Resonance Raman quantification of the redox state of cytochromes b and c in-vivo and in-vitro

We observe the redox state changes with respiration of cytochromes b and c in mitochondria in a living Saccharomyces cerevisiae cell as well as in isolated mitochondria with the very use of Raman microspectroscopy. The possibility of monitoring the respiration activity of mitochondria in vivo and in vitro by Raman microspectroscopic quantification of the cytochrome redox states is suggested. It will lead to a new means to assess mitochondrial respiration activity in vivo and in vitro without using any labelling or genetic manipulation.

Superresolution vibrational imaging by simultaneous detection of Raman and hyper-Raman scattering

We have developed a superresolution vibrational imaging method by simultaneous detection of Raman and hyper-Raman scattering. Raman and hyper-Raman images obtained with the same laser spot carry independent information on the sample spatial distribution, owing to different signal dependence (linear in Raman and quadratic in hyper-Raman) on the incident light intensity. This information can be quantitatively analyzed to recover the incident light intensity distribution at the focal plane. A superresolution vibrational image is then derived by the constrained deconvolution of the images by the obtained incident light intensity distribution. This method has been applied to a TiO₂ nanostructure and the obtained superresolution image was compared with a scanning electron microscopy image. The spatial resolution achieved by the present method is evaluated to be 160 nm, which is more than twice better than the diffraction limited resolution.

1064 nm Deep near-infrared (NIR) excited raman microspectroscopy for studying photolabile organisms

We have constructed a 1064 nm deep near-infrared (NIR) excited multichannel Raman microspectrometer using an InP/InGaAsP multichannel detector. This microspectrometer achieves high sensitivity suitable for in vivo measurements of single living cells with lateral resolution of 0.7 μm and depth resolution of 3.1 μm. It has been applied to the structural analysis of living cyanobacterial cells, well-known model organisms for photosynthesis research, which are too photolabile to be measured with visible laser excitation. High signal-to-noise ratio (S/N) Raman spectra have been obtained from carotenoid, chlorophyll α, and phycocyanin in a single living cyanobacterial cell with no appreciable interference from autofluorescence or photodamage. Sub-micrometer mapping of Raman intensities provides clear distribution images of the three pigments inside the cell.

The "Raman spectroscopic signature of life" is closely related to haem function in budding yeasts

HEM1 gene encodes δ-aminolevulinate synthase that is required for haem synthesis. It is an essential gene for yeast survival. The Raman spectra of HEM1 knockout (hem1Δ) yeast cells lacks a Raman band at 1602 cm(-1) that has been shown to reflect cell metabolic activity. This result suggests that the molecule giving rise to the"Raman spectroscopic signature of life" is closely related to haem functions in the cell. High amount of squalene is also observed in the hem1Δ strain, which is another new discovery of this study.

Multifocus confocal Raman microspectroscopy for fast multimode vibrational imaging of living cells

We have developed a multifocus confocal Raman microspectroscopic system for the fast multimode vibrational imaging of living cells. It consists of an inverted microscope equipped with a microlens array, a pinhole array, a fiber bundle, and a multichannel Raman spectrometer. Forty-eight Raman spectra from 48 foci under the microscope are simultaneously obtained by using multifocus excitation and image-compression techniques. The multifocus confocal configuration suppresses the background generated from the cover glass and the cell culturing medium so that high-contrast images are obtainable with a short accumulation time. The system enables us to obtain multimode (10 different vibrational modes) vibrational images of living cells in tens of seconds with only 1 mW laser power at one focal point. This image acquisition time is more than 10 times faster than that in conventional single-focus Raman microspectroscopy.

Fast low frequency (down to 10 cm(-1)) multichannel Raman spectroscopy using an iodine vapor filter

We have constructed a multi-channel Raman spectrometer that is capable of recording the low frequency region down to 5 cm(-1) with a measurement time of a few tenths of a second. An iodine vapor filter, which uses a narrow (approximately 0.03 cm(-1)) absorption line of iodine for Rayleigh scattering elimination, is combined with a multi-channel Raman spectrometer composed of a single polychromator and a charge-coupled device (CCD) camera. Thanks to the high Rayleigh scattering elimination efficiency of the filter, which is over 10(6), Raman spectra of microcrystalline L-cystine from -300 cm(-1) to 1000 cm(-1) are simultaneously measurable with a small gap of 10 cm(-1) (-5 cm(-1) to 5 cm(-1)). Although raw spectra contain many sharp spikes due to the fine structures of iodine absorption, they can be correctly compensated with the use of a transmittance spectrum measured under the same experimental conditions. Many Raman bands including the 9.8 cm(-1) band are measured with a high signal-to-noise ratio in both the Stokes and anti-Stokes sides with a measurement time as short as 0.2 s.