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Emirate Peptides
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Peptide calculator

Two calculators for laboratory work. The first gives the molecular mass of a peptide from its sequence. The second gives the concentration of a solution, in mg/mL and in molarity, from what you weighed and the volume you made it up to.

Neither calculates a dose. They are for preparing solutions for experiments and for checking a certificate of analysis.

  1. Molecular mass from a sequence

Length
15 residues
Molecular formula
C62H98N16O22
Monoisotopic mass
1418.7042 Da
Average molecular weight
1419.54 g/mol
[M+H]⁺
1419.7114
[M+2H]²⁺
710.3594
[M+3H]³⁺
473.9087

How it works. It adds the residue mass of each amino acid, then one water for the two free ends, and adjusts for the modifications you tick: an acetyl group adds 42.011 Da, an amide in place of the C-terminal acid takes away 0.984 Da, and each disulfide bridge takes away two hydrogens. Amino acid codes lists the residue masses.

Use it to check a certificate. The mass measured by mass spectrometry on a batch certificate should match the mass expected from the sequence. If the certificate reports an [M+H]⁺ ion, expect the monoisotopic mass plus 1.007.

  1. Concentration of a solution

mg
mL
g/mol
%
%
Concentration
1 mg/mL
Molar concentration
0.7045 mM
704.5 µM
Target peptide in the powder
4.195 mg
Target peptide concentration
0.8389 mg/mL
591 µM

How it works.

  • Concentration (mg/mL) = mass (mg) ÷ volume (mL).
  • Molarity (mmol/L) = concentration (mg/mL) ÷ molecular weight (g/mol) × 1,000.
  • Target peptide = mass × net peptide content × HPLC purity.

Why the last line matters. A peptide powder is part water and counter-ion. Five milligrams of a powder with 85.0% net peptide content and 98.7% purity holds 4.195 mg of the peptide itself. Leave that out and every concentration you report is about 16% too high. Peptide purity explained

What this calculator is not

It is not a dosing or injection calculator. It does not convert to syringe units, and we do not provide one that does. Our products are for laboratory research and for cosmetic manufacturing, and we give no advice on use in people.

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