Polyvinylidene Diflouride Research Articles

Effect of micelle concentration on degumming of sesame oil (Sesamum indicum L) with ultrafiltration membrane

Abstract Sesame oil (Sesamum indicum L.) is obtained from roasted and pressed sesame seeds. The existence of phospholipids and contaminants in sesame oil is unfavorable, as it induces a darkening of the oil’s hue, thereby diminishing its oxidative stability. Failure to eliminate phospholipids compounds from sesame oil through the degumming process leads to a deterioration in quality thus influencing consumer acceptability. This research aimed to investigate the impact of micelle concentrations in hexanes-sesame oil mixture on the degumming process employing ultrafiltration membranes. This investigation involved the preparation of sesame oil through a procedure that entailed roasting at 180°C for 30 minutes, followed by pressing at a pressure of 140 kN for 5 minutes. Micelles of sesame oil roasted with hexane were prepared at concentrations of 20%, 25% and 30%. Moreover, the degumming of sesame oil micelles was accomplished by utilizing PES (Polyether sulfone) and PVDF (Polyvinylidene diflouride) ultrafiltration membranes and then by analyzing the resulting sesame oil’s properties. The results indicated that using a PVDF membrane for sesame oil degumming resulted in a higher permeate flux than a PES membrane. Furthermore, treatment with a 30% micelle concentration resulted in a yield of 70.63%, with phospholipid levels of 13.96 ppm and membrane rejection value of 92.9%.

Preparation and optimization of PVDF thin films for miniaturized sensor and actuator applications

This paper demonstrates the key process optimizations that need to be carried out in order to leverage the piezoelectric property of polyvinylidene diflouride (PVDF) thin films for miniaturized sensor and actuator applications. The emphasis of the paper is two fold. Firstly, innate material and piezoelectric properties of PVDF thin films were thoroughly investigated and the processing conditions for achieving minimally porous, smooth thin film exhibiting superior piezoelectric response was experimentally figured out. Along with that, as a proof of concept, a working prototype of piezoelectric micromachined ultrasonic transducer (PMUT) was fabricated and tested using optimized PVDF thin films. The key bottleneck of adhesion of PVDF with underlying metal layers is addressed by using adhesion promoter (3-aminopropyl)triethoxysilane. This small, yet significant modification enabled the fabrication of PMUT device using PVDF as membrane material. The fabricated device has exhibited a electromechanical coupling coefficient value of 15.66% and a resonance frequency of 129.5 kHz.

Cirrhosis of liver: Comparative cross reactivity for quantification of SERPINA4/Kallistatin

Cirrhosis of liver is an end stage of chronic liver insults from varied etiologies which leads to impaired liver functions. Proteins expressed from liver and enters into circulation reflects degree of liver dysfunction. Serpins (Serine protease inhibitors) are class of plasma proteins expressed from liver; SERPINA4/Kallistatin is a multifunctional serpin clade A protein expressed from liver and concentration in serum is the reflection of extent of liver dysfunction. The present study aimed to compare cross reactivity of serpins for polyclonal and monospecific antibodies in both cirrhotic liver and healthy subjects. Blood samples were collected from 20 subjects (10 cirrhotic liver, 10 healthy) from R. L. Jalappa Hospital and Research Centre, Kolar, Karnataka, India. Separation of proteins was carried out by SDS-PAGE. Cross reactivity study was analyzed using western blot. Proteins present in cirrhotic liver and healthy subject’s serum were separated by SDS PAGE. There was no band detection on both (cirrhotic liver and healthy) PVDF (polyvinylidene diflouride) membranes with polyclonal antibodies. However, a significant band was observed with protein of interest in healthy PVDF membrane with monospecific antibodies. There was no band in cirrhotic liver PVDF membrane even with monospecific antibodies. Comparative cross reactivity analysis of serpins in quantification of SERPINA4/Kallistatin in the present study demonstrated that there will not be any immunological cross reactivity between serpins and SERPINA4/Kallistatin due to the absence of identical epitope in cirrhotic liver and healthy subjects.

Cirrhosis of liver: Interference of serpins in quantification of SERPINA4 – A preliminary study

BackgroundCirrhosis of liver is a pathological condition, wherein functions of liver are impaired by chronic liver exploitations. Due to decrease in synthetic capacity, expressions of plasma proteins tend to decrease in blood stream. Serpins (Serine protease inhibitors) are class of plasma proteins expressed from liver with structural similarities and diverse functions. SERPINA4 (Kallistatin) is a multifunctional serpin clade A protein expressed from liver and concentration in serum is the reflection of extent of liver dysfunction. ObjectiveTo identify interference of other serpins by immunological cross reactivity with SERPINA4 in cirrhotic liver and healthy subjects. Materials and methodsBlood samples were collected from 20 subjects (10 cirrhotic liver, 10 healthy) from R.L. Jalappa Hospital and Research Centre, Kolar, Karnataka, India. Separation of proteins was carried out by SDS-PAGE. Cross reactivity study was analyzed using western blot. ResultsProteins present in cirrhotic liver and healthy subject's serum were separated by SDS PAGE. There was no band detection on both (cirrhotic liver and healthy) PVDF (polyvinylidene diflouride) membranes. However, a significant band was observed with recombinant kallistatin. ConclusionStructurally similar serpins with minor amino acid sequence similarities did not show any immunological cross reactivity with SERPINA4 due to non identical epitope in cirrhotic liver and healthy subjects. Present study revealed that there is no interference of serpins for immunological reactions in quantitative estimation of kallistatin which needs further validation.

CsHSO4 as proton conductor for high-temperature polymer electrolyte membrane fuel cells

The influence of CsHSO4 inorganic solid acid was evaluated as a possible proton conductor in the catalyst layer of ABPBI (poly(2,5-benzimidazole))-based high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Gas diffusion electrodes (GDEs) were prepared with fixed polytetrafluoroethylene (PTFE) and polyvinylidene diflouride (PVDF) binder content, while the CsHSO4 loading was varied. Porosimetry data showed that the addition of 10 % CsHSO4 to the PVDF GDE increased the porosity across all the pore regions, whereas the addition of 10 % CsHSO4 to the PTFE GDE decreased the GDEs porosity. The CsHSO4 MEAs showed good proton transfer dynamics and low resistance for fuel cell operation. An optimum loading of 10 % CsHSO4 in conjunction with either of the binders was observed, with CsHSO4–PVDF GDE achieving peak power of 498.2 mW cm−2 at a cell voltage of +352 mV. Higher CsHSO4 loadings increased the charge transfer resistance and lowered the cell performance of these GDEs.

Muscle sparing in muscle RING finger 1 null mice: response to synthetic glucocorticoids

Skeletal muscle atrophy occurs under a variety of conditions and can result from alterations in both protein synthesis and protein degradation. The muscle-specific E3 ubiquitin ligases, MuRF1 and MAFbx, are excellent markers of muscle atrophy and increase under divergent atrophy-inducing conditions such as denervation and glucocorticoid treatment. While deletion of MuRF1 or MAFbx has been reported to spare muscle mass following 14 days of denervation, their role in other atrophy-inducing conditions is unclear. The goal of this study was to determine whether deletion of MuRF1 or MAFbx attenuates muscle atrophy after 2 weeks of treatment with the synthetic glucocorticoid dexamethasone (DEX). The response of the triceps surae (TS) and tibialis anterior (TA) muscles to 14 days of DEX treatment (3 mg kg(-1) day(-1)) was examined in 4 month-old male and female wild type (WT) and MuRF1 or MAFbx knock out (KO) mice. Following 14 days of DEX treatment, muscle wet weight was significantly decreased in the TS and TA of WT mice. Comparison of WT and KO mice following DEX treatment revealed significant sparing of mass in both sexes of the MuRF1 KO mice, but no muscle sparing in MAFbx KO mice. Further analysis of the MuRF1 KO mice showed significant sparing of fibre cross-sectional area and tension output in the gastrocnemius (GA) after DEX treatment. Muscle sparing in the MuRF1 KO mice was related to maintenance of protein synthesis, with no observed increases in protein degradation in either WT or MuRF1 KO mice. These results demonstrate that MuRF1 and MAFbx do not function similarly under all atrophy models, and that the primary role of MuRF1 may extend beyond controlling protein degradation via the ubiquitin proteasome system.

Human Phenotypically Distinct TGFBI Corneal Dystrophies Are Linked to the Stability of the Fourth FAS1 Domain of TGFBIp

Mutations in the human TGFBI gene encoding TGFBIp have been linked to protein deposits in the cornea leading to visual impairment. The protein consists of an N-terminal Cys-rich EMI domain and four consecutive fasciclin 1 (FAS1) domains. We have compared the stabilities of wild-type (WT) human TGFBIp and six mutants known to produce phenotypically distinct deposits in the cornea. Amino acid substitutions in the first FAS1 (FAS1-1) domain (R124H, R124L, and R124C) did not alter the stability. However, substitutions within the fourth FAS1 (FAS1-4) domain (A546T, R555Q, and R555W) affected the overall stability of intact TGFBIp revealing the following stability ranking R555W>WT>R555Q>A546T. Significantly, the stability ranking of the isolated FAS1-4 domains mirrored the behavior of the intact protein. In addition, it was linked to the aggregation propensity as the least stable mutant (A546T) forms amyloid fibrils while the more stable variants generate non-amyloid amorphous deposits in vivo. Significantly, the data suggested that both an increase and a decrease in the stability of FAS1-4 may unleash a disease mechanism. In contrast, amino acid substitutions in FAS1-1 did not affect the stability of the intact TGFBIp suggesting that molecular the mechanism of disease differs depending on the FAS1 domain carrying the mutation.

Flexibility of the Thrombin-activatable Fibrinolysis Inhibitor Pro-domain Enables Productive Binding of Protein Substrates

We have previously reported that thrombin-activatable fibrinolysis inhibitor (TAFI) exhibits intrinsic proteolytic activity toward large peptides. The structural basis for this observation was clarified by the crystal structures of human and bovine TAFI. These structures evinced a significant rotation of the pro-domain away from the catalytic moiety when compared with other pro-carboxypeptidases, thus enabling access of large peptide substrates to the active site cleft. Here, we further investigated the flexible nature of the pro-domain and demonstrated that TAFI forms productive complexes with protein carboxypeptidase inhibitors from potato, leech, and tick (PCI, LCI, and TCI, respectively). We determined the crystal structure of the bovine TAFI-TCI complex, revealing that the pro-domain was completely displaced from the position observed in the TAFI structure. It protruded into the bulk solvent and was disordered, whereas TCI occupied the position previously held by the pro-domain. The authentic nature of the presently studied TAFI-inhibitor complexes was supported by the trimming of the C-terminal residues from the three inhibitors upon complex formation. This finding suggests that the inhibitors interact with the active site of TAFI in a substrate-like manner. Taken together, these data show for the first time that TAFI is able to form a bona fide complex with protein carboxypeptidase inhibitors. This underlines the unusually flexible nature of the pro-domain and implies a possible mechanism for regulation of TAFI intrinsic proteolytic activity in vivo.

Effects of particle size on the thermal stability of lithiated graphite anode

The thermal behavior of fully lithiated natural graphite flakes with different particle sizes has been investigated using differential scanning calorimetry (DSC). For DSC measurements, a fully lithiated graphite anode was heated in a hermetically sealed high pressure pan with a poly vinylidene diflouride (PVdF) binder and 1 M LiPF 6 solution in ethylene carbonate (EC)–diethyl carbonate (DEC) mixture. It has been founded that the particle size has a strong influence on the thermal stability of the lithiated graphite anode. The heat generation due to the solid electrolyte interface (SEI) decomposition increases with decreasing the particle size. The onset temperatures for exothermic reactions after initial SEI decomposition appear to be lower for graphite electrodes with smaller particle sizes. This is attributed to a thermal induced delithiation facilitated by reduced diffusion path and higher surface area in smaller graphites. The structural changes in graphites during DSC scan have been investigated by ex situ X-ray diffraction (XRD) and Raman spectrometer.

Conserved ETS Domain Arginines Mediate DNA Binding, Nuclear Localization, and a Novel Mode of bZIP Interaction

The DNA-binding ETS transcription factor Spi-1/PU.1 is of central importance in determining the myeloid-erythroid developmental switch and is required for monocyte and osteoclast differentiation. Many monocyte genes are dependent upon this factor, including the gene that codes for interleukin-1beta. It has long been known that the conserved ETS DNA-binding domain of Spi-1/PU.1 functionally cooperates via direct association with a diverse collection of DNA-binding proteins, including members of the basic leucine zipper domain (bZIP) family. However, the molecular basis for this interaction has long been elusive. Using a combination of approaches, we have mapped a single residue on the surface of the ETS domain critical for protein tethering by the C/EBPbeta carboxyl-terminal bZIP domain. This residue is also important for nuclear localization and DNA binding. In addition, dependence upon the leucine zipper suggests a novel mode for both protein-DNA interaction and functional cooperativity.

Comparison of different transition metal ions for immobilized metal affinity chromatography of selenoprotein P from human plasma

Cu 2+, Ni 2+, Zn 2+, Co 2+ and Cd 2+ were evaluated in metal ion affinity chromatography for enrichment of selenoprotein P, and immobilized Co 2+ affinity chromatography was found to be the most selective chromatographic method. The chromatography was performed by fast protein liquid chromatography and the fractionation was followed by analysis of the collected fractions for selenium by inductively coupled plasma mass spectrometry. By the combination of immobilized Co 2+ affinity chromatography and heparin affinity chromatography a simple method was developed yielding a 14 800-fold enrichment of selenoprotein P. The purity of the protein was determined by SDS–PAGE and by sequencing from polyvinylidene diflouride blots of SDS–PAGE gels.

Secretion of type-1-fimbriae binding proteins from human neutrophil granulocytes.

Granule matrix proteins secreted from human neutrophils after ionomycin stimulation were separated by SDS-PAGE, blotted onto a polyvinylidene diflouride (PVDF) membrane and overlaid with the mannose-binding lectin concanavalin A (Con A) or Escherichia coli bacteria exposing type-I-fimbriae. Four proteins of approximately 30, 40, 70 and 80 kD, respectively, derived from both the azurophil and the specific granules were shown to expose mannose-containing structures by binding of Con A. Such reactivity was also shown for a 90-kD protein from the light membrane fraction enriched in plasma membrane and secretory vesicles. When blots of granule matrix proteins were exposed to type-I-fimbriated bacteria, a total of seven proteins was recognized; four of the five Con A-binding proteins (40, 70, 80 and 90 kD) was detected also by the bacteria in addition to three proteins not detected by Con A (50, 60 and 100 kD). The role of the secreted type-1-fimbriae binding proteins as anti-adhesin candidates is discussed.

Sample centrifugation onto membranes for sequencing

This paper presents a new method for adsorption of proteins in solution onto a polyvinylidene diflouride (PVDF) membrane using centrifugation. The technique uses a low molecular weight cut-off membrane (LMW) placed underneath a PVDF membrane. The paired membranes are placed in a receptacle which in turn fits into a microcentrifuge tube. During sample centrifugation, the LMW acts to increase the amount of protein that is concentrated and adsorbed onto the hydrophobic surface of the PVDF membrane. By alternating between two receptacle sizes, this method can accomodate large (>10 μg) and small (<10 μg) amounts of sample. This paper demonstrates sample recovery for a variety of proteins as quantitated by radioactivity and amino acid analysis after centrifugation onto PVDF. Amino acid and sequence analysis results demonstrate the efficiency with which interfering buffers and sodium dodecyl sulfate are removed as a result of sample centrifugation and washing. Finally, we demonstrate the utility of this technique with samples in the low picomole range to obtain useful sequence information following electrophoretic isolation of cyanogen bromide fragments purified by high performance electrophoresis chromatography.

A method for preparing proteins and peptides for microsequencing

We present simple methods for the generation and separation of peptides suitable for automated amino acid sequencing using Edman chemistry. We describein-situ CNBr cleavage of proteins electrophoretically separated in polyacrylamide gels. The generated peptides are separated by gel electrophoresis and blotted onto polyvinylidene diflouride membrane. Membranebound peptides are detected by Coomassie Blue staining and directly applied to an automated sequencer.