1.2 Molecular biophysics

As mentioned before, biophysics covers a wide range of topics related to living systems. The object of study includes biomolecules, cells, organisms and ecosystems. Some studies focus on the structure of the elements such as proteins, membranes, tissues, etc. Some others focus on the dynamics such as protein folding, cell motility, self-assembly. Another topic is systems biology, that focuses on the dynamics of complex systems such as networks of proteins or population growth.

Molecular biophysics is a sub-topic of biophysics that studies the structure, function and kinetics of biomolecules. There are two main types of biomolecules: nucleic acids (DNA and RNA) and proteins, which include enzymes and molecular motors. Biomolecules are the building blocks of cells and they are also made of subunits (amino acids, nucleotides). So biomolecules are located in the middle level within the hierarchy of organization of the living systems (from atoms to ecosystems). The physical regime of biomolecules is governed by thermal fluctuations. The typical interactions of biomolecules involve weak bonds such as hydrogen bonds or Van der Waals forces. These bonds can be broken by thermal fluctuations. So the properties of biomolecules are determined by bonds that have similar energies to the ones of the surrounding thermal bath. Here emerges on of the most interesting questions in molecular biophysics. How can molecules work embedded in such thermal fluctuations?

Hot topics in molecular biophysics are RNA and protein folding, mechanochemistry of molecular motors, ionic channel transportation and DNA-protein interaction. The range of experimental techniques available is very wide. Apart from the well known biochemical techniques such as PCR and electrophoresis, biophysicists use X-ray diffraction, calorimetry, nuclear magnetic resonance, electronic and confocal microscopy among others. Finally, the development of single-molecule techniques such as AFM or optical tweezers have provided a new insight in molecular biophysics. The quantitative measurements obtained with these techniques allow biophysicists to understand the structure and the function of biomolecules and formulate models to characterize and predict their behavior. This will be discussed in the next section.

JM Huguet 2014-02-12