The Limits of Litmus Tests

A conversation with Nadia Marano, George F. Baker Associate Professor and Chair of the Department of Chemistry

Deborah Dudley

Most people already know what a litmus test is. They have likely used litmus paper in elementary school science class as an acid-base indicator, where the colors of the litmus paper correlate along a simple pH scale from acidic (0) to neutral (7) to basic or alkaline (14). 

The test originated in the 14th century, when scientists discovered that litmus, a mixture of colored organic compounds obtained from lichen, turns red in acid solutions and blue in alkaline solutions. It turned out to be a handy indicator to help determine how compatible a substance is with other life forms.

In the last century, however, a “litmus test” has also come to be used as a cultural indicator. The term is used figuratively to refer to any single factor that establishes the defining character of something or someone, often a test used to make a judgment on an individual’s position or belief to determine if a person is compatible with a moral, political or social agenda. But what do litmus tests really tell us?

To learn more about the limits of litmus tests, I asked Nadia Marano, George F. Baker Associate Professor and Chair of the Department of Chemistry.

“Generally, life likes a fairly neutral pH where the ions are in balance,” explains Marano. “If things are not in balance, there can be extremes that cause random chemical reactions and stuff breaks down. The more extreme it is, the less compatible it is with life.”

Marano explains that there are a few kinds of archaea, unicellular bacteria-like organisms, that can thrive in an alkaline or other extreme environments. There are also systems within some organisms that operate at one extreme or the other with built-in protections that allow for, and function in extreme conditions. The human stomach, Marano explains, is a good example of a system that is built to accommodate an extremely acidic environment. However, she repeats, “Most life is not compatible with extremes.”

“Any short contact of extremes on the outside of the body is usually tolerable,” Marano says, “but for example, if you breath in ammonia, it can be very dangerous.” The inside of the body is very precise, like the circulatory system, which exists primarily at a pH of 7.2 to 7.4. “Any small shifts in pH of 0.1-0.3 in the blood stream can be very serious and even result in death.”

Although litmus tests might be good for getting a general idea about the conditions of your garden soil, they are not very useful when it comes to the work in the lab. Marano explains, “pH paper has a wider range of pH values (maybe from 2-13 within about 1 pH unit) and colors because it contains a mixture of different indicators, each of which covers a different range.”

In the lab, a pH meter is used to get an exact measurement. More importantly, Marano notes, “different levels of precision are determined by what you want assessed.” In other words, there is always more to it.

For Marano, it is important that St. Lawrence students first assess the properties of any substance starting at the atomic level and then evaluate how that informs the behaviors at a more macro level. “We look at connecting the structures to the properties, not only to be able to make calculation, such as the pH, but to understand why one substance behaves one way and another behaves another way.”

“We start by looking at something students are all familiar with, like water,” says Marano. “Start with something that you know and expand that to the molecular structure of other things.”

Assessment does not always end with the lab work. Marano recently traveled to University of Genoa in Italy with recent graduate Jordan Koloski ’16, to compare the behavior of a mutant human protein with normal proteins, a research project funded by St. Lawrence’s CIIS Fellows Program. Although the focus was on the research, Koloski was also able to evaluate the academic and professional structures of the sciences in a European context and compare it to working in the U.S.

“The fundamentals are similar,” says Marano, but there are very distinct differences between the scientific community hierarchies and cultures.

Born in Tripoli, Libya, to Italian parents and moving with her family to Tarrytown, New York, as a child, Marano is familiar with navigating different environments. “Growing up, I was always better at science and math-type stuff than the humanities.” This interest is what informed Marano’s pursuit of biochemistry and chemistry.

As far as figurative litmus tests go, being a woman in the sciences was and is a defining characteristic that comes with its own challenges. For Marano however, gender was never a relevant indicator informing her academic pursuits and the expectation from her Italian parents was that she would excel academically in any environment.

Marano’s current research focuses on amyloid fibers formed by bacteria to help provide structure and protection to colonies known as biofilms. Among the many instruments Marano uses in the research, and a tool that is ubiquitous in all biochemistry and chemistry labs, is the pH meter. 

“A pH meter is used when we prepare growth medium for the bacteria and solutions for studying the proteins to ensure the correct pH,” says Marano. Litmus tests are far too limited. They might be good for getting a general idea about the conditions, but as Marano exhibits in her teaching and research, there is always more to it.