Abstract

MARTINEZ REYES, José; GONZALEZ PARTIDA, Eduardo  and  PEREZ, Renee J.. Use of oligonucleotid physicochemical properties as biomarkers. Bol. Soc. Geol. Mex [online]. 2009, vol.61, n.2, pp.167-175. ISSN 1405-3322.

Biological markers (biomarkers) are complex molecular fossils from biomolecules in living organisms. Due to their general are resistant to weather, the biodegradation, evaporation and other biological processes, as commonly preserved in rocks and can be used by geologists, geochemists, archaeologists, etc. for information on organic matter in source rocks, the presence of oil, environmental conditions during sedimentation (diagenetic process), the thermal maturity experienced by the oil and / or rock (catagenetic process), the degree of biodegradation, some aspects of mineralogy of the source rock (lithology), the age of fossils and characterization of DNA (deoxyribonucleic acid). Biomarkers can be oligonucleotides, which are stretches of DNA molecules of simple fixed-length string. DNA from fossils can form cross-links among themselves or with other molecules to the passage of time, hindering the use of techniques such as PCR for study, therefore, in this work was applied to oligonucleotides a technique for determining the pK_a values (potential of the ionization constant), by UVspectrophotometry in the basic pH range, using as the model oligonucleotide d-AAAGAAA in NaCl aqueous solution, titrating it with NaOH solution. Also in the presence of a pH buffer solution (NaHCO3). Furthermore pK_a values were determined for the same compound at different conditions of temperature, salts and mixtures of alcohol-water as solvent. We also assessed the pK_a oligonucleotides d-CCCGCCC and d-AAGAA. pK_a values were obtained on a range between 9 and 12. These results are a contribution to the knowledge of the physical properties of oligonucleotides, such data may be particularly useful in the aforementioned case of difficulty using other techniques such as PCR for the characterization and interpretation of oligonucleotides as biomarkers.

Keywords : oligonucleotides; biomarkers; potential of ionization constants.