Barbara Offenhartz

Physical Chemist

Physical Chemist Barbara Offenhartz
Physical Chemist Barbara Offenhartz

“Take a deep breath.” Maybe a doctor, a yoga teacher, or someone wanting to help you in some way has suggested this to you.  It’s good advice: breathing keeps us alive and gives us energy.  

Throughout our lives, our bodies engage in respiration, a process that gives us the energy we need to do everything from playing basketball, baseball, or soccer to doing homework for school to keeping our bodies themselves running well. You could say that respiration begins with breathing in oxygen, which our lungs pass on to our blood.  The blood brings oxygen all over our bodies, where it’s used to produce energy.  

Sometimes, we don’t get as much oxygen as we need.  Asthma, a bad cold, or another illness might cause the oxygen levels in our blood to go down.  How can a doctor or a nurse measure the oxygen saturation level — how close our blood is to carrying as much oxygen as it’s able to? This form of measurement is called oximetry.  Physical Chemist Barbara Offenhartz is one of the scientists who helped figure out how to use light to measure oxygen levels in blood.

“Eat your vegetables” might be something a parent, teacher, or other person in your life says to you. Eating healthy food (vegetables and fruits of different colors and shapes; whole grains (barley, rice, spelt, faro, etc.); legumes (peanuts and beans); dairy products like yogurt, cheese, and milk; nuts and seeds (walnuts, almonds, sesame seeds, quinoa, etc.); meat — food that has not been ground up, mixed with sugar and various chemicals, and packaged into a box that sits on a shelf for long amounts of time) helps you get protein, carbohydrates, healthy fats, minerals, and vitamins.  Eating meat, eggs, dairy products, and nori (a type of seaweed) helps your body get one key vitamin everyone needs — vitamin B12.

(Illustration by Mikhaela Fishman)

Offenhartz’s work at the University of Pennsylvania, where she got her PhD in physical chemistry, focused on vitamin B12. Professor Philip George, with whom she worked, was “at that time at the forefront of figuring out the spatial structure of molecules like hemoglobin.” (Hemoglobin is the protein that makes blood red and carries oxygen.) Vitamin B12 helps our bodies build hemoglobin.

“Anything you learn in your geometry lessons in junior high school or even grade school” can help you understand the chemistry of vitamin B12. You learned about triangles (three-sided figures), quadrilaterals (four-sided shapes, including rectangles, parallelograms, and trapezoids). “Do you know what a hexagon is?” asks Offenhartz. (A hexagon is a two-dimensional / flat shape with six sides.) How about an octagon? (An octagon is a two-dimensional shape with eight sides.)

Let’s move on to three-dimensional shapes. A cube has six faces, as does any rectangular prism (the shape of most boxes). An octahedron is a three-dimensional shape with eight faces. That’s the shape of a hemoglobin molecule and also of a molecule of vitamin B12.

The chemical formula for vitamin B12 is C63H88CoN14O14P.  Imagine an octahedron “spatially with an atom” of carbon (C), hydrogen (H), oxygen (O), or nitrogen (N) at each vertex (corner). “At each little angle, there’s an atom and altogether the octahedron describes the essence of a hemoglobin molecule [and also] the essence of a vitamin B12 molecule.” The phosphorous atom in each molecule of vitamin B12 forms bonds with four oxygen atoms to form a phosphate group (PO4). Vitamin B12 has a cobalt (Co) molecule at its center.

Offenhartz looked at the spectral properties of vitamin B12 and other cobalt compounds. She investigated the ways they interact with light. In England, she met Dorothy Crowfoot Hodgkin, a crystallographer who had been the first scientist to find the structure of penicillin (a kind of antibiotic medicine) and discovered the cobalt atom in vitamin B12.

“I was so used to being the only woman wherever I studied or worked who would do this.” Offenhartz and her husband, Physical Chemist Peter Offenhartz, had been invited to a conference, as postdoctoral students working with a professor in Cambridge, England. “I happened to run into Dorothy Hodgkin in the ladies room. I sort of cornered her — I hadn’t met her before.”

Introducing herself, Offenhartz told Hodgkin “‘I’m really excited about what I’m doing.’” Later, when Hodgkin presented her own work at the conference, she announced to the audience that “‘there’s a wonderful graduate student — there she is in the audience right now: Barbara Offenhartz. And why don’t you tell us about what you’re doing?’”

Says Offenhartz about opportunities like the one Hodgkin gave her, “I tried to do the same with my students at conferences.”

Born in Boston, Barbara Offenhartz (then Barbara Hopf) spent her childhood in Bayerisch-Gmain, in southern Germany, in the lower Alps mountain range, near Austria. “My main influence was my grandfather, who lived with us during the war, having escaped Berlin,” where he led a music school. “The two of us sort of plotted against my parents.”

As a child, Barbara was exposed to “lots of music; lots of science.” War also shaped her parents’ lives.

My father was a famous mathematician and my mother was a physics student at the University of Berlin, where she met my dad. She never finished her physics degree because she was the youngest of two daughters. Her older sister [Barbara’s aunt] became a medical doctor. She [Barbara’s mother] had to take care of her mother, who was very ill. [Later, she] married my dad and became a housewife.

In the Second World War, she was conscripted [drafted] by the Germans to do ‘war work.’ She ended up writing a newspaper for the soldiers at the German front. [This was fortunate because it got her] out of having to sort bloody uniform garments which came to this particular army base.

My father was very anti-Nazi, so they made him feel that at every end of the spectrum. He was much too outspoken for his own good.

In 1948, a few years after the war ended, Barbara’s parents moved their family back to the United States. After graduating from high school in Bloomington, Indiana, Offenhartz continued her travels, starting at Swarthmore College, in Pennsylvania, where she met Peter.

“I was bounced on the lap of famous mathematicians because they were friends of my dad’s,” Offenhartz remembers. “I loved the math I was exposed to” but by the time she studied math in college, she had begun to find it “too austere, too abstract for me. I was interested in living things and how they worked. So the progression to biochemistry was quite natural in college. I majored in chemistry and minored in math, biology, and physics.”

After getting her PhD in physical chemistry from the University of Pennsylvania, Offenhartz did postdoctoral work at Cambridge University, in England, and at the Institute for Solid State Physics, in Tokyo. She later taught college chemistry in Colorado and Massachusetts.  Massachusetts is also where Offenhartz began working as a chemical engineer for companies including Corning Biomedical and Orion Instruments.

Drawing on her studies of physical chemistry, Offenhartz worked as an engineer, developing medical instruments to help doctors measure things like the amount of oxygen in blood. Living in the Boston area, where there are many doctors, hospitals, and people doing medical research, Offenhartz became part of the teams that helped figure out how to use the wavelengths of light for oximetry.

“Nowadays, you put a little clasp on your finger and the technology that you use is all light-oriented.” (It gently pinches your finger, sort of like a clothespin might.) This instrument identifies “the wavelength of what turns out to be hemoglobin,” looking at the peak in its spectrum. That determines a person’s oxygen saturation level, telling his or her doctor whether s/he’s getting enough oxygen. “It’s these spectra and their relationship to the [hemoglobin] molecule” that was the focus of Offenhartz’s research, helping her and others in the process of “developing the tools for measuring all of this.”