Biological Physics is Exciting and Challenging

RLM 4.102
Physics Department Oakes Lecture - Dr. Hans Frauenfelder
Los Alamos National Laboratory
Biological Physics is Exciting and Challenging
Biological physics is the exploration of biological systems by physicists.
The goal is to find general concepts and principles. Stan Ulam, a famous
mathematician, once said to me: "Ask not what physics can to for biology,
but what biology can do for physics." The challenge comes not only from the
complexity of even "simple" biological system, but also from the fact that
biological physics interacts with biology, chemistry, computing, and

Myoglobin, the protein that stores dioxygen in muscles, is the hydrogen atom
of biological physics. Myoglobin and hemoglobin were the first proteins
whose structures were determined by Kendrew and Perutz. Their X-ray
structures convey the impression that each atom is in its own place. But how
could they function with just one conformation? Indeed, low temperature
experiments that we performed a long time ago proved that a protein can
assume many conformations and that function is based on motions from one
conformation to another.

Another surprise came from examining what controls the motions. A protein is
surround by a hydration shell, one or two layers of water. Fluctuations in
the shell control internal motions. Two techniques prove this fact. The
fluctuations in the hydration shell are measured with dielectric
spectroscopy; the internal motions are measured with the Mössbauer effect.
Surprisingly, the Mössbauer effect in proteins displays two unexpected
features, an apparent dynamic transitions and a broad line. A new look shows
that both features are two sides of the same phenomenon; they are caused by
the fluctuations in the hydration shell. Similar to the two-slit experiment,
they involve the Heisenberg uncertainty principle and cannot be explained

What are the concepts that have emerged so far? Possibly the most important
one is the hierarchically organized free energy landscape. A second one is
the role of  environmental fluctuations in controlling protein dynamics.

50 years ago myoglobin was "fully understood".  Now we know that we still
have a long way to go even for this "simple" protein. And, remember, most
biologic phenomena are much more complex.