Promega currently offers five different loading buffers: Blue/Orange Loading Dye, 6X (Cat.# G1881), STR 2X Loading Solution (Cat.# DV4331), Blue Dextran Loading Solution (Cat.# DV4351), Gel Tracking Dye (Cat.# DV4361), and Bromophenol Blue Loading Solution (Cat.# DV4371). Each buffer has a unique purpose. The STR 2X Loading Solution, Blue Dextran Loading Solution, Gel Tracking Dye and Bromophenol Blue Loading Solution are designed for use with our GenePrint® STR Systems. All five buffers are discussed in greater detail below.
The Blue/Orange Loading Dye, 6X (Cat.# G1881)
This solution is used for loading DNA samples onto nondenaturing gels. The buffer is designed to be used at a 1X final concentration. In a 0.5-1.4% agarose gel (in 0.5X TBE), xylene cyanol FF migrates at approximately 4kb; bromophenol blue, approximately 300bp; and orange G, approximately 50bp.
Composition of Blue/Orange Loading Dye, 6X: 0.03% bromophenol blue, 0.03% xylene cyanol FF, 0.4% orange G, 15% Ficoll® 400, 10mM Tris-HCl (pH 7.5) and 50mM EDTA (pH 8.0).
STR 2X Loading Solution (Cat.# DV4331)
This solution is used for loading DNA samples onto denaturing polyacrylamide gels. The STR 2X Loading Solution is designed to be used at a 1X final concentration. In a 4% (19:1 crosslinking ratio) denaturing polyacrylamide gel, the bromophenol blue migrates at approximately 40 bases and the xylene cyanol FF migrates at approximately 170 bases. In a 6% (19:1 crosslinking ratio) denaturing polyacrylamide gel, the bromophenol blue migrates at approximately 25 bases and the xylene cyanol FF component at approximately 105 bases.
Composition of STR 2X Loading Solution: 95% formamide, 10mM NaOH, 0.05% bromophenol blue and 0.05% xylene cyanol FF.
Blue Dextran Loading Solution (Cat.# DV4351)
This solution is designed for use in loading DNA samples onto denaturing polyacrylamide gels when using the ABI® 373 and ABI PRISM® 377 DNA sequencers. This solution is designed to be used in a 1:1 dilution with DNA samples.
Composition of Blue Dextran Loading Solution: 88.25% formamide, 15mg/ml blue dextran and 4.1mM EDTA.
This solution is designed for use as a visual indicator of electrophoresis. It should not be added to DNA or RNA samples; rather, the dye should be added to blank wells of the gel. In a 4% (19:1 crosslinking ratio) denaturing polyacrylamide gel, the bromophenol blue migrates at approximately 40 bases and the xylene cyanol FF migrates at approximately 170 bases. In a 6% (19:1 crosslinking ratio) denaturing polyacrylamide gel, the bromophenol blue migrates at approximately 25 bases and the xylene cyanol FF component at approximately 105 bases.
Composition of Gel Tracking Dye: 95% formamide, 10mM NaOH, 0.05% bromophenol blue and 0.05% xylene cyanol FF.
Bromophenol Blue Loading Solution (Cat.# DV4371)
This solution is used for loading DNA samples onto a denaturing polyacrylamide gel and for tracking migration during electrophoresis when using the Hitachi FMBIO® and Hitachi FMBIO® II Fluorescent Imaging Systems. The solution is designed to be diluted 1:1 with the DNA sample prior to loading onto a polyacrylamide gel. In a 4% (19:1 crosslinking ratio) denaturing polyacrylamide gel, the bromophenol blue migrates at approximately 40 bases. In a 6% (19:1 crosslinking ratio) denaturing polyacrylamide gel, the bromophenol blue migrates at approximately 25 bases.