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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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2
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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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Cao F, Xia Y, Chen D, Xu N, Hemar Y, Li N, Sun Y. Insights on the structure of caseinate particles based on surfactants-induced dissociation. Food Hydrocoll 2020. [DOI: 10.1016/j.foodhyd.2020.105766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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4
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Huppertz T, Gazi I, Luyten H, Nieuwenhuijse H, Alting A, Schokker E. Hydration of casein micelles and caseinates: Implications for casein micelle structure. Int Dairy J 2017. [DOI: 10.1016/j.idairyj.2017.03.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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5
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Metwalli E, Hermes HE, Calzada E, Kulozik U, Egelhaaf SU, Müller-Buschbaum P. Water ingress into a casein film quantified using time-resolved neutron imaging. Phys Chem Chem Phys 2016; 18:6458-64. [PMID: 26862596 DOI: 10.1039/c5cp07072d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The migration of water into a casein film was probed with neutron radiography. From the neutron transmission images, the evolution of the water saturation profiles was extracted. The results indicate that the water influx is dominated by imbibition but also contains a diffusional component. The time dependence of the water ingress was quantified using a diffusion-like equation previously also applied to imbibition. A water transport coefficient D = 0.9 × 10(-9) m(2) s(-1) was found. This value and direct observation of the images indicate that the time taken for a typical adhesive casein-based layer to become saturated with water is of the order of hours.
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Affiliation(s)
- E Metwalli
- Technische Universität München, Physik-Department, Lehrstuhl für Funktionelle Materialien, James-Franck-Str.1, 85748 Garching, Germany.
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6
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Retinol binding to β-lactoglobulin or phosphocasein micelles under high pressure: Effects of isostatic high-pressure on structural and functional integrity. Food Res Int 2014. [DOI: 10.1016/j.foodres.2013.11.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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7
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Chatterton DE, Nguyen DN, Bering SB, Sangild PT. Anti-inflammatory mechanisms of bioactive milk proteins in the intestine of newborns. Int J Biochem Cell Biol 2013; 45:1730-47. [DOI: 10.1016/j.biocel.2013.04.028] [Citation(s) in RCA: 251] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 04/25/2013] [Accepted: 04/28/2013] [Indexed: 01/04/2023]
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8
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Lowth BR, Kirstein-Miles J, Saiyed T, Brötz-Oesterhelt H, Morimoto RI, Truscott KN, Dougan DA. Substrate recognition and processing by a Walker B mutant of the human mitochondrial AAA+ protein CLPX. J Struct Biol 2012; 179:193-201. [PMID: 22710082 DOI: 10.1016/j.jsb.2012.06.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 05/14/2012] [Accepted: 06/07/2012] [Indexed: 10/28/2022]
Abstract
The mitochondrial matrix of mammalian cells contains several different ATP-dependent proteases, including CLPXP, some of which contribute to protein maturation and quality control. Currently however, the substrates and the physiological roles of mitochondrial CLPXP in humans, has remained elusive. Similarly, the mechanism by which these ATP-dependent proteases recognize their substrates currently remains unclear. Here we report the characterization of a Walker B mutation in human CLPX, in which the highly conserved glutamate was replaced with alanine. This mutant protein exhibits improved interaction with the model unfolded substrate casein and several putative physiological substrates in vitro. Although this mutant lacks ATPase activity, it retains the ability to mediate casein degradation by hCLPP, in a fashion similar to the small molecule ClpP-activator, ADEP. Our functional dissection of hCLPX structure, also identified that most model substrates are recognized by the N-terminal domain, although some substrates bypass this step and dock, directly to the pore-1 motif. Collectively these data reveal, that despite the difference between bacterial and human CLPXP complexes, human CLPXP exhibits a similar mode of substrate recognition and is deregulated by ADEPs.
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Affiliation(s)
- Bradley R Lowth
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
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9
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Functional properties of milk protein concentrates: Emulsifying properties, adsorption and stability of emulsions. Int Dairy J 2011. [DOI: 10.1016/j.idairyj.2010.07.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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10
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Effect of iron chelates on oil–water interface, stabilized by milk proteins: The role of phosphate groups and pH. Prediction of iron transfer from aqueous phase toward fat globule surface by changes of interfacial properties. Food Hydrocoll 2010. [DOI: 10.1016/j.foodhyd.2009.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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11
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Pitkowski A, Nicolai T, Durand D. Stability of caseinate solutions in the presence of calcium. Food Hydrocoll 2009. [DOI: 10.1016/j.foodhyd.2008.07.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Metwalli E, Moulin JF, Gebhardt R, Cubitt R, Tolkach A, Kulozik U, Müller-Buschbaum P. Hydration behavior of casein micelles in thin film geometry: a GISANS study? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:4124-4131. [PMID: 19714832 DOI: 10.1021/la802602g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The water content of casein micelle films in water vapor atmosphere is investigated using time-resolved grazing incidence small-angle neutron scattering (GISANS). Initial dry casein films are prepared with a spin-coating method. At 30 degrees C, the formation of a water-equilibrated casein protein film is reached after 11 min with a total content of 0.36 g of water/g of protein. With increasing water vapor temperature up to 70 degrees C, an increase in the water content is found. With GISANS, lateral structures on the nanometer scale are resolved during the swelling experiment at different temperatures and modeled using two types of spheres: micelles and mini-micelles. Upon water uptake, molecular assemblies in the size range of 15 nm (mini-micelles) are attributed to the formation of a high-contrast D2O outer shell on the small objects that already exist in the protein film. For large objects (>100 nm), the mean size increases at high D2O vapor temperature because of possible aggregation between hydrated micelles. These results are discussed and compared with various proposed models for casein micelle structures.
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Affiliation(s)
- E Metwalli
- Technische Universität München, Physik Department E13, James-Franck-Str.1, 85747 Garching, Germany
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13
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Zhu F, Kapitan J, Tranter GE, Pudney PDA, Isaacs NW, Hecht L, Barron LD. Residual structure in disordered peptides and unfolded proteins from multivariate analysis and ab initio simulation of Raman optical activity data. Proteins 2008; 70:823-33. [PMID: 17729278 DOI: 10.1002/prot.21593] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Vibrational Raman optical activity (ROA), measured as a small difference in the intensity of Raman scattering from chiral molecules in right- and left-circularly polarized incident light, or as the intensity of a small circularly polarized component in the scattered light, is a powerful probe of the aqueous solution structure of proteins. The large number of structure-sensitive bands in protein ROA spectra makes multivariate analysis techniques such as nonlinear mapping (NLM) especially favorable for determining structural relationships between different proteins. We have previously used NLM to map a large dataset of peptide, protein, and virus ROA spectra into a readily visualizable two-dimensional space in which points close to or distant from each other, respectively, represent similar or dissimilar structures. As well as folded proteins, our dataset contains ROA spectra from many natively unfolded proteins, proteins containing both folded and unfolded domains, denatured partially structured molten globule and reduced protein states, together with folded proteins containing little or no alpha-helix or beta-sheet. In this article, the relative positions of these systems in the NLM plot are used to obtain information about any residual structure that they may contain. The striking differences between the structural propensities of proteins that are unfolded in their native states and those that are unfolded due to denaturation may be responsible for their often very different behavior, especially with regard to aggregation. An ab initio simulation of the Raman and ROA spectra of an alanine oligopeptide in the poly(L-proline) II-helical conformation confirms previous suggestions that this conformation is a significant structural element in disordered peptides and natively unfolded proteins. The use of ROA to identify and characterize proteins containing significant amounts of unfolded structure will, inter alia, be valuable in structural genomics/proteomics since unfolded sequences often inhibit crystallization.
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Affiliation(s)
- Fujiang Zhu
- WestCHEM, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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Friedman R, Nachliel E, Gutman M. Molecular dynamics of a protein surface: ion-residues interactions. Biophys J 2005; 89:768-81. [PMID: 15894639 PMCID: PMC1366628 DOI: 10.1529/biophysj.105.058917] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Accepted: 04/28/2005] [Indexed: 11/18/2022] Open
Abstract
Time-resolved measurements indicated that protons could propagate on the surface of a protein or a membrane by a special mechanism that enhanced the shuttle of the proton toward a specific site. It was proposed that a suitable location of residues on the surface contributes to the proton shuttling function. In this study, this notion was further investigated by the use of molecular dynamics simulations, where Na(+) and Cl(-) are the ions under study, thus avoiding the necessity for quantum mechanical calculations. Molecular dynamics simulations were carried out using as a model a few Na(+) and Cl(-) ions enclosed in a fully hydrated simulation box with a small globular protein (the S6 of the bacterial ribosome). Three independent 10-ns-long simulations indicated that the ions and the protein's surface were in equilibrium, with rapid passage of the ions between the protein's surface and the bulk. However, it was noted that close to some domains the ions extended their duration near the surface, thus suggesting that the local electrostatic potential hindered their diffusion to the bulk. During the time frame in which the ions were detained next to the surface, they could rapidly shuttle between various attractor sites located under the electrostatic umbrella. Statistical analysis of the molecular dynamics and electrostatic potential/entropy consideration indicated that the detainment state is an energetic compromise between attractive forces and entropy of dilution. The similarity between the motion of free ions next to a protein and the proton transfer on the protein's surface are discussed.
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Affiliation(s)
- Ran Friedman
- Laser Laboratory for Fast Reactions in Biology, Department of Biochemistry, The George S. Wise Faculty for Life Sciences, Tel Aviv University, Israel
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15
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Malin EL, Brown EM, Wickham ED, Farrell HM. Contributions of Terminal Peptides to the Associative Behavior of αs1-Casein. J Dairy Sci 2005; 88:2318-28. [PMID: 15956295 DOI: 10.3168/jds.s0022-0302(05)72910-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The N- and C-terminal segments of bovine alphas1-casein-B (f1-23 and f136-196) were characterized under conditions that promoted or inhibited self-association to determine the relative contributions of each fragment to the interaction of alphas1-casein with itself or with other caseins. In earlier studies of f1-23, nuclear magnetic resonance (NMR) data and circular dichroism (CD) spectra showed that its conformation was thermostable between 10 degrees and 25 degrees C. In contrast, NMR studies of f136-196 indicated temperature sensitivity between 10 and 60 degrees C, as did near-UV and far-UV CD data, suggesting a molten globule-like structure at higher temperatures. To compare the effects of temperature on conformational attributes of alphas1-casein and its terminal peptides, additional CD studies were conducted over a broader temperature range (10 to 70 degrees C). The far-UV CD spectra indicated little temperature sensitivity for alphas1-casein, and the N-terminal peptide remained thermostable. During molecular dynamics simulations, the N-terminal peptide conformation did not change significantly, but the conformation of the C-terminal peptide (f136-196) was dramatically altered. These changes are correlated with the thermal instability observed by both CD and NMR in f136-196. Analytical ultracentrifugation studies of the self-association reactions of genetic variants A, B, and C of alphas1-casein showed that at 37 degrees C the associative state is primarily dimeric; the amounts of higher order polymers significantly decreased when temperature was increased from 20 to 37 degrees C. In all 3 genetic variants, the C-terminal portion of the whole molecule showed thermal instability with respect to aggregation to higher polymers, confirming the predictions of CD data and molecular dynamics simulations. The temperature dependency of these conformational changes suggests a possible function for alphas1-casein in facilitating casein-casein interactions in casein micelle formation.
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Affiliation(s)
- E L Malin
- US Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, PA 19038, USA.
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Malin EL, Alaimo MH, Brown EM, Aramini JM, Germann MW, Farrell HM, McSweeney PL, Fox PF. Solution structures of casein peptides: NMR, FTIR, CD, and molecular modeling studies of alphas1-casein, 1-23. JOURNAL OF PROTEIN CHEMISTRY 2001; 20:391-404. [PMID: 11732691 DOI: 10.1023/a:1012232804665] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
To determine its potential for interacting with other components of the casein micelle, the N-terminal section of bovine alphas1-casein-B, residues 1-23, was investigated with nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies, and molecular modeling. NMR data were not consistent with conventional alpha-helical or beta-sheet structures, but changes in N-H proton chemical shifts suggested thermostable structures. Both CD and FTIR predicted a range of secondary structures for the peptide (30-40% turns, 25-30% extended) that were highly stable from 5 degrees C to 25 degrees C. Other conformational elements, such as loops and polyproline II helix, were indicated by FTIR only. Molecular dynamics simulation of the peptide predicted 32% turns and 27% extended, in agreement with FTIR and CD predictions and consistent with NMR data. This information is interpreted in accord with recent spectroscopic evidence regarding the nature of unordered conformations, leading to a possible role of alphas1-casein (1-23) in facilitating casein-casein interactions.
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Affiliation(s)
- E L Malin
- Eastern Regional Research Center, ARS, USDA, Wyndmoor, Pennsylvania 19038, USA.
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Secondary structural studies of bovine caseins: temperature dependence of β-casein structure as analyzed by circular dichroism and FTIR spectroscopy and correlation with micellization. Food Hydrocoll 2001. [DOI: 10.1016/s0268-005x(01)00080-7] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Nandi N, Bhattacharyya K, Bagchi B. Dielectric relaxation and solvation dynamics of water in complex chemical and biological systems. Chem Rev 2000; 100:2013-46. [PMID: 11749282 DOI: 10.1021/cr980127v] [Citation(s) in RCA: 688] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- N Nandi
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, 560012, India
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Malin EL, Brown EM. Molecular modelling of conformational changes in solvated αs1-casein peptides. Int Dairy J 1999. [DOI: 10.1016/s0958-6946(99)00062-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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21
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Groth-Vasselli B, Kumosinski TF, Farnsworth PN. Computer-generated model of the quaternary structure of alpha crystallin in the lens. Exp Eye Res 1995; 61:249-53. [PMID: 7556488 DOI: 10.1016/s0014-4835(05)80044-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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