Biomedical subjects

Natallia Uzunbajakava

Publications and source records attributed to Natallia Uzunbajakava.

4 recordsLinked to original sources

PubMed2006

Low-cost spectroscopy with a variable multivariate optical element.

Here, successful realization of a variable multivariate optical element (VMOE) based on a transmissive liquid crystal (LC) panel is reported. In contrast to conventional multivariate optical elements (MOEs), a single VMOE is a dynamic system, allowing measurement of numerous analytes in different mixtures. Furthermore, VMOE has superior spectral resolution in comparison to a conventional MOE. It is demonstrated here that the system implemented in a Raman spectrometer predicts the concentration of each individual component in toluene-acetonitrile-cyclohexane mixtures with a prediction error of <6% (mass percentage). With a dedicated optical design of the setup, a prediction error smaller than 2% is expected to be feasible for the current chemical system.

Journal Article↗

PubMed2005

Spectroscopy and quantum chemical modeling reveal a predominant contribution of excitonic interactions to the bathochromic shift in alpha-crustacyanin, the blue carotenoprotein in the carapace of the lobster Homarus gammarus.

To resolve the molecular basis of the coloration mechanism of alpha-crustacyanin, we used (13)C-labeled astaxanthins as chromophores for solid-state (13)C NMR and resonance Raman spectroscopy of [6,6',7,7']-(13)C(4) alpha-crustacyanin and [8,8',9,9',10,10',11,11',20,20']-(13)C(10) alpha-crustacyanin. We complement the experimental data with time-dependent density functional theory calculations on several models based on the structural information available for beta-crustacyanin. The data rule out major changes and strong polarization effects in the ground-state electron density of astaxanthin upon binding to the protein. Conformational changes in the chromophore and hydrogen-bond interactions between the astaxanthin and the protein can account only for about one-third of the total bathochromic shift in alpha-crustacyanin. The exciton coupling due to the proximity of two astaxanthin chromophores is found to be large, suggesting that aggregation effects in the protein represent the primary source of the color change.

Animals↗

PubMed2003

Combined Raman and continuous-wave-excited two-photon fluorescence cell imaging.

We demonstrate a confocal optical microscope that combines cw two-photon-excited fluorescence microscopy with confocal Raman microscopy. With this microscope fast image acquisition with fluorescence imaging can be used to select areas of interest for subsequent chemical analysis with spontaneous Raman imaging. The distribution of the UV-absorbing fluorophore Hoechst 33342 in the apoptotic HeLa cells is measured in the combined cw two-photon-excited fluorescence and Raman microscopy modes. The 647-nm line of a Kr-ion laser is used to excite both the Raman scattering and the two-photon-excited fluorescence emission. The lateral and axial resolutions in the two imaging modes are compared by use of the Gaussian beam approximation and backprojection of the focal volume through the confocal pinhole.

Absorption↗

PubMed2003

Resonance Raman imaging of the NADPH oxidase subunit cytochrome b558 in single neutrophilic granulocytes.

We have employed confocal resonance Raman (RR) imaging to visualize the subcellular distribution of the NADPH oxidase subunit cytochrome b558 in both resting and phagocytosing neutrophils. Our Raman microscopic technique is a label-free, chemical (vibrational) imaging method that can be applied to individual, intact cells, thus probing cytochrome b558 in its native environment. The Raman signal from cytochrome b558 is resonantly and selectively enhanced in neutrophils by using 413 nm excitation. Experiments on resting neutrophils show a cytoplasmic distribution of cytochrome b558, with several areas of high content. Upon phagocytosis of polystyrene particles, we found that part of the cytochrome b558 is translocated toward the ingested beads. This is in accordance with immunocytochemistry studies combined with electron and fluorescence microscopy. As compared to these methods, RR microscopy requires minimal sample preparation and disturbance. Moreover, it allows the determination of the redox state of cytochrome b558 inside the cell, which reflects its NADPH oxidase activity.

Cytochrome b Group↗