454-9. [PMID: 7607215 DOI: 10.1111/j.1432-1033.1995.tb20582.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Solid-state magic-angle spinning 31P-NMR spectroscopy was used to characterize the structure and composition of native casein micelles. The features of the magic-angle spinning 31P-NMR spectra, including overlapping resonances from mobile/immobile phosphorylated serine residues and inorganic calcium phosphates, have been determined using different experimental techniques and assigned by comparison with spectra of the presumed constituents within the casein micelle. Comparison with 31P-NMR spectra of alpha s1-, alpha s2-, and beta-caseins in dissolved and freeze-dried forms demonstrated that a major fraction of the phosphoserines in these proteins was in an immobilized state within the micelle. Likewise, from 31P-NMR spectra of the C-terminal part of kappa-casein, it was shown that this region of the micelle has a considerable conformational mobility. Finally, magic-angle spinning 31P-NMR spectra for a series of inorganic calcium phosphates and mineralized bone tissue revealed that the micellar inorganic calcium phosphates exhibit structural similarities to hydroxyapatite and hence resemble mineralized bone tissue.
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Affiliation(s)
- J K Thomsen
- Department of Chemistry, University of Aarhus, Denmark
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30
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Kumosinski TF, King G, Farrell HM. Comparison of the three-dimensional molecular models of bovine submicellar caseins with small-angle X-ray scattering. Influence of protein hydration. JOURNAL OF PROTEIN CHEMISTRY 1994; 13:701-14. [PMID: 7710660 DOI: 10.1007/bf01886953] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To test the applicability of two energy-minimized, three-dimensional structures of the bovine casein submicelle, theoretical small-angle X-ray scattering curves in the presence and absence of water were compared to experimental data. The published method simulates molecular dynamics of proteins in solution by employing adjustable Debye-Waller temperature factors (B factors) for the protein, for the solvent, and for protein-bound water. The programs were first tested upon bovine pancreatic trypsin inhibitor beginning with its known X-ray crystal structure. To approximate the degree of protein hydration previously determined by NMR relaxation experiments (0.01 g water/g protein), 120 water molecules were docked into the large void of the kappa-casein portion of the structure for both the symmetric and asymmetric casein submicelle models. To approximate hydrodynamic hydration (0.244 g water/g protein), 2703 water molecules were added to each of the above structures using the "droplet" algorithm in the Sybyl molecular modeling package. All structures were then energy-minimized and their solvation energies calculated. Theoretical small-angle X-ray scattering curves were calculated for all unhydrated and hydrated structures and compared with experimentally determined scattering profiles for submicellar casein. Best results were achieved with the 120-bound-water structure for both the symmetric and asymmetric submicelle models. Comparison of results for the protein submicelle models with those for the theoretical and literature values of bovine pancreatic trypsin inhibitor demonstrates the applicability of the methodology.
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Affiliation(s)
- T F Kumosinski
- USDA, ARS, Eastern Regional Research Center, Philadelphia, Pennsylvania 19118, USA
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31
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Mozersky SM, Farrell HM, Barford RA. Evaluation by Sedimentation Field-Flow Fractionation of the Susceptibility of Nonfat Dry Milk Proteins to Aggregation. SEP SCI TECHNOL 1991. [DOI: 10.1080/01496399108050544] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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32
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Mozersky S, Farrell H, Barford R. The Effects of Sucrose and Lactose on the Sizes of Casein Micelles Reconstituted from Bovine Caseins. J Dairy Sci 1991. [DOI: 10.3168/jds.s0022-0302(91)78412-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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33
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Kumosinski TF, Farrell HM. Calcium-induced associations of the caseins: thermodynamic linkage of calcium binding to colloidal stability of casein micelles. JOURNAL OF PROTEIN CHEMISTRY 1991; 10:3-16. [PMID: 2054060 DOI: 10.1007/bf01024650] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The caseins occur in milk as colloidal complexes of protein aggregates, calcium, and inorganic phosphate. As determined by electron microscopy, these particles are spherical and have approximately a 650 A radius (casein micelles). In the absence of calcium, the protein aggregates themselves (submicelles) have been shown to result from mainly hydrophobic interactions. The fractional concentration of stable colloidal casein micelles can be obtained in a calcium caseinate solution by centrifugation at 1500 g. Thus, the amount of stable colloid present with varying Ca2+ concentrations can be determined and then analyzed by application of equations derived from Wyman's Thermodynamic Linkage Theory. Ca(2+)-induced colloid stability profiles were obtained experimentally for model micelles consisting of only alpha s1- (a calcium insoluble casein) and the stabilizing protein kappa-casein, eliminating the complications arising from beta- and minor casein forms. Two distinct genetic variants alpha s1-A and B were used. Analysis of alpha s1-A colloid stability profiles yielded a precipitation (salting-out) constant k1, as well as colloid stability (salting-in) parameter k2. No variations of k1 or k2 were found with increasing amounts of kappa-casein. From the variation of the amount of colloidal casein capable of being stabilized vs. amount of added kappa-casein an association constant of 4 L/g could be calculated for the complexation of alpha s1-A and kappa-casein. For the alpha s1-B and kappa-casein micelles, an additional Ca(2+)-dependent colloidal destabilization parameter, k3, was added to the existing k1 and k2 parameters in order to fully describe this more complex system. Furthermore, the value of k3 decreased with increasing concentration of kappa-casein. These results were analyzed with respect to the specific deletion which occurs in alpha s1-casein A in order to determine the sites responsible for these Ca(2+)-induced quaternary structural effects.
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Affiliation(s)
- T F Kumosinski
- USDA, Eastern Regional Research Center, Philadelphia, Pennsylvania 19118
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34
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Tertiary and quaternary structural differences between two genetic variants of bovine casein by small-angle X-ray scattering. Arch Biochem Biophys 1991; 284:133-42. [PMID: 1989491 DOI: 10.1016/0003-9861(91)90275-n] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The casein complexes of bovine milk consist of four major protein fractions, alpha s1, alpha s2, beta, and kappa. Colloidal particles of casein (termed micelles) contain inorganic calcium and phosphate; they are very roughly spherical with an average radius of 650 A. Removal of Ca2+ leads to the formation of smaller protein aggregates (submicelles) with an average radius of 94 A. Two genetic variants, A and B, of the predominant fraction, alpha s1-casein, result in milks with markedly different physical properties, such as solubility and heat stability. To investigate the molecular basis for these differences, small-angle X-ray scattering was performed on the respective colloidal micelles and submicelles. Scattering curves for submicelles of both variants showed multiple Gaussian character; data for the B variant were previously interpreted in terms of two concentric regions of different electron density, i.e., a "compact" core and a relatively "loose" shell. For the submicelle of A, there was a third Gaussian, reflecting a negative contribution due to interparticle interference. Molecular parameters for submicelles of both A and B are in agreement with hydrodynamic data in the literature. Data for the micelles, for which scattering yields cross-sectional information, were fitted by a sum of three Gaussians for both variants; for these, the corresponding two lower radii of gyration represent the two concentric regions of the submicelles, while the third reflects the average packing of submicelles within the micellar cross section. Most of the molecular parameters obtained showed small but consistent differences between A and B, but for submicelles within the micelle several differences were particularly notable: A has a greater molecular weight for the "compact" region of the constituent submicelle (82,000 vs 60,000) and a much greater submicellar packing number (6:1 vs 3:1). Reasons for these and other differences are to be sought in sequence differences and in differences in calcium-binding sites and charge distribution.
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35
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Kumosinski TF, Pessen H, Farrell HM. Protein-water interactions from 2H NMR relaxation studies: influence of hydrophilic, hydrophobic, and electrostatic interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 302:541-60. [PMID: 1746349 DOI: 10.1007/978-1-4899-0664-9_29] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The importance of water interactions with proteins in food systems is well documented. A controversy exists, however, as to the nature of these interactions and the effect of protein structural changes on them. To clarify these questions, a method has been developed for determining hydration from the protein concentration-dependence of deuteron resonance relaxation rates. Measurements were made in D2O on beta-lactoglobulin A to study effects of hydrophilic interactions, and on both casein micelles and submicelles to study hydrophobic and electrostatic effects. From the protein concentration-dependent relaxation rates, the second viral coefficients of the proteins were obtained by nonlinear regression analysis. Using either an isotropic tumbling or an intermediate asymmetry model, hydrations, upsilon, and correlation times, tau c, were calculated for the protein-associated water; from tau c, the Stokes radius, R, was obtained. Variations in upsilon and R were in accord with known structural changes in molecular states of the proteins. The NMR results are compared with hydrations and structural information derived independently from small-angle X-ray scattering.
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Affiliation(s)
- T F Kumosinski
- U.S. Department of Agriculture, ARS, Eastern Regional Research Center, Philadelphia, PA 19118
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36
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Jang HD, Swaisgood HE. Characteristics of the interaction of calcium with casein submicelles as determined by analytical affinity chromatography. Arch Biochem Biophys 1990; 283:318-25. [PMID: 2275545 DOI: 10.1016/0003-9861(90)90649-j] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Interaction of calcium with casein submicelles was investigated in CaCl2 and calcium phosphate buffers and with synthetic milk salt solutions using the technique of analytical affinity chromatography. Micelles that had been prepared by size exclusion chromatography with glycerolpropyl controlled-pore glass from fresh raw skim milk that had never been cooled, were dialyzed at room temperature against calcium-free imidazole buffer, pH 6.7. Resulting submicelles were covalently immobilized on succinamidopropyl controlled-pore glass (300-nm pore size). Using 45Ca to monitor the elution retardation, the affinity of free Ca2+ and calcium salt species was determined at temperatures of 20 to 40 degrees C and pH 6.0 to 7.5. Increasing the pH in this range or increasing the temperature strengthened the binding of calcium to submicelles, similar to previous observations with individual caseins. However, the enthalpy change obtained from the temperature dependence was considerably greater than that reported for alpha s1- and beta-caseins. Furthermore, the elution profiles for 45Ca in milk salt solutions were decidedly different from those in CaCl2 or calcium phosphate buffers and the affinities were also greater. For example, at pH 6.7 and 30 degrees C the average dissociation constant for the submicelle-calcium complex is 0.074 mM for CaCl2 and calcium phosphate buffers, vs 0.016 mM for the milk salt solution. The asymmetric frontal boundaries and higher average affinities observed with milk salts may be due to binding of calcium salts with greater affinity in addition to the binding of free Ca2+ in these solutions.
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Affiliation(s)
- H D Jang
- Department of Food Science, Southeast Dairy Foods Center, North Carolina State University
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Farrell H, Pessen H, Brown E, Kumosinski T. Structural Insights into the Bovine Casein Micelle: Small Angle X-Ray Scattering Studies and Correlations with Spectroscopy. J Dairy Sci 1990. [DOI: 10.3168/jds.s0022-0302(90)79062-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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38
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Kakalis LT, Kumosinski TF, Farrell HM. A multinuclear, high-resolution NMR study of bovine casein micelles and submicelles. Biophys Chem 1990; 38:87-98. [PMID: 2085653 DOI: 10.1016/0301-4622(90)80043-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
High-resolution, natural abundance 13C[1H] (100.5 MHz), 31P[1H] (161.8 MHz) and 1H (400.0 MHz) NMR spectroscopy was used to identify the calcium-binding sites of bovine casein and to ascertain the dynamic state of amino acid residues within the casein submicelles (in 125 mM KCl, pD = 7.4) and micelles (in 15 mM CaCl2/80 mM KCl, pD = 7.2). The presence of numerous, well-resolved peaks in the tentatively assigned 13C-NMR spectra of submicelles (90 A radius) and micelles (500 A radius) suggests considerable segmental motion of both side chain and backbone carbons. The partly resolved 31P-NMR spectra concur with this. Upon Ca2+ addition, the phosphoserine beta CH2 resonance (65.8 ppm vs DSS) shifts upfield by 0.2 ppm and is broadened almost beyond detection; a general upfield shift (up to 0.3 ppm) is also observed for the 31P-NMR peaks. The T1 values of the alpha CH envelope for submicelles and micelles are essentially identical corresponding to a correlation time of 8 ns for isotropic rotation of the caseins. Significant changes in the 31P T1 values accompany micelle formation. Data are consistent with a loose and mobile casein structure, with phosphoserines being the predominant calcium-binding sites.
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Affiliation(s)
- L T Kakalis
- U.S. Department of Agriculture, Eastern Regional Research Center, Philadelphia, PA 19118
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39
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Pessen H, Kumosinski TF, Farrell HM. Water interactions in bovine casein: 2H NMR relaxation and small-angle X-ray scattering studies. BASIC LIFE SCIENCES 1990; 56:175-97. [PMID: 2078171 DOI: 10.1007/978-1-4684-5868-8_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- H Pessen
- ERRC, USDA, Philadelphia, PA 19118
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40
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Humphreys SH. Freeze-fracture of manufactured foods. JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1989; 13:300-8. [PMID: 2681574 DOI: 10.1002/jemt.1060130405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Manufacture of food products with desired texture and stability increasingly benefits from an understanding of the food microstructure. Freeze-fracture is advantageous in gaining this understanding because it avoids alterations of hydration, retains fat, and maximally preserves air cells. This paper reviews insightful applications of freeze-fracture to various food crystals, colloids, gels, emulsions, and foams.
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Affiliation(s)
- S H Humphreys
- Department of Anatomy and Cell Biology, School of Medicine, University of Illinois, Chicago 60612
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