Author: Kari Kenefick

What Drives Muscle Fiber Shifts in Obesity and Type ll Diabetes?

Posted on by Kari Kenefick

Skeletal muscle is the body’s main consumer of glucose derived from food.

Muscle Fiber Types
Skeletal muscle is composed of two types of muscle fiber: Type I (slow-twitch) and Type II (fast-twitch).
Type I fibers contract slowly and can maintain contraction over long periods of time. They are rich in mitochondria and myoglobin and are well vascularized. These fibers rely mostly on aerobic metabolism to make the ATP that fuels cells. Type I muscle fibers are fatigue-resistant and efficient—great for supporting posture, distance running, cycling and any activity that needs steady output.

Type II fibers contract quickly, produce more force and power, but also fatigue more quickly. They have fewer mitochondria and less vasculature and rely more on anaerobic pathways like glycolysis (using glucose without oxygen).

Type I muscle fibers are smaller in diameter and generate less peak force but excel at endurance and heat management. Type II fibers are typically larger, produce more force and speed and handle explosive tasks like sprinting, jumping or heavy lifting.

Most muscles are a mix of fiber types, and genetics sets the starting ratio of Type l to Type ll, but fibers are adaptable. With aging and disuse, Type II fibers tend to atrophy more, which is one reason that power declines faster than endurance.

Another distinction important for this story: Type I fibers are more insulin-sensitive than Type II fibers. Additionally, these fiber types differ in different body types.

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How Thalidomide and Molecular Glues Are Redefining Drug Discovery

Posted on by Kari Kenefick

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 system—in particular, the ubiquitin-proteasome pathway—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 result—selective protein destruction—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 – and Why Helicases Are Stealing the Spotlight

Posted on by Kari Kenefick

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 “spend” it to move cargo, remodel nucleic acids, pump ions, or fold proteins. These ATP-hydrolyzing enzymes—collectively known as ATPases—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-ATPases—all drawing on ATP to power their molecular work.

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Base Editing Brilliance: David Liu’s Breakthrough Prize and Its Impact

Posted on by Kari Kenefick

On April 5, 2025, Dr. David R. Liu stood in the spotlight at the Barker Hangar in Santa Monica, California, to receive the Breakthrough Prize in Life Sciences—one of the most prestigious honors in science.
Dubbed the “Oscars of Science,” the Breakthrough Prizes were launched in 2012 by tech philanthropists including Sergey Brin, Mark Zuckerberg and Priscilla Chan, Yuri and Julia Milner and Anne Wojcicki. These prizes recognize groundbreaking achievements in life sciences, physics, and mathematics, with each laureate receiving a $3 million award—more than twice the amount of a Nobel Prize.

The winners are selected by panels of previous Breakthrough Prize recipients, ensuring peer-driven recognition. The annual ceremony brings together not only the best minds in science but also celebrities, filmmakers, and tech industry leaders, creating an uncommon crossover between pop culture and research, in an effort to bring more public attention as well as funding to scientific achievement.

Dr. Liu was honored for inventing base editing and prime editing, technologies that allow precise, programmable rewriting of DNA to correct mutations linked to genetic disease—without introducing double-stranded breaks. These tools have rapidly transitioned from the bench to the clinic, with at least 15 clinical trials currently underway worldwide targeting diseases like sickle cell anemia, T-cell leukemia, and others.

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Neurons’ Role in FBP2 Regulation

Posted on by Kari Kenefick

Neuronal extracellular vesicles (NEVs) play a significant role in the communication between neurons and astrocytes, particularly by influencing metabolic processes such as glycolysis and lactate production. NEVs carry signaling molecules that affect the expression, degradation and oligomeric state of fructose 1,6-bisphosphatase 2 (Fbp2) in astrocytes, altering their metabolism (1).

Basic Backstory on CNS Architecture
The central nervous system (CNS) is composed of an intricate cellular communications complex, divided generally into neurons and glial cells. Neurons form the electrical signaling network, with dendrites receiving and integrating signals via chemical synapses, and axons, some up to 1 meter in length, rapidly transmitting the signals.

Glial cells, including astrocytes, microglia and other cells, interact with neuronal cells to sustain this network. For example, glial cells regulate synapse formation and provide metabolic support to promote CNS homeostasis. Glial cell dysfunction contributes to most neural diseases and can even drive neurodegenerative processes (2).

What are Neuronal Extracellular Vesicles (NEVs)?
NEVs are formed by neurons via endocytosis and are released into the extracellular space where they interact with astrocytes. These transport vesicles carry a variety of molecules, including proteins and RNA, that influence cellular processes in recipient astrocytes.

NEV and Astrocyte Interactions
Fbp2 is an important enzyme involved in glycogen synthesis that also has nonenzymatic functions, including support of neuronal processes like long-term potentiation (LTP). LTP underlies synaptic strength and plasticity and is important in both learning and memory formation.

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Fluorescent Ligands in Biological Research: Where We’ve Been, Where We’re Headed

Posted on by Kari Kenefick

Fluorescent tags (fluorophores), have become excellent tools for labeling cells and cellular components. They can be used for imaging large molecules like proteins, on down to cellular components and enzymes such as transcription factors. Once labeled, these molecules can be tracked in tissue or inside a cell, when the right tag is used.

What is the ‘right’ tag? It’s a tag with bright signal, with low background and good photostability. For small cell components like organelles, the tag must be cell-permeable and small enough to not interfere with normal cellular processes such as transcription and metabolism.

Significant advances have been made in fluorescent tags in the past two decades. Here we look at several papers noting these advances.

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Cell-Based Target Engagement and Functional Assays for NLRP3 Inhibitor Profiling Help Identify Successes and Failures

Posted on by Kari Kenefick

Identifying Inflammasome Inhibitors: What’s Missing
The NLRP3 inflammasome is implicated in a wide range of diseases. The ability to inhibit this protein complex could provide more precise, targeted relief to inflammatory disease sufferers than current broad-spectrum anti-inflammatory compounds, potentially without side effects.

Studies of NLRP3 inflammasome inhibitors have relied on cell-free assays using purified NLRP3. But cell-free assays cannot assess physical engagement of the inhibitor and target in the cellular micro-environment. Cell-free assays cannot show if an NLRP3 inhibitor enters the cell, binds the target and how long the inhibitor binding lasts.

Cell-based assays that interrogate the physical interaction of the NLRP3 target and inhibitor inside cells are needed.

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Illuminating the Brain with a New Bioluminescence Imaging Substrate

Posted on by Kari Kenefick

Bioluminescence imaging is a powerful tool for non-invasive studies of the effect of treatments on cells and tissues. The luminescent signal is strong, and can be used in vivo, enabling repeated observations over time, allowing longitudinal study of cellular changes for hours or days. Bioluminescence imaging can be used in live animals over varying periods of time, without interfering with normal cellular processes.

Fluorescence imaging is also used in cellular studies. Although it can provide a stronger signal than luminescence, fluorescence requires light for excitation, and thus its in vivo use is limited at a tissue or cell depth greater than 1mm.

NanoLuc® Luciferase. Small, bright and now useful in brain bioluminescence imaging.

In addition, autofluorescence can be an issue with fluorescence imaging, as cellular components and surrounding proteins and cells can fluoresce when exposed to light. Autofluorescence can result in high background signals, making it difficult to distinguish true fluorescence from background.

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Made Just for You: Promega Custom Reagents

Posted on by Kari Kenefick

At promega.com you’ll find reagents designed for use in your life science research, whether you need to isolate DNA or RNA, determine cell viability or signaling, gain metabolic assay insights, run a reporter bioassay or isolate nucleic acid from wastewater.

Did you know that we also create unique custom reagents? Whether you’re looking for an extra-large size of a compound, a unique type of packaging or package labeling, or a reagent or assay target that’s unique to your project, Promega custom reagents can help.

What Types of Custom Reagents Are Available?
We currently supply custom-made reagents in the areas of amplification, bioluminescence, nucleic acid purification, protein analysis and protein purification. See this Promega Custom Products and Technologies web page for details.
Need a unique master mix for your amplification reaction? This short video provides examples of how we can customize an amplification master mix.

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Real-Time Analysis for Cell Viability, Cytotoxicity and Apoptosis: What Would You Do with More Data from One Sample?

Posted on by Kari Kenefick

Originally posted May 25, 2017. Updated 2022

You are studying the effects of a compound(s) on your cells. You want to know how the compound affects cell health over a period of hours, or even days. Real-time assays allow you to monitor cell viability, cytotoxicity and apoptosis continuously, to detect changes over time.

Why use a real-time assay?
A real-time assay enables you to repeatedly measure specific events or conditions over time from the same sample or plate well. Repeated measurement is possible because the cells are not harmed by real-time assay reagents. Real-time assays allow you to collect data without lysing the cells.

Advantages of  Real-Time Measurement
Real-time assays allow you to:

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