The potential of Raman spectroscopy for the analysis of diagenetically transformed carotenoids

Abstract

Recently, carotenoids have received much attention as target compounds for astrobiological prospecting principally because they are a group of molecules that display unique diagnostic Raman spectra that can be assigned to organic material of unequivocal biological origin. However, no work has been performed on assessing the potential of Raman spectroscopic detection of carotenoids from fossilized microbes. Here, we report the first Raman spectra acquired from ‘perhydro’ derivatives of β-carotene and lycopene formed by hydrogenation of the polyene chain during diagenesis, resulting in much less specific fossil hydrocarbons such as β-carotane and lycopane, respectively. We propose here that diagenetically altered carotenoids formed by hydrogenation reactions during the fossilization processes also provide unique diagnostic spectra that can be interpreted as a biological signature.

Remote Raman Spectroscopy for Planetary Exploration: A Review

“…49,73 Carotenoids, like beta-carotene, can indicate the presence of algae or bacteria, and Raman has been proven capable of distinguishing between different types of carotenoids. 82 Sharma showed a timeresolved standoff system was capable of making Raman measurements of a tomato and a poinsettia leaf, thereby showing the capability of Raman to measure carotenoids in different matrices, including within a tomato (Fig. 10).…”

“…9 Diagenetically-reduced carotenoids are formed when biological material is fossilized, creating a possible indicator of past life. 82 In addition, chlorophyll in leaves has been analyzed using standoff, time-resolved Raman systems. 83 …”

Degradation of microbial fluorescence biosignatures by solar ultraviolet radiation on Mars

“…Instruments designed to detect organic molecules or other potential tracers of life on Mars include gas chromatography mass spectrometry (GCMS), as installed aboard NASA's Mars Science Laboratory (Mahaffy et al 2012) and proposed for the ESA-Roscosmos ExoMars rover (Evans-Nguyen et al 2008;Goesmann et al 2009); Raman spectroscopy (Ellery & Wynn-Williams 2003;Jorge Villar & Edwards 2006;Marshall & Olcott Marshall 2010;Rull et al 2010), and antibody-based systems such as the Life Marker Chip (Sims et al 2005). Such instrumentation can offer very high sensitivity and discriminatory power, but often requires sample preparation, long exposure times or limited resources or reagents.…”

Understanding the Application of Raman Spectroscopy to the Detection of Traces of Life

“…By comparison, the diagenetically transformed carotenoid b-carotane has additional bands than that of the b-carotene spectrum. The band at 1455 cm À1 is assigned to d(CH 2 ) scissoring mode of methylene, numerous bands between 1390-1000 cm À1 are assigned to n(C-C) stretching, and bands between 1000-800 cm À1 are assigned to a combination of d(C ¼ CH) methyl in-plane rocking and d(C-H) out-of-plane bending modes (Marshall and Marshall, 2010). From an astrobiological perspective, it is desirable to target organic molecules that are clearly distinguished from abiogenic compounds.…”

“…4 is a stack plot comparison of Raman spectra produced by an extant endolithic community dominated by cyanobacterium (Nostoc sp. ), synthetic b-carotene (purchased from Sigma Aldrich), synthetic b-carotane [purchased from Chiron and prepared as in Marshall and Marshall (2010)], a thermally immature acid-extracted [standard HF=HCl preparation as described in Marshall et al (2005)] acritarch Tanarium conoideum (ca. 590-565 Ma, from Observatory Hill #1 drill core, Tanana Formation, Australia), a thermally mature acid-extracted acritarch Shuiyousphaeridium macroreticulatum [ca.…”