Human DNA Topoisomerase I

What it means: DNA Topoisomerases — the enzyme class this product belongs to.

Why it matters:

• It tells you which reaction the enzyme carries out, so you can match it to your assay.
• Enzymes of the same class often share substrates, cofactors and readouts.
• The class helps you find related enzymes and assay kits in the catalog.
• Knowing the class helps you choose suitable controls and reference inhibitors.
• It makes it easier to compare your results with published work on the same enzyme class.
• Grouping by class also helps when you build a selectivity panel of related enzymes.

For this product: DNA Topoisomerases — DNA relaxation is the reaction in which human DNA topoisomerase I (topo I) turns supercoiled circular DNA into its relaxed form.

Tip: Use the matching ProFoldin protocols (under Documents) as a starting point for reaction conditions.

What it means: Human — the organism the enzyme or protein comes from.

Why it matters:

• Enzymes from different organisms can differ in activity and in inhibitor sensitivity.
• Using the organism of your study keeps results relevant to that organism.
• Comparing the same enzyme from several organisms shows how selective an inhibitor is.
• The organism helps you choose the matching assay kit and controls.
• Stating the organism makes your methods easy to report and repeat.
• Results from one organism do not always carry over to the matching enzyme of another organism.

For this product: Human — use this human enzyme for human-target studies or as a selectivity counter-screen against bacterial and viral enzymes.

Tip: Use the matching ProFoldin protocols (under Documents) as a starting point for reaction conditions.

What it means: 500 U/µl or 2,000 U/µl — the concentration of the supplied stock.

Why it matters:

• The stock concentration decides how far you dilute the enzyme for each reaction.
• Knowing it helps you plan how many reactions one vial supports.
• Keeping the same final enzyme amount in every well keeps results comparable.
• It lets you compare your conditions with the matching kit protocol.
• A known stock value makes dilution steps easy to document.
• Keep the final enzyme concentration the same when you change the reaction volume, and check the linear range for your conditions.

For this product: 500 U/µl or 2,000 U/µl — each vial holds 20 µl of 500 U/µl purified human topoisomerase I from Sf9 cells, plus 1 ml of 10 x assay buffer; this is the smallest size, see Product Description for the others.

Tip: Dilute just before use, keep the enzyme on ice, and prepare only the amount needed for the day.

What it means: Frozen — how the product is shipped.

Why it matters:

• Frozen shipping keeps the product cold during transport.
• Knowing the shipping condition helps you arrange for someone to receive and store the package.
• The product should be moved to cold storage as soon as it arrives.
• Checking the package on arrival helps you spot transport problems early.
• Planning storage space in advance avoids delays on delivery day.
• Frozen products should not be left at room temperature after delivery.

For this product: Frozen — the vial is shipped frozen; move it to cold storage as soon as it arrives.

Tip: Check the package on arrival, move the vial to cold storage right away, and contact us if it is not frozen.