Terahertz time domain spectroscopy (THz-TDS) of hydrated biomolecular polymers and monomers.

摘要

Terahertz Time Domain Spectroscopy (THz-TDS) was utilized to obtain the complex dielectric spectra of hydrated biomolecules, betwixt the frequency range of 50 GHz to 2 THz. Two biological systems are observed; nucleic acid and carbohydrates. Monomers and polymers will be of interest for both. Utilizing both the Debye relaxation model and the suspension model, we observed both the mobility of biomolecules in solution as well as the influence they have on their surrounding water.;Nucleotides and glucose (monomers) were found to have a small part in the overall dynamics of the polymers. Hydrated nucleotides were shown to form transition materials. The pyrimidine nucleotides act much like an ion where they break up the original structure of water and set up a less complicated structure (smaller main relaxation times than water) than water. Purine nucleotides act more like a hydrogen bond building material they set up a more complex hydrogen bond network (larger main relaxation times than water) than water. These nucleotides were shown to have an influence in water out to four water layers.;The concentration studies that were preformed on native DNA, shows that concentration in the hydrated state is an important factor in the dielectric response. In addition, it was found that impurities in our samples did not play an important role in the dielectric response of our DNA solutions. Native DNA was shown to have a reach of six hydration layers.;The influence temperature has on DNA solutions was observed, temperature has a large influence on hydrated DNA. It was found that hydrated DNA is more susceptible to change in temperature then that of bulk water. The main relaxation time increases at a much larger proportion to that of water.;Using two synthetic DNA molecules with the same structure but different compositions and two carbohydrates with different structures but the same composition we found that the structure of a biopolymer is the most domination factor, rather than that of composition. It was determined that the length of the synthetic DNA was more important than that of the composition. Similarly, for the hydrated carbohydrate structures the amount of helices determines the amount hydrophobic dielectric behavior.