Colloidal Silica Media

Colloidal silica media are not true solutions, but are colloidal suspensions of silica particles coated with polyvinylpyrolidone (PVP) with a diameter of 15-30 nm. The most widely known colloidal silica medium is Percoll®. The polyvinylpyrrolidone minimizes the particle interactions with biology material and stabilized the colloid. Being a colloid, the osmotic strength of Percoll is extremely low and changes little with density. The osmolality of Percoll gradients can be used adjusted by adding appropriate amounts of sucrose or buffer solution. Percoll gradients self-forming when centrifuged in fix-angle rotors (swing out rotors are not satisfactory for self-forming gradients). Percoll can be removes from suspensions by differential pelleting. Percoll gradients are mainly used in isopycnic separations of cell, organelles, membrane vesicles, and even some viruses. The main limitation is that the sample particles size must be larger than the colloidal silica particles, otherwise the particles of silica pellet before the sample bands.

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GE17-0891-01 Percoll® GE Healthcare, 17-0891-01, pack of 1 L
GE17-0891-02 Percoll® GE Healthcare, 17-0891-02, pack of 250 mL
GE17-0891-09 Percoll® GE Healthcare, 17-0891-09, pack of 6 × 1 L
P1644 Percoll® pH 8.5-9.5 (20 °C)
P4937 Percoll® pH 8.5-9.5 (25 °C), cell culture tested
GE17-5445-01 Percoll® PLUS GE Healthcare, 17-5445-01, pack of 1 L
GE17-5445-02 Percoll® PLUS GE Healthcare, 17-5445-02, pack of 250 mL