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
