[Separation and characterization of Gastrodia elata polysaccharides based on asymmetrical flow field-flow fractionation: steric transition phenomenon].

Asymmetrical flow field-flow fractionation (AF4), a gentle tool for the separation and characterization of particles and macromolecules, has attracted increased interest in recent years owing to its broad dynamic size range and utilization of "open channel" voids in the packing or stationary phase. A steric transition phenomenon in which the sample elution mode change from the normal mode to the steric/hyperlayer mode occurs. Accurate characterization by AF4 requires the absence of steric transition, particularly when the sample has a broad size distribution, because the effect of the combination of different modes is difficult to interpret. In this study, the relative molecular mass (M), radius of gyration (Rg), and conformation of Gastrodia elata polysaccharides (GEPs) were characterized using AF4 coupled with online multi-angle light scattering (MALS) and differential refractive index (dRI) detection (AF4-MALS-dRI). Steric transition was observed during GEP separation by AF4 owing to the broad size distribution of the molecules. This phenomenon would result in the inaccurate characterization of the GEPs in terms of M and Rg because two GEP groups of different sizes may elute together. In this study, the effects of constant and exponentially decaying cross-flow rates, sample mass concentration, and spacer thickness on steric transition were systematically investigated. The results indicated that a high GEP mass concentration (i. e., 0.75 mg/mL) can lead to steric transition. The spacer thickness affected the resolution and retention time of the GEPs and changed the steric transition point (di). An exponentially decaying cross-flow rate not only adjusted the di of the polydisperse GEP samples but also improved the GEP resolution and shortened the analysis time. The influence of steric transition was solved under the following operating conditions: injected GEP mass concentration=0.5 mg/mL; injection volume=50 µL; spacer thickness=350 µm; detector flow rate=1.0 mL/min; and cross-flow rate exponentially decayed from 0.2 to 0.05 mL/min with a half-life of 2 min. Moreover, the influence of GEP origins and ultrasound treatment time on the M and Rg distributions and conformation of GEPs were investigated under the optimized operating conditions. The results showed that the M and Rg distributions of Yunnan and Sichuan GEPs decreased with increasing ultrasound time. When the ultrasound treatment time was 15 min, the Yunnan GEPs had a loosely hyperbranched chain conformation, whereas the Sichuan GEPs had a spherical conformation. When the ultrasound treatment time was increased to 30 or 60 min, the GEPs from both Yunnan and Sichuan had a hyperbranched chain conformation, indicating that ultrasound treatment resulted in GEP degradation. Under the same extraction conditions, GEPs from Yunnan had larger M and Rg values than those from Sichuan. AF4-MALS-dRI showed good repeatability for the characterization of GEPs under the optimized operating conditions. The relative standard deviations of Rg and M were 0.5% and 1.7%, respectively. The data presented in this study can be used as a starting point for in-depth studies on the structural bioactivity of GEPs.

VR-10 Thrombospondin-1 Synthetic Polypeptide's Impact on Rhesus Choroid-Retinal Endothelial Cells.

BACKGROUND/AIMS: This study aimed to investigate the effects of the VR-10 TSP-1 synthetic polypeptide on cytokines and the proliferation and migration of endothelial cells, as well as exploring a new method for anti-ocular neoangiogenesis. METHODS: We measured the proliferation of RF/6A cells by an MTT assay and investigated the migration of RF/6A cells by a Transwell chamber assay. We examined the mRNA transcript levels of TGF-ß2, VEGF, PEDF, Bcl-2 and FasL in RF/6A cells by RT-PCR and evaluated the expression of Fas and caspase-3 proteins in RF/6A cells by western blot analysis. RESULTS: 1. TSP-1 (1 µg/ml) and synthetic peptide VR-10 (0.1 µg/ml, 1 µg/ml and 10 µg/ml) inhibited the proliferation of RF/6A cells in a time and dose-dependent way. 2. TSP-1 and synthetic peptide VR-10 could inhibit the migration of RF/6A cells in a Transwell chamber (P < 0.001). It was demonstrated that 10 µg/ml synthetic peptide VR-10 had the strongest effect. 3. The expression of TGF-ß2 mRNA in RF/6A cells increased after treatment with 1 µg/ml TSP-1 (P < 0.0001). However, there was no significant difference between the synthetic peptide VR-10 and the control group (P > 0.05). Expression of PEDF mRNA in RF/6A cells was increased after treatment with 1 µg/ml TSP-1 and synthetic peptide VR-10. We demonstrated that 10 µg/ml synthetic peptide VR-10 had the strongest effect (P < 0.001). There were significant differences between groups (P < 0.001). Expression of TGF-ß2 mRNA in RF/6A cells increased after treatment with 1 µg/ml TSP-1 (P = 0.000). There was no significant difference between the synthetic peptide VR-10 and the control group (P > 0.05). PEDF mRNA expression in RF/6A cells decreased after 1 µg/ml TSP-1 and synthetic peptide VR-10 therapy, among which 10 µg/ml synthetic peptide VR-10 demonstrated the strongest effect (P < 0.001). There were significant differences between groups (P < 0.001), except for the 1 µg/ml synthetic peptide VR-10 and 1 µg/ml synthetic peptide VR-10 groups (P = 0.615). 4. Compared with the control group, FasL mRNA expression was significantly increased in the 10 µg/ml synthetic peptide VR-10 treatment group; however, Bcl-2 mRNA expression was decreased. 5. Western blotting showed that RF/6A cells in the control group mainly expressed the 32 kD procaspase-3 forms. For the 10 µg/ml synthetic peptide, VR-10 treatment group, it showed decreased expression of procaspase-3 (32 kD) and concomitant increased expression of its shorter pro apoptotic forms (20 kD). Compared with the control group, Fas protein expression significantly increased in the 10 µg/ml synthetic peptide VR-10 treatment group. CONCLUSIONS: Synthetic peptide VR-10 had an inhibitory action on the proliferation and migration of RF/6A cells. VR-10 inhibited angiogenesis by its combined actions, which included up-regulating the expression of an anti-angiogenesis gene, namely, pigment epithelium-derived factor (PEDF), down-regulating the expression of the pro-angiogenic vascular endothelial growth factor (VEGF), and mediated endothelial cell apoptosis.

Facile synthesis of tin phosphite nanosheets via exfoliated bulk crystals: Electronic structure and piezoelectric property.

Tin phosphite nanosheets were synthesized by a facile exfoliation method. SnHPO3 nanosheets with a thickness of ∼2.6nm readily form a stable colloidal suspension in ethanol using ultrasonic method. Structures and optical properties of the obtained nanosheets were investigated. The prepared SnHPO3 nanosheets exhibit an obvious blue-shift in UV absorbance compared with bulk SnHPO3 crystal materials. Moreover, the piezoelectric coefficients of SnHPO3 monolayer were calculated based on density functional theory, which are larger than that of h-BN monolayer, indicating this material could be a good candidate for designing electro-optical nano-devices.