Measure for Measure: An Interview with Anne Chaka

On a wooded, 578-acre campus outside of Washington, D.C., the National Institute of Standards and Technology (NIST) measures what can be measured. From neutron-beam experiments to the weathering patterns of sandstone to forensic examination of wreckage from the World Trade Center, NIST determines and maintains standard reference materials (SRMs) for use in medicine, industry, engineering, agriculture, telecommunications, law enforcement, and environmental conservation. SRMs are samples of substances—from river sediment to carbon steel to human liver tissue—whose chemical and physical properties have been analyzed according to a government-certified standard. Manufacturers use SRMs to test their own analytic methods and apparatus to be sure their measurements meet the standards. Anne Chaka is Chief of NIST’s Physical and Chemical Properties Division. She spoke at her office with Frances Richard about everything from the vibrations of cesium-123 to absolute cranberry juice.

Cabinet: How did there come to be a National Institute of Standards and Technology?

Anne Chaka: NIST was founded in 1901, to ensure, basically, that a pound in Philadelphia was equal to a pound in New York. Then, in 1904, there was a terrible fire in Baltimore. Fire trucks came from communities all around, but their hose couplings didn’t fit the hydrants. This alerted the federal government to the fact that hose and hydrant couplings had to be standardized. This also had to be done with railroad tracks, so that a train crossing a state border didn’t derail—because everybody might have thought they were measuring to the same gauge, but they weren’t. This was what NIST did early on, and is why it belongs to the Commerce Department. But we’ve evolved, especially over the last fifty years, to focus on fundamental measurements enabling fundamental science.

You were telling me, as we walked through the display of historical artifacts in the lobby, that there’s a movement away from keeping the standard, say, meter, in physical form in a vault towards deriving constant formulae?

We are interested now in measurements geared to fundamental properties of matter. So, for example, to guarantee the length of a second, rather than having a clock that ticks—that produces “a second” by mechanical reference—it’s now measured via the vibrational frequency associated with transitions of a cesium atom kept at temperatures very close to absolute zero. That measure will never change, no matter what phase of the moon we’re in, or how humidity levels fluctuate, or according to any other external factor. You measure that frequency now, or a billion years from now, and it will be the same.

For example, we are working with Newton’s Second Law, which states that force equals mass times acceleration, or f = ma. You have to measure the mass, and you have to measure the acceleration. If your mass is a brass kilogram, and it’s oxidized, or somebody’s left fingerprints on it, or it got scratched, it’ll change a little bit. Over time, somebody’s using a scratched one, and somebody’s using an oxidized one, and that leads to small differences that have an impact on calculations and the application of those calculations. So we’re exploring a fundamental force constant, which consists of actually taking a strand of DNA and pulling on it. You pull and nothing happens, and then all of a sudden it doubles in length. The force required is on the order of sixty piconewtons—which is 1 x 10-12 newtons, named in honor of Sir Isaac, of course.

Newtons are measures of gravitational force?

Of any force. Gravitational force, electromagnetic force, positive or negative.

So a newton is a unit used to determine how much oomph is exerted on A by B, no matter what kind of oomph it is?

Right. We’re exploring, as a baseline, a DNA molecule that has a defined structure, so that at any time, anybody in the world can pull on this DNA molecule and it will take the same amount of force to double its length.

It’s impossible that DNA would mutate to a different force-capacity, or that the cesium atom measuring the second would break down?

A cesium-123 atom is always going to be a cesium-123 atom. Period. If it breaks down, then it becomes something else. Genes can mutate, of course. But there are four letters in the DNA alphabet. All the richness of life comes from how we arrange those four letters in their pairs—G with C; A with T. We are looking at how much you can reshuffle the letters, or mutate the DNA molecule, and still require the same force to double the molecule’s length.

What you’re saying is that NIST encompasses micro-measured, almost fantastical levels of precision, and then very tangible, real-world, macro forms, like how big a pound or a kilogram is, or whether a train jumps a misaligned track.

We work on force and measurement for all relevant scales. So we’re experimenting on this nanoscale with the DNA molecule, but we also have facilities for testing bridge abutments—big shaker-tables to study how well they’re going to receive millions of tons of force. If you’re building a bridge to withstand so much weight from traffic, and so much stress from an earthquake, then how do you test it without building the bridge and waiting for it to fall down? Another of our facilities is the fire-research lab, which tests things like the melting point of steel, or the speed and intensity with which mattresses burn. It was the fire-research lab that studied the failure-point of the various kinds of steel in the World Trade Center, along with fuel distribution, architectural geometry, wind conditions on that day, and whatever other factors were relevant.

It’s a question of working across useful orders of magnitude. The strict definition of “micro” is one millionth, or 10 x -6. For the DNA force experiment, micro is enormous. That measurement goes past micro and nano to pico, and beyond that we come to femto. Knowing how many piconewtons are necessary to effect DNA’s length can allow us to predict and measure things on the molecular scale, like which drug binds to a protein to stop a harmful metabolic process. But it also provides a foundation for measuring larger forces. The repercussions for health and medicine, or engineering, or commerce all involve the measurement of forces on these fundamental scales.

Speaking of newtons, tell me the story of NIST’s Isaac Newton apple tree. How has it come down through time to Gaithersburg, Maryland?

Legend has it that Newton was sitting under an apple tree in his garden, trying to understand the motion of the planets. The apple fell, and inspired him to conceive the theory of gravity. He thought that what makes the apple fall toward the earth is not different from what holds Earth to the sun, and the moon to Earth. To some degree, you could think that, even as this apple is falling down, the earth is moving up to meet it. Proportionally to their masses, that is—the earth does not move very much. But he realized that gravitation exists, and it’s a two-way street.

Newton’s original tree died in the early 1800s. A cutting was made, however, and the US Department of Agriculture eventually obtained a few scions from the descendents of that cutting. There are various stories about how this happened. But one of the seedlings was planted at the original location of the National Bureau of Standards—“Technology” was added to the name later—in Washington. Our tree is a cutting from that tree. It was planted here when NIST moved to the suburbs in the 1960s. It has flourished, and we give away a couple of cuttings every year to various other institutions; we just donated one to the National Measurement Institute of Japan. Most of us have eaten an apple from it at one time or another. They’re a bit mealy. But they’re not shiny hybrids designed for looks, or even taste—it’s an apple for inspiration. We joke that we hope to get some eureka moment. We’ve had three Nobel prize winners at NIST, but it hasn’t happened to all of us.

To go back to the Department of Commerce-related interests of NIST, I understand that you are the regulating body that establishes standards for testing the nutritional content of foods, and the chemical composition of various products. How does that work?

I brought along a sampler of what are called Standard Reference Materials (SRMs). There are labeling laws that require manufacturers to list total calories, minerals, proteins, etc. How good are their in-house measurements? Plus or minus ten percent? Off by a factor of two? How much salt is in the peanut butter, how much fat, how much carbohydrate—how do you know? That’s why we have SRMs. This is cranberry juice, for example, in a sealed glass ampoule. There’s an inert gas in there as well, probably argon. And this is dried extract of saw palmetto. We’re doing SRMs for nutraceuticals now.

So if you take St. John’s Wort, or echinacea, you’ll know what you’re getting.

So that you can measure for certain how much of a given medicinal substance you’re ingesting in that dose. Regarding cranberries, there’s a lot of interest, currently, in anti-oxidant properties, as well as antibiotic properties to promote urinary-tract health. There is some evidence to support anecdotal testimony that this works. So the National Institutes of Health are conducting research, and we help them with their studies and trials by measuring the amount of, in this case, anti-oxidants and organic acids.

An example is the suite we put together on ephedra. The cranberries will follow the same protocol, along with blueberries and bilberries. There are five stages. There’s a botanical garden in Missouri that has a spectacular collection of herbs and medicinal plants. We get from them specimens of ephedra sinica that have been verified by botanists as the species that produces the ephedrine alkaloids. We take samples from these certified plants, and produce what’s called the native extract. In industry—whether the plant in question is saw palmetto or cranberry or whatever—the source material is juiced or dried into an extract, which might be augmented with other properties that have been determined to be beneficial, and then sold to vitamin or supplement companies to make commercial, oral-dosage forms. But you need to be able to verify whether you’re actually getting 100 mg of what you’re supposed to be getting, in each pill—or is it 185 mg, or all filler? You need to be able to measure accurately, and you need a standard against which to measure. With your ruler, in your factory, you can measure your sample against the SRM—your freeze-dried cranberries or your cranberry juice can be compared to the NIST standard dried cranberry or juice.

And the five stages in the process are to measure the pure plant parts, the refined extract, the extract plus helpful extras, the commercial-grade extract, and the dosage form.

Right. At the moment, we’ve got cranberries that have been sent to be freeze-dried, and from there we will make the powdered cranberries, and measure everything about them that could be of possible interest. We’ve done the same thing for gingko biloba.

Suppose I’m a cranberry juice manufacturer, and I need to be in compliance with the standards represented by these samples. How does your information come into my factory?

We are not a regulatory agency. We set standards, but we have no ability to make anybody comply. That’s up to the FDA, the EPA, Congress, etc. SRMs are available for companies to buy if they choose. These are considered the primary standards, and they’re rather expensive. But certified labs can then use these to calibrate their own instruments, and companies can, in turn, use those.

The SRMs exist like the cesium-123 second, as absolutes. Practical real-world measures are based on the standard, and the standard is here to guarantee the relation between “identical” units.

Yes. The SRMs exist here in building 301. Analytical chemists and technicians in pharmaceutical companies, and potted-meat companies, and what have you, can compare their products to these, so that when you get a label that says your milk has so much calcium per serving, and so many calories from saturated and so many from unsaturated fats, these quantities are traced back to a solid measurement.

Do agencies like the National Institutes of Health provide you with lists of things to test for?

Yes. There are regulatory standards, and research standards. For example, infant formula is the most highly regulated food on the market. That’s why we have what’s called the Baby Food Composite SRM. The Infant Formula Act was passed in 1980, so there’s been SRM formula and baby food around for many years. Then came the Nutrition Labeling and Education Act of 1990, followed by the Dietary Supplement Health and Education Act of 1994—that started the testing on the gingkos.

What’s in Baby Food Composite?

It’s a mix of meat, vegetable, and fruit. It’s all mushed into one. We also have SRM infant formula that’s milk-based. We come out with new ones every so often. We have SRM Spinach Slurry, which measures, in addition to nutritional information, trace pesticides. We have SRM Spam, supplied courtesy of the Hormel Company—other suppliers don’t want to have their brand names associated with the samples that they’ve given us. We have SRM trout. SRM beta-carotene and other carotenoids from carrots and leafy greens. SRM baking chocolate. SRM coconut oil. SRM cigarettes—which measure the ignition threshold of cigarettes, going back to those mattress fires.

Do other countries have their own NISTs?

The European Union has theirs, as do countries like Japan.

If the Japanese are measuring how many anti-oxidants are in an ounce of cranberry juice, or how many cesium-123 oscillations occur in a second, they should come up with an answer identical to yours. Is there a meta-NIST that tests the Japanese measurements against the American, and so forth?

From time to time we have round-robin comparative studies. They don’t always agree. Then we try to understand if there’s a systematic error going on. Europe, especially, is very concerned about genetically modified organisms—how can you tell if there is GMO corn oil in what you’re buying? So we share that kind of data. These comparisons can lead to fundamental discoveries. But often the differences between the national measurement labs are very, very small—maybe more than we would like, but as far as how much sodium is in your peanut butter, it’s not going to create an international incident.