Astrobiology

Radiation damage of single bio molecules in vacuum and in nanodroplets

by Prof. Henrik Cederquist (Physics Department, Stockholm University)

Europe/Stockholm
Description
By means of the electrospray technique, it is now possible to perform detailed experiments on the radiation damage of single bio-molecules in vacuum and in nanodroplets. In this talk, I will report on a recent experiment in which we studied the fragmentation of the AMP molecule in vacuum and with specified numbers of water molecules attached to it (AMP stands for AdenosineMonoPhosphate and is a nucleotide - an important building block of the DNA molecule). The energy transfer to the AMP(H2O)n- ions, necessary in order to provoke fragmentation on the time scale of the experiment, was achieved by acceleration of the molecules to 50 keV and subsequent collisions with target gases of Ne or Na. We find that 13 water molecules are sufficient in order to completely protect the AMP from radiation damage (fragmentation) which otherwise is an important reaction channel for lower numbers of attached water molecules [1]. This conclusion was reached [1] for collisions in which the AMP(H2O)n- complexes were excited through so called collision induced excitation processes (i.e. excitation processes without accompanying electron transfer). However, when carefully studying the much weaker processes with accompanying electron transfer forming dianion AMP systems we found that these very often lead to selective loss of a single H atom. The larger the number of attached water molecules, the larger is the probability for the AMP to be damaged (i.e. to lose an H-atom) through the (weak) electron transfer channel. The radiation damage phenomena studied here relates to question on the general relevance for experimental results for bio molecules in vacuum for properties and functionality in native environments. The present results may also be a starting point for a discussion on what protective environments bio molecules may need in order to survive in space and in transports through planetary atmospheres.

[1] Collision-induced dissociation of hydrated adenosine monophosphate nucleotide ions: Protection of the ion in water nanoclusters, Liu, B, Nielsen, S. Brondsted, Hvelplund P, Zettergren H., Cederquist, H., Manil, B., and Huber, B. A. , PHYSICAL REVIEW LETTERS 97 (13): Art. No. 133401 SEP 29 2006

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