Structural changes of casein micelles in a calcium gradient film.
Calcium gradients are prepared by sequentially filling a micropipette with casein solutions of varying calcium concentration and spreading them on glass slides. The casein film is formed by a solution casting process, which results in a macroscopically rough surface. Microbeam grazing incidence small-angle X-ray scattering (microGISAXS) is used to investigate the lateral size distribution of three main components in casein films: casein micelles, casein mini-micelles, and micellar calcium phosphate. At length scales within the beam size the film surface is flat and detection of size distribution in a macroscopic casein gradient becomes accessible. The model used to analyze the data is based on a set of three log-normal distributed particle sizes. Increasing calcium concentration causes a decrease in casein micelle diameter while the size of casein mini-micelles increases and micellar calcium phosphate particles remain unchanged.
Gebhardt
Ronald
R
European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex 09, France. ronald.gebhardt@esrf.fr
Burghammer
Manfred
M
Riekel
Christian
C
Roth
Stephan Volkher
SV
Müller-Buschbaum
Peter
P
D001709:Biotechnology / Q000379:methods; D002118:Calcium / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry; D002364:Caseins / Q000737:chemistry*; D004573:Electrolytes; D008823:Micelles; D008854:Microscopy, Electron; D015233:Models, Statistical; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D012542:Scattering, Radiation; D013499:Surface Properties
D002130:Calcium Phosphates; D002364:Caseins; D004573:Electrolytes; D008823:Micelles; C020243:calcium phosphate; D002118:Calcium