Study Of Biomolecule Detection In Water By Resonance Raman Spectra

The development of biomolecules brings about great advances in human civilization, the study of biomolecules not only promotes the rapid process in life science, but also has extreme effect on medicine, agriculture and chemistry etc. Study of the structure, property and detection of biomolecules is the main content and hot topic. It is well-known that the biological process and biological function of biomolecules carry through in water. So, the biomolecules in water are detected, distinguished and controlled, which has the important theory signification and application value frontier task. However, water is a polar molecule with high electric state energy. The study proves that the Raman spectrum is enhanced in the higher electric state energy molecule in binary solution, while the other Raman spectra are suppressed. Thus Raman spectrum detecting the biomolecules in water is very difficulty. And the solvent effect of water is so complex, water solution includes electrostatic force, dipole force, hydrogen bond and Van de Waals force etc, which make the biomolecules in water be located in many forces, the structure and property of biomolecule are affected. Water molecule absorbs the infrared spectrum, and the Raman scattering cross section is also small, so biomolecules detection in water, especially low concentration dectetion (single molecule) is a challenging work. In this paper, we select theβ-carotene molecule that has the special molecule structure, and use the resonance Raman spectrum technic in liquid-core optical fiber (LCOF), to study of biomolecules detection in water and gain the expected results.β-carotene is linear chain molecule which contains the 9 CC conjugate double bonds, it has the broadband fluorescence and large nonlinear coefficient, especially in low concentration solution it will generate the coherent weakly damping CC stretching vibrations, and it has the big Raman active and large Raman scattering cross section (intensive Raman spectrum). It is possible thatβ-carotene is detected in low concentration solution.LCOF can increase Raman spectrum intensity 3 order of magnitude, and resonance Raman spectrum technic can increase Raman spectrum intensity 6 order magnitude. When low concentration solution is used to core medium of LCOF, the resonance Raman effect on LCOF is generated, which can increase the Raman spectrum intensity 9 order of magnitude. These characteristics make it be possible that biomolecule (β-carotene) is deteced in water of low concentration.β-carotene is dissolved in pyridine and water solution that is as the core medium of LCOF, and the Raman spectra of concentrations of 10-7-10-9 mol/L are measured. The Teflon fiber is used to measureβ-carotene water solution, whose concentrations are from 10-9 to 10-10 mol/L.For realizing the water physical property, we also study high pressure and intensive laser action on Raman spectra of water.Raman spectra of ice VII phase are obtained at room temperature, when the pressure is from 2.5-23GPa. The experimental results indicate: the oxygen atoms distance do-o of ice are decreased with pressure increase, which results in that hydrogen bond is shorten, O-H bond is lengthen, force constant is reduced, and Raman spectra are red shift. The order of proton (hydrogen atom) first increases and then decreases with varying pressure, which leads to the Raman intensity increase first and then decrease, and Raman linewidth decreases first and then increases and the linewidth reaches its minimum when the pressure is 13GPa.Water will generate the plasma at the laser radiation, the plasma is generated when the pump energy is 4mJ; the Stokes line intensity of water OH stretching vibration and the Stokes line bandwidth of it are increased. As the pump laser energies are from 5mJ to 15mJ, and the center wavelength of Stokes become blue-shift; the anti-Stokes line of water OH stretching vibration is generated, when the pump laser energy is 15mJ. The experimental phenomena are explained by the laser-induced plasma enhances stimulated Raman scattering of water cluster, and the results are according with the theory.We use the resonance Raman spectrum technic in LCOF to study of biomolecule in water, especially to study linear chain polyene biomolecules, which will have an important theory and application.