2.5
mL
2,500
μL
0
mM
2.5
mL
2,500
μL
0
mM
Resuspension is the process of re-dissolving a dried, pelleted, or precipitated compound in a solvent to achieve a desired mass concentration (mg/mL). While similar to reconstitution, resuspension typically refers to preparing solutions where the target concentration is expressed in mass-per-volume units rather than molar units. This is common when working with polymers, complex natural products, crude extracts, antibodies, and materials where an exact molecular weight may not be known.
The resuspension formula is straightforward: V = mass / C, where V is the volume of solvent to add, mass is the amount of compound, and C is the desired concentration. This calculator takes mass in milligrams and desired concentration in mg/mL to compute the required volume. Optionally, if you provide the molecular weight, it also calculates the equivalent molar concentration in millimolar.
Proper resuspension technique is essential in pharmaceutical formulations, protein biochemistry, materials science, and natural product chemistry. The choice of solvent, temperature, agitation method, and concentration all affect whether the compound dissolves completely and remains stable in solution. This calculator helps you determine the exact volume needed for reproducible solution preparation.
The resuspension calculation is based on the definition of mass concentration:
C = mass / V, therefore V = mass / C
Where:
The result is expressed in both mL and μL for convenience. If the molecular weight is provided (optional advanced input), the calculator also computes the equivalent molar concentration:
Molarity (mM) = C (mg/mL) / Mw (g/mol) × 1000
This conversion uses the fact that mg/mL = g/L, and molarity = (g/L) / (g/mol) = mol/L. Multiplying by 1000 gives mM.
Key considerations for resuspension:
The volume output tells you how much solvent to add to achieve the target concentration. A common stock concentration for proteins and antibodies is 1-10 mg/mL. For small molecules, 10-50 mg/mL stocks are typical. If the calculated volume seems impractically small (below your pipette's accuracy), reduce the target concentration.
The optional molar concentration output allows comparison with literature values often reported in molar units. For example, 10 mg/mL of a 500 g/mol compound equals 20 mM.
Inputs
Results
Resuspending 100 μg (0.1 mg) of an IgG antibody (MW ≈ 150,000 g/mol) in 100 μL of PBS gives 1 mg/mL stock — a standard working concentration for Western blot and immunoassay applications. The molar concentration is 6.7 nM.
Inputs
Results
Dissolving 50 mg of crude plant extract in 2 mL of DMSO gives a 25 mg/mL stock. Since crude extracts have no single molecular weight, the molar concentration is not applicable (molecular weight set to 0).
The terms are often used interchangeably, but reconstitution specifically means dissolving a lyophilized (freeze-dried) material back into solution, while resuspension more broadly refers to re-dissolving or dispersing any solid material in a liquid. In practice, reconstitution usually targets molar concentrations, while resuspension often uses mass concentrations (mg/mL).
Mass concentration (mg/mL) is preferred when the molecular weight is unknown (crude extracts, polymer mixtures), approximate (heterogeneous biomolecules like polyclonal antibodies), or irrelevant to the application. Protein concentrations are almost always expressed in mg/mL because protein activity correlates with mass rather than mole count.
Use an analytical balance with 0.01 mg or 0.001 mg readability for sub-milligram quantities. For very small amounts (below 1 mg), some suppliers provide pre-weighed vials with a certified mass. Alternatively, dissolve in a larger volume to reduce the impact of weighing error, then dilute further as needed.
If the material does not fully dissolve, it may be above its solubility limit, or the solvent may be incompatible. Try adding more solvent, switching solvents, warming gently, or sonicating. For some applications (e.g., nanoparticle suspensions), a uniform suspension is acceptable if kept well-mixed during use.
Follow the manufacturer's recommendations. General guidelines: aqueous protein solutions at 4°C for short-term (days) or −20°C/−80°C for long-term. DMSO stocks at −20°C. Add preservatives (e.g., 0.02% sodium azide) to prevent microbial growth in buffer solutions stored at 4°C. Aliquot to avoid freeze-thaw cycles.
Yes: mg/mL = g/L = 1000 ppm (for aqueous solutions). To convert to molarity: M = (mg/mL) / Mw × 1000, where Mw is in g/mol. To convert to % w/v: % = (mg/mL) / 10. For example, 10 mg/mL = 10 g/L = 1% w/v.
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