Vibrational Optical Activity of Intermolecular, Overtone, and Combination Bands: 2-Chloropropionitrile and α-Pinene.

Spectroscopy of vibrational optical activity has been established as a powerful tool to study molecular structures and interactions. In most cases, only fundamental molecular transitions are analyzed. In the present study, we analyze a broader range of vibrational frequencies (40-4000 cm-1), which could be measured on a new Raman optical activity (ROA) instrument. An unexpectedly strong vibrational Raman optical activity of 2-chloropropionitrile has been observed within the low-frequency region (40-150 cm-1). On the basis of combined molecular dynamics and density functional theory simulations, it could be assigned to intermolecular vibrations. A detailed analysis also revealed connection between spectral shapes and molecular structure and flexibility, such as bending of the CCN group. At the other edge of the scale, within ∼1500-4000 cm-1, for the first time, many combination and overtone ROA bands have been observed for 2-chloropropionitrile and α-pinene. These were also partially assigned, using quantum-chemical computations. The band assignment was confirmed by a comparison with Raman, absorption, and vibrational circular dichroism spectra. The measurement in the broader vibrational range thus significantly extends the information that can be obtained by optical spectroscopy, including intermolecular interactions of chiral molecules and liquids.

The effect of photodynamic treatment on the morphological and mechanical properties of the HeLa cell line.

High resolution imaging of biological structures and changes induced by various agents such as drugs and toxins is commonly performed by fluorescence and electron microscopy (EM). Although high-resolution imaging is possible with EM, the requirements for fixation and staining of samples for image contrast severely limits the study of living organisms. Atomic force microscopy (AFM), on the other hand, is capable of simultaneous nanometer spatial resolution and piconewton force detection, allowing detailed study of cell surface morphology and monitoring cytomechanical information. We present a method that images and studies mechanically characterized cells using AFM. We used a HeLa cell line (cervix carcinoma cell), which is sensitive to photodynamic treatment (PDT); growth media as a scanning surrounding; atomic force microscopy NT-MDT Aura for cytomechanical measurement; and scanning electron microscope Hitachi Su 6600 for control images of the cells. The modulus of elasticity for intact and photodynamically damaged cells can indicate mechanical changes to the main properties of cells. Cell elasticity changes can provide information on the degree or value of cell damage, for example after PDT. Measurements were carried out on approximately sixty cells, including three independent experiments on a control group and on sixty cells in a photodamaged group. Cells before PDT show higher elasticity: the median of Young´s modulus on the nucleus was 35.283 kPa and outside of the nucleus 107.442 kPa. After PDT, the median of Young's modulus on the nucleus was 61.144 kPa and outside of the nucleus was 193.605 kPa.

Sealing of open dentinal tubules by laser irradiation: AFM and SEM observations of dentine surfaces.

Dentin of human teeth is a vital hydrated tissue. It is strongly sensitive to dehydration and drying that are commonly used in preparation of samples for scanning electron microscopy. Experience in examination of dentine surfaces of extracted human third molars using contact mode atomic force microscopy under moist conditions is described. The examined dentine surfaces are modified by laser radiation produced by a pulsed Nd:YAG laser that leads to sealing of open dentinal tubules under suitable conditions that are reached after covering dentine surfaces with dye agents. Out of four investigated dye agents erythrosin solution in water has been found the most suitable and the lower and upper limits of pulse energies for sealing of dentinal tubules have been set.

Examination of dentin surface using AFM (our experience).

Atomic force microscopy (AFM) as one the technique of Scanning Probe Microscopy is useful for imaging of surface structure. This method can yield three-dimensional high-resolution topographic images of sample surfaces by using a scanning technique for conductors and insulators on atomic scale. It is based upon mapping of atomic-forces on a surface of an investigated sample. The method is useful not only in physics and chemistry; it can be also applied in biological fields. Special construction of AFM scanner enables to follow biological samples in liquid environments. Artifacts caused by dehydration of samples are removed this way. Dentin of human teeth is a vital hydrated tissue. It is strongly sensitive to dehydration and drying that are commonly used in preparation of samples in examinations by Scanning Electron Microscopy (SEM). We describe our experience in examination of dentin surfaces of extracted human third molars using contact method of AFM under moist conditions.