Sublimation extraction coupled with gas chromatography-mass spectrometry: A new technique for future in situ analyses of purines and pyrimidines on Mars

International audienceWe have developed a sublimation technique coupled with chemical derivatization and gas chromatography mass spectrometry (GC-MS) to detect nucleobases and other volatile organic compounds derived from bacteria in Mars analog materials. To demonstrate this technique, a sample of serpentine inoculated with Escherichia coli (E coli) cells was heated to 500 degrees C for several seconds under Martian ambient pressure. The sublimate was collected on a cold finger, then derivatized and analyzed by GC-MS. We found that adenine, cytosine, thymine and uracil were the most abundant molecules detected in the sublimed E coli extract by GC-MS. In addition, nucleobases were also detected in sublimed extracts of a deep-sea sediment sample, seawater, and soil collected from the Atacama Desert in Chile after heating the samples under the same conditions. Our results indicate that nucleobases can be easily isolated directly from natural samples using sublimation and then detected by GC-MS after chemical derivatization. The sublimation-based extraction technique is one approach that should be considered for use by future in situ instruments designed to detect organic compounds relevant to life in the Martian regolith

Design and validation of a questionnaire about the perceptions of dual career student-athletes (ESTPORT) [Diseño y validación del cuestionario de percepción de los estudiantes universitarios-deportistas de alto nivel sobre la carrera dual (ESTPORT)]

The purpose of this paper was to design and validate a questionnaire about the perceptions of elite studentathletes at university relating to their dual career. In the initial creation of the instrument, constructs were defined and three dimensions were established: academic life, sporting life and sports tutor. After a process of ‘back translation’, experts (n = 8) agreed the construct to ensure content validity, the dimensions and the questionnaire questions. Statistical analysis of the items showed adequate comprehension to confirm content validity of participants (n = 30). In construct validity (n = 73), the results showed correct psychometric quality, internal consistency, reliability and adequacy of the structural model. The instrument had evidence of external validity, since the results were congruent with the main findings of the research. This questionnaire was found to be a valid and reliable assessment instrument, consisting of 84 questions (in Spanish and English language), that enables the perception of elite student-athletes to be known about their dual career whilst at university. © 2016, Universidad Catolica San Antonio Murcia. All rights reserved

Aspartic acid racemization rate in narwhal (Monodon monoceros) eye lens nuclei estimated by counting of growth layers in tusks

Ages of marine mammals have traditionally been estimated by counting dentinal growth layers in teeth. However, this method is difficult to use on narwhals (Monodon monoceros) because of their special tooth structures. Alternative methods are therefore needed. The aspartic acid racemization (AAR) technique has been used in age estimation studies of cetaceans, including narwhals. The purpose of this study was to estimate a species-specific racemization rate for narwhals by regressing aspartic acid d/l ratios in eye lens nuclei against growth layer groups in tusks (n=9). Two racemization rates were estimated: one by linear regression (r2=0.98) based on the assumption that age was known without error, and one based on a bootstrap study, taking into account the uncertainty in the age estimation (r2 between 0.88 and 0.98). The two estimated 2kAsp values were identical up to two significant figures. The 2k Asp value from the bootstrap study was found to be 0.00229±0.000089 SE, which corresponds to a racemization rate of 0.00114−yr±0.000044 SE. The intercept of 0.0580±0.00185 SE corresponds to twice the (d/l)0 value, which is then 0.0290±0.00093 SE. We propose that this species-specific racemization rate and (d/l)0 value be used in future AAR age estimation studies of narwhals, but also recommend the collection of tusks and eyes of narwhals for further improving the (d/l)0 and 2kAsp estimates obtained in this study