R&D Profile: Optical spectroscopy of amino acid micro crystals: W. Bacsa
Dr. Bacsa and his team has recently discovered that drying of droplets of amino-acids and proteins on silicon wafers leads to crystallization, enhancing considerably the optical signal using Raman spectroscopy.
Dr. Bacsa is a Professor at the University of Toulouse, France and visiting Research Professor at Boston University, USA. Dr. Wolfgang Bacsa is an expert in the emerging field of Nano-Optics and Carbon Nanotubes. He has a Ph.D. from the Swiss Federal Institute of Technology (ETH) Zürich in Physics and has extensive experience in condensed matter physics, optics, microscopy, synthesis of ultra-thin films and nanostructured carbon. His research interests are in interference scanning optical probe microscopy and carbon nanotubes. Dr. Bacsa has more than 20 years of research experience and published more than 100 scientific papers.
Dr. Bacsa provided Nano World News with an exclusive overview of a research paper that will be presented at the upcoming NSTI Nanotech conference June 1-5, 2008, in Boston, MA.
Abstract: Raman study and DFT calculations of amino acids micro crystals grown on silica
Authors: Vanessa Sonois, Alain Estève, Antoine Zwick, Peter Faller, Wolfgang Bacsa
Keywords: Raman spectroscopy, surface, amino acids, density functional calculations, scanning electron microscopy
Overview and Context of Presentation
We have recently discovered that drying of droplets of amino-acids and proteins on silicon wafers leads to crystallization, enhancing considerably the optical signal using Raman spectroscopy. We made this observation first using histidine and we have now extended our study to amino acids such as glycine and valine. We find that the pH of the solution, which defines the protonation states, has a clear influence on crystallization. Combining H/D substitution and density functional calculations we are able to assign the rich optical spectrum containing 20-30 spectral lines. We estimate that we can detect amino-acids at the 10 nanogram level at low laser power levels (<10mW, 488nm) and relative short integration times (60s).
For obtaining Raman spectra from amino acids and proteins in solutions one needed up to now considerably higher laser power levels (x10) and longer integration times (x30). Increasing the signal by using resonant excitation, demands cost intensive lasers emitting in the deep UV (200nm). Spectra obtained from solutions contain only a few spectral bands which and are strongly broadened (x10). Spectra obtained from powders need milligram quantities and can contain a strong luminescence background. Both limit the quantitative use of the spectra for the understanding bio-molecular processes.
Funding, Partnerships, and Societal Impacts of the Research
This research has been financed (ANR-France) by encouraging collaboration between chemistry, biology (V. Sonois, P. Faller) and physics (A. Estève, W. Bacsa). It shows how interdisciplinary projects between biology, chemistry and physics can lead to unexpected advancement in detection and understanding of biomolecular processes. Fast optical detection and interpretation of the spectra of small amounts of biomolecules will be useful in investigating on structure/function relationships of a large range of biomolecules and the aggregation of peptides or proteins. Such aggregates are one of the hallmarks of several neurodegenerative diseases including Alzheimer disease. The study of the formation of aggregates using high content spectroscopic techniques is expected to have a major impact in the understanding of neurodegenerative diseases. Technological progress at this point is limited by current funding opportunities.
