Supramolecular Structure of the Casein Micelle

Transmission electron micrographs of (A) low-magnification field of view of freeze-dried poly-l-lysine immobilized casein micelles on a parlodion-coated copper grid, and (B, C, D) high-magnification view of individual casein micelles of different sizes.

Transmission electron micrographs of freeze-dried poly-l-lysine immobilized casein micelles (A) without uranyl oxalate impregnation, and (B) showing increased contrast obtained with uranyl oxalate impregnation.

Transmission electron micrograph of freeze-dried poly-l-lysine immobilized casein micelles that have been (A) calcium depleted with EDTA, and (B) fixed with glutaraldehyde.

Stereo-pair of transmission electron micrograph of a freeze-dried immobilized and uranyl oxalate-stained casein micelle.

Anaglyphic version of transmission electron micrographs of (A) a freeze-dried immobilized and uranyl oxalate-stained casein micelle, and (B) a digitally magnified peripheral region of a casein micelle.

(A) Transmission electron micrograph of a freeze-dried immobilized and uranyl oxalate-stained casein micelle: (box) a peripheral portion of a casein micelle was digitally magnified as a stereo-pair and a single plane of electron-dense spots was identified and then (B) color-coded based on the number of immediately adjacent spots (red=1 neighbor, green=2 neighbors, blue=3 neighbors, black=4 or more neighbors), with those not in the same plane deleted from the digital image; then on the same image (C), the intersecting locations were overlaid with a dark gray circle of 4.8nm in diameter representing a calcium phosphate nanocluster, and (D) the remainder of the electron-dense spots were overlaid with a light gray circle of 8nm in diameter representing casein molecules.

Schematic diagram of an interlocking lattice model of the casein micelle with casein-calcium phosphate aggregates throughout the entire supramolecule and chains of proteins extending between them. Drawn as cross-sectional scaled views of (A) the complete supramolecule, and (B) a portion of the supramolecule periphery. Calcium phosphate nanoclusters are shown with a diameter of 4.8nm and approximately 18nm apart, and caseins are shown with a hydrodynamic diameter of 8nm.

Transmission electron micrographs of freeze-dried immobilized and uranyl oxalate-stained casein micelles from (A) human milk, (B) mare milk, and (C) pygmy goat milk.