The analysis of thymine and its derivatives by electron-ionisation and chemical-ionisation mass spectrometry - Essay Example

Aromaticity of Thymine is due to the alignment of conjugated double bond and empty orbital of Nitrogens in the ring. Resonance also plays part in stabilizing the molecule. Thymine exists in different tautomeric form but the lactam form is the most stable and the form present in DNA structure. Thymine has the structure of an aromatic heterocyclic ring with two carbonyl attached to 2nd and 4th Carbon. A methyl group is attached to 5th Carbon. The first and third position of the ring is a Nitrogen atom.

Both Nitrogen has unoccupied orbital that participates in stabilizing aromatic property of the molecule. Coupling of Thymine and 2-Deoxyribose creates the nucleoside Deoxythymidine which is commonly called Thymidine. One common mutations found in DNA are two adjacent pyrimidine bases commonly Thymidine that upon irradiation with UV-light will cause mutagenesis and therefore inhibits the process of translation. Thymine Thymidine Mass Spectrometry A mass spectrometer produces a spectrum of masses based on the structure of a molecule.

The mass spectrum is not a spectrum with respect to electromagnetic radiation, as in the case or IR and NMR. Instead, it is a spectrum of plot of distribution of ion masses corresponding to the formula weight of the molecule, fragments derive from the molecule, or both. For the past years, advances in technology leads to well developed and precise mass spectrometric technique primarily used for structure determination and quantitative work. Mass spectrometers for structure elucidation can be classified according to the method of separating the charged particles.

Most common methods are Magnetic Field Deflection, Quadrupole mass Spectrometry, Time of Flight, Ion-Cyclotron resonance and MS/MS (Tandem Mass spectrometry). The general procedure for a mass spectral analysis comes in subsequent steps. Feedingof sample in the Mass Spectrometer and undergoes vaporization. Vaporization is required if the starting substance is in liquid form. In most cases, this comes from an HPLC unit. GC-MS has been widely renowned for its convenience and accuracy. Components are then ionized using variety of techniques.

This step is the determining factor for which kind of substance the mass spectrometer can effectively analyze. Biological sample are often ionized using Electron impact, Chemical ionization and the most recent Electron Spray Ionization. Contact with ions creates charge to various species of the sample. They are then separated according to their mass to charge ratio in a mass analyzer. The ions are detected by a transducer and then reported as spectral lines in mass spectra. Mass Spectral Analysis of Thymine Mass Spectra using Electron Ionization technique for Thymine has Molecular Ion peak at 126 m/z at almost 100% abundance.

The intensity of the molecular ion peak depends on the stability of the molecular ion. Thymine is an Aromatic molecule so has the greatest stability of the molecular ion. M+1 ion is also evident as consequence of using Electron Ionization technique in ionization step. Lower m/z lines were due to fragments of Thymine. Mass Spectroscopic Analysis of Thymidine Derivatives Oxidation of Thymine in DNA Changes in DNA structure such as oxidations in DNA bases pose a major role in mutagenic initiation and degenerative diseases.

Peroxyl radicals (ROO) has been found to cause must of the oxidations in the body. The