Eur. Phys. J. D 20, 309–316 (2002) DOI: 10.1140/epjd/e2002-00185-0 T HE EUROPEAN P HYSICAL JOURNAL D Editorial Molecular physics of building blocks of life under isolated or defined conditions R. Weinkauf 1 , J.-P. Schermann 2 , M.S. de Vries 3 , and K. Kleinermanns 1 1 Institut f¨ ur Physikalische Chemie I, Lichtenbergstrasse 1, 40225 D¨ usseldorf, Germany 2 Laboratoire de Physique des Lasers, Insitut Galil´ ee, Universit´ e Paris-Nord, 93430 Villetaneuse, France 3 Dept. of Chemistry and Biochemistry, Santa Barbara, California 93106, USA Received 29 August 2002 Published online 13 September 2002 –c  EDP Sciences, Societ` a Italiana di Fisica, Springer-Verlag 2002 Abstract. In this paper we motivate the study of biomolecular building blocks under isolated or well defined conditions. We explain why we believe that especially gas phase investigations in combination with quantum chemical calculations can provide new insights into molecular properties, such as structure, molecular recognition, reactivity and photostability. Although the gas phase represents far from in situ conditions, these findings are important for a detailed understanding of biology. We give a short historic overview of gas phase studies of biomolecular building blocks under isolated conditions, present some examples and report the current status of this field. We explain the new quality of synergy between experiment and quantum theory and the unique opportunities therein to discover new pathways for reactivity and to understand biological processes on an atomic level. We sketch the content of this special issue and give a further perspective of the research field of “Spectroscopy of biomolecular building blocks under isolated or defined conditions” and explain the possible connectivity to biology. Introduction The success of life on earth is based on the high chemical and photochemical stability of the building blocks of life, the highly confident and fast reproduction mechanisms of organisms, the high efficiency and selectivity of biochemi- cal processes and the endless time for optimization by the trial and error of evolution. Life in its different forms is very complex. The understanding of life on a molecular level is therefore one of the most interesting and challeng- ing research subjects of humanity. Molecular biologists, biochemists, biophysicists, physicists, chemists and theo- reticians work in this field. A good example of such inter- disciplinary cooperation is the discovery of the DNA struc- ture by Watson and Crick, a physicist and a chemist [1]. Nowadays the modular structure of biological relevant molecules, such as DNA, RNA and peptides is reason- ably well understood and the transcription codes are well known. Most of the current research in biology and bio- chemistry is based on this knowledge and has achieved great progresses in the understanding and in the ma- nipulation of these processes. However, still fundamental aspects concerning the building blocks of life and their inter- and intramolecular properties are not yet fully un- derstood. Therefore the investigation of peptide, protein, DNA and RNA structures, dynamics and reactivity on an atomic level is still a highly relevant research field which is especially important for the understanding of biologi- cal function and the selectivity of biological processes by molecular recognition. Since biology takes place in a condensed medium, the most widely used experimental approaches have been X- ray crystallography, NMR, IR and UV spectroscopy. Mod- elling by force-fields is needed to support the assignments of spectral data and for visualization of molecular pro- cesses. With the help of these methods it has been pos- sible to unravel many macromolecular structures. The experimental methods work best for frozen, rigid molecu- lar structures and their resolution typically suffers when thermal motion causes disorder resulting in a broad dis- tribution of molecules with different conformations, dif- ferent charge states (protonated molecules, deprotonated molecules, zwitter ions), different tautomeric forms or dif- ferent environments, such as different solvents or just dif- ferent solvent orientation. In such broad ensembles the spectroscopic information of the individual molecule is washed out or manipulated by the environment. As a re- sult, important properties of the bare molecules are buried under the inhomogeneous broadening and it is difficult to distinguish which property are intrinsically intramolecular as opposed to being imposed by the environment is still poor.