Published papers

The characteristics of ion solvation are important for electrochemical and biophysical phenomena because all such phenomena occur under the presence of solvated ions. In this study, we performed an all-atom molecular dynamics simulation of aqueous NaCl ranging from 0.5 to 3.0 M, and aqueous NaF, NaBr and NaI in 2.0 M, to investigate the time-averaged velocity auto-correlation function (TAVAF) of ions and water molecules. By comparing the concentrations and ion pairs, we observed three behaviours: (i) in the case of NaCl, the velocity auto-correlation of Cl− becomes weaker as the concentration increases, whereas those of Na+ are not clearly different, (ii) the intensity of fluctuations of the TAVAF gradually decreases following the decrease in ionic radius and (iii) every TAVAF of water molecules in ionic solutions is clearly lower than that of bulk because of the cage effect. Furthermore, we observed that the first minimum of the TAVAF in the cluster is smaller than that of the isolated ions. These results indicate that the diffusion of ions and water molecules is affected by cage effect, and that the generation of ion cluster affects the diffusion of ions.

Interionic distances are shorter in concentrated ionic solutions, thus instigating the interaction and overlap of hydration shells, as ions become separated by only one or two layers of water molecules. The simultaneous interaction of water with two oppositely charged ions has, so far, only been investigated by computer simulation studies, because the isolated vibrational spectroscopic signature of these molecules remains undetected. Our combined near-infrared spectroscopic and molecular dynamics simulation studies of alkali halide solutions present a distinct spectral feature, which is highly responsive to depletion of bulk water and merging of hydration shells. The analysis of this spectral feature demonstrates that absorption trends are in good agreement with the law of matching affinities, thus providing the first successful vibrational spectroscopic treatment of this topic. Combined with commonly observed near-infrared bands, this feature provides a spectral pattern that describes some relevant aspects of ionic hydration.

Freezing is usually used for preservation and storage of biological samples; however, this process may have some adverse effects such as cell membrane damage. Aquaporin (AQP), a water channel protein, has been suggested to play some roles for cryopreservation although its molecular mechanism remains unclear. Here we show that membrane damage caused by ultra-quick freezing is rescued by the expression of AQP4. We next examine if the expression of AQP combined with ultra-quick freezing can be used to select cells efficiently under freezing conditions where most cells are died. CHO cells stably expressing AQP4 were exclusively selected from mixed cell cultures. Having identified the increased expression of AQP4 during ES cell differentiation into neuro-ectoderm using bioinformatics, we confirmed the improved survival of differentiated ES cells with AQP4 expression. Finally we show that CHO cells transiently transfected with Endothelin receptor A and Aqp4 were also selected and concentrated by multiple cycles of freezing/thawing, which was confirmed with calcium imaging in response to endothelin. Furthermore, we found that the expression of AQP enables a reduction in the amount of cryoprotectants for freezing, thereby decreasing osmotic stress and cellular toxicity. Taken together, we propose that this simple but efficient and safe method may be applicable to the selection of mammalian cells for applications in regenerative medicine as well as cell-based functional assays or drug screening protocols.

Nanocomposites made of magnetic spinel oxide Co1+yAl2−yO4 particles dispersed in an amorphous SiO2 matrix were synthesized by a sol–gel technique. Samples with various mass fractions of Co1+yAl2−yO4 in composite x, and with various Co concentrations in spinel y were studied. The grain sizes were below 100 nm with a large size distribution. The paper represents thorough investigation of magnetic properties, but special attention was given to peculiar effects and low temperature magnetic frozen states. Magnetic measurements reveal multiple magnetic ground states at the lowest temperature. The frequency dependent ac susceptibility measurements indicate spin-glass behavior of these ground states at low temperatures. The samples, with higher concentration x of Co1+yAl2−yO4 in SiO2, showed very similar Curie–Weiss paramagnetic behavior with antiferromagnetically interacting Co ions (θ ≈ −100 K). Other samples, with lower x, showed complex behavior, spin-glass magnetic freezing at the lowest temperatures and lower absolute value of θ and consequently lower exchange constant.

In this paper the authors present the results of surface characterisation of a lead telluride alloy conducted by atomic force microscopy and magnetic force microscopy. Relationship between surface morphology, in the range of several nanometres, and the magnetic properties allows precise determination of nanomagnetic particles size with their distribution within a scanned area. This method allows the characterisation of nanoparticles in dimensional and magnetic sense since the paramagnetic and diamagnetic range can be examined.

Hydrogen bond has dual property, classical (electrostatic interaction based on Coulomb's law) and quantum (wave function based on Schrödinger equation). Since Planck's constant is one of the main criteria for decision which process is quantum, or how much is close to be quantum, we use electrical and magnetic forces of valence electrons, as point of departure, to develop method for opto-magnetic fingerprint of matter. During the study of different type of matter we observed phenomena from spectral convolution data of digital images which characterize matter from both covalent and non-covalent bonding. Since water is matter that is most abundant with hydrogen bonds, we present results of 18.2 MΩ water investigation on different temperature and under influence of constant and variable magnetic fields by opto-magnetic method. Bearing in mind that Linus Pauling, in his book Nature of the Chemical Bond (Cornel University Press, 1939), for the first time presented the systematic concept of the hydrogen bond to the molecular world and its machinery, this paper is written in honor to him and 70th anniversary of one of the most important scientific paradigm.

Motivated by characterization of paramagnetic materials (Al, Mn and Ti) and diamagnetic materials (Cu, C and Zn) by opto-magnetic method that is based on light-matter interaction using digital imaging, we present results of Epstein-Barr virus (EBV) and cytomegalovirus (CMV) detection in blood plasma. To investigate light-blood plasma interaction we use wavelength difference of diffuse white light and reflected polarized light in red and blue channels of digital images (opto-magnetic method). Digital images of samples are analyzed by spectral convolution algorithm for light-matter interaction analysis. Since opto-magnetic method can detect very small difference between normal and pathological tissue states it is advantageous in comparison with classical methods. Especially it is important for early detection of suspicious tissue states and detection of viral infection presence in plasma. We compared our results with results of standard biomedical test for EBV and CVM, as a reference, and found out for group of 40 samples significant correlation of 93.6%.

In this paper we present applied physics research results of gas-permeable contact lenses (CL) that are manufactured from fluorosilicone acrylate based material (Boston™ type). During contact lenses production the conformation states of polymers belonging to near surface layers of CL surface are changed. Since CL quality crucially depends on surface roughness and optical properties, the properties of surface molecules conformation state and their orientation come into perspective as important factors acting on the molecular level. Therefore, we investigated CL surface by phase contrast atomic force microscopy (PC-AFM), magnetic force microscopy (MFM), and optomagnetic fingerprint (OMF) technique and found out that surface quality and magnetic properties of contact lenses have influence on physical properties of light transmission and that these changes can be detected on the nanolevel of magnetism, as well as optomagnetism. These results carry important biophysically based implications for CL industry, biomedical application industry and applied optical science.

An inhomogeneous system of aggregates of Co3O4 nanocrystallites dispersed in an amorphous SiO2 matrix has been studied. X-ray diffraction and atomic force microscopy reveal a bimodal distribution of crystallite sizes, smaller nanocrystallites with dimension below 10 nm and larger nanocrystallites of about 20 nm. The Co3O4 nanocrystallites enter the composition of nanograins with dimension 20–60 nm. The nanograins build aggregates with dimension 200–500 nm. A large value of the effective magnetic moment per Co2+ ion obtained from the high-temperature susceptibility measurements indicates possible disturbance of the normal spinel structure in which a fraction of Co3+ ions also possesses magnetic moment. An analysis based on the temperature dependence of the coercive field has shown that the smaller nanocrystallites behave as superparamagnetic particles with a blocking temperature of about 10 K. Simultaneous existence of two relaxation processes is observed in the frequency dependence of the imaginary part of the ac magnetic susceptibility in the vicinity of T = 15.8 K. The temperature dependence of the width of the distribution function of relaxation times obtained from the Cole–Cole diagrams exhibits behaviour characteristic for spin glass dynamics in a temperature range above 17.6 K and is temperature independent below 15.8 K, which is a property of superparamagnetic particles. The variation of the width of the distribution function between 17.6 and 15.8 K indicates that interference of the superparamagnetic and spin glass dynamics occurs. It has been found that average relaxation time increases with decreasing temperature from τc<10−4 s at 17.6 K to 1.5 × 10−1 s at 15 K. The increase of the average relaxation time with decreasing temperature, the observed blocking temperature of the superparamagnetic moments at about 10 K and interference appearing between the two spin dynamics suggest that the magnetic moments in the smaller as well as in the larger nanocrystallites are subject to a thermally activated blocking process at low temperatures.

Experimental autoimmune encephalomyelitis (EAE) induced by ventricular injection of antimyelin oligodendrocyte antibodies in DA rats showed severe clinical signs 4 to 5 days after injection. Immunocytochemically, connexin 43 (Cx43) expression increased in the choroid plexus and in the subventricular and subgranular zones of the hippocampus during the development of acute EAE, and decreased after the beginning of the remission phase of the disease. Quantitative computing analysis showed a significantly increased Cx43 expression in the choroid plexus at the peak of the disease. Plaque-pattern expression of the Cx43 in the choroid plexus (CP) of acute EAE correlated with the increased docking and coupling of the Cx43 hemichannels revealed by atomic force microscopy (AFM). The inner diameter of the gap junction (GJ) channels decreased in the CP of acute EAE, measured by AFM. Cell structure conformational changes showed influences the channels' flexibility in acute EAE.

Application of scanning probe microscopy techniques in evaluating process quality is presented. We conducted a surface characterization and comparison of topographical and magnetic features for three steel plate samples that were processed with the same milling parameters. The topographical features have presented an interesting discourse with magnetic features leading us to propose the magnetic fingerprint of matter on the nanometer level as a possible guideline in early crack detection and process parameter optimization.