No abstract

Some biological substances control the nucleation and growth of inorganic crystals. Antifreeze proteins, which prohibit ice crystal growth in living organisms, promise are also important as biological antifreezes for medical applications and in the frozen food industries. In this work, we investigated the crystallization of ice in the presence of a new cryoprotector, carboxylated ε-poly-L-lysine (COOH-PLL). In order to reveal the characteristics and the mechanism of its antifreeze effect, free-growth experiments of ice crystals were carried out in solutions with various COOH-PLL concentrations and degrees of supercooling, and the depression of the freezing point and growth rates of the tips of ice dendrites were obtained using optical microscopy. Hysteresis of growth rates and depression of the freezing point was revealed in the presence of COOH-PLL. The growth-inhibition effect of COOH-PLL molecules could be explained on the basis of the Gibbs-Thomson law and the use of Langmuir's adsorption isotherm. Theoretical kinetic curves for hysteresis calculated on the basis of Punin-Artamonova's model were in good agreement with experimental data. We conclude that adsorption of large biological molecules in the case of ice crystallization has a non-steady-state character and occurs more slowly than the process of embedding of crystal growth units.

Ice-binding proteins (IBPs) affect ice crystal growth by attaching to crystal faces. We present the effects on the growth of an ice single crystal caused by an ice-binding protein from the sea ice microalga (IBP) that is characterized by the widespread domain of unknown function 3494 (DUF3494) and known to cause a moderate freezing point depression (below 1 °C). By the application of interferometry, bright-field microscopy, and fluorescence microscopy, we observed that the IBP attaches to the basal faces of ice crystals, thereby inhibiting their growth in the direction and resulting in an increase in the effective supercooling with increasing IBP concentration. In addition, we observed that theIBP attaches to prism faces and inhibits their growth. In the event that the effective supercooling is small and crystals are faceted, this process causes an emergence of prism faces and suppresses crystal growth in the direction. When the effective supercooling is large and ice crystals have developed into a dendritic shape, the suppression of prism face growth results in thinner dendrite branches, and growth in the direction is accelerated due to enhanced latent heat dissipation. Our observations clearly indicate that the IBP occupies a separate position in the classification of IBPs due to the fact that it suppresses the growth of basal faces, despite its moderate freezing point depression.

The aim of this study was to investigate the application of optical coefficients obtained from cross-polarization optical coherence tomography (CP OCT) data to differentiat e breast cancer tissues from normal breast tissues. For this, surgically obtained breast specimens from 35 patients were investigated using CP OCT in order to construct pseudocolor en face OCT maps based on a calculation of three optical coefficients: the commonly used, rate of attenuation in the co-channel (Att co-) and, additionally, the attenuation in the cross-channel (Att cross-); and the interchannel attenuation difference (uD). It was shown that the use of these optical coefficients significantly increased the information available from the OCT data in comparison with unprocessed images, and that this enabled objective quantification for differentiating non-tumorous and tumorous tissue (adipose tissue, normal stroma, tumor stroma and agglomerates of tumor cells). The Att cross-and the uD provided greater contrast for the visualization of the different breast cancer structures compared to the Att co-coefficient. While the Att co-of tumor cells was significantly higher (p < 0.05) than that of adipose tissue, the Att codifference between normal or tumor stroma and tumor cells was not observed. On the other hand, normal or tumor stroma was associated with significantly higher (p < 0.05) Att cross-and significantly lower (p < 0.05) uD as compared to tumor cells. Furthermore, Att cross-of tumor stroma was significantly higher (p < 0.05) than that of normal (non-tumor) stroma. The findings of this study suggest that CP OCT and an assesment of the optical coefficients of such breast cancer images may, in the future, enable real-time feedback to the surgeon about accurate resection margin locations in patients with breast cancer.