Abstract: The heat sink plate of an electrophoresis unit is mounted to a fixed support with studs on the heat sink plate received in sleeves secured to the fixed frame. Compression springs encircle the sleeves and interpose between the heat sink plate and the fixed frame so that when clamping of a gel slab sandwich to the electrophoresis unit is made, a flat face of the heat sink plate orients in substantially full planar face-to-face contact with a flat face of a gel slab sandwich plate and can have following movement with the sandwich plate that is a pivoting thereof about at least two orthogonally disposed axes passing through the heat sink plate so that with said following movement, face-to-face contact is uniform across the plates and hence, heat transfer from the gel slab maintained uniform.