Dextran - N, N ′ -methylene-bisacrylamide gels (Sephacryl):

Sephacryl is a dextran gel manufactured by cross linking allyl dextran with N, N ′ - methylene-bisacrylamide. There are cross links not only in dextran but methylene- bisacrylamide molecules also bind to each other. A hypothetical structure of Sephacryl gel is shown Figure.

Figure:  A schematic representation of partial structure of Sephacryl

The cross connections reactions make the gel partly macroreticular and the gels can be produced with fractionation ranges extending up to high molecular masses. They are mechanically rigid and bear high pressures (upto 1M Pa) without compressing the bed. These gels are intended mainly for use with aqueous eluants. Two types of Sephacryl gels are available. Those are Sephacryl-200 Superfine and Sephacryl S-300 Superfine. The fractionation ranges cover the most common molecular masses of water soluble proteins. Since in these gels, the structure is macroreticular, the slope of the selectivity curve is less than the microreticular Sephadex gel. Because of large amount of methylene bis-acrylamide within the gel, the adsorption effects are more pronounced than with Sephadex.