Valdas Sablinskas

Non‐linear optical microscopy of kidney tumours

The unregulated cancer cell growth leads to strong alterations in morphology and composition of the tissue. The combination of coherent anti-Stokes Raman scattering, two-photon excited fluorescence and second harmonic generation enables a high resolution imaging with strong information on tissue composition and can then provide useful information for tumour diagnosis. Here we present the potential of multimodal non-linear microscopy for imaging of renal tumours. Using cryosections of human oncocytoma and carcinoma, the method gave a detailed insight in cancer morphology and composition, enabling to discern between normal kidney tissue, tumour and necrosis. Several features significant for the diagnosis were clearly visualised without use of any staining. Translation of this method in clinical pathology will greatly improve speed and quality of the analyses.

Temperature-controlled kinetics of the growth and relaxation of alcohol clusters in an argon matrix

The clustering processes of monohydric alcohols (from methanol to hexanol) were investigated by FTIR spectroscopy using the isolation in an argon matrix technique. The transformation of the FTIR bands of the free O–H groups (3600–3800 cm−1) into diffuse bands (3000–3600 cm−1), which were assigned to the stretching vibrations of the H-bonded O–H groups in various clusters, was monitored in its initial stage during softening of the matrices by heating from 20 to 50 K. Band-shape analysis was carried out for the investigated systems. The magnitude of the inhomogeneous broadening due to the matrix effect was evaluated from the bandwidth of the monomer species. The H-bond dissociation times in matrices were evaluated from the cluster bandwidths. These data correlate with those measured directly in ultra-fast infrared experiments of alcohols in solution.

Infrared Absorption Spectra of Monohydric Alcohols

FTIR spectra of homologous series of monohydric alcohols which belong to the class of partly ordered liquids were registered. The molecules of monohydric alcohols containing hydroxyl group are able to form hydrogen-bonded clusters in the condensed phase. The existence of clusters is clearly observed from the position and the contour of the stretch OH band in the vibrational spectra of liquid alcohols. In this work, the experimentally registered FTIR spectra of liquid n-alcohols from methanol to decanol are presented as well as the same spectra of methanol, ethanol, propanol, butanol, pentanol, and hexanol in gas phase.

Theoretical study of the C-H/O-H stretching vibrations in malonaldehyde.

IR and Raman spectra of the malonaldehyde molecule and its deuterated analogues were calculated in the B3LYP/cc-pVQZ approximation. Anharmonicity effects were taken into account both in the context of a standard model of the second order perturbation theory and by constructing the potential energy surfaces (PES) with a limited number of dimensions using the Cartesian coordinates of the hydroxyl hydrogen atom and the stretching coordinates of С-Н, C-D, O-H, and O-D bonds. It was shown that in each of the two equivalent forms of the molecule, besides the global minimum, an additional local minimum at the PES is formed with the energy more than 3,000 cm(-1) higher than the energy in the global minimum. Calculations carried out by constructing the 2D and 3D PESs indicate a high anharmonicity level and multiple manifestations of the stretching О-Н vibrations, despite the fact that the model used does not take into account the splitting of the ground-state and excited vibrational energy levels. In particular, the vibration with the frequency 3,258 cm(-1) may be associated with proton transfer to the region of a local minimum of energy. Comparing the results obtained with the experimental data presented in the literature allowed us to propose a new variant of bands assignments in IR and Raman spectra of the molecule in the spectral region 2,500-3,500 cm(-1).

Structure and vibrational spectra of gauche- and trans-conformers of ethanol: Nonempirical anharmonic calculations and FTIR spectra in argon matrices

Low-temperature infrared absorption spectra are obtained for ethanol isolated in an argon matrix at temperatures of 20–45 K range for ratios of the numbers of the molecules being studied to the numbers of matrix atoms of 1:1000 and 1:2000. A preliminary interpretation of the spectra is obtained on the basis of the temperature variations in the spectra and published data. The structure of the ethanol conformers, rotational constants, and internal rotation barriers of the methyl and hydroxyl groups are calculated in the B3LYP/cc-pVQZ approximation. The harmonic and anharmonic IR spectra of the gauche- and trans-conformers are calculated in the same approximation. The force fields of the two conformers and the distributions of the potential energy of the normal vibrations are calculated and compared for a general set of dependent coordinates. Anharmonicity effects are taken into account by introducing spectroscopic masses for the hydrogen atoms when calculating the normal vibrations in the harmonic approxima...

Pyridine N-oxide/trichloroacetic acid complex in acetonitrile: FTIR spectra, anharmonic calculations and computations of 1-3D potential surfaces of O-H vibrations.

FTIR spectra of pyridine N-oxide and trichloroacetic acid H-bonded complex in acetonitrile were studied at 20 and 50°C. The calculations of equilibrium configurations of the complex and their IR spectra in harmonic- and anharmonic approximations were carried out at the level of B3LYP/cc-pVTZ/PCM. However both approximations turned out to be incompetent determining the frequency of the O-Н stretching vibration. In order to reveal the causes of essential discrepancies between calculated and experimental data one-, two- and three-dimensional potential energy surfaces (PES) of the O-H…O bridge proton motion in the frame of fixed other atoms in the complex were calculated. The frequencies of O-H…O stretching and bending vibrations were calculated by numerical solution of the Schrödinger equation. It is shown that only the approach of proton motion on the 3D PES allows obtaining a good agreement between the calculated and the experimental values of the frequencies of the О-Н stretching vibrations.

Gender determination of fertilized unincubated chicken eggs by infrared spectroscopic imaging

Each year, billions of day-old layer chicks are produced in the world. Since only female chicks are reared for egg production, the chicks must be sexed and the unwanted male layer chicks are culled. The culling of male chicks is a serious problem, both in terms of animal welfare and waste disposal. The germinal disc in fertilized but unincubated eggs contains already several thousands of blastoderm cells. The cellular DNA in birds is different for male and female chicks. The difference in DNA content between male and female chicks is around 2% and is measurable by Fourier transform infrared (FT-IR) spectroscopy. In this study, small amounts of blastoderm cells from 22 chicken eggs were characterized by attenuated total reflection FT-IR spectroscopic imaging and classified by linear discriminant analysis. Polymerase chain reaction (PCR) was used as a reference method to determine the gender. The spectroscopic results demonstrate that male blastoderm cells exhibit a higher content of DNA than cells from female blastoderm. The spectroscopic-based gender determination led to the same result as the PCR analysis. FT-IR spectroscopic imaging allows the gender determination of unincubated eggs within a few seconds based on the accurate determination of the different DNA contents in blastoderm cells of both sexes.

FTIR/PCA study of propanol in argon matrix: The initial stage of clustering and conformational transitions

FTIR spectra of 1-propanol in an argon matrix were studied in the range 11–30 K. Principal component analysis of dynamic FTIR spectra and nonlinear band shape fitting has been carried out. The peaks of monomer, open dimer, mixed propanol-water dimer and those of higher H-bond clusters have been resolved and analyzed. The attribution of certain FTIR peaks has been supported by proper density functional theory calculations. Analyzing dependences of the integral band intensities of various aggregates on temperature it has been deduced that in the initial stage of clustering monomers and dimers are the basic building blocks forming higher H-bond clusters. The peaks assigned to two conformers of monomers and mixed propanol-water dimers were investigated processing the temperature dependences of their integral intensities in Arrhenius plot. The obtained values of 0.18 kJ·mol−1 for propanol monomer and 0.26 kJ·mol−1 for mixed dimer are well comparable with the energy differences between the global minimum confor...

Infrared spectroscopic imaging of renal tumor tissue.

Fourier transform infrared (FTIR) spectroscopic imaging has been used to probe the biochemical composition of human renal tumor tissue and adjacent normal tissue. Freshly resected renal tumor tissue from surgery was prepared as a thin cryosection and examined by FTIR spectroscopic imaging. Tissue types could be discriminated by utilizing a combination of fuzzy k-means cluster analysis and a supervised classification algorithm based on a linear discriminant analysis. The spectral classification is compared and contrasted with the histological stained image. It is further shown that renal tumor cells have spread in adjacent normal tissue. This study demonstrates that FTIR spectroscopic imaging can potentially serve as a fast and objective approach for discrimination of renal tumor tissue from normal tissue and even in the detection of tumor infiltration in adjacent tissue.

Biochemical Monitoring of Spinal Cord Injury by FT-IR Spectroscopy—Effects of Therapeutic Alginate Implant in Rat Models

Spinal cord injury (SCI) induces complex biochemical changes, which result in inhibition of nervous tissue regeneration abilities. In this study, Fourier-transform infrared (FT-IR) spectroscopy was applied to assess the outcomes of implants made of a novel type of non-functionalized soft calcium alginate hydrogel in a rat model of spinal cord hemisection (n = 28). Using FT-IR spectroscopic imaging, we evaluated the stability of the implants and the effects on morphology and biochemistry of the injured tissue one and six months after injury. A semi-quantitative evaluation of the distribution of lipids and collagen showed that alginate significantly reduced injury-induced demyelination of the contralateral white matter and fibrotic scarring in the chronic state after SCI. The spectral information enabled to detect and localize the alginate hydrogel at the lesion site and proved its long-term persistence in vivo. These findings demonstrate a positive impact of alginate hydrogel on recovery after SCI and prove FT-IR spectroscopic imaging as alternative method to evaluate and optimize future SCI repair strategies.