Structural and Spatial Analysis of Carotenoids in a Single Cell Monitored by Raman Spectroscopy
Carotenoids are particularly convenient subjects to study by means of Raman spectroscopy due to very high Raman scattering cross-section associated with their chain vibrations. Raman studies of carotenoids in single cells have a variety of applications st
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Structural and Spatial Analysis of Carotenoids in a Single Cell Monitored by Raman Spectroscopy Agnieszka Kaczor and Marta Pilarczyk Abstract Carotenoids are particularly convenient subjects to study by means of Raman spectroscopy due to very high Raman scattering cross-section associated with their chain vibrations. Raman studies of carotenoids in single cells have a variety of applications starting from monitoring of growth and morphogenesis of unicellular algae and ending with differentiation of cancerous versus non-cancerous tissues in humans. Examples illustrating the potential of Raman spectroscopy to investigate carotenoids structure and distribution with a particular impact on studies using chemometric and computational methods as a tool to analyze experimental data are reviewed in this chapter. Keywords Carotenoids • Raman • Imaging • Chemometrics • quantum-chemical calculations • unicellular algae
11.1 Introduction Raman spectroscopy is a particularly convenient method to study carotenoids due to the long chain of alternating double and single bonds in their structures, responsible for unusually high Raman scattering cross-section associated with the chain vibrations. Additionally, upon excitation in the visible absorption range, the resonance effect is observed for carotenoids resulting in an enhancement factor of about five orders of magnitude compared to nonresonant conditions [1]. It makes Raman spectroscopy suitable technique to study carotenoids in low-concentration conditions such as human skin [2], eye [3], human cells [4–6] or immune system [7–10]. Such biochemical studies gain significantly if the pigment localization in a cell or
A. Kaczor () · M. Pilarczyk Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland e-mail: [email protected] A. Kaczor Jagiellonian Centre of Experimental Therapeutics (JCET), Jagiellonian University, Bobrzynskiego 14, 30-348 Krakow, Poland M. Baranska (ed.), Optical Spectroscopy and Computational Methods in Biology and Medicine, Challenges and Advances in Computational Chemistry and Physics 14, DOI 10.1007/978-94-007-7832-0_11, © Springer Science+Business Media Dordrecht 2014
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tissue can be accurately determined. In this context, a Raman spatially sensitive technique—Raman imaging emerges a particularly promising tool of study. Raman imaging is a non-invasive technique of studying components distribution and concentration in a sample. The technique combines the structural specificity of Raman spectroscopy with the high spatial resolution of microscopy (lateral resolution of 360 nm and depth resolution of ca. 1 µm @ 532 nm excitation) resulting in possibility of measuring sample microstructure at the subcellular level. 3D images of tissue and cellular components, illustrating high heterogeneity of the studied objects, have been already obtained with the application of confocal Raman microimaging [11]. Due to the complexity and heterogenity of studied biochemical samples, data analysis is usua
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