Tecklenburg Group Research

Raman Spectroscopic Studies of 

Molecular Structure and Conformation

In my research vibrational spectroscopy is used to solve problems dealing with molecular structure.  Nearly any type of sample can be analyzed by Raman spectroscopy because of the flexibility of using a focused laser beam as the light source. My current focus is on apatite, a form of calcium phosphate, which is the major constituent of bone and is also found as a natural mineral in rocks.  We are also studying a silane hydrolysis process, developing a Raman detection method and studying the kinetics of the process. The materials I study are diverse and have included proteins containing the heme group (hemoglobin and cytochrome oxidase), inorganic glasses (germanium diselenide doped with metals), and polymers (azoaromatic polyethers).  A new project is to study bone by Raman spectroscopy and to model the inorganic material in bone with substituted hydroxyapatites.   Modern computational modeling of molecular structure and conformation augments my experimental studies.

Bone and Biomineralization

Bone is an impure form of hydroxyapatite,

a calcium phosphate. The goal of the project

is to make hydroxyapatite with various impurity ions, both chemically and computationally, and study the vibrational spectra. We also collaborate with geologists using Raman spectroscopy to analyze minerals and fluid inclusions in rocks.

The distribution of chemical species in the growth and development of bone can be monitored by Raman spectroscopy.  The structure of bone mineral is similar to but not identical to hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂.  Many other ions are present in bone including, Na⁺, Mg²⁺ and K⁺ and the anions CO₃^2-, HPO₄^2-, Cl^- and F^-.  Carbonate is present at levels of 4 – 8 %.   Changes in the environment of phosphate in mature and newly mineralized bone are reflected in Raman peak shifts.  Our goal is to interpret the Raman spectra of bone tissue by modeling bone in two ways. First, we prepare hydroxyapatite with biologically significant ions as standards for comparison of Raman spectra with that of newly mineralized bone.   Second, we theoretically model bone structure with  first principles calculations of fragment structure and Raman spectra using density functional theory (DFT).  The theoretical models allow us to investigate the effects of position and orientation of ions on the Raman spectrum of apatite-bone models.

Raman scattered light (red). Raman spectrometer, diode laser (785 nm) and microscope