when we are making band shift assays we use "normal" sample buffer for
agarose gels (0.25% bromphenolblue, 0.25% xylenecyanide, 30% glycerol) as
front marker in an extra lane. Our (colorless) 5 x loading buffer for
protein/dna complexes is made as follows: 200 mM KCl, 5 mM MgCl2, 0.5 mM
EGTA, 2.5 mM DTT, 100 mM Hepes (pH 7.9) and 50% Glycerol.
Perhaps you should try this, may be it works.