Measure Engagement to Target Proteins within Complexes: Why Context Matters

This blog was written by guest contributor Tian Yang, Associate Product Manager, Promega, in collaboration with Kristin Huwiler, Manager, Small Molecule Drug Discovery, Promega.

For target-based drug discovery programs, biochemical assays using purified target proteins are often run for initial hit discovery, as these assays are target-specific, quantitative and amenable for high-throughput screens, allowing for precise characterization of target-compound interactions. However, proteins do not act in isolation inside the cells. Instead, proteins form complexes with other cellular components to drive cellular processes, signaling cascades, and metabolic pathways. Just as the interactions between a target protein and its binding partners can influence the target function, compound engagement with target proteins can vary depending on the protein complex formed.

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At the Forefront of Biologics Characterization: Insights from Promega R&D Scientistsย 

As biologics grow more complex, so do the tools required to understand, validate, and ensure their quality. From monoclonal antibody cocktails to antibody-drug conjugates (ADCs) and cell therapies, developers are navigating new frontiers in potency, purity, and functional characterization. 

Promegaโ€™s R&D scientists have been actively contributing to this evolving dialogue through respected industry platforms like BioCompare and BEBPA. Through ongoing collaboration with industry experts, Promega scientists are developing innovative assays and strategies that address the complex challenges of biologics development and quality assurance. 

This article highlights key takeaways from five recent publications featuring Promega experts and collaborators, with insights spanning from early research to quality assurance in manufacturing. 

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Cellular Selectivity Profiling: Unveiling Novel Interactions and More Accurate Compound Specificity

This blog was written by guest contributor Tian Yang, Associate Product Manager, Promega, in collaboration with Kristin Huwiler, Manager, Small Molecule Drug Discovery, Promega.

Determining the selectivity of a compound is critical during chemical probe or drug development. In the case of chemical probes, having a clearly defined mechanism of action and specific on-target activity are needed for a chemical probe to be useful in delineating the function of a biological target of interest in cells. Similarly, optimizing a drug candidate for on-target potency and reducing off-target interactions is important in the drug development process (1,2). A thorough understanding of the selectivity profile of a drug can facilitate drug repurposing, by enabling approved therapeutics to be applied to new indications (3). Interestingly, small molecule drugs do not necessarily require the same selectivity as a chemical probe, since some drugs may benefit from polypharmacology to achieve their desired clinical outcome.

Selectivity profiling panels based on biochemical methods have commonly been used to assess compound specificity for established target classes in drug discovery and chemical probe development. Biochemical assays are target-specific and often quantitative, enabling direct measurements of compound affinities for targets of interest and facilitate comparison of compound engagement to a panel of targets. As an example, several providers offer kinase selectivity profiling services using different assay formats and kinase panels comprised of 100 to 400 kinases (4). However, just as biochemical target engagement does not always translate to cellular activity, selectivity profiles based on biochemical platforms may not reflect compound selectivity in live cells (5).

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Is Your Lab Environment Messing with Your Results? How to Spot the Signs Early

This blog was contributed by guest Avi Aggarwal, 2025 summer intern at Promega.

If you’ve ever scratched your head over inconsistent experimental results, especially ones that seem to fluctuate for no obvious reasonโ€”youโ€™re not alone. Sometimes the problem isnโ€™t your pipetting, your reagents, or even your protocol. It might be the room itself.

Changes in temperature, humidity, or even invisible dust particles can quietly throw off your results. Something as simple as moving your thermocycler under an air vent or setting up a plate reader where sunlight hits it in the afternoon could cause subtle but significant issues.

Scientist removes samples from liquid nitrogen tank, affecting the immediate laboratory environment.
Any number of things can affect the laboratory environment, from opening a cryo tank to moving an instrument under an air vent.

Our Project to Learn How Subtle Environmental Changes Can Affect Sensitive Lab Equipment

We spent some time developing an environmental anomaly detection framework aimed at helping scientists understand how subtle environmental changes can affect sensitive lab equipment and experimental results. Our team set out to monitor real-world lab conditions using temperature and humidity sensors, including live testing with a GloMaxยฎ Discover platform and Sensirion SHT45 sensors. We also worked with open-source environmental datasets to simulate a variety of lab-like conditions, such as daily cycles, sudden temperature spikes, and slow humidity drifts.

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Unlocking the Power of Live-Cell Kinetics in Degrader Development

In targeted protein degradation (TPD), timing is everything. Understanding not just whether a degrader worksโ€”but how fast, how thoroughly and how sustainablyโ€”can dramatically influence early discovery decisions. Dr. Kristin Riching (Promega) dove into the real-time world of degradation kinetics in the webinar: Degradation in Motion: How Live-Cell Kinetics Drive Degrader Optimization, sharing how dynamic data provides a clearer view of degrader performance than traditional endpoint assays.

Whether youโ€™re exploring your first PROTAC or optimizing a molecular glue series, the expertise offered in Dr. Richingโ€™s presentation gives you actionable insights that will help you connect kinetic data to better therapeutic design.

3D visualization of a protein structure within a live-cell environment, highlighting the interaction site relevant to targeted protein degradation, set against a dark cellular background to emphasize kinetic dynamics.
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How Thalidomide and Molecular Glues Are Rede๏ฌning Drug Discovery

Targeted protein degradation (TPD) is a strategy used to selectively remove proteins from cells, rather than simply blocking their activity. Traditional small-molecule drugs work by binding to a protein and inhibiting its function, leaving the protein intact. In contrast, TPD harnesses the cell waste-disposal systemโ€”in particular, the ubiquitin-proteasome pathwayโ€”to tag the target protein for destruction. Once tagged, the protein is chopped up and recycled by the proteasome, eliminating it from the cell.

Perhaps the best known TPD approach uses PROTACs (proteolysis-targeting chimeras), which are bifunctional molecules: one end binds the protein of interest, and the other recruits an E3 ubiquitin ligase. By bringing the protein and ligase together, the PROTAC triggers ubiquitin tagging and subsequent degradation.

How NanoBRET works image.

Molecular glues achieve the same end resultโ€”selective protein destructionโ€”in a different way. Instead of acting as a physical bridge between the protein and the E3 ligase, molecular glues bind to one protein (often the ligase) and subtly change its shape or surface properties, improving interaction with the target protein. This induced fit causes the target protein to be ubiquitinated without a large, two-part molecule like a PROTAC.

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ATP-Powered Proteins Beyond Kinases โ€“ and Why Helicases Are Stealing the Spotlight

This blog was written by guest author Michael Curtin, Senior Product Manager, Small Molecule Drug Discovery.

ATP is the universal energy currency of cells, and thousands of proteins outside the kinase family โ€œspendโ€ it to move cargo, remodel nucleic acids, pump ions, or fold proteins. These ATP-hydrolyzing enzymesโ€”collectively known as ATPasesโ€”span functional classes including motor proteins, transporters, chaperones, chromatin remodelers, ligases, and, crucially for genome stability, helicases.

From DNA replication to RNA processing, helicases are essential players. DNA/RNA helicases such as MCM, XPB/XPD, WRN, and members of the DDX family sit alongside AAA+ unfoldases, ABC transporters, and V-ATPasesโ€”all drawing on ATP to power their molecular work.

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Matching Luciferase Reporter Assays to Your Experimental Goals

Luciferase reporter assays are highly versatile, but their true power comes when the reporter system youโ€™ve selected is well aligned with your experimental objectives. Whether you’re tracking transcriptional changes or pathway activity, assessing miRNA/siRNA regulation, or using as a readout in CRISPR-based screens, choosing a reporter and detection assay format that fit your specific research goal is critical for meaningful, reproducible results.

You may have already read about how to choose a luciferase reporter assay, but now, we will walk through how to match luciferase reporter systemsโ€”reporter types, detection chemistries, and formatsโ€”to your specific experimental needs. While luciferases like NanoLuc have applications beyond gene expression, this blog focuses on genetic reporter applications and the workflows that support them.

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HiBiT-Based NanoBRETยฎ Assay Sheds Light on GPCRโ€“Ligand Binding in Live Cells

G-protein-coupled receptors (GPCRs) are among the most important drug targets in human biology, mediating signals across nearly every physiological system. But not all GPCRs are equally easy to studyโ€”especially those that interact with peptide ligands. These ligands tend to be flexible, fast-moving, and hard to trace in live cells by standard methods. Historically, radioligand binding assays have filled this gap, offering a way to measure peptideโ€“receptor interactions with high sensitivity. However, these assays are typically performed using isolated membrane preparations or cells under non-physiological conditions, and they donโ€™t allow for real-time or kinetic measurements.

Artistic Image of Hibit Tag

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20 Years of Organ Transplant Testing with Maxwellยฎ Instrumentation

MacKenzie Gartner, Lead Technologist at DCi, operates a Maxwellยฎ instrument.
MacKenzie Gartner, Lead Technologist at DCi, operates a Maxwellยฎ instrument.

For twenty years, the transplant lab at Dialysis Clinic, Inc. (DCi) in Nashville, TN has depended on Maxwell instruments for their automated nucleic acid purification. In fact, the lab was the first to purchase the instrument when it debuted in 2005. Today, theyโ€™ve scaled up to three of the latest Maxwellยฎ Instruments.

โ€œTheyโ€™re great little instruments,โ€ says Christina Sholar, Clinical Supervisor at DCi. โ€œI think this is our third generation, and we still have the original in the basement. We love them.โ€

Christinaโ€™s lab runs critical tests to ensure compatibility between donors and recipients for solid organ and stem cell transplants. With precious samples and urgent demands, they need tools they can depend on for high-quality results. Their Maxwellยฎ instruments help them ensure successful downstream analysis to support important clinical decisions.

Precious Samples, Urgent Timelines

A DCi lab technician adds a sample to a cartridge before loading the Maxwellยฎ instrument.
Hailey, a technician at DCi, loads a Maxwellยฎ cartridge.

Founded in 1971 as a non-profit dialysis clinic, DCi now supports a broad spectrum of kidney health issues, including transplants. The company has also expanded its operations to support organ transplants through federally designated organ procurement organizations. Christinaโ€™s lab runs the tests to ensure compatibility between donors and recipients.   

โ€œWe cover the state of Tennessee,โ€ Christina says. โ€œWe do the typing and antibody analysis for solid organ transplants, and then we follow them post-transplant to see if theyโ€™ve developed antibodies to the donor. We also do stem cell workups and follow-ups.โ€

The lab processes 150-200 samples per week. In addition to managing the high sample throughput, the team also must be available 24/7 for urgent calls when an organ donor passes away.

โ€œWe used to average about 50 donors a month, but thatโ€™s creeping up,โ€ Christina says.

Christina says her team needs a workflow built for speed and minimal hands-on processing. With downstream assays including NGS and qPCR, they also need to trust theyโ€™ll have a high-quality DNA sample to work with. Thatโ€™s what led them to the Maxwell platform in 2005.

Instrumentation for Easy, Reliable Results  

โ€œMaxwell purifications are an easy thing to start new employees with, because they can get quality DNA very easily,โ€ says MacKenzie Gartner, Lead Technologist in Christinaโ€™s lab at DCi. โ€œTechs pick up on it very quickly, and itโ€™s something they can feel confident in doing by themselves.โ€

Twenty years ago, the lab was using manual methods to purify all their nucleic acids. Unlike MacKenzie, Christina remembers those days and admits they werenโ€™t fun. The protocols were labor-intensive, and much more prone to human error. Now, they donโ€™t even teach manual methods anymore.

The DCi lab currently operates three Maxwellยฎ instruments.
The DCi lab currently operates three Maxwellยฎ instruments.

โ€œWhen I came on nine years ago, they were teaching a manual method as backup for the Maxwell instruments, but they never got around teaching it to me because it was needed so rarely,โ€ MacKenzie says. โ€œNow itโ€™s not even in the training materials.โ€

MacKenzie works hands-on with the Maxwell instruments almost every day. The lab mainly uses the Maxwellยฎ Buffy Coat DNA Kit and Maxwellยฎ Buccal Swab DNA Kit. Buccal swabs require 20 minutes of passive pre-processing, but buffy coats can be added directly to the Maxwell cartridges. From there, the automated protocol is only 45 minutes.

โ€œItโ€™s nice that both of them can be run on the same instrument, which gives us flexibility knowing that all three instruments can be available no matter what weโ€™re doing,โ€ MacKenzie adds.

One of the lab's original Maxwellยฎ instruments, still in storage in the basement.
One of the lab’s original Maxwellยฎ instruments, still in storage in the basement.

Christina says the Maxwell instruments provide much cleaner DNA eluates than their past manual methods. This is invaluable for lab efficiency, but itโ€™s even more important with stem cell testing.

โ€œWith stem cells, they may only send one tube but want three or four different tests,โ€ she explains. โ€œWe donโ€™t have room for error โ€“ those samples are precious.โ€

โ€œWe keep the instruments pretty active,โ€ MacKenzie adds. โ€œThat room constantly has their little noises going. But theyโ€™re so dependable โ€“ they donโ€™t take much maintenance, and we can count on having one available even when we get some urgent samples from a donor.โ€

Long-Term Partnership for Success

โ€œPromega is probably our favorite company to work with, as far as support goes,โ€ Christina says. โ€œWe rarely have issues, but when we do, we get great responses very quickly.โ€

As a leader, Christina values strong relationships with her suppliers. Though the labโ€™s sales representative has changed a few times over the past two decades, she says each one has been reliable and helpful in keeping the lab operations running smoothly. The lab has also benefited from regularly scheduled preventive maintenance visits from Promega service engineers.

โ€œOverall, I just love how dependable the instruments are,โ€ Christina says. โ€œWeโ€™re using them all the time. Theyโ€™re truly our workhorses.โ€

All photos credit: DCi