Spatial inhomogeneity, interfaces and complex vitrification kinetics in a network forming nanocomposite.

A detailed calorimetric study on an epoxy-based nanocomposite system was performed employing bisphenol A diglycidyl ether (DGEBA) cured with diethylenetriamine (DETA) as the polymer matrix and a taurine-modified MgAL layered double hydroxide (T-LDH) as the nanofiller. The -NH2 group of taurine can react with DGEBA improving the interaction of the polymer with the filler. The combined X-ray scattering and electron microscopy data showed that the nanocomposite has a partially exfoliated morphology. Calorimetric studies were performed using conventional DSC, temperature modulated DSC (TMDSC) and fast scanning calorimetry (FSC) in the temperature modulated approach (TMFSC) to investigate the vitrification and molecular mobility dependent on the filler concentration. First, TMDSC and NMR were used to estimate the amount of the rigid amorphous fraction which consists of immobilized polymer segments at the nanoparticle surface. It was found to be 40 wt% for the highest filler concentration, indicating that the interface dominates the overall macroscopic properties and behavior of the material to a great extent. Second, the relaxation rates of the α-relaxation obtained by TMDSC and TMFSC were compared with the thermal and dielectric relaxation rates measured by static FSC. The investigation revealed that the system shows two distinct α-relaxation processes. Furthermore, two separate vitrification mechanisms were also found for a bulk network-former without geometrical confinement as also confirmed by NMR. This was discussed in terms of the intrinsic spatial heterogeneity on a molecular scale, which becomes more pronounced with increasing nanofiller content.

Initial Solvent-Driven Nonequilibrium Effect on Structure, Properties, and Dynamics of Polymer Nanocomposites.

Unusual structures and dynamic properties found in polymer nanocomposites (PNCs) are often attributed to immobilized (adsorbed) polymers at nanoparticle-polymer interfaces, which are responsible for reducing the intrinsic incompatibility between nanoparticles and polymers in PNCs. Although tremendous effort has been made to characterize the presence of immobilized polymers, a systematic understanding of the structure and dynamics under different processing conditions is still lacking. Here, we report that the initial dispersing solvent, which is not present after producing PNCs, drives these nonequilibrium effects on polymer chain dynamics at interfaces. Employing extensive small-angle scattering, proton NMR spectroscopy, and rheometry experiments, we found that the thickness of the immobilized layer can be dependent on the initial solvent, changing the structure and the properties of the PNC significantly. In addition, we show that the outcome of the initial solvent effect becomes more effective at particle volume fractions where the immobile layers begin to interact.

Relationship between AHSP gene expression, ß/α globin mRNA ratio, and clinical severity of the ß-thalassemia patients.

BACKGROUND: Alpha hemoglobin stabilizing protein (AHSP) is a chaperone-like molecule specialized for erythroid series which binds to free α-globin chain. According to this characteristic, AHSP can be considered an important factor which reduces beta thalassemia symptoms. MATERIALS AND METHODS: Reticulocytes RNA extraction and a subsequent cDNA synthesis were performed, followed by Relative qRT-PCR for AHSP, alpha, and beta globin chain genes. The beta actin gene was used as an endogenous reference as well. The relationship between AHSP gene expression, disease severity, and the ß/α globin mRNA ratio was studied among different homozygote ß-thalassemia patients (mild, moderate and severe) and compared with minor thalassemia and the normal population. RESULTS: Analysis of the ß-globin/α-globin mRNA ratio has shown that disease severity enhanced with a decrease in this proportion. Evaluation of the correlation between AHSP gene expression and the average of the ß-globin/α-globin expression ratio indicated a significant but indirect relationship in considered groups. Our results demonstrated that the AHSP gene expression increases in accordance with augmentation of clinical symptoms. CONCLUSIONS: Although one of the main reasons for reduced clinical severity in homozygote ß-thalassemia can be the high level of AHSP gene expression as a chaperon molecule, our findings indicated that AHSP gene expression decreased in a mild category as compared to that in severe and moderate groups.

Analysis of ß/α globin ratio by using relative qRT-PCR for diagnosis of beta-thalassemia carriers.

BACKGROUND: Current routine tests for premarital screening of ß-thalassemia carriers are not applicable for diagnosis of rare atypical minor ß-thalassemia cases. A more specialized laboratory evaluation for them is the measurement of ß/α chain synthesis ratio with the assistance of radioactive amino acids. This method is also no longer routinely accessible. Consequently it is required to establish a rapid, trouble-free, and reliable method that encompasses all the cases of ß-thalassemia carriers. Therefore we have determined ß/α-globin mRNA ratio by applying relative qRT-PCR in various ß-thalassemia patients. METHODS: Reticulocytes RNA extraction and subsequent cDNA synthesis were performed, followed by relative qRT-PCR for α- and ß-globin chain genes and ß-actin gene as an endogenous reference. ß/α-Globin gene ratio was then evaluated with the Pfaffl method. RESULTS: The mean of ß/α ratio was 0.99, 0.81, 0.69, and 0.69 for normal population, minor, intermediate, and major ß-thalassemia, respectively. Approximately 6% of cases with minor thalassemia RBC index and normal HbA2 and having a decreased ß/α ratio were located in the minor ß-thalassemia group. The mean of ß/α mRNA ratio in normal individuals and minor ß-thalassemia was significantly different with all other groups (P-value < 0.05). Nevertheless, there was no such association between ß/α mRNA ratio in major and intermediate ß-thalassemia. CONCLUSION: According to the significant differences achieved, no overlapping between minor ß-thalassemia and normal group, capability of diagnosing atypical minor ß-thalassemia, and accessibility of this technique, we can declare that this method could be suggested as a routine premarital screening test for ß-thalassemia carriers.