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SUMMARY:Chemical-physics properties\, complexity and chirality measures fo
 r the amino acids of the isoleucine series from Antarctic meteorites - Fab
 iana Da Pieve
DTSTART:20181107T113000Z
DTEND:20181107T123000Z
UID:TALK114397@talks.cam.ac.uk
CONTACT:Nick Woods
DESCRIPTION:With the observation of liquid water and active geology on the
  Jupiter’s moon Europa and Saturn’s moon\nEnceladus\, solid organic ma
 tter on Titan\, water ice in the shallow subsurface of Mars\, and the expe
 cted\nincrease in the number of observed exoplanets\, planetary exploratio
 n is making fundamental steps in the\nsearch for life in the Universe [1].
  However\, current strategies for biosignatures detection can be affected\
 nby the underlying assumption that life elsewhere in the Universe would be
  based on a chemistry similar to\nthe terrestrial one. Recent works on new
  strategies for the detection of universal life biosignatures suggest\na p
 aradigm shift from the traditional spectroscopic identification of known b
 iomolecules to new approaches\nbased on geometrical/topological complexity
  measures of the molecules or biologically-derived objects.\n\n\nBeing the
  building units of proteins\, amino acids are high priority targets in the
  search for biosignatures\,\neither in the gas phase as formed by lighteni
 ng in planetary atmospheres\, or in condensed assemblages in\nmineral matr
 ices on planetary surfaces\, icy crusts of outer Solar System’s Moons or
  icy mantles of small\nbodies. However\, meteoritic samples exhibit a larg
 e set of amino acids\, most of them unknown to our\nbiosphere [2\,3]\, sug
 gesting that amino acids are not unambiguous indicators of life. Here we p
 resent an\ninvestigation of the underlying link between complexity\, chira
 lity and physico-chemical properties of\namino acids of the isoleucine ser
 ies\, found with large enantiomeric excess in Antarctic meteorites. Such\n
 series features amino acids which are either involved in protein synthesis
 \, or featured in human plasma\, or\nexternal to our biosphere. For both t
 he gas and the condensed phase\, we analyze\, via Density Functional\nTheo
 ry\, wavefunction-based approaches and perturbation theory\, the link betw
 een the electronic properties\n(the HOMO-LUMO and the band gap)\, a comple
 xity measure informing on the delocalization of the\nelectronic cloud [6]\
 , a chirality measure (as the distance for each amino acid to the closest 
 achiral object) and the H-bonding network. The results [7] show that: a) u
 pon condensation\, L-isoleucine (involved in protein biosynthesis) gains i
 n complexity and chirality w.r.t. to the gas phase\; b) its complexity is 
 slightly\nhigher than the value for D-allo-isoleucine (not present in livi
 ng systems)\, while its chirality degree is lower\;\nc) it has a slightly 
 weaker and less intricate H-bonding network. The findings might serve to e
 xpand the\nstrategy for the search of biosignatures towards complementary 
 approaches allowing for a mean to score\nknown and unknown amino acids on 
 a universal complexity/electronic/bonding properties scale.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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