Nycodenz® is an off-white powder, freely soluble in water. Solutions up to 80% (v/w) with a density of 1.426 g/ml can be prepared. Nycodenz® was originally developed as an X-ray contrast medium and has therefore been subjected to rigorous clinical testing. Nycodenz® can be used for the isolation of cells, subcellular organelles and membranes, macromolecules and viruses.
Nycodenz® is non-ionic, non-toxic to cells and metabolically inert.
Nycodenz® forms true solutions. It is therefore easy to remove the medium from the cells after fractionation.
Nycodenz® is resistant to bacterial degradation.
Nycodenz® solutions can be autoclaved.
Nycodenz® is the trademark name for iohexol, whose systematic name is 5-(N-2,3-dihydroxypropylacetamido) 2,4,6-tri-iodo-N-N'-bis(2,3-dihydroxypropyl)isophthalamide. It has a molecular weight of 821. The chemical properties and stability of Nycodenz® are related to its structure. Its high density derives from the presence of a substituted triiodobenzene ring linked to a number of hydrophilic groups which are responsible for the high water solubility of Nycodenz®. It is a non-ionic derivative of metrizoic acid; the carboxyl group present in metrizoic acid is linked to the amine group of 3-amino-1,2- propanediol. The dihydroxypropylacetamido side chain is responsible for the very low toxicity of Nycodenz® compared to metrizamide. The iodinated aromatic nucleus absorbs strongly in the ultraviolet region of the spectrum with an absorbtion maximum of 244 nm.
Gradients of Nycodenz® can be generated by:
Diffusion of a discontinuous gradient; simple preparation within 45 minutes.
Tilted tube rotation (Gradient Master™).
Two-chamber gradient maker.
Freezing/thawing of a solution of uniform density.
Centrifugation (self-generated gradient).
The density of Nycodenz® in solution can be determined by measuring the refractive index or it can be calculated from absorbance measurements
Nycodenz® is a non-colloidal medium therefore the distribution of cells in gradients can be determined using a haemocytometer, electronic particle counter or by light scattering measurements using a spectrophotometer.
Nycodenz® does not interfere with the orcinol and diphenylamine reactions for the estimation of nucleic acids nor with the very sensitive dye binding assays for protein and DNA.
Polysaccharides and sugars can be determined in the presence of Nycodenz® using the phenol/H2SO4 assay.
Fluorimetric assays of nucleic acids and proteins can also be carried out in the presence of Nycodenz®.
Nycodenz® does not interfere with most assays for the marker enzymes of subcellular components, also commercial scintillants are compatible with Nycodenz®.
Nycodenz® can be removed from samples by dialysis, ultrafiltration or gel filtration.
Cells, subcellular organelles and other particulate matter can be isolated from Nycodenz ® by centrifugation without the risk of contaminating the pellet with Nycodenz®.