6-aminocaproic acid, spacer molecules

Several chemical approaches may be used to form the amine- or carboxyl-terminal dextran derivative. The simplest procedure may be to prepare polyaldehyde dextran according to the procedure of Section 2.1, and then make the spacer arm derivative by reductively animating an amine-containing organic compound onto it. For instance, short diamine compounds such as ethylene diamine or diaminodipropylamine (3,3 -iminotepropylamine) can be coupled in excess to polyaldehyde dextran to create an amine-terminal derivative. Carboxyl-terminal derivatives may be prepared similarly by coupling molecules such as 6-aminocaproic acid or p-alanine to polyaldehyde... 

However, as was observed, the described chromatography of chymotrypsin on unsubstituted Sepharose does not provide sufficient evidence of non-specific sorption. On the contrary, Hofstee [47] demonstrated for Sepharose with coupled e-aminocaproyl-D-tryptophan methyl ester that it sorbed, for example, serum albumin or y-globulin quite non-specifically. Thus, it was found that a series of substances contained hydrophobic regions on the surface of their molecules, by which they were capable of being bound to hydrophobic spacers, such as hexa-methylenediamine or e-aminocaproic acid. The utilization of this phenomenon for the separation of a number of biological macromolecules gave rise to a new technique, the hydrophobic chromatography [14,15]. 

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