Forensic and biological applications of vibrational spectroscopy
Determination of the age of a bloodstain can be used to establish the time when a crime was committed. As blood ages, deoxyhemoglobin (HbO 2) is converted into methemoglobin (MetHb), which is evident by the color change from red to brown. Fluctuations in temperature will cause blood to age at a non-constant rate. It has been shown that higher temperatures cause deoxyhemoglobin to oxidize more rapidly to methemoglobin. ^ Human blood from vein and capillary vessels was used in this investigation. The samples were prepared by placing blood on various substrates such as gauze and watch glasses. Mid-IR and near-IR spectra of the samples were measured periodically at ambient conditions for one month. Changes in the spectra can be interpreted in terms of chemical changes in the samples. Loss of water plays a significant role in establishing the initial changes in the spectra. A substantial decrease of water was observed in the spectra of bloodstain samples during the first hour. Other spectral changes were observed for the next 21 days. ^ Mid-infrared, near-infrared, and Raman spectra of biomolecules such as carbohydrates, nucleic acids, lipids and proteins provide information as to structure of biomolecules, nature of molecular interactions and characterization of protonated groups. Vibrational spectroscopy is a sensitive technique for detecting very small structural changes in biomolecules such as hydrogen bond formation or protonations of basic functionalities. However, the full potential of vibrational spectroscopy is limited by the inability to identify overlapping bands in spectra of complex molecules. ^ The objective of this research was to develop methodologies for improving assignments and interpretation of mid-infrared, Raman and near-infrared spectra of biomolecules. Two-dimensional correlation can assist in the interpretation of spectra and provide assignments of unknown component bands. In addition to assigning bands, this method gives information about inter- and intramolecular interactions, which is especially useful for interpreting spectra of peptides and polypeptides. ^
"Forensic and biological applications of vibrational spectroscopy"
Dissertations and Master's Theses (Campus Access).