Mixed-Mode Chromatography Resins

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-27

Quick Answer

Mixed-mode chromatography resins combine two or more interaction mechanisms, such as anion exchange and hydrophobic interaction, on a single ligand to create orthogonal selectivity for proteins that resist purification on single-mode resins.
Select a mixed-mode resin based on the target protein's isoelectric point, hydrophobicity, and the contaminants that co-elute in your current single-mode step, then screen pH and salt conditions in small-scale trials before scaling.
Mixed-mode resins require careful method development because simultaneous interactions complicate prediction, and no single resin formulation works universally across different protein classes.

At a Glance

Resin Type	Interaction Mechanisms	Typical Application	Key Limitation
Anion-exchange/hydrophobic mixed-mode	Electrostatic attraction plus hydrophobic interaction	Capture of acidic proteins from complex lysates where contaminants are hydrophobic	Binding may require high salt that also promotes unwanted hydrophobic aggregation
Cation-exchange/hydrophobic mixed-mode	Electrostatic attraction plus hydrophobic interaction	Purification of basic proteins or antibodies from clarified cell culture	Elution often requires both pH and salt changes, complicating buffer exchange
Multimodal ligand with hydrogen bonding	Electrostatic, hydrophobic, and hydrogen-bonding interactions	Flow-through polishing to remove aggregates and host-cell proteins	Selectivity is highly sensitive to pH, so small pH drift changes the separation profile

Understanding Mixed-Mode Chromatography

Mixed-mode chromatography refers to a class of chromatographic resins in which the ligand on the stationary phase presents more than one type of interaction site to the protein being purified. The most common combinations are ion exchange with hydrophobic interaction, but some resins also incorporate hydrogen bonding or thiophilic interactions. These resins are sometimes called multimodal chromatography resins, and the terms are used interchangeably in the literature.

The practical reason for using a mixed-mode resin is that some proteins do not behave well on a single-mode column. A protein may bind to an anion exchanger but co-elute with a persistent contaminant that has a similar charge. Alternatively, a protein may be too hydrophobic for a standard hydrophobic interaction column, causing it to bind irreversibly or precipitate. Mixed-mode resins provide an additional dimension of selectivity because the protein must satisfy two or more interaction requirements to bind and elute in a given condition.

The molecular mechanism is straightforward. The ligand contains a charged group, such as a quaternary amine or a carboxyl group, and a hydrophobic group, such as a phenyl or butyl moiety. When the mobile phase conditions are set so that the protein carries a net charge opposite to the ligand, electrostatic attraction occurs. At the same time, if the mobile phase contains a salt concentration that promotes hydrophobic interactions, the hydrophobic portion of the ligand can interact with hydrophobic patches on the protein surface. The protein binds only when both interactions are favorable, and it elutes when either interaction is disrupted.

This dual requirement creates a selectivity that is not available on a single-mode resin. For example, two proteins with identical net charge but different surface hydrophobicity will bind differently to a mixed-mode resin even though they would behave identically on a pure ion-exchange resin. Conversely, two proteins with similar hydrophobicity but different charge will separate on the mixed-mode resin even though they would co-elute on a pure hydrophobic resin.

The practical consequence is that mixed-mode resins are often used for the difficult separations that remain after a conventional purification scheme has been attempted. They are also used as a capture step for proteins that are unstable at the high salt concentrations required for hydrophobic interaction chromatography, or for proteins that do not bind well to ion-exchange resins at the pH values that are compatible with protein stability.

Core Principles of Mixed-Mode Interactions

Electrostatic Interactions in Mixed-Mode Resins

The electrostatic component of a mixed-mode resin works on the same principle as a conventional ion-exchange resin. The resin carries a charged group, and the protein carries a net surface charge that depends on the pH of the mobile phase relative to the protein's isoelectric point. When the pH is below the isoelectric point, the protein is positively charged and will bind to a cation-exchange ligand. When the pH is above the isoelectric point, the protein is negatively charged and will bind to an anion-exchange ligand.

In a mixed-mode resin, the electrostatic interaction is one of two or more forces that determine binding. The pH of the mobile phase therefore has a dual role. It controls the protein's net charge, and it also controls the ionization state of the ligand if the ligand has a titratable group. Some mixed-mode ligands contain a group that changes charge with pH, which means the resin itself can switch between a positively charged and a negatively charged state as the pH changes. This property is used in some commercial resins to allow both capture and elution to be controlled by pH alone.

The practical implication is that pH is the most important variable to screen when developing a mixed-mode purification method. A small change in pH can change the protein from a binding state to a nonbinding state, and it can also change the selectivity between the target protein and a contaminant. The pH range that is useful for a given protein is limited by the protein's stability, so the screening should be done within the pH range where the protein remains soluble and active.

Hydrophobic Interactions in Mixed-mode Resins

The hydrophobic component of a mixed-mode resin is the same type of interaction that occurs in a hydrophobic interaction chromatography resin. The resin ligand contains a hydrophobic group, and the protein binds to it when the mobile phase has a high concentration of a salt that promotes hydrophobic interactions. Salts such as ammonium sulfate and sodium citrate are commonly used to promote hydrophobic binding because they are strongly hydrated and therefore increase the surface tension of the water, which drives the protein onto the hydrophobic ligand.

In a mixed-mode resin, the hydrophobic interaction is often used to provide the selectivity that is missing from the electrostatic interaction. Two proteins with the same net charge may have different surface hydrophobicity, and the mixed-mode resin will separate them based on the hydrophobic difference. The salt concentration in the mobile phase is the primary control for the hydrophobic interaction, and it is the second variable to screen after pH.

The combination of pH and salt concentration creates a two-dimensional space that can be explored to find the conditions where the target protein binds and the contaminants do not. This is a more complex optimization than a single-mode resin, but it also provides more opportunities to find a selective condition.

Hydrogen Bonding and Other Interactions

Some mixed-mode resins include a ligand that can form hydrogen bonds with the protein. The hydrogen bonding interaction is weaker than the electrostatic and hydrophobic interactions, but it can contribute to the overall selectivity of the resin. The hydrogen bonding is often provided by a group such as an amide or a hydroxyl group on the ligand.

The presence of a hydrogen bonding group means that the resin can interact with the protein in a way that is not purely charge-based or hydrophobicity-based. This can be useful for separating proteins that have similar charge and hydrophobicity but differ in the arrangement of hydrogen bond donors and acceptors on their surface.

The practical consequence is that the mixed-mode resin may have a selectivity that is difficult to predict from the protein's primary sequence or even from its three-dimensional structure. The selectivity must be determined empirically by running a small-scale binding and elution experiment with the actual protein sample.

Practical Workflow for Mixed-Mode Purification

Step 1: Define the Separation Problem

The first step in using a mixed-mode resin is to define the separation problem in concrete terms. The researcher should know the identity of the target protein, its isoelectric point, its approximate hydrophobicity, and the identity of the contaminants that are present in the starting material. The starting material is typically a cell lysate, a clarified culture supernatant, or a partially purified protein solution.

The separation problem should be stated as a specific goal. For example, the goal might be to remove a single contaminant that co-elutes with the target protein on the current ion-exchange column, or the goal might be to capture the target protein from a dilute feed stream with a high binding capacity. The goal determines which mixed-mode resin chemistry is most likely to be useful.

The researcher should also consider the scale of the purification. A small-scale screening experiment can be done with a few milliliters of resin in a gravity column or a spin column, but a large-scale purification requires a chromatography system with a pump, a detector, and a fraction collector. The screening conditions should be developed at small scale and then scaled up with the same resin and the same buffer conditions.

Step 2: Select the Resin Chemistry

The choice of resin chemistry depends on the properties of the target protein and the contaminants. The following general rules apply:

If the target protein is basic and the contaminants are acidic, a cation-exchange/hydrophobic mixed-mode resin may be useful.
If the target protein is acidic and the contaminants are basic, an anion-exchange/hydrophobic mixed-mode resin may be useful.
If the target protein is hydrophobic and the contaminants are hydrophilic, a mixed-mode resin with a strong hydrophobic component may be useful.
If the target protein is hydrophilic and the contaminants are hydrophobic, a mixed-mode resin with a weak hydrophobic component may be useful.

These rules are only starting points. The actual selectivity must be determined experimentally because the surface properties of the protein are not fully described by the isoelectric point or the average hydrophobicity.

Step 3: Design the Binding and Elution Conditions

The binding and elution conditions are designed by varying the pH and the salt concentration. The binding condition is the pH and salt concentration at which the target protein binds to the resin and the contaminants do not. The elution condition is the pH or salt concentration at which the target protein is released from the resin.

A typical screening experiment uses a small column with a few milliliters of resin. The resin is equilibrated with a binding buffer, the sample is applied, and the flow-through is collected. The column is then washed with the binding buffer, and the bound protein is eluted with a series of buffers that change the pH or the salt concentration. The fractions are collected and analyzed by a protein assay or by gel electrophoresis.

The screening should be done in a systematic way. The pH should be varied in small steps, such as 0.5 pH units, and the salt concentration should be varied in small steps, such as 0.1 M. The results should be recorded in a table that shows the binding and elution behavior at each condition.

Step 4: Optimize the Separation

The initial screening will identify a set of conditions where the target protein binds and elutes. The next step is to optimize the separation by adjusting the conditions to maximize the purity and the recovery of the target protein. The optimization may involve changing the pH gradient, the salt gradient, or the column length.

The optimization should be done with the actual starting material, not with a pure sample of the target protein. The reason is that the contaminants in the starting material will affect the binding and elution behavior of the target protein, and the separation must be tested under the real conditions.

The optimization should also be done with a quantitative assay for the target protein. The assay should be specific for the target protein and should not be affected by the contaminants. The assay should be validated before the optimization begins, and the same assay should be used throughout the optimization.

Step 5: Scale Up and Validate

Once the separation conditions are optimized at the small scale, the method is scaled up to the larger column that will be used for the actual purification. The scale-up should be done by keeping the same linear flow rate, the same bed height, and the same buffer conditions. The column volume is increased, and the sample volume is increased in proportion to the column volume.

The scaled-up method should be validated by running the purification several times with the same starting material and the same conditions. The purity and the recovery of the target protein should be consistent between the runs. The validation should also include a test for the removal of the contaminants that were the original problem.

Options and Tradeoffs in Mixed-Mode Resin Selection

Anion-Exchange/Hydrophobic Mixed-Mode Resins

Anion-exchange/hydrophobic mixed-mode resins combine a positively charged ligand with a hydrophobic group. The resin binds proteins that are negatively charged at the binding pH, and the hydrophobic group provides an additional interaction that can be used to separate proteins with the same charge.

The main advantage of this resin type is that it can be used at a pH where the target protein is negatively charged, which is often the pH where the protein is most stable. The main disadvantage is that the hydrophobic interaction may be too strong, causing the protein to bind so tightly that it is difficult to elute without denaturing the protein.

The elution is typically done by increasing the pH to reduce the electrostatic interaction and by decreasing the salt concentration to reduce the hydrophobic interaction. The elution can be done as a step or as a gradient, and the gradient is often more effective for separating the target protein from the contaminants.

Cation-Exchange/Hydrophobic Mixed-Mode Resins

Cation-exchange/hydrophobic mixed-mode resins have a negatively charged group and a hydrophobic group. They are used for proteins that are positively charged at the binding pH, which is typically a pH below the isoelectric point.

The advantage of this resin type is that it can be used for basic proteins that are difficult to purify with anion-exchange resins. The disadvantage is that the binding pH may be below the pH where the protein is stable, and the protein may precipitate or lose activity during the binding step.

The elution is typically done by lowering the pH to reduce the electrostatic interaction, or by decreasing the salt concentration to reduce the hydrophobic interaction. The elution conditions must be chosen to avoid the precipitation of the protein.

Multi-Modal Resins with Hydrogen Bonding

Some mixed-mode resins include a hydrogen bonding group in addition to the electrostatic and hydrophobic groups. These resins are sometimes called "multi-modal" resins because they have more than two interaction mechanisms.

The advantage of these resins is that they can provide a very high selectivity for a specific protein. The disadvantage is that the selectivity is difficult to predict, and the method development can be more time-consuming because there are more variables to screen.

The elution of these resins is often done by changing the pH, which affects all three interactions. The pH change can be used to disrupt the electrostatic interaction, the hydrophobic interaction, and the hydrogen bonding interaction at the same time.

Records and Measurements for Mixed-Mode Purification

What to Record During Method Development

The method development for a mixed-mode purification should be documented in a laboratory notebook or an electronic record. The record should include the following information:

The identity and lot number of the resin
The column dimensions and the bed volume
The buffer composition and the pH of each buffer
The flow rate and the sample volume
The binding, washing, and elution conditions
The fraction volumes and the analysis of each fraction

The record should also include the observations that are made during the run, such as the appearance of the column, the pressure, and the UV absorbance. These observations can be useful for troubleshooting if the purification does not work as expected.

How to Measure the Purification Performance

The performance of the mixed-mode purification is measured by the purity and the recovery of the target protein. The purity is the fraction of the total protein that is the target protein, and the recovery is the fraction of the target protein that is recovered in the elution.

The purity is typically measured by SDS-PAGE or by a specific activity assay. The SDS-PAGE is a qualitative method that shows the protein bands, and the specific activity assay is a quantitative method that measures the activity of the target protein per unit of total protein.

The recovery is measured by comparing the total amount of the target protein in the starting material with the total amount in the elution. The recovery is expressed as a percentage, and it should be close to 100% for a good purification.

The Role of Protein Quantification

Protein quantification is an essential part of the purification method development. The protein concentration in the starting material, the flow-through, the wash, and the elution must be measured to calculate the recovery and the purity.

The protein quantification method should be validated for the specific protein and the specific buffer. The method should be linear over the range of concentrations that are measured, and the method should not be affected by the buffer components. The validation should include a standard curve and a test for the interference of the buffer.

The protein quantification method should be the same throughout the purification development, so that the results are comparable. The method should be documented in the laboratory notebook, and the standard curve should be recorded.

Common Failure Patterns and Troubleshooting

The Protein Does Not Bind to the Resin

The most common failure in a mixed-mode purification is that the protein does not bind to the resin. The cause is usually that the pH or the salt concentration is not correct for the protein. The protein may not have the correct net charge at the pH, or the hydrophobic interaction may not be strong enough at the salt concentration.

The troubleshooting step is to change the pH or the salt concentration and repeat the binding experiment. The pH should be changed in the direction that increases the net charge of the protein, and the salt concentration should be changed in the direction that increases the hydrophobic interaction.

The Protein Binds Too Tightly and Does Not Elute

The opposite failure mode is that the protein binds too tightly and does not elute. The cause is usually that the hydrophobic interaction is too strong, or that the pH change is not sufficient to disrupt the electrostatic interaction.

The troubleshooting step is to change the elution conditions. The pH should be changed in the direction that reduces the net charge of the protein, and the salt concentration should be changed in the direction that reduces the hydrophobic interaction. The elution may also be done with a gradient instead of a step.

The Protein Elutes with the Contaminants

The third failure mode is that the protein elutes with the contaminants. The cause is that the selectivity of the resin is not sufficient to separate the protein from the contaminants under the chosen conditions.

The troubleshooting step is to change the binding or the elution conditions to improve the selectivity. The pH or the salt concentration should be changed in small steps, and the fractions should be analyzed to determine the best conditions.

The Protein Is Denatured or Inactivated During the Purification

The fourth failure mode is that the protein is denatured or inactivated during the purification. The cause is usually that the pH or the salt concentration is too extreme for the protein.

The troubleshooting step is to change the conditions to a less extreme pH or salt concentration. The protein may also be stabilized by adding a stabilizing agent, such as a glycerol or a detergent, to the buffer.

Biosafety and Regulatory Context for Mixed-Mode Purification

Biosafety Principles for Protein Purification

The purification of proteins from biological sources is subject to the biosafety principles that are described in the Biosafety in Microbiological and Biomedical Laboratories. The researcher should perform a risk assessment before starting the purification, and the risk assessment should consider the source of the starting material, the potential for the presence of infectious agents, and the procedures that will be used.

The risk assessment should be done in consultation with the institutional biosafety committee, and the work should be done at the appropriate biosafety level. The researcher should use the appropriate personal protective equipment, and the work should be done in a biosafety cabinet if the risk assessment requires it.

The purification of proteins from recombinant organisms is also subject to the NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules. The researcher must follow the guidelines for the containment of the recombinant organism and the disposal of the waste.

The Safety of the Buffers and the Resin

The buffers that are used in the mixed-mode purification may contain salts, acids, bases, or organic solvents. The researcher must be aware of the hazards of the buffers and use the appropriate personal protective equipment. The buffers should be prepared in a well-ventilated area, and the waste should be disposed of according to the institutional regulations.

The resin itself is a solid material that is not hazardous in its dry form, but the resin may contain a preservative or a storage solution that is hazardous. The researcher should read the safety data sheet for the resin and follow the recommendations.

The Institutional Oversight

The purification of a protein from a biological source is a laboratory procedure that is subject to the institutional oversight. The researcher must have the approval of the institutional biosafety committee for the work, and the work must be done according to the approved protocol. The researcher must also follow the institutional regulations for the use of the laboratory equipment and the disposal of the waste.

The institutional oversight is described in the NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules, and the researcher should be familiar with the guidelines before starting the work.

Quality Control and Reproducibility

The Role of Standards and Calibration

The quality of the mixed-mode purification is dependent on the quality of the buffers and the resin. The buffers should be prepared with the same quality of water and the same quality of the salts, and the pH should be measured with a calibrated pH meter. The resin should be stored according to the manufacturer's instructions, and the resin should be tested for the performance before the use.

The standards and the calibration are described in the NIST Laboratory Programs. The researcher should use the standards and the calibration to ensure that the measurements are accurate and reproducible.

The Reproducibility of the Purification

The purification method should be reproducible across the runs. The reproducibility is measured by the variation in the purity and the recovery of the target protein. The variation should be small, and the method should be validated by running the purification multiple times.

The reproducibility is affected by the quality of the starting material, the quality of the buffers, and the quality of the resin. The starting material should be prepared in the same way for each run, and the buffers should be prepared fresh for each run. The resin should be regenerated and stored according to the manufacturer's instructions.

The Reporting of the Purification Results

The purification results should be reported in a way that is transparent and reproducible. The report should include the details of the method, the conditions, and the results. The report should also include the validation of the protein assay and the quality of the starting material.

The reporting of the results is described in the MIQE Guidelines for the qPCR, and the same principles of transparency and the control apply to the protein purification. The report should be detailed enough that another researcher can reproduce the purification.

Practical Implementation Steps

Step 1: Prepare the Starting Material

The starting material should be prepared according to the standard protocol for the protein. The starting material should be clarified to remove the cell debris and the particulate matter, and the starting material should be in a buffer that is compatible with the mixed-mode resin.

The starting material should be analyzed for the protein concentration and the purity before the purification. The analysis should be done with the same protein assay that will be used for the purification.

Step 2: Equilibrate the Column

The column should be packed with the mixed-mode resin and equilibrated with the binding buffer. The binding buffer should be the buffer that is used for the binding step, and the column should be equilibrated with at least 5 column volumes of the binding buffer.

The equilibration should be done at the same flow rate that will be used for the sample loading. The pH and the conductivity of the column effluent should be the same as the pH and the conductivity of the binding buffer.

Step 3: Load the Sample

The sample should be loaded onto the column at the same flow rate that was used for the equilibration. The sample volume should be small enough that the protein binds to the resin, and the sample should be loaded in a single step or in a series of steps.

The flow-through should be collected and analyzed for the protein concentration. The flow-through should contain the contaminants that do not bind to the resin, and the flow-through should be analyzed to determine the binding efficiency.

Step 4: Wash the Column

The column should be washed with the binding buffer to remove the contaminants that are not bound to the resin. The wash should be done with at least 5 column volumes of the binding buffer, and the wash should be collected and analyzed.

The wash should be continued until the absorbance of the wash is the same as the absorbance of the binding buffer. The wash should not contain the target protein, and the wash should be analyzed to confirm that the target protein is not being lost.

Step 5: Elute the Target Protein

The target protein should be eluted with the elution buffer. The elution buffer should be the buffer that was determined in the screening experiment, and the elution should be done as a step or as a gradient.

The elution should be collected in fractions, and the fractions should be analyzed for the protein concentration and the purity. The fractions that contain the target protein should be pooled, and the pooled fractions should be analyzed for the recovery and the purity.

Step 6: Regenerate the Column

The column should be regenerated after the elution. The regeneration should remove the proteins that are still bound to the resin, and the regeneration should be done with a buffer that is strong enough to remove the bound proteins.

The regeneration buffer should be a high salt buffer or a low pH buffer, and the regeneration should be done with at least 5 column volumes of the regeneration buffer. The column should then be re-equilibrated with the binding buffer for the next run.

The Role of the Mixed-Mode Resin in the Purification Scheme

The mixed-mode resin is often used as a capture step or as a polishing step in the purification scheme. The capture step is the first step in the purification, and the capture step is used to concentrate the target protein and to remove the bulk of the contaminants. The polishing step is the last step in the purification, and the polishing step is used to remove the remaining contaminants and to achieve the final purity.

The mixed-mode resin can be used for either the capture or the polishing step, depending on the properties of the protein and the contaminants. The mixed-mode resin is often used for the capture step when the protein is difficult to bind to a single-mode resin, and the mixed-mode resin is often used for the polishing step when the protein is difficult to separate from the contaminants.

The mixed-mode resin can also be used in a flow-through mode, where the target protein does not bind to the resin and the contaminants bind to the resin. The flow-through mode is useful for the polishing step, because the target protein is recovered in the flow-through and the contaminants are removed.

The Limitations of the Mixed-Mode Resin

The mixed-mode resin has several limitations that should be considered before the use. The first limitation is that the selectivity of the resin is difficult to predict, and the method development can be time-consuming. The second limitation is that the binding and the elution conditions are often more extreme than the conditions for a single-mode resin, and the protein may be denatured or inactivated.

The third limitation is that the mixed-mode resin may have a lower binding capacity than a single-mode resin, because the protein must satisfy the multiple interactions to bind. The fourth limitation is that the mixed-mode resin may be more expensive than a single-mode resin, and the cost of the resin should be considered in the purification scheme.

The limitations should be considered when the mixed-mode resin is chosen for the purification. The mixed-mode resin should be used when the single-mode resin is not sufficient, and the mixed-mode resin should be used with the understanding of the limitations.

The Professional Escalation Criteria

The researcher should escalate the problem to a more experienced colleague or to the manufacturer of the resin when the purification does not work as expected. The escalation should be done when the troubleshooting steps have been exhausted and the problem is not resolved.

The escalation should include the details of the method, the conditions, and the results. The escalation should also include the details of the troubleshooting steps that have been tried. The professional should be able to provide the advice on the method or the conditions.

The escalation should also be done when the protein is not stable under the conditions, or when the protein is not pure enough for the intended use. The professional should be able to provide the advice on the alternative methods or the alternative resins.

Frequently Asked Questions

What is the difference between mixed-mode and single-mode chromatography?

Mixed-mode chromatography uses a resin with more than one interaction mechanism, such as ion exchange and hydrophobic interaction, while single-mode chromatography uses a resin with only one interaction mechanism. The mixed-mode resin provides a different selectivity because the protein must satisfy multiple interactions to bind.

When should I use a mixed-mode resin instead of a single-mode resin?

A mixed-mode resin should be used when a single-mode resin does not provide sufficient selectivity for the target protein. The mixed-mode resin is often used for proteins that are difficult to purify with a single-mode resin, such as proteins that co-elute with contaminants or proteins that are not stable under the conditions of the single-mode resin.

What are the most common mixed-mode resin chemistries?

The most common mixed-mode resin chemistries are the anion-exchange/hydrophobic, the cation-exchange/hydrophobic, and the multi-modal with hydrogen bonding. The choice of the resin chemistry depends on the properties of the target protein and the contaminants.

How do I choose the binding and elution conditions for a mixed-mode resin?

The binding and elution conditions are chosen by screening the pH and the salt concentration. The pH is chosen to give the protein the correct net charge, and the salt concentration is chosen to give the correct hydrophobic interaction. The conditions are optimized by varying the pH and the salt concentration in small steps.

What is the most common failure mode in a mixed-mode purification?

The most common failure mode is that the protein does not bind to the resin. The cause is usually that the pH or the salt concentration is not correct for the protein. The troubleshooting step is to change the pH or the salt concentration and repeat the binding experiment.

How do I validate the protein assay for the mixed-mode purification?

The protein assay should be validated by preparing a standard curve and testing the interference of the buffer. The assay should be specific for the target protein, and the assay should be reproducible across the runs. The validation should be documented in the laboratory notebook.

What is the role of the biosafety in the mixed-mode purification?

The biosafety is the risk assessment and the containment of the biological material. The researcher must perform a risk assessment before the purification, and the work must be done according to the institutional biosafety regulations. The biosafety is described in the Biosafety in Microbiological and Biomedical Laboratories.

How do I scale up the mixed-mode purification method?

The mixed-mode purification method is scaled up by increasing the column volume and the sample volume in proportion. The linear flow rate and the bed height are kept the same, and the buffer conditions are kept the same. The scaled-up method is validated by running the purification multiple times.

Using the Evidence

Source	Best use in this topic	Important limitation
Molecular Biology and Laboratory Methods	official guidance	Check the linked page for current local requirements
Biosafety in Microbiological and Biomedical Laboratories	official guidance	Check the linked page for current local requirements
NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules	official guidance	Check the linked page for current local requirements

Related Molecular Biology Guides

References and Further Reading

Molecular Biology and Laboratory Methods. National Library of Medicine.
Biosafety in Microbiological and Biomedical Laboratories. CDC and NIH.
NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules. National Institutes of Health.
Addgene Protocols. Addgene.
MIQE Guidelines. Clinical Chemistry.
NIST Laboratory Programs. National Institute of Standards and Technology.
A high-throughput approach to developing and optimizing mixed-mode membrane chromatography for protein purification.. Biotechnology progress, 2023.
Mixed-Mode Chromatography and Its Role in Monoclonal Antibody Purification.. Methods in molecular biology (Clifton, N.J.), 2023.
Isoform Separation by a Mixed-mode Resin, TOYOPEARL MX-Trp-650M.. Current protein & peptide science, 2019.
Mixed Mode Chromatography: A Novel Way Toward New Selectivity.. Current protein & peptide science, 2019.
Non-Affinity Purification of Antibodies.. Antibodies (Basel, Switzerland), 2023.

This article is educational and does not replace validated laboratory procedures, institutional biosafety review, manufacturer instructions, or professional interpretation.