Primer Tm Planning for Q5 Workflows
A Q5 primer set needs careful temperature planning. Small changes can affect yield, specificity, and clean band formation. This calculator gives a structured estimate for daily PCR setup. It checks each primer sequence, removes spacing, and accepts only A, T, G, and C bases. It then reports length, base counts, GC percentage, Wallace Tm, salt adjusted Tm, primer balance, and a suggested annealing range.
Why This Calculator Helps
Primer pairs often look acceptable by eye. Still, one primer may be much richer in GC bases. Another may be too short, too long, or poorly matched with its partner. The tool highlights those differences before a reaction is prepared. It also gives a pair average and the lower primer Tm. That lower value is important because the weaker primer often limits annealing.
Formula Logic
The short primer estimate uses the Wallace rule. It adds two degrees for each A or T base. It adds four degrees for each G or C base. The longer estimate uses a simple salt correction. It combines GC percentage, sequence length, and monovalent salt level. This is not a replacement for a validated lab protocol. It is a screening aid for fast planning and record keeping.
Using the Results
Start by entering the forward primer. Add the reverse primer when you want pair guidance. Set primer concentration and salt values to match your reaction notes. Choose whether to include a Q5 adjustment. Press Calculate. The result appears above the form. Review the warning notes before using the suggested temperature.
Good PCR Practice
A calculated value should not be treated as final proof. Run a gradient when the template is difficult, GC rich, or very long. Use the cleanest primer pair you can design. Avoid strong primer dimers. Keep notes for every run. Download the CSV file for spreadsheets. Download the PDF file for a compact report. Together, these records make troubleshooting easier and faster.
Practical Notes
Use matched primers when possible. Keep both Tm values close. A difference above five degrees may need redesign. Check the full amplicon plan too. Extension time, template amount, cycle count, and additives can change performance. Clean calculations support better choices during routine PCR work.