Discovering Cyclic Peptides with a “One-Pot” Synthesis and Screening Method

In the evolving landscape of drug discovery, cyclic peptides represent an exciting opportunity. These compounds offer a unique balance of size and specificity that positions them to bridge the gap between small molecule drugs and larger biologics like antibodies.

However, most cyclic peptides demonstrate low oral bioavailability: they are digested in the stomach before they can enter the bloodstream, or they’re not absorbed into the bloodstream by the gastrointestinal tract and can have little therapeutic effect (1). Biologics face a similar challenge and are administered intravenously rather than with a more convenient pill form.

A 384 well plate next to a collection of pills of different sizes and shapes.


To address the challenge of low oral bioavailability of cyclic peptides, a team from the Ecole Polytechnique Fédérale de Lausanne in Switzerland developed a “one-pot” method to synthesize a diverse library of cyclic peptides, which they then screened for stability, activity and permeability (1). Their method, which was published December 2023 in Nature Chemical Biology, streamlined the process of identifying and optimizing cyclic peptides and marked a substantial improvement from their earlier studies, where the developed cyclic peptides exhibited almost no oral bioavailability (%F). Using this new method, the team successfully developed a cyclic peptide with 18%F oral bioavailability in rats.

This blog covers the details of this study as well as a brief background on cyclic peptides.

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Will Artificial Intelligence (AI) Transform the Future of Life Science Research?

Artificial intelligence (AI) is not a new technological development. The idea of intelligent machines has been popular for several centuries. The term “artificial intelligence” was coined by John McCarthy for a workshop at Dartmouth College in 1955 (1), and this workshop is considered the birthplace of AI research. Modern AI owes much of its existence to an earlier paper by Alan Turing (2), in which he proposed the famous Turing Test to determine whether a machine could exhibit intelligent behavior equivalent to—or indistinguishable from—that of a human.

The explosive growth in all things AI over the past few years has evoked strong reactions from the general public. At one end of the spectrum, some people fear AI and refuse to use it—even though they may have unwittingly been using a form of AI in their work for years. At the other extreme, advocates embrace all aspects of AI, regardless of potential ethical implications. Finding a middle ground is not always easy, but it’s the best path forward to take advantage of the improvements in efficiency that AI can bring, while still being cautious about widespread adoption. It’s worth noting that AI is a broad, general term that covers a wide range of technologies (see sidebar).

AI personified looking at a dna double helix against an abstract cosmic background
Image generated with Adobe Firefly v.2.

For life science researchers, AI has the potential to address many common challenges; a previous post on this blog discussed how AI can help develop a research proposal. AI can help with everyday tasks like literature searches, lab notebook management, and data analysis. It is already making strides on a larger scale in applications for lab automation, drug discovery and personalized medicine (reviewed in 3–5). Significant medical breakthroughs have resulted from AI-powered research, such as the discovery of novel antibiotic classes (6) and assessment of atherosclerotic plaques (7). A few examples of AI-driven tools and platforms covering various aspects of life science research are listed here.

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Designing Science: A Behind-the-Scenes Look at Our Recent Journal Cover Art

A 3D illustration showing RAF inhibitor LXH254 engages BRAF or CRAF protomers (orange), but spares ARAF (red). Unoccupied ARAF is competent to trigger downstream mitogenic signaling, which is demonstrated with lightning bolts. Red cells in the background are fluorescently labeled RAS proteins, expressed in live cells. The Cell Chemical Biology cover type superimposes the image.
Image adapted from original artwork by iSO-FORM LLC.

We made the cover! Of Cell Chemical Biology, that is.

This July, Cell Chemical Biology editors accepted a study from Promega scientists and invited the research team to submit cover art for the issue. The study in question details a BRET-based method to quantify drug-target occupancy within RAF-KRAS complexes in live cells. Promega scientists Matt Robers and Jim Vasta collaborated with one of our talented designers, Michael Stormberg, to craft an image that accurately represents the science in a dynamic and engaging way.

You can check out the paper and cover art in the November 16 issue of Cell Chemical Biology.

I spoke with Michael Stormberg to learn more about the creative process that went into creating this cover art and how he worked with the research team and other collaborators.

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Reviewing the Importance of circRNA

In recent years following the COVID-19 pandemic, RNA has gained attention for its successes and potential use in vaccines and therapeutics. One avenue of interest in RNA research is a non-coding class of RNA first identified almost 50 years ago, circular RNA (circRNA).

In 1976, Sanger et al. first identified circRNA in plant viroids, and later additions to the field found them in mice, humans, nematodes, and other groups. Unlike linear RNA, circRNA are covalently closed loops that don’t have a 5′ cap or 3′ polyadenylated tail. Following its discovery, researchers thought circRNA was the product of a rare splicing event caused by an error in mRNA formation leading to low interest in researching the subject (1).

In the early 2010s, following the development of high throughput RNA sequencing technology, Salzman et al. determined that circRNAs were not a result of misplicing, but a stable, conserved, and widely sourced form of RNA with biological importance. Since noncoding RNA makes up the majority of the transcriptome it’s an incredibly important field of study. We now recognize circRNAs for their potential as disease biomarkers and importance in researching human disease (2).

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Insects and Science: Optimizing Work with Sf9 Insect Cells

Insects are a keystone species in the animal kingdom, often providing invaluable benefits to terrestrial ecosystems and useful services to mankind. While many of them are seen as pests (think mosquitos), others are important for pollination, waste management, and even scientific research.

Insect biotechnology, or the use of insect-derived molecules and cells to develop products, is applied in a diverse set of scientific fields including agricultural, industrial, and medical biotechnology. Insect cells have been central to many scientific advances, being utilized in recombinant protein, baculovirus, and vaccine and viral pesticide production, among other applications (5).

Therefore, as the use of insect cells becomes more widespread, understanding how they are produced, their research applications, and the scientific products that can be used with them is crucial to fostering further scientific advancements.

Primary Cell Cultures and Cell Lines

Cell culture - Cell lines - Insect Cells

In general, experimentation with individual cells, rather than full animal models, is advantageous due to improved reproducibility, decreased space requirements, less ethical concerns, and a reduction in expense. This makes primary cell cultures and cell lines essential contributors to basic scientific research.

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Have No Fear, qPCR Is Here: How qPCR can help identify food contamination

Foodborne disease affects almost 1 in 10 people around the world annually, and continuously presents a serious public health issue (9).

Food Contamination-Strawberries-Blueberries-Magnifying glass
Food Contamination is common and can be seen in a variety of forms and food products.

More than 200 diseases have evolved from consuming food contaminated by bacteria, viruses, parasites, and chemical substances, resulting in extensive increases in global disease and mortality rates (9). With this, foodborne pathogens cause a major strain on health-care systems; as these diseases induce a variety of different illnesses characterized by a multitude of symptoms including gastrointestinal, neurological, gynecological, and immunological (9,2).

But why is food contamination increasing?

New challenges, in addition to established food contamination hazards, only serve to compound and increase food contamination risks. Food is vulnerable to contamination at any point between farm and table—during production, processing, delivery, or preparation. Here are a few possible causes of contamination at each point in the chain (2):

  • Production: Infected animal biproducts, acquired toxins from predation and consumption of other sick animals, or pollutants of water, soil, and/or air.
  • Processing: Contaminated water for cleaning or ice. Germs on animals or on the production line.
  • Delivery: Bacterial growth due to uncontrolled temperatures or unclean mode of transport.
  • Preparation: Raw food contamination, cross-contamination, unclean work environments, or sick people near food.

Further emerging challenges include, more complex food movement, a consequence of changes in production and supply of imported food and international trade. This generates more contamination opportunities and transports infected products to other countries and consumers. Conjointly, changes in consumer preferences, and emerging bacteria, toxins, and antimicrobial resistance evolve, and are constantly changing the game for food contamination (1,9).

Hence, versatile tests that can identify foodborne illnesses in a rapid, versatile, and reliable way, are top priority.

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It Is Not Just You—Burnout Is Real

“I just feel burned out.” I heard those words recently from my college junior. For him, the spring semester is barreling to a close and he is feeling tired, unmotivated and unproductive. He isn’t alone; most of us have said (or thought) those words at some point in our lives. We use the words when we are feeling tired, stressed or overwhelmed at work (or school), but burnout is more than just an emotional response to workload or other job-related challenges. Burnout can quickly cascade into more physical symptoms and take a toll on both our personal and professional lives.

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The Power of Pet Ownership

International Pet Day, observed each year on April 11th, provides the purrfect opportunity to reciprocate all the labored love and affection our pets so freely give us. There’s no doubt that our furry, feathered, and scaley friends greatly improve our quality of life. But did you know there are benefits to this human-animal bond beyond their incredible cuteness? Read about some of the paw-some science-approved benefits that can come with pet ownership.

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PARP and DDR Pathways: Targeting the DNA Damage Response for Cancer Treatment

Our cells, and the DNA they contain, are under constant attack from external factors such as ionizing radiation, ultraviolet light and environmental toxins. Internal cellular processes can also generate metabolites, such as reactive oxygen species, that damage DNA. In most cases, DNA damage results in permanent changes to DNA molecules, including DNA mismatches, single-strand breaks (SSBs), double-strand breaks (DSBs), crosslinking, or chemical alteration of bases or sugars. If left unchecked, DNA damage can cause genome instability, mutations and aberrant transcription, and oncogenic transformation.

PARP DDR pathway for drug discovery

Fortunately, our cells have also evolved multiple pathways to repair damaged DNA, collectively known as the DNA damage response (DDR). The type of repair mechanism depends on the nature of the damage, and whether the damage occurs in mitochondrial or nuclear DNA. These mechanisms have been reviewed extensively (1,2). Recently, considerable attention has focused on pathways for repairing SSBs and DSBs, mediated by the ADP-ribosylating enzyme known as poly (ADP-ribose) polymerase 1, or PARP-1.

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Confronting an Emerging Pathogen: Candida auris

Candida auris illustration
Candida auris is a fungal infection sweeping through healthcare sites across the U.S.

HBO’s The Last of Us has successfully brought fungal pathogens to the forefront of the pandemic discourse, raising questions as to whether a fungus could really pose a significant threat to humans. While scientists agree that the fungus featured in the show, cordyceps, won’t be making the required inter-species jump any time soon, there is a fungal pathogen that has been taking root in hospitals across the U.S. which gives some cause for concern: Candida auris.

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