Murine IgG1 binds Protein A weakly, so Protein G is the standard capture ligand for most mouse monoclonals — but the format choice is narrower than for Protein A. Packed-bed Protein G resins dominate the lab scale; for higher throughput, MonoCore™ Protein G offers recombinant Protein G on a cross-linked cellulose monolith with a dynamic binding capacity of 10 mg IgG/mL, a 15 µm channel size and UNF 10-32 connectors, in 1.8 mL and 5.4 mL capsules that run on any standard FPLC system. Because transport through the monolith is convective, capacity stays largely independent of flow rate, and capture cycles run at up to ten times the flow rate a packed-bed Protein G resin sustains.
Why Protein G, not Protein A
Ligand specificity, not preference, drives this choice.
Human IgG1, IgG2, IgG4 bind both ligands strongly.
Human IgG3 binds Protein A weakly and Protein G strongly.
Mouse IgG1 — the decisive case — binds Protein A weakly and Protein G strongly.
Mouse IgG2a, IgG2b and IgG3 bind both ligands well.
Rat IgG binds Protein A weakly to moderately depending on subclass, and Protein G more strongly.
Goat, sheep, bovine and equine IgG bind Protein A weakly and Protein G strongly.
Canine and feline IgG bind Protein A unevenly across subclasses; Protein G gives broader coverage.
Two practical consequences follow.
A large share of murine monoclonals from hybridoma lines is IgG1 — exactly the subclass Protein A handles poorly. Running it on Protein A costs yield in the capture step.
Veterinary antibody programmes with caninised and felinised formats face the same problem, because canine and feline IgG subclasses bind Protein A unevenly. Protein G is the more reliable ligand there.
One detail worth checking on any product: native Protein G also binds serum albumin. Recombinant Protein G ligands have the albumin-binding domain removed. MonoCore™ Protein G uses recombinant Protein G.
What is available, and where each format fits
Spin columns and gravity formats cover microgram to milligram amounts. They are the fastest path for a single sample, but they are not a process step.
Packed-bed Protein G resin covers lab to pilot scale and is well established across suppliers. It is diffusion-limited: flow rate and cycle time are capped by pressure and bed compression.
Cellulose monolith — MonoCore™ Protein G covers lab to pilot scale in 1.8 mL and 5.4 mL, larger on request. Transport is convective, so capacity stays largely independent of flow rate, cycles are short, and the open channel structure tolerates complex feeds. Its limit: capacity per millilitre is lower than that of a modern Protein A resin, as Protein G ligands generally are.
Membrane adsorbers with Protein G are fast and disposable, but the choice of chemistry is limited and process-scale options are few.
The binding capacity of a packed bed collapses as the flow rate rises, because the antibody has to diffuse into the bead pores. In a monolith the mobile phase flows through the channels, so residence time is set by geometry rather than by diffusion. That is why the same capture step can run in minutes instead of an hour.
Where it does not help: if the bottleneck is capacity per millilitre rather than time, a high-capacity packed-bed resin remains the more economical choice.
MonoCore™ Protein G at a glance
Ligand: recombinant Protein G
Matrix: cross-linked cellulose monolith
Dynamic binding capacity: 10 mg IgG/mL
Channel size: 15 µm standard; other sizes on request, selected per column
Format: 1.8 mL · 5.4 mL · larger on request
Connectors: UNF 10-32 coned port, 1/16″ OD tubing
Recommended flow: 15 mL/min at 1.8 mL · 45 mL/min at 5.4 mL
Maximum pressure: 0.8 MPa (8 bar)
pH stability: 4–13 long term · 2–14 short term
Capsules ship pre-assembled and connect to a standard FPLC system, a peristaltic pump or a syringe. Detailed performance data are available on request.
Frequently asked questions
Does murine IgG1 bind Protein A at all?
Weakly and inconsistently. Some IgG1 clones bind well enough to be captured, most do not. Protein G binds murine IgG1 reliably, which is why it is the default ligand for hybridoma-derived monoclonals.
Which elution conditions does Protein G need?
Protein G usually requires a lower pH than Protein A, commonly between pH 2.5 and 3.0. Neutralise immediately after elution. For formats that do not tolerate a low-pH hold, this is the step that limits the process.
Can a Protein G monolith be cleaned with sodium hydroxide?
Yes, within the limits given on the datasheet. As with every proteinaceous affinity ligand, the number of cleaning cycles — not the number of bind-and-elute cycles — determines the service life.
Is binding capacity really independent of flow rate?
Largely, not entirely. Convective transport removes the diffusion limit inside the medium; film transport and ligand kinetics still matter. In practice, capacity holds over a flow range where a packed bed would already have lost a large part of it.
What sizes are available above 5.4 mL?
Larger formats are built on request. Talk to us about the volume and the cycle time you need.