Antifreeze glycoproteins (AFGPs) are a necessary tool for the survival of fish that live in subfreezing environments [Yeh, Y.; Feeney, R. E. Antifreeze proteinssStructures and mechanisms of function. Chem. ReV. 1996, 96 (2), 601-617]. Although scientists agree that these proteins arrest ice crystal growth by a surface adsorption mechanism, the exact nature of the interaction remains an open question. Here, we study the adsorption kinetics of AFGPs during solution ice crystal growth using confocal fluorescence microscopy within and just below the freezing-melting temperature hysteresis region. The AFGP kinetics at the ice surface reveal a two-step inhibition process: (i) incomplete adsorption or a weak interaction that modifies the surface for (ii) a stronger interaction to achieve the complete adsorption necessary to halt growth. The growth is modified from a rough interface to a faceted one, and growth is halted at supercoolings less than 0.05°C. However, growth resumes, and the proteins desorb, return to the solution phase, and are not incorporated into the ice crystal as previously proposed. Our findings are contrary to an AFGP mechanism described by the Gibbs-Thomson model. We argue that an alternative explanation must include a solvated protein interacting with a solvated ice surface. While thermodynamics considerably alter the interfacial region, antifreeze action is a purely kinetic phenomenon.
Annealing was carried out in air into an open joule furnace; the temperature was monitored with a K-type thermocouple. Samples were kept separated from the furnace walls by ceramic spacers. An uncoated quartz substrate was annealed at the same time. The thermal treatment did not cause any alteration in the substrate optical properties.UPS and XPS were performed in a ultrahigh vacuum analysis chamber (base pressure < 1 10 ±6 Pa) equipped with an electrostatic hemispherical analyzer. An Mg-anode source (1253.6 eV) was used for XPS, while He I (21.2 eV) and He II (40.8 eV) resonance lines were utilized for UPS. The overall energy resolution was about 1 eV in XPS and 0.1 eV in UPS. The Fermi level was identified by UPS measurement on a metallic sample. The sputtering of the films was performed by Ar ions (1.5 keV, 3.5±4.2 lA, 30 min each at 1 10 ±4 Pa). The AFM characterization was performed using a Digital Instruments Multimode Nanoscope IIIa atomic force microscope operated in tapping mode and equipped with single-crystal silicon tips. The average crystallite (grain) sizes of the samples were extracted from AFM images using software developed in our laboratory.UV-vis transmittance measurements were obtained with a JAS-CO 7850 spectrophotometer, while the optical gap values were extracted from transmittance measurements using the Tauc Polymer-based composite materials with functional organic molecules such as organic dyes have often been made by dispersing functional molecules in amorphous polymers or amorphous regions of crystalline polymers. However, such composite materials combined with functional organic molecules in the crystalline regions of polymers have not been developed hitherto, since the unit cell of most polymers has been considered to have insufficient space to store functional organic molecules. Nevertheless, the clathration of functional organic molecules within polymer crystalline regions has the advantages of preventing them from coagulation and making it possible to control their arrangement by regulating the orientation of the polymer crystalline regions. In this paper, we demonstrate the first examples of composite materials formed from organic dyes and the crystalline regions of a polymer and control of the dye-molecule orientation, both of which can be accomplished by technically simple methods. COMMUNICATIONS
Summary: Selective absorption uptake during the guest‐exchange processes in the δ form of syndiotactic polystyrene (sPS) was confirmed by IR spectroscopy. When films of the δ form were immersed in hexane/decane or chloroform/decane mixtures, decane molecules were incorporated preferentially in the δ form. Sorbate uptake by the δ form was greatly accelerated when the sorbate was mixed with a solvent penetrable to the amorphous region of sPS.Concentration changes in a δ‐form film during sorption processes: sorption of a chloroform(D)/decane(H) mixture (1:1 molar ratio).magnified imageConcentration changes in a δ‐form film during sorption processes: sorption of a chloroform(D)/decane(H) mixture (1:1 molar ratio).
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