Increase In Isoelectric Point Research Articles

Synthesis of pH and Glucose Responsive Silk Fibroin Hydrogels.

Silk fibroin (SF) has attracted much attention due to its high, tunable mechanical strength and excellent biocompatibility. Imparting the ability to respond to external stimuli can further enhance its scope of application. In order to imbue stimuli-responsive behavior in silk fibroin, we propose a new conjugated material, namely cationic SF (CSF) obtained by chemical modification of silk fibroin with ε-Poly-(L-lysine) (ε-PLL). This pH-responsive CSF hydrogel was prepared by enzymatic crosslinking using horseradish peroxidase and H2O2. Zeta potential measurements and SDS-PAGE gel electrophoresis show successful synthesis, with an increase in isoelectric point from 4.1 to 8.6. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) results show that the modification does not affect the crystalline structure of SF. Most importantly, the synthesized CSF hydrogel has an excellent pH response. At 10 wt.% ε-PLL, a significant change in swelling with pH is observed. We further demonstrate that the hydrogel can be glucose-responsive by the addition of glucose oxidase (GOx). At high glucose concentration (400 mg/dL), the swelling of CSF/GOx hydrogel is as high as 345 ± 16%, while swelling in 200 mg/dL, 100 mg/dL and 0 mg/dL glucose solutions is 237 ± 12%, 163 ± 12% and 98 ± 15%, respectively. This shows the responsive swelling of CSF/GOx hydrogels to glucose, thus providing sufficient conditions for rapid drug release. Together with the versatility and biological properties of fibroin, such stimuli-responsive silk hydrogels have great potential in intelligent drug delivery, as soft matter substrates for enzymatic reactions and in other biomedical applications.

An update to the pathogenesis for monoclonal gammopathy of renal significance.

Monoclonal gammopathy of renal significance (MGRS) is characterized by the nephrotoxic monoclonal immunoglobulin (MIg) secreted by an otherwise asymptomatic or indolent B-cell or plasma cell clone, without hematologic criteria for treatment. The spectrum of MGRS-associated disorders is wide, including non-organized deposits or inclusions such as C3 glomerulopathy with monoclonal glomerulopathy (MIg-C3G), monoclonal immunoglobulin deposition disease, proliferative glomerulonephritis with monoclonal immunoglobulin deposits and organized deposits like immunoglobulin related amyloidosis, type I and type II cryoglobulinaemic glomerulonephritis, light chain proximal tubulopathy, and so on. Kidney biopsy should be conducted to identify the exact disease associated with MGRS. These MGRS-associated diseases can involve one or more renal compartments, including glomeruli, tubules and vessels. Hydrophobic residues replacement, N-glycosylated, increase in isoelectric point in MIg causes it to transform from soluble form to tissue deposition, causing glomerular damage. Complement deposition is found in MIg-C3G, which is caused by an abnormality of the alternative pathway and may involve multiple factors including complement component 3 nephritic factor, anti-complement factor auto-antibodies or MIg which directly cleaves C3. The effect of transforming growth factor beta and platelet-derived growth factor-β on mesangial extracellular matrix is associated with glomerular and tubular basement membrane thickening, nodular glomerulosclerosis, and interstitial fibrosis. Furthermore, inflammatory factors, growth factors and virus infection may play an important role in the development of the diseases. In this review, for the first time, we discussed current highlights in the mechanism of MGRS-related lesions.

An update to the pathogenesis for monoclonal gammopathy of renal significance.

Monoclonal gammopathy of renal significance (MGRS) is characterized by the nephrotoxic monoclonal immunoglobulin secreted by an otherwise asymptomatic or indolent B cell or plasma cell clone, without hematologic criteria for treatment. These MGRS-associated diseases can involve one or more renal compartments, including glomeruli, tubules, and vessels. Hydrophobic residue replacement, N-glycosylated, increase in isoelectric point in monoclonal immunoglobulin (MIg) causes it to transform from soluble form to tissue deposition, and consequently resulting in glomerular damage. In addition to MIg deposition, complement deposition is also found in C3 glomerulopathy with monoclonal glomerulopathy, which is caused by an abnormality of the alternative pathway and may involve multiple factors including complement component 3 nephritic factor, anti-complement factor auto-antibodies, or MIg which directly cleaves C3. Furthermore, inflammatory factors, growth factors, and virus infection may also participate in the development of the diseases. In this review, for the first time, we discussed current highlights in the mechanism of MGRS-related lesions.

Coupled removal of bisphenol A and copper ion by titanate nanotubes fabricated at different calcination temperatures

One-dimensional (1-D) nanotubes are promising nanostructured materials for a wide variety of environmental applications. In this study, the 1-D titanate nanotubes (TNTs) were fabricated using an alkaline hydrothermal method and then calcined at various temperatures ranging from 200 to 600°C in air for 4h for coupled removal of bisphenol A (BPA) and Cu(II) ion. The as-synthesized TNTs showed tubular structures with diameter of 8–10nm and length of few μm. After calcination at 400–600°C, the well-crystallized anatase TiO2 nanoparticles were produced on the tube walls to form titania/TNT nanocomposites, resulting in the decrease in specific surface area and the increase in isoelectric point. The as-synthesized and calcined TNTs have good Cu(II) adsorption capacity, and the maximum Langmuir adsorption capabilities decreased from 160mg/g for as-synthesized TNTs to 35mg/g for TNT-600, presumably due to the decrease in specific surface area. In addition, the calcined TNT showed a good photocatalytic activity towards BPA degradation when compared with the as-synthesized TNTs. The coexistence of Cu(II) ion and BPA exhibited the synergistic effect on the enhancement of photocatalytic activity of calcined TNTs. Electron spin resonance results indicated that the copper ion was first adsorbed onto the negatively charged TNTs, and then served as the electron trap to prolong to retention time of photo-generated radicals, resulting in the enhancement of photodegradation efficiency and rate of BPA by calcined TNTs.

Purification and characterization of a human sialoglycoprotein antigen expressed in immature thymocytes and fetal tissues.

The monoclonal antibody UN1 was previously produced in our laboratory on the basis of selective reactivity with human thymocytes and has been classified as unclustered by the 5th and 6th International Workshop and Conference on Human Leukocyte Differentiation Antigens. The antigen recognized by mAb UN1 was found to be expressed on the cell surface of immature human thymocytes, a subpopulation of peripheral T lymphocytes and on several fetal tissues including thymus. The UN1 antigen is purified from children's thymus by ion-exchange and affinity chromatography. Two-dimensional electrophoresis shows that the purified antigen displays microheterogeneity appearing as multiple spots over a pI range 4.4-5.0 at 100-120 kDa. Treatment with neuraminidase results in a retarded migration in SDS-PAGE, an increase in isoelectric point and a reduction in carbohydrate content, indicating a substantial content of sialic acid. Glycosidase digestion and lectin-binding analysis indicate that the carbohydrate residues are essentially O-linked. A preliminary analysis has detected the UN1 antigen in human breast carcinoma tissues but not in normal breast. The biochemical features and the pattern of expression of the UN1 antigen indicate that this molecule may have the characteristics typical of the family of cell-membrane-associated mucin-like glycoproteins; a number of these molecules are thought to have a role in cell-cell interaction, tumor progression and metastasis.

Electrokinetic behavior of spherical colloidal particles of cadmium sulfide

The electrophoretic behavior of monodisperse, spherical cadmium sulfide particles is analyzed in this work with the aim of contributing new data on the electrical nature of the surface of this material. The electrophoretic mobility, μ e, of CdS particles is studied as a function of both pH and concentration of several electrolytes. As in many metal sulfides, the surface characteristics are very sensitive to its degree of oxidation, as demonstrated by the slight increase in isoelectric point (iep) of samples obtained with longer synthesis times. The iep of CdS is found to be between pH 1 and 1.5, this value being unaltered by the addition of NaCl at different concentrations. The effect of the lattice ions (Cd 2+ and S 2−, or rather HS −) on the mobility is very significant: HS − anions adsorb on the particles, increasing the negative values of μ e whereas the behavior in the presence of Cd 2+ salts suggests surface precipitation of Cd(OH) 2. The cations Ag +, Cu 2+, Mn 2+ and La 3+ can be considered as activating species for the cadmium sulfide/solution interface: their hydrolysis products adsorb onto the CdS particles and provoke up to three pH values of inversion of the sign of μ e. The effect is most important for Cu 2+, Ag + and La 3+ cations, for which μ e reversals can be achieved for initial concentrations as low as 10 −4 and 5 × 10 −5 M, respectively. If MnCl m2 solutions are used, their concentration must be ⩾ 10 −3 M to observe the same phenomenon.

Surface charge characteristics of aluminum hydroxycarbonate as influenced by carbonate equilibrium

AbstractThe isoelectric point of aluminum hydroxycarbonate suspension increases upon dilution with deionized water. The increase in the isoelectric point is directly related to the degree of dilution. Dilution with bicarbonate ion-containing solutions reduced the change in isoelectric point in comparison to dilution with deionized water. The change in isoelectric point was inversely related to the concentration of bicarbonate ion in the diluting solution. The increase in isoelectric point observed following dilution with deionized water was reversed by the addition of bicarbonate ion. The observations suggest that carbonate ions occupying potential determining sites in the primary particles are in equilibrium with carbonate/bicarbonate ions in solution. Formulation or processing factors which affect the equilibrium will affect the isoelectric point of aluminum hydroxycarbonate suspensions and will influence their physical properties.

Post-translational processing of p21ras is two-step and involves carboxyl-methylation and carboxy-terminal proteolysis.

We have studied the post-translational processing of p21ras proteins. The primary translation product pro-p21 is cytosolic and is rapidly converted to a cytosolic form (c-p21) of higher mobility on SDS-PAGE. c-p21 is converted in turn to the membrane-bound mature palmitoylated form (m-p21) of slightly higher mobility. These processing steps are accompanied by increases in isoelectric point and in hydrophobicity as judged by Triton X-114 partitioning. Although the increases in electrophoretic mobility and hydrophobicity precede acylation we show that mutation of Cys186, which has been shown to block acylation, also abolishes the pro-p21 to c-p21 conversion. Thus the Cys186 residue is involved in the processing steps prior to acylation. We have identified two processing events which contribute to the pro-p21 conversion. Site-directed mutagenesis to insert tryptophan, which is not present in the wild type, followed by metabolic labelling with [3H]tryptophan has allowed us to map a proteolytic processing event which removes the three C-terminal residues. In addition, both the c-p21 and m-p21 forms are carboxyl-methylated. Approximately one methyl group is incorporated per molecule of p21 at steady state, which can partially account for the increase in isoelectric point. Unlike palmitate, methyl group turnover is not observed.

Control of late G0/G1 progression and protein modification by SmC/IGF I.

Somatomedin C/insulin-like growth factor I (SmC/IGF I) mediates traverse of late G0/G1 in density-arrested BALB/c-3T3 cells from a distinct growth arrest point in mid-G0/G1 (the V point) to the initiation of DNA synthesis. As a prelude to future studies aimed at defining the mechanism of action of SmC/IGF I, we investigated the level (e.g., transcriptional, translational) at which SmC/IGF I modulates V to S traverse. The post-V point progression of cells arrested at the V point by amino acid starvation and released into amino acid-replenished medium containing SmC/IGF I, insulin, or platelet-poor plasma (PPP) did not require either mRNA synthesis or an increase in the overall level of protein synthesis. Although two-dimensional gel analysis of proteins prepared from SmC/IGF I-treated cells did not reveal any preferentially synthesized proteins, several SmC/IGF I-induced protein modifications, which result in an increase in isoelectric point (pI) and occur in the absence of mRNA synthesis, were evident. These findings suggest that SmC/IGF I modulates late G0/G1 progression by a posttranscriptional process that may involve protein modification.

Reductive Methylation of β-Lactoglobulin

The effect of reductive methylation on the properties of β-lactoglobulin was studied with preparations in which 6, 32, or 80% of the amino groups were methylated. Content of sulfhydryl groups was not changed and little difference in electrophoretic mobility of the protein was evident on polyacrylamide gel electrophoresis. Thin-layer isoelectric focusing from pH 4 to 6 indicated that protein in which 80% of the amino groups were modified showed an increase in isoelectric point of no more than .1 pH unit for each electrophoretic component, compared with untreated β-lactoglobulin (A plus B variants). Reductive methylation with [carbon-14] formaldehyde at low reagent concentration yielded a product which contained approximately one mole of [carbon-14] methyl groups for each mole of β-lactoglobulin. Tracer [carbon-14]β-lactoglobulin added to skim milk exhibited a heat-denaturation curve similar to that described for unmodified β-lactoglobulin. Such a radio-actively labeled derivative will be useful for studying protein interactions in milk.