Percoll(R) is a well-referenced media for density gradient centrifugation of cells viruses and subcellular particles. Percoll(R) is composed of colloidal silica coated with polyvinylpyrrolidone (PVP).Percoll(R) is a low viscosity density gradient medium for preparation of cells subcellular particles and larger viruses. The low viscosity of the medium enables cell preparation on preformed gradients in only a few minutes using low centrifugal forces (200 to 1000 x g). The medium is available in easy-to-open resealable 250 mL and 1 l bottles.Percoll(R) consists of silica particles (15 to 30 nm diameter) coated with non-dialyzable polyvinylpyrrolidone (PVP). free PVP is present at only 1% to 2%. Percoll(R) is non-toxic almost chemically inert and does not adhere to membranes. Percoll(R) gradients can be formed within the density range of 1.0 to 1.3 g/mL and are iso-osmotic throughout.Percoll(R) can be stored unopened at room temperature for five years. At -20 C it can only be store