ABSTRACT
A detailed investigation of phonon modes in DNA macromolecules is presented. This work presents experimental evidence to confirm the presence of multiple dielectric resonances in the submillimeter-wave spectra (i.e., approximately 0.01-10 THz) obtained from DNA samples. These long-wave (i.e., approximately 1-30 cm(-1)) absorption features are shown to be intrinsic properties of the particular DNA sequence under study. Most importantly, a direct comparison of spectra between different DNA samples reveals a large number of modes and a reasonable level of sequence-specific uniqueness. This work establishes the initial foundation for the future use of submillimeter-wave spectroscopy in the identification and characterization of DNA macromolecules.
Subject(s)
Biophysics/methods , DNA/chemistry , Nucleic Acid Conformation , Models, Theoretical , Spectrum Analysis/methodsABSTRACT
We present a detailed analysis of the structure and infrared spectra of 1,4-thioxane. The vibrational frequencies of the 1,4-thioxane molecule were analyzed using standard quantum chemical techniques. Frequencies were calculated at the MP2 and DFT levels of theory using the standard 6-31G* basis set. The structural transformation of the chemical agent bis (2-chloroethyl) sulfide (HD, mustard gas) and the related symmetry to a previously study compound(4) makes the symmetry of the 1,4-thioxane molecule an interesting candidate for study. The molecule exists normally in a Cs configuration similar to the chair form of cyclohexane. High-energy forms of 1,4-thioxane with C1 and C2 symmetry also exist.
Subject(s)
Heterocyclic Compounds, 1-Ring/chemistry , Models, Chemical , Chromatography, Gas , Hexanes/chemistry , Models, Theoretical , Molecular Conformation , Mustard Gas/metabolism , Spectroscopy, Fourier Transform Infrared , Spectrum Analysis, Raman , Temperature , Thermodynamics , VibrationABSTRACT
Developing methods for alternative testing is increasingly important due to dwindling funding resources and increasing costs associated with animal testing and legislation. We propose to test the feasibility of a new and novel method for detecting DNA mutagenesis using millimeter wave spectroscopy. Although millimeter wave spectroscopy has been known since the 1950s, the cost was prohibitive and studies did not extend to large biological proteins such as DNA. Recent advances have made this technology feasible for developing laboratory and field equipment. We present preliminary findings for lesion-induced vibrational modes in DNA observed from 80 to 1000 gigahertz (GHz). These findings suggest that there are vibrational modes that can be used as identification resonances. These modes are associated with localized defects of the DNA polymers. They are unique for each defect/lesion, and should be easy to detect. We described a field-detecting detector based on the local modes.
Subject(s)
Animal Testing Alternatives/methods , Carcinogens/toxicity , DNA/analysis , Mutation/drug effects , Spectrophotometry/methods , Animals , DNA Damage , VibrationABSTRACT
Computation of Mueller matrix elements by infrared scattering from randomly rough two-dimensional surfaces and results of a method for graphic display of the data are presented. A full wave electromagnetic scattering model first generates raw data elements of the 4 × 4 Mueller matrix F(θ, nλ, kλ, σs(2), ?h(2)?) in beam backscattering angle (θ) ranging from normal to oblique incidence, in refractive index of the beam scatterer (nλ - ikλ) spanning the 9 ≤ λ ≤ 12.5 µm midinfrared band, and in mean-squared slope ((σS(2)) and mean-squared height (?h(2)?) of the scattering surface. These data are next compressed into a graphics format file occupying considerably less computer storage space and mapped into color images of the Mueller elements as viewed on a high-resolution graphics terminal. The diagonal and two off-diagonal elements are animated in the λ-θ plane according to varitions in σs(2) and ?h(2)?. Predicted elements for polarized IR beam energies on vibrational resonance of the surface molecules, and particularly the off-diagonal elements, show subtle properties of the scatterer as viewed in the animation sequences.
ABSTRACT
The literature on "dry socket" is reviewed. The diagnosis, incidence and predisposing factors are discussed in relation to its aetiology. Treatment regimes are outlined; in particular, the use of anti-fibrinolytic drugs.
