Frequently Asked Questions


The amount of product in the tubes may vary from batch to batch. Before use, spin the tubes down at maximum 1000g and at the temperature matching the storage temperature.

We purify new enzymes on a regular basis to make sure that they are always fresh and perform optimally. The results of individual purifications will vary a bit from time to time giving rise to enzyme preparations with slightly different concentrations and/or activity.

The exact activity of TOP1 per ng depends on many factors such as the time spend at 4°C during purification and small impurities in the enzyme preparation such as other proteins. In fact, very pure TOP1 has poor activity per ng, we therefore recommend to do activity studies using our less pure (80% pure) enzyme preparations. Such enzyme preparations also have longer shelf life than ultra-pure TOP1 preparations.

We havedeveloped kits to fit the availability of equipment in different laboratories. For this reason, there is an option to choose between fluorescence, colorimetric (TMB), or chemiluminescence (ECL) readouts. In all cases, the kits can be used as a quantitative tool for the measurements of TOP1 activity in crude cell extracts or using purified enzyme. The kits can be ordered with or without purified TOP1.

This is the most sensitive and precise assay that we have and in order to get maximum performance you will need a fluorescence microscope with a 60-70x objective. For the green fluorescent readout you will need a 488 nm laser paired with a GFP or FAM filter. For the red fluorescent redout you will need a 532 nm laser paired with a TAMRA filter. Alternatively, a fluorescence scanner can be used, using the laser and filter setting matching the exctitation and emission of ATTO 488 or ATTO 532.

Our TOP1 is highly concentrated and very active and will be good for our REEAD assays, Western blotting, Immunoprecipitation, relaxation, DNA cleavage and ligation assays, mobility shift assays, ICE assays and more. Upon request we can make ultra-pure and highly concentrated TOP1 preparation for crystallization, biochemical analyses such as biacore (SPR), single molecule studies and more specialized visualization assays. If you are interested to know more about the use of our hTOP1 for your specific assays we will be happy to assist you. Click here to contact us.


Some buffers contain components that are insensitive to temperature variations. However, most buffers and reagents such as e.g. enzymes, dNTP, ATP etc. require to be stored at specific temperatures to retain their quality.

Yes, it is important that the freezer used for storage has a temperature between -18C to -20C. Lower temperatures may cause freezing of enzyme preparations, which will destroy them and higher temperatures will be insufficient to prevent degradation, oxidation etc. over prolonged storage time.


Yes, you can see your order history when logged in.


All our enzymes are stored in 50% glycerol because freezing will seriously hamper their activity. The temperature of the enzyme packages during shipment is kept between -20C and 4C to preserve activity of the enzymes and avoid freezing.