Investigation of the effects of starch on the physical and biological properties of polyacrylamide (PAAm)/starch nanofibers

Abstract Here, we report the development of a new polyacrylamide (PAAm)/starch nanofibers’ blend system and highlight its potential as substrate for efficient enzyme immobilization. PAAm was synthesized and blended with starch. The final blend was then electrospun into nanofibers. The response surface methodology was used to analyze the parameters that control nanofiber’s diameter. Electrospun mat was then modified either by cross-linking or phytase immobilization using silane coupling agent and glutaraldehyde chemistry. Physico-chemical properties of blends were investigated using spectroscopic and thermal studies. The evaluation of immobilized enzyme kinetics on both pure and the starch blended PAAm nanofibers was performed using Michaelis–Menten kinetic curves. Fourier transform infrared spectroscopy results along with differential scanning and X-ray diffraction confirmed that blending was successfully accomplished. TGA analysis also demonstrated that the presence of starch enhances the thermal degradability of PAAm nanofibers. Finally, it was shown that addition of starch to PAAm increases the efficacies of enzyme loading and, therefore, significantly enhances the activity as well as kinetics of the immobilized enzyme on electrospun blend mats

Posttranscriptional Regulation of the Human LDL Receptor by the U2-Spliceosome.

Background: The low-density lipoprotein receptor (LDLR) in the liver is the major determinant of LDL-cholesterol levels in human plasma. The discovery of genes that regulate the activity of LDLR helps to identify pathomechanisms of hypercholesterolemia and novel therapeutic targets against atherosclerotic cardiovascular disease. Methods: We performed a genome-wide RNA interference screen for genes limiting the uptake of fluorescent LDL into Huh-7 hepatocarcinoma cells. Top hit genes were validated by in vitro experiments as well as analyses of datasets on gene expression and variants in human populations. Results: The knockdown of 54 genes significantly inhibited LDL uptake. Fifteen of them encode for components or interactors of the U2-spliceosome. Knocking down any one of 11 out of 15 genes resulted in the selective retention of intron 3 of LDLR. The translated LDLR fragment lacks 88% of the full length LDLR and is detectable neither in non-transfected cells nor in human plasma. The hepatic expression of the intron 3 retention transcript is increased in non-alcoholic fatty liver disease as well as after bariatric surgery. Its expression in blood cells correlates with LDL-cholesterol and age. Single nucleotide polymorphisms and three rare variants of one spliceosome gene, RBM25, are associated with LDL-cholesterol in the population and familial hypercholesterolemia, respectively. Compared to overexpression of wild type RBM25, overexpression of the three rare RBM25 mutants in Huh-7 cells led to lower LDL uptake. Conclusions: We identified a novel mechanism of post-transcriptional regulation of LDLR activity in humans and associations of genetic variants of RBM25 with LDL-cholesterol levels