Reactions: Endotoxin testing, human sex, policy in chemistry class, and more

Letters to the editor

Comparing endotoxin testing methods

As thoroughly covered in your recent article (C&EN, Oct. 28, 2024, page 26), the issue of replacing the traditional natural product test for endotoxin, limulus amoebocyte lysate (LAL), with a synthetic alternative is extremely complex. Leaving aside regulatory politics and the large volume of public misinformation regarding both the chemical differences between LAL and synthetic alternatives as well as the threats to the horseshoe crab, there are additional reasons for the slow adoption of a synthetic alternative.

Although recent data indicate that more horseshoe crabs were collected for bait than LAL manufacture, bait’s 100% mortality still makes it the greatest threat to horseshoe crabs. In contrast, LAL’s upper mortality estimate is 30%. Conservation efforts continue to benefit the horseshoe crab, and in my state of Massachusetts, populations remain stable if not slightly increasing.

Economics also plays a large role. Horseshoe crabs have remained a low-cost raw material. They are abundant close to the locations of the current LAL manufacturers and are easily collected.

Perhaps the biggest reason for the acceptance of a synthetic alternative is related to chemistry. LAL may be one of the most sensitive biological assays. Femtogram/milliliter amounts of endotoxin (lipopolysaccharide) can be detected. The recombinant factor C (rFC) assay is nowhere near as sensitive. While true that rFC is comparable in its ability to detect endotoxin with LAL in its sensitivity range in pure water, most pharmaceutical products are by their nature inhibitory to both LAL and rFC. The simplest method to test these products is to make sequential dilutions with pure water until the inhibition is removed. Thus, sensitivity rapidly becomes a limiting factor. In addition, the rFC test relies on fluorescence, which is required to boost sensitivity (versus color detection). However, the fluorescent signal has the additional drawback of being quenched by many pharmaceuticals. A fluorescent signal also requires a specific reader. Up until recently, fluorescent readers were expensive, and anyone wishing to replace LAL with the synthetic would require serious retooling and technical training.

Only recently have true synthetic LAL replacement assays appeared. These consist of a complete suite of the enzymes that compose the natural cascade and are truly plug and play with existing LAL equipment and technical training.

I know firsthand the ubiquitous nature of endotoxin and the difficulty in keeping it from contaminating LAL during its production, so it remains to be seen if an economically viable, true LAL alternative is feasible regardless of regulatory acceptance.
Thomas J. Novitsky
East Falmouth, Massachusetts

Defining the sexes

The article “Scientists Reject a Binary View of Human Sex at NIH Symposium,” by Max Barnhart (C&EN, Oct. 21, 2024, page 20), was very informative. There are two points that were not addressed that for legal and ethical reasons remain to be discussed and some scientific basis formalized. First, how do we define woman, especially for athletic competitions? I think that most would agree that women cannot compete against men in track and field, football, basketball, etc. How do you define woman so that women can compete against one another on a level playing field? Regardless of the complexities described in this article, a working (legal) definition must be easily understood and logical; otherwise it will be looked upon as an attempt by the “elite” to game the system and will give rise to all sorts of conspiracy theories. It is ironic that a person identifying as a woman cannot give a legal definition of woman: a US Supreme Court justice comes to mind. Second, for how many or for which of the gender/sex groups does the pharmaceutical industry need to design therapeutics or else they will be accused of some sort of bias? With the large number of variations described in this article, trying to design precision medicine for all of them will be quite expensive. Who is going to pay that cost?

p.s. I agree absolutely that there need to be more gender-neutral bathrooms (page 24)!

Kenneth B. Sloan
Durham, North Carolina

Discussing policy in a chemistry class

As a first-semester chemistry faculty member, I was not prepared for teaching the day after the presidential election. A mentor of mine had advised that, regardless of the outcome, the day after was likely to be filled with strong emotions. So I was sure not to schedule any exams for the week of the election, and I also avoided scheduling due dates for major assignments the day before and after.

As election day crept, and then sprinted, closer, I read advice from learning experts that encouraged faculty to acknowledge external events and how they may affect students. I reflected on the fact that anxiety and stress, almost certainly heightened by the barrage of political ads in a swing state, could interfere with students’ memory and ability to focus. However, on election day, I still didn’t have a plan to acknowledge students’ joy, fear, frustration, apathy, sadness, or whatever else they may be feeling come Wednesday morning.

I woke abruptly at 2:00 a.m. after election day, panicked because I still had no plan for how I would begin my quantum chemistry lecture, now less than 10 h away. After tossing and turning for about an hour, I decided to leave the format of my lecture up to democracy.

I drafted a poll allowing my students to vote on whether we should proceed with the planned lecture or have a discussion about civic engagement as chemists. The majority chose the latter, so that’s what we did. We sat outside in the courtyard of Dickinson College’s science building, where I handed out copies of the American Chemical Society 2024 Public Policy Agenda to prompt discussion. Students expressed uncertainty about what would come next, especially for environmental sustainability policy and climate change mitigation. For an hour, they exchanged ideas about things like regulating materials in manufacturing, planned obsolescence, and action that could be taken by individuals as well as by ACS as an organization.

While we don’t yet know the implications of the US presidential election for chemistry, it is clear that acknowledging and even incorporating discussions about policy—both policies that benefit chemistry (e.g., related to scientific research funding) and policies that are benefited by chemistry (e.g., environmental protection)—in the classroom are important. I encourage my fellow chemistry educators to not ignore events like elections but to acknowledge them and give students a place to discuss them through the lens of chemistry.

Olivia Harper Wilkins
Carlisle, Pennsylvania

Corporate action on climate change

In follow-up to my July letter to the editor, I’m reiterating a call to action for global corporate responsibility to limit global warming to 1.5 °C as set by the Intergovernmental Panel on Climate Change.

Without government regulation, industry is encouraged to set standards to stabilize global warming and set policy for climate mitigation. Some companies have already done this. It remains to be seen if this kind of self-discipline works.

Again, I encourage the American Chemical Society to support the enterprise community in understanding that this is an urgent global call for action.

Martha Dibblee
Portland, Oregon

Open data

This Oct. 28 editorial “Show Us the Data” (page 2) is excellent and exactly to the point—there is no acknowledgment of the data used for the creation of AlphaFold, RoseTTAFold, etc. A recent presentation by Janet Thornton described the 170,000 protein structures provided by the Protein Data Bank (PDB) for training AlphaFold and how essential so much of the previous chemical and crystallography work was in reaching this threshold.

A note is that almost all the protein crystal structures were determined with cryo-cooling to reduce the radiation damage during the X-ray analysis (developed more than 50 years ago). This enabled all the X-ray data to be collected from one crystal. See figure 1 provided by Elspeth Garman and Markus Gerstel in “The Early History of Cryo-cooling for Macromolecular Crystallography” (IUCrJ 2020, DOI: 10.1107/S2052252519016993). More than 90% of the protein structures in the PDB were cryo-cooled. With the aid of modern crystallization techniques, cryo-cooling, the development of synchrotrons, and modern computers, AlphaFold was able to come into existence.

David Haas
Suffern, New York