Abstract: A method of sample displacement chromatography separation which comprises applying a multicomponent sample to one end of a chromatography bed comprising stationary phase material having affinity for components of the sample, causing components of the sample to become distributed along the chromatography bed by passage over the bed of a non-eluting mobile solvent phase, and recovering a desired component of the sample from at lest a portion of the chromatography bed, in which the sample components are applied to the chromatography bed in a non-homogeneous manner such that the concentration of at least one component with relatively low affinity for the stationary phase material is enhanced during an earlier part of sample application and/or the concentration of at least one component with relatively high affinity for the stationary phase material is enhanced during a later part of sample application.

Abstract: Sample displacement chromatography is performed at low operating pressures (less than 30 bar) and/or at high sample loading (in excess of 500 mg/cm2 column area), with product recovery being effected in a non-gradient manner. The low operating pressures permit the use of simple and inexpensive apparatus. Non-gradient product recovery allows the desired product to be allowed in solutions with advantageously high concentration. Materials which may be purified include pharmaceuticals, pharmaceutical excipients, fine chemicals, biochemicals, X-ray contrast agents, chelating agents, peptides, proteins, oligonucleotides and vaccines. Apparatus embodiments include sample displacement chromatography apparatus comprising one or more ion exchange columns in direct combination with one or more desalting columns, and multicolumn chromatography apparatus permitting switching between a series separation mode and a parallel extraction mode.

Abstract: Dipeptide compounds are disclosed, the two peptide chains being joined together at a C.alpha.-atom of a non-terminal amino acid by a divalent bridging group --A--. The C.alpha.-atoms joined to group --A-- are located in equivalent positions in each peptide and each lack their native .alpha.-side chain. The bridged dipeptide compounds disclosed have a stimulating activity on cell division, especially for myelopoietic and bone marrow cells.