At the Nexus of Physics and Biology
Eugenie V. Mielczarek
Department of Physics
George Mason University
About the Lecture
Genetics specifies the organism but all of its functions are determined by gravity, electromagnetism, thermodynamics and quantum mechanics. From the mechanics of fueling cells, to the automotive-like clutches of E.coli bacteria, and the ability of geckos to walk on the ceiling, the physics of living organisms is remarkable. In 2008 the National Academies of Sciences published “Inspired by Biology: From Molecules to Materials to Machines,” examining how research at the intersection of the physics and biology will lead to new materials and devices, with applications ranging from nanotechnology to medicine. This lecture will describe several of these systems and the physics which governs their motion.
About the Speaker
EUGENIE VORBURGER MIELCZAREK is Emeritus Professor of Physics at George Mason. Her experimental researches in materials science, chemical physics and biological physics have been published in The Physical Review, the Journal of Chemical Physics and the Biology of Metals. She has been a visiting scientist at the National Institutes of Health, and a visiting Professor at the Hebrew University of Jerusalem. She is a recipient of the Distinguished Faculty Award at George Mason University. She has advised National Public Radio, judged the U. S. Steel-American Institute of Physics prize for science journalism, and written book reviews for Physics Today. She was the primary editor of “Key Papers in Biological Physics.” She is the author of a popular science book. Her most recent article was a review of research frontiers linking Physics and Biology.
President Larry Millstein called the 2,251st meeting to order at 8:23 pm March 6, 2009 in the Powell Auditorium of the Cosmos Club. The minutes of the 2,250th meeting were read and approved after some questions were resolved.
Mr. Millstein announced that this was the David Franklin Bleil Memorial Lecture, and he reviewed some of the contributions the late Mr. Bleil made to the Society. He then introduced the speaker of the evening, Ms. Eugenie Mielczarek, emeritus professor of George Mason University. Ms. Mielczarek spoke on “At the Nexus of Physics and Biology.”
“Genetics determines the organism, but all of its functions operate within the laws of physics,” Ms. Mielczarek said. Gravity, electromagnetism, thermodynamics, and quantum mechanics all affect the lives of organisms as surely and effectively as genes do. Biology is not simply writing information; it is doing something about it, she said.
As Richard Feynman said, a biological system can be exceedingly small. Many of the cells are very tiny, but they are very active; they manufacture various substances; they walk around; they wiggle; they do all kinds of marvelous things – all on a very small scale. She quoted John Bush – “Most every problem you can imagine has been solved by nature. All that is left is to rationalize nature’s designs, many of which are remarkably subtle.”
In the 1930's, Max Delbruck, working with radiation, deduced from mutations in fruit flies that genetic information must be carried by a long chain molecule. Erwin Schrodinger, in 1944, reasoned that because the organization of living systems was orderly, they must be governed by thermodynamics and statistical laws.
For an astounding example of physics and biology, consider the feet of the gecko. Tiny scales, two nanometers thick, grip the tiny particles of surfaces. E. Coli have a rotary motor built into them. Kinesin and actin work together to form a linear motor on a track. Molecular sensing immune processes, quantum control of photosynthesis, intriguing materials in sea sponges, and bio-optics in brittle stars: these are all wonderful examples of biology and physics co-acting.
The gecko’s feet represent remarkable engineering. It takes 90 pounds of force to pull a gecko from where he wants to stay. She recounted being in a hotel room in India and seeing a gecko on a wall. She asked a clerk to do something. His response: “Don’t worry. They never come down.” These feet stick to almost any surface. The orientation of the gripping structure is anisotropic. The feet are self-cleaning. Despite the powerful adhesion, geckos can scamper along very rapidly, lifting and placing their toes almost too fast to see. They have tiny gripping ridges called spatulae, located on setae, tiny bristles. There are 100 to 1000 spatulae on each seta, 1099 per gecko. Each tiny surface is placed on the wall and the center retracted and it is done in milliseconds. The system works for 10,000 cycles. Industrial applications of such a system are being discussed in the Journal of Nanotechnology. Medical applications are also possible.
Consider the wiggling action of e coli. They have bodies with flagellae. While it is hard to see, the flagellae don’t just wiggle, they actually rotate. This rotation works well for them; scaled to human proportions, they would be swimming 40 miles an hour. She showed a picture of the flagella structure, and it looked very mechanical. It is, in fact, a clutch and motor that make it work, she said. She showed a cartoon of the structure labeled with names of car parts. The diameter of the motor is 40 nm, .1 of the wavelength of light. The motor produces 20 picoNewtons of torque, but it spins 1 micron/second. Its power output is 13,600 watts/kilogram. It is the most powerful motor yet discovered.
Life’s energy usually comes from carbon based chemistry, and that chemistry is 19 times more efficient with oxygen. Oxygen only arrived on earth about 3 billion years ago, but 4 billion years ago, there was life at the bottom of the seas. It was based on sulfur.
She discussed tube worms found at geothermal vents in the sea. They have a type of hemoglobin, although there is no oxygen there. There are also organisms there with light sensitive molecules in them, although there is no light there. These facts led scientists to speculate that perhaps life, even our kind of life, originated there.
The greatest amount of light from the sun is in green. It is not an accident that photosynthesis is a very efficient process. It is also interesting that green light makes e coli start to move very fast and red slows them down. This may lead to applications such as artificial retinas, protein based field effect transistors, and optical holographic processors.
She discussed molecular transport, the process by which molecules get from the outside cells into the biochemical working factory of the cell's interior. The carrier is a molecule of kinesin; this molecule steps along a track of actin. The molecule is fueled by atp-adp chemistry. Stepping along the track carrying a food molecule into the cell, the kinesin looks rather like a lean Michelin Tire Man packing a load. As the atp and adp move along, energy is transduced into a force that actually pulls the kinesin forward. This kinesin motor is 50% efficient, about twice as good as a gasoline motor. The kinesin makes 100 steps a second, each 8 nm.
When red blood cells hit lungs, each hemoglobin takes up an O2. When one O2 gets in there is a conformational change that makes it 75% more likely others will get in. This is what doesn’t work for people with sickle cell anemia. In sickle cell disease, after O2 is dropped off in the capillary, the genetic anomaly causes the hemoglobin to form polymers – the cells stiffen and clog the vein. Thus less cells enter the lungs for O2 replenishment.
There is a possibility that we may change from manufacturing goods to growing them in culture. Chemical analyses suggest it would be cheaper. If that change happens, these little mechanisms that are part of our biology will be strangers amongst us no longer.
The first questioner asked, is there a size limitation? Is there a minimum size below which things cannot be alive? Ms. Mielczarek did not give a definite answer, but said that evidence points to the minimum size being that of a mitochondria, about the size of a bacteria. This was seconded by the former director of NSF, a biologist. The discussion did recall the “Martian meteorite statement” in which a group of NASA people, on the eve of a budget decision, from a White House podium, claimed to have seen evidence of life in Martian meteorites. No experts joined in the announcement; the small size of the structures observed was inconsistent with examples of life, and it developed eventually that the meteorites were not from Mars.
Another questioner challenged Ms. Mielczarek on her reasoning that the commonalities between our kind of life and those at the sea bottom argue for joint origin. The commonalities could also have been produced by the passage of eons.
Another person clarified that the sulfur in sea bottom life replaces carbon, not oxygen.
Someone asked, why would animals in ocean trenches have molecules that would not be useful to them? Ms. Mielczarek said she did not know. You would have to ask an evolutionary biologist.
After the discussion, Mr. Millstein presented a plaque commemorating the occasion to Ms. Mielczarek. He announced the next meeting. He discussed improving programs and invited suggestions for speakers. He made the parking announcement. He encouraged people to join and to get involved. There are many things to do, he said. Finally, at 9:46 pm, he adjourned the 2,251st meeting to the social hour.
The weather: Cool and mild
The temperature: 10°C
Ronald O. Hietala,