Scientists Develop Revolutionary Method to Visualize Molecules in Living Cells

A team of scientists led by Carolyn Bertozzi at the University of California, Berkeley, made a groundbreaking advancement in biochemistry by developing a method to visualize molecules in living organisms. This innovative process, published in 2007, has transformed the way researchers observe cellular activities in real time.

For years, Bertozzi’s lab focused on the challenge of visualizing glycans, complex carbohydrate molecules that are critical for various biological functions and have been linked to diseases and inflammation. Traditional methods struggled to effectively highlight these important biomolecules, which are one of the three major classes alongside proteins and nucleic acids.

Bertozzi built upon the concept of “click chemistry,” initially proposed by biochemists K. Barry Sharpless and Morten Meldal. Click chemistry allows scientists to rapidly construct intricate biological molecules by connecting smaller molecular parts. Historically, chemists faced difficulties in creating these connections due to the reluctance of carbon atoms to bond. This often forced the use of lengthy, cumbersome processes that generated unwanted byproducts—an issue for large-scale pharmaceutical production.

In their pioneering work, Sharpless and Meldal identified a key reaction between two compounds: azide and alkyne, which, when combined with copper as a catalyst, produced an efficient and highly reliable connection. The reaction yielded a success rate exceeding 99.9% and did so without generating byproducts.

Yet, Bertozzi encountered a significant obstacle: copper’s toxicity to living cells. To address this, she investigated existing literature and discovered that if the alkyne was modified into a ring shape, it would react explosively with azide without requiring a catalyst. By 2004, her team successfully demonstrated that this innovative reaction could attach azide molecules to living cells safely.

By 2007, Bertozzi and her colleagues utilized this method to visualize glycans in living hamster cells. Their technique involved incorporating a carbohydrate molecule modified with azide into the glycans. Once they introduced a ring-shaped alkyne bound to a green fluorescent protein, the azide and alkyne reacted, illuminating the glycans within the cell.

Bertozzi coined the term “bioorthogonal” click chemistry to describe this process, emphasizing its compatibility with biological functions. This method has been vital for understanding the movement of small molecules in living systems. It has enabled researchers to track glycans in zebrafish embryos and investigate how cancer cells evade immune detection using sugar molecules. Furthermore, bioorthogonal click chemistry has been instrumental in developing radioactive tracers for biomedical imaging.

The broader implications of click chemistry have significantly accelerated drug discovery processes across various fields. In recognition of their contributions, Sharpless, Meldal, and Bertozzi were awarded the Nobel Prize in Chemistry in 2022, highlighting the transformative potential of their work in the realm of science and medicine.

This innovative approach not only marks a significant milestone in biochemistry but also sets the stage for future advancements in understanding complex biological processes. The ability to visualize molecular interactions in real time has opened new avenues for research, promising to enhance our knowledge of cellular behavior and disease mechanisms.