Ice structuring collagen peptides (ISCPs) from porcine skin collagen hydrolysates were isolated by an affinity adsorption system, and then its antifreeze and cryoprotection activity, ice-binding mechanism and making performance of steamed bread were investigated. The results showed ISCPs with maximal thermal hysteresis activity (2.768C) were obtained with a collagen hydrolysate concentration of 1 mg/mL, adsorption time of 10 hr and adsorption temperature of 258C during the second round of adsorption. After purification, MS spectrum analyzed one of the ISCPs and inferred to be GLLGPLGPRGLL with a molecular weight of 1163.8 Da. The binding of ISCP to ice could be attributed to the structural match and hydrogen bond formation between ice surface and the ISCP.Compared with the control group, the baking and textural characteristics of frozen dough were significantly improved by ISCP at an addition concentration of 0.3% (wt/vol) after 4 weeks frozen storage.
Practical applicationsPorcine skin represents a problematic by-product in meat manufacturing industry due to its high pollutant load, and it is usually discarded as waste or used for low value purposes. In order to find potential applications for this by-product, ISCPs from porcine skin hydrolysates were isolated by an affinity adsorption system. The result demonstrated that ISCPs exhibited a strong antifreeze and cryoprotection activity, and had a potential application in food preservation and cryoprotection of cells and tissues.
K E Y W O R D Scryoprotection activity, frozen dough, ice affinity adsorption system, ice-binding interaction, ice structuring collagen peptides
On low-k flexible substrates, we obtained InAs films with thickness ranging from several hundreds of nm to sub-10-nm, by epitaxial lift-off and van der Waals bonding. Using Hall measurements, we investigated the electron mobility and sheet concentration depending on the InAs film thickness L. In spite of the undoped InAs films, we do not observe electron depletion even for sub-10-nm thickness L, owing to the Fermi level pinning above the conduction band bottom. We observed three regimes of the behavior of the electron mobility μ with decrease in L: almost constant or slightly increasing μ with decrease in L for ≳150 nm, weakly decreasing μ for 150 nm≳L≳15 nm, and more rapidly decreasing μ proportional to Lγ with γ≃ 5–6 for L≲15 nm. By using Poisson-Schrödinger calculation, we examined the electron distribution in the film depending on L and the associated scattering mechanisms contributing to the behavior of μ, such as phonon, Coulomb, and thickness fluctuation scattering.
We investigated InAs ultrathin films on flexible substrates. InAs layers grown on GaAs(001) are separated by epitaxial lift-off (ELO), followed by van der Waals bonding (VWB) on flexible substrates. We employed “normal” and “inverted” VWB; in the former, top and bottom sides are maintained during ELO and VWB, while inverted in the latter. From the InAs on flexible substrates, we fabricated Hall-bar devices with recess etch-thinning, using which electron transport properties depending on InAs layer thickness were characterized. For the inverted VWB, we observe very high electron mobilities of InAs ultrathin films, such as ∼10 000 cm2/V s for ∼100 nm thickness and ∼7000 cm2/V s for ∼20 nm. These carrier mobilities are highest not only for thin films on flexible substrates but also for InAs thin films; higher than those of InAs films grown on GaAs(111)A and membranes fabricated from them.
The aim of this study was to compare the results, in terms of temperature, colour change and morphology, of two different laser wavelengths with two different concentrations of hydrogen peroxide (HP). The lasers used were KTP (potassium-titanyl-phosphate) laser (λ = 532 nm (PD = 1.98 W/cm2)) and Er:YAG laser (λ = 2940 nm (PD = 2.54 W/cm2)). The bleaching gels used were PolaOffice 35% HP gel and PolaOffice+ 6% HP gel (SDI, Australia). Thirty-six extracted human teeth were selected and divided into two groups. For the 35% HP treatment, 18 teeth were randomly assigned to three subgroups: (1) HP gel without laser irradiation vs. HP gel + KTP laser irradiation; (2) HP gel without laser irradiation vs. HP gel + Er:YAG irradiation; and (3) HP gel + KTP laser irradiation vs. HP gel + Er:YAG irradiation. The same protocol was used for the 6% HP bleaching treatment. The bleaching results were analysed by a spectrophotometer, the thermal elevation by K thermocouples and the enamel surface by a scanning electron microscope (SEM). The Kruskal-Wallis test and the Mann-Whitney test were performed, and the data were analysed using the software StatView and the free Web statistics tool BiostaTGV. The thermal elevation of the Er:YAG groups was higher than KTP, while only the group 35% HP gel vs. 35% HP gel + Er:YAG showed significant colour differences (p < 0.05). SEM photographs showed slight enamel surface morphologic alterations after bleaching treatment. The Er:YAG laser may improve the bleaching results of 35% HP even if it increases the gel temperature, when compared to the KTP laser.
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