Frequently asked questions

Our Scientific Applications Support team has assembled a list of frequently asked questions to help you find answers quickly. Filter using one or more categories to focus on specific topics, or use the search bar to perform a text search.

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What molar concentrations of oligonucleotide and salts are used to calculate the Tm reported on specification sheets?

The Tm value reported on our spec sheets uses a 25 µM oligonucleotide and a 50 mM salt concentration. It does not take into account dNTP or Mg2+ concentrations. To get an accurate Tm for your specific application, all of these concentrations should be input and adjusted to match the reaction conditions you plan to use. The free IDT OligoAnalyzer SciTool® ( calculates Tm for the concentrations you input.