C6. Commission on Biological Physics

Report to the 2002 General Assembly for 1999-2002
Berlin, Germany
October 7-12, 2002

ACTIVITIES

C6 had one meeting of on July 30, 2002, in Kyoto where nearly all members were present. All other contacts have been performed by e-mail.

The commission was involved in two conferences, sponsored by the IUPAP. The first one was organized by the ESRF, Grenoble, from October 11 to 14, 2000 with the topic: "Biological Physics & Synchrotron Radiation." The second one was the "Fourth International Conference on Biological Physics" held in Kyoto from July 30 to August 3. Again, the conference covered an increasing broad field including also brain research. There were 677 participants registered including 181 students with 619 scientific contributions. This demonstrates the growing interest in Biological Physics. The program also showed the increasing overlap with the activities of IUPAB.

The Commission agreed and decided that the next Conference on Biological Physics will be held in Göteborg, Sweden. The International Program Committee should include the C6 Commission members automatically, other international and national

members should be added later. The precise topics of the conference will be decided later. Meanwhile, the date is fixed to August 23-27, 2004. It will be at the conference center at Chalmers Institute of Technology. Chairman is Clas Blomberg, vice-chairman Mats Jonson and secretary Leif Matsson.

In the present time, the availability of large-scale facilities becomes more and more important for experimental Biological Physics. Therefore, the Commission was also active in the IUPAP "Working Group on Facilities for Condensed Matter Physics (WGFCMP)" with the subgroup "International Commission on the Future of Neutron Sources (ICFNS)." This activity should be continued.

The Commission C6 is well aware of the fact that "physics and life science" is of increasing interest for different scientific organizations. There are two main streams: On one side there is the IUPAB on the international level, the EBSA on the European level and the national biophysical societies. On the other side are the IUPAP with the Commission C6 on the international level. Recently, the European Physical Society created the "Division on Physics in Life Sciences (DPL)" and there are the groups like the "American Physical Society-Division on Biological Physics (APS-DBP) on the national basis. It is important that this diversity yields a reinforcement of the whole field and not a weakening by competition.

NEW DEVELOPMENTS IN THE FIELD:

The human genomic project has been finished successfully. In principle, the plan of a human being is in our hand. The new high light in life sciences is proteomic, the investigation of the collectively acting proteins in a cell. From a physical point of view these developments reinforce the importance of an understanding of dynamics and function on the level of three-dimensional structures with atomic resolution.

Large experimental facilities became indispensable in biological physics. Synchrotron radiation yields a dramatic increase of the number of protein structures determined with atomic resolution. Protein structure factories will manifold this knowledge. The large number of well-known structures may help to understand the folding problem. Here, the final goal is the calculation of the three-dimensional structure from the sequence. Synchrotron radiation crystallography made possible the structure determination of functional macromolecular assemblies like ribosome or photosystem. Here we are just at the beginning. Another important field that has been opened by synchrotron radiation is the time resolved X-ray structure analysis of conformational changes in proteins. Structural relaxations triggered by laser flashes can be registrated on the time scale of picoseconds and nanoseconds. At present only few systems have been investigated. The data analysis has still to be improved. Many light sensitive systems wait for the inquiry.

The development of new equipment for the protein structure analysis with neutrons allow structure determinations with the resolution common for X-rays. This opens the possibility of a detailed study of hydrogen positions. Such experiments can decide if theoretically calculated hydrogen positions are correct. The experiments may also be helpful to improve the energy functions describing a protein molecule.

One of the most fascinating topics in "Biological Physics" is the Single Molecule Spectroscopy. Fluorescence marking allows following motions in molecules like in ATP Synthase. Atomic Force Microscopy has developed from a pure imaging instrument to a precise machine for the measurement of forces. This enables us to watch biological nanomachines at work. It became possible to see the motion of individual motor proteins along filaments of the cytoskeleton. The obtained data are not the result of statistical averaging but are meaningful for a single molecule. Several experiments also tell us how the measured quantities vary from one molecule to another. It is obvious that single molecule investigation have a great future. Will this technique supersede investigations which yield only ensemble averages? This is very unlikely. Biological single molecules are individuals. Going from state A to state B individual molecules do not necessarily follow the same kinetic path. It is like in demography. The statistic average will not tell you anything about the individual fate. The study of individual fates may not reflect the general picture. Single molecule investigations and ensemble average measurements are complementary. Nevertheless, there is a strong backlog demand for single molecule investigation.

There may be a new strategy to understand evolution. One may start from a random polypeptide library and investigate the development to functional proteins. This approach could give an important clue for deciding whether the universality of proteins originates from the single evolutionary history on the Earth or from physicochemical properties of this heteropolymer. Moreover, it would yield images on the fitness landscape in the sequence space of proteins, which is one of the main issues in physics of molecular evolution.

Besides "Molecular Biological Physics" the cellular aspects will gain attention. The viskoelastic properties are important for the shape of the cells and the reaction to external forces. The complex interplay of short-range forces controlling the cell adhesion needs further investigation. The electrical interfacing of nerve cells and semiconductor chips improved our understanding of neuronal networks. This research may lead in future to systems that are applicable in neurobiology and medicine.

There is a large growth potential for theory. How does the brain represent the outside world? What information is hidden in the protein data bank and in the results of the human genome project? It is also obvious that increasing computer capacities will be needed to understand the function of protein aggregates on the basis of quantum physics.

Beside all fascinating new developments Biological Physics should reserve some room for a very detailed investigation of some biomolecules in order to extract basic concepts. One should not forget that semiconductor physics and several chapters of solid state physics have been developed by studying only two materials: germanium and silicon. Everyone knows the tremendous consequences of this research.