1. What is DNA Oligo Molecular Weight?

The molecular weight (MW) of a DNA oligonucleotide is the sum of the molecular weights of its constituent nucleotides, adjusted for water molecules lost during polymerization. It's essential for various molecular biology applications including PCR, sequencing, and hybridization.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• Base masses: A=313.21, T=304.20, C=289.18, G=329.21 g/mol
• 18.015 g/mol — Molecular weight of water (lost during phosphodiester bond formation)
• n — Number of bases in the oligo

Explanation: The calculator sums the molecular weights of individual bases and subtracts the weight of water molecules lost during polymerization (one less than the number of bases).

3. Importance of Molecular Weight Calculation

Details: Knowing the molecular weight is crucial for:

• Determining oligo concentration
• Calculating molar ratios for experiments
• Designing primers with similar melting temperatures
• Estimating purification yields

4. Using the Calculator

Tips:

• Enter the DNA sequence in 5' to 3' direction
• Only standard bases (A, T, C, G) are accepted
• Case insensitive (ATGC or atgc both work)
• Sequence length is limited to 100 bases for practical purposes

5. Frequently Asked Questions (FAQ)

Q1: Does this calculator account for modified bases?
A: No, this calculator only works for standard DNA bases (A, T, C, G). Modified bases require special calculations.

Q2: How accurate is this calculation?
A: The calculation is theoretically accurate for standard DNA oligos under normal conditions. Actual measured weights may vary slightly due to isotopic distribution.

Q3: What about single-stranded vs double-stranded DNA?
A: This calculator provides the molecular weight for single-stranded DNA. Double-stranded DNA would be approximately twice this value.

Q4: Does it include 5' phosphate groups?
A: No, this calculates the molecular weight of the oligo without any terminal modifications.

Q5: Can I calculate molecular weight for RNA?
A: No, this is for DNA only. RNA has different base compositions (U instead of T) and slightly different molecular weights.