Special reversed C4 (butyl) phase with monomerically bonded alkyl chains, brush type structure. Based on the original NUCLEOSIL silica gel. It is one of the first spherical silicas for HPLC and was originally developed by MACHEREY-NAGEL in 1974. It is exclusively manufactured in Germany and is still one of the most used HPLC silicas in quality control around the globe. Predominantly hydrophobic forces with a small portion of hydrophilic interactions. The dynamic protein binding capacity per g packing - 14 mg BSA, 27 mg cytochrome C. especially suited for the purification of larger, hydrophobic peptides and very different proteins. Maximum separation efficiency can be achieved when the injected protein mass does not exceed 1–2 % of the maximum protein loading capacity.