Polyvinyl Difluoride Membranes Research Articles

Fibrous PVDF membranes modified by anchored g-C3N4@GO composite with enhanced photocatalytic activity

Recently, the development of fibrous membranes for pollutant filtration from air or water has been a topic of great interest. However, these filters’ high and rapid fouling has limited their use. In response, we have prepared photocatalytic active membranes that harness the synergic effect between graphene oxide (GO) and graphitic carbon nitride (g-C3N4). Theresultingcomposite demonstrated the highest photocatalytic activity (kobs = 88 × 10−3 min−1). This g-C3N4@GO composite was then carefully deposited on/in an electrospun polyvinyl difluoride (PVDF) fibrous membrane. The reproducible results of the chemical bonding ofthecomposite to the PVDF matrix were evident during photocatalytic experiments after ten Rhodamine B (Rh B) photocatalytic degradation cycles. Importantly, the fiber structure analysis post-reaction did not reveal any fiber cracks or void formation defects, indicating the excellent chemical stability of the PVDF fibrous matrix. This research offers a promising, sustainable, eco-friendly, and efficient solution for removing pollutants from different environments, inspiring further exploration and development in this field.

Enhancing photocatalytic g-C3N4/PVDF membranes through new insights into the preparation methods

Fibrous membranes are crucial on the filtration of pollutants from air and water, but continued use can lead to a failure in effectiveness due to pollutant accumulation. To enhance durability, incorporating photocatalytic submicroparticles into these membranes appear as a solution.Here, we prepared a set of polyvinyl difluoride (PVDF) fibrous membranes modified with graphitic carbon nitride (g-C3N4) using three different methodologies. Their photocatalytic efficiency was investigated using phenol as model pollutant compound under visible light irradiation.Using g-C3N4 fibrous membranes modified by electrospinning blend a pseudo first-order kinetic constant (kapp) of 2.51 × 10-4 min-1 was observed for phenol degradation after 240 min reaction. Despite minimal particle adhesion the thermal treatment increased kapp to 5.41 × 10-4 min-1. The membranes prepared via chemical activation of PVDF exhibited the highest photocatalytic activity (kapp of 21.7 × 10-4 min-1). This superior activity was attributed to covalent bonds between PVDF and g-C3N4, allowing the formation of oxidative species.

Biofilm Formation and Biofouling Development on Different Ultrafiltration Membranes by Natural Anaerobes from an Anaerobic Membrane Bioreactor.

Biofouling in anaerobic membrane bioreactors (AnMBRs) has not been studied widely. Moreover, the effect of membrane surface properties on biofilm formation beyond initial deposition is controversial. We investigated biofouling with polyvinyldifluoride, polyacrylonitrile, and zwitterion-modified polyethersulfone ultrafiltration membranes having different properties during 72 h filtration using natural anaerobes isolated from AnMBR and analyzed biofilm characteristics by physicochemical and molecular techniques. A decrease in membrane performance was positively correlated with biofilm formation on polyvinyldifluoride and polyacrylonitrile membranes, and as expected, physical cleaning effectively mitigated biofilm on hydrophilic and low-roughness membranes. Surprisingly, while the biofilm on the hydrophilic and low-surface roughness zwitterion-modified membrane was significantly impaired, the impact on transmembrane pressure was the highest. This was ascribed to the formation of a soft compressible thin biofilm with high hydraulic resistance, and internal clogging and pore blocking due to high pore-size distribution. Anaerobe community analysis demonstrated some selection between the bulk and biofilm anaerobes and differences in the relative abundance of the dominant anaerobes among the membranes. However, correlation analyses revealed that all membrane properties studied affected microbial communities' composition, highlighting the system's complexity. Overall, our findings indicate that the membrane properties can affect biofilm formation and the anaerobic microbial population but not necessarily alleviate biofouling.

Garlic peel based mesoporous carbon nanospheres for an effective removal of malachite green dye from aqueous solutions: Detailed isotherms and kinetics

Biowaste based nanoadsorbents have gained much attention in the recent times for wastewater decolourization owing to their low cost, high surface area and high adsorption capacities. In the present research, garlic peel based nanoparticles (GCNP) were synthesized at different temperatures by a one step pyrolytic green approach for the effective removal of cationic dye, malachite green from the aqueous medium. The surface properties of Garlic nanoparticles were elucidated by N2 adsorption- desorption and all the GCNP samples were found to exhibit Type IV(a) isotherm indicating the presence of mesopores in carbon matrix. Using BET calculations, highest surface area (380 m2/g) was obtained for GCNP synthesized at 1000 ◦C. Characterization of nanoparticles was done by XRD, EDAX, SEM and FTIR studies before and after the dye treatment. Adsorption studies conducted using different parameters like contact time, concentration and pH and dosage of adsorbent showed removal efficiency above 90% for the contact time of 70 min. Best adsorption experimental results were obtained for GCNP synthesized at 1000 °C ascribable to its high surface area, higher total pore volume (0.26 cm2/g) and higher carbon content. Four adsorption isotherm models were used to validate batch equillibrium studies and the results showed data in good agreement with Langmuir and Freundlich isotherms with maximum Langmuir adsorbtion capactiy to be 373.7 mg/g. Kinetic modelling of the data showed best fit with the Pseudo second order model with rate constant value of 48.726 g mg−1 min−1. Regenerative studies were conducted conducted upto 6 cycles. Also the GC nanoparticles were tested for their compatibility in membrane form wherein, removal efficiency results were obtained for GCNP anchored in polyvinyl difluoride (PVDF) and polysulfone (PSF) membrane matrix for dye adsorption.

Western Blotting of Membrane-Bound Proteins in Yarrowia lipolytica.

With the discovery of Western blotting as first described by Towbin et al. in 1979, the transfer and visualization of electrophoretically separated proteins on membranes has become the de facto method for the qualitative and quantitative detection of proteins of interest. In this method, proteins are resolved by electrophoresis on a polyacrylamide gel, followed by a transfer of the separated proteins onto a nitrocellulose or polyvinyl difluoride (PVDF) membrane. Once immobilized on these membranes, the protein of interest can be detected and visualized by exploiting antigen-antibody interactions. However, not all proteins are amenable to easy detection by Western blotting. Integral membrane proteins are a class of proteins that are attached to a biological membrane through a series of transmembrane segments that span the width of the membrane. Due to the inherent hydrophobicity of these proteins and their tendency to aggregate, the characterization and detection of these proteins can be challenging. In this methods chapter, we present a protocol for the easy detection and quantification of these proteins in the industrially important oleaginous yeast Yarrowia lipolytica. The first protocol describes a Western blotting procedure to quantify soluble cytosolic proteins of interest in Yarrowia lipolytica from its total cell lysate. The second protocol describes modifications to the first that are done to enhance detection and quantification of membrane-bound proteins in Yarrowia lipolytica from its total cell lysate, without the need for isolating the membrane-bound proteins, for use in Western blotting. The immunoblotting strategies described here should serve as an efficient and simple guide to quantify both cytosolic and the intractable membrane-bound proteins in Yarrowia lipolytica.

Uncovering the effects of PEG porogen molecular weight and concentration on ultrafiltration membrane properties and protein purification performance

Developing ultrafiltration (UF) membranes for protein purification requires a critical understanding of the pore engineering and active-layer morphological control. In this study, we systematically explored the use of polyethylene glycol (PEG) with molecular weights (MW, 600–6000 g⋅mol−1) and concentration (3–7.5 wt%) as a pore modifier to prepare polyvinyl difluoride (PVDF) membranes via the non-solvent phase-inversion process. The membranes demonstrated a high degree of control of the structure-property-performance relationship for improving the water flux, bovine serum albumin (BSA) rejection and antifouling properties. We found that the morphology of PEG-modified membranes showed the membrane surface crystal spherulite remarkably decreased, whilst surface pore size increased with increasing porogen MW. Similarly, the increase in membrane pore size correlated very well with porogen MW and concentration exponentially and linearly respectively. Furthermore, the PEG-MW membrane series showed a flux and rejection trade-off, whereas the PEG-concentration membrane series can produce a high BSA rejection and improve the flux owing to the presence of a dense active layer. Overall, the optimized membrane with the best protein separation properties was produced by using 6 wt% PEG with 600 g⋅mol−1, which reached a competitive permeate flux of ~60 LMH⋅bar−1, with excellent flux recovery rate of >90%, and a high BSA rejection rate of 90% at the end of the three test cycle. The results in this study have elucidated and advanced the fundamental knowledge of the interrelationship between porogen and membrane property-performance.

Preparation of high-purity R-phycoerythrin and R-phycocyanin from Pyropia yezoensis in membrane chromatography

R-phycoerythrin and R-phycocyanin are the main light-harvesting pigment-protein complexes in Pyropia yezoensis. They have bright colors and a high degree of fluorescence, and are now widely used in biomedicine, food, and cosmetic industries. Therefore, membrane chromatography was used to isolate and purify phycobiliprotein from P. yezoensis. Algal cells were disrupted by repeated freeze-thaw cycles. Then ammonium sulfate was added into the crude phycobiliprotein extract, so that the saturation of ammonium sulfate in the solution reached 20%, 30%, and 40% in sequence. At 30% and 40% ammonium sulfate saturation, precipitates of R-phycoerythrin and R-phycocyanin mixture in different proportions were obtained. The precipitates were ultra-filtrated to remove the salt, and then, the retentate was taken for membrane chromatographic treatment. In the membrane chromatographic treatment, salt-sensitive PVDF (polyvinyl difluoride) membranes were used for the follow-up experiments. By adjusting the concentration of ammonium sulfate, the membrane system changed the binding strength of various proteins, and then separated different types of phycobiliproteins. The final products of R-phycoerythrin (Aλmax/A280 purity 4.25, yield 45%) and R-phycocyanin (two purity grades: purity 5.8, yield 14.70% and purity 4.18, yield 39.89%) were obtained and then characterized by spectrophotometric and fluorometric measurements and SDS-PAGE. However, the large-scale production of R-phycocyanin and R-phycoerythrin remains a bottleneck as the column chromatography is difficult to be applied for industrial production. This method avoids the problem of easy clogging of column chromatography and can be useful for mass-production of R-phycoerythrin and R-phycocyanin in the future based on the laboratory results.

Anisotropic performance of a superhydrophobic polyvinyl difluoride membrane with corrugated pattern in direct contact membrane distillation

A novel surface-corrugated superhydrophobic polyvinylidene fluoride (PVDF) membrane (C-PVDF) was prepared for direct contact membrane distillation (DCMD) using a micromolding phase separation (μPS) method. The membrane showed a static contact angle of 159.0 ± 4.0°. However, dynamic measurements of the sliding angles revealed a lower value of 9.1 ± 0.8° when a water droplet slides in parallel to the ridge, and a higher value of 14.6 ± 1.6° if perpendicular to the ridge. This anisotropic property was also reflected in the DCMD fluxes for both feed of deionized water and 4.0 wt% NaCl solution: in case the feed flows in parallel to the ridge, a higher flux is resulted than it flows perpendicular to the ridge. Anisotropic MD performance cannot be explained by the Dusty-Gas model because the average characteristics of the membrane in the model are intrinsically the same for both flow modes. Instead, anisotropic wetting and sliding in the parallel and perpendicular orientation revealed that the MD performance has both thermodynamic and hydrodynamic origins.

Análisis térmico y espectrometría de masas en conductores protónicos (PVDF/H3PO2) para implementación en celdas de combustible

Se prepararon membranas de Polivinil Difluoruro y Acido Hipofosforoso (PVDF/H3PO2) con diferentes concentraciones de ácido. Los resultados de calorimetría diferencial de barrido (DSC), presentan un escalón característico de la transición vítrea alrededor de 250 K. También se observan dos anomalías endotérmicas: una cercana a 357 K debido a la evaporación de agua, y otra cerca a los 422 K atribuida a la fusión de la fase cristalina del PVDF. Los análisis de Espectrometría de masas (MS) acoplado con Termogravimetría (TGA), revelan la posible presencia de moléculas de (C2H2O) y ácido fluorhídrico (HF), esto plantea la posibilidad de que el H3PO2 perdió un átomo de hidrógeno y se enlazó a la cadena polimérica del PVDF desplazando un átomo de flúor. Se evidencia la presencia de moléculas de agua a diferentes temperaturas, que sugiere la formación de agua superficial, interna y estructural en el sistema polímero-acido. Esta característica, hace que el sistema PVDF/H3PO2 sea propuesto como electrolito solido en celdas de combustible.

Biofouling on microfiltration membranes in MBRs: Role of membrane type and microbial community

Cross-flow filtration experiments were performed using three model biofoulants with increasing complexity: a monospecies assay using Pseudomonas aeruginosa or Escherichia coli, a duospecies assay using both microorganisms, and finally a multispecies assay using activated sludge spiked with P. aeruginosa. Three different microfiltration membranes were tested: polyvinyldifluoride, polyethylene and polysulfone. The biofouling was characterized in terms of cell density, community composition and relative permeability decrease caused by the different biofoulants. The data show that a good biofilm pioneer, like P. aeruginosa, was able to bind to any kind of membrane. However, when activated sludge spiked with P. aeruginosa was used, an enhanced biofouling behavior by the activated sludge members was found on the polyvinyldifluoride membrane. This paper highlights the importance of the kind of species, the microbial interactions and the community composition during the biofouling development.

Microbial Adhesion and Biofilm Formation on Microfiltration Membranes: A Detailed Characterization Using Model Organisms with Increasing Complexity

Since many years, membrane biofouling has been described as the Achilles heel of membrane fouling. In the present study, an ecological assay was performed using model systems with increasing complexity: a monospecies assay using Pseudomonas aeruginosa or Escherichia coli separately, a duospecies assay using both microorganisms, and a multispecies assay using activated sludge with or without spiked P. aeruginosa. The microbial adhesion and biofilm formation were evaluated in terms of bacterial cell densities, species richness, and bacterial community composition on polyvinyldifluoride, polyethylene, and polysulfone membranes. The data show that biofouling formation was strongly influenced by the kind of microorganism, the interactions between the organisms, and the changes in environmental conditions whereas the membrane effect was less important. The findings obtained in this study suggest that more knowledge in species composition and microbial interactions is needed in order to understand the complex biofouling process. This is the first report describing the microbial interactions with a membrane during the biofouling development.

Solubility and in vitro transdermal diffusion of riboflavin assisted by PAMAM dendrimers

PAMAM dendrimers of full generation (Gn) and half generation (Gn.5) were used as solubility enhancers of riboflavin (B2 vitamin) in methanol. They were found to weakly enhance solubility of B2 (7.2–10.3 times) according to the order: G2≫G2.5>G3≫G3.5>G4. The homogeneous mixtures of Gn (or Gn.5) with B2 of 1:1 molar ratio were obtained by removal of methanol to form oily host-guest complexes. The complexes were released from o/w emulsions and the transdermal permeation of B2 through polyvinyldifluoride (PVDF) and pig ear skin (PES) membranes was estimated. PAMAM dendrimers were demonstrated to promote permeation of B2 according to the order: G2>G3≫G2.5>G3.5>G4 (none). The permeation of fluorescein labeled dendrimers is faster than B2; the diffusion of G2 dendrimer through PES was the slowest of all studied Gn dendrimers, presumably due to absorption inside the skin. On the other hand the G2 was the best permeation enhancer for B2. The water soluble PAMAM dendrimers G2 and G3 can be successfully applied in cosmetic and dermatologic emulsions for this weakly water soluble vitamin.

A New Allergen from Ragweed (Ambrosia artemisiifolia) with Homology to Art v 1 from Mugwort

Art v 1, the major pollen allergen of the composite plant mugwort (Artemisia vulgaris) has been identified recently as a thionin-like protein with a bulky arabinogalactan-protein moiety. A close relative of mugwort, ragweed (Ambrosia artemisiifolia) is an important allergen source in North America, and, since 1990, ragweed has become a growing health concern in Europe as well. Weed pollen-sensitized patients demonstrated IgE reactivity to a ragweed pollen protein of apparently 29-31 kDa. This reaction could be inhibited by the mugwort allergen Art v 1. The purified ragweed pollen protein consisted of a 57-amino acid-long defensin-like domain with high homology to Art v 1 and a C-terminal proline-rich domain. This part contained hydroxyproline-linked arabinogalactan chains with one galactose and 5 to 20 and more alpha-arabinofuranosyl residues with some beta-arabinoses in terminal positions as revealed by high field NMR. The ragweed protein contained only small amounts of the single hydroxyproline-linked beta-arabinosyl residues, which form an important IgE binding determinant in Art v 1. cDNA clones for this protein were obtained from ragweed flowers. Immunological characterization revealed that the recombinant ragweed protein reacted with >30% of the weed pollen allergic patients. Therefore, this protein from ragweed pollen constitutes a novel important ragweed allergen and has been designated Amb a 4.

PVDF-TiO2coated microfiltration membranes: preparation and characterization

Organic fouling and biofouling pose a significant challenge to the membrane filtration process. Photocatalysis-membrane hybrid system is a novel idea for reducing these membranes fouling however, when <TEX>$TiO_2</TEX> photocatalyst nanoparticles are used in suspension, catalyst recovery is not only imposes an extra step on the process but also significantly contributes to increased membrane resistance and reduced permeate flux. In this study, <TEX>$TiO_2$</TEX> photocatalyst has been immobilized by coating on the microfiltration (MF) membrane surface to minimize organic and microbial fouling. Nano-sized <TEX>$TiO_2$</TEX> was first synthesized by a sol-gel method. The synthesized <TEX>$TiO_2$</TEX> was coated on a Poly Vinyl Difluoride (PVDF) membrane (MF) surface using spray coating and dip coating techniques to obtain hybrid functional composite membrane. The characteristics of the synthesized photocatalyst and a functional composite membrane were studied using numerous instruments in terms of physical, chemical and electrical properties. In comparison to the clean PVDF membrane, the <TEX>$TiO_2$</TEX> coated MF membrane was found more effective in removing methylene blue (20%) and E-coli (99%).

PAMAM dendrimers as solubilizers and hosts for 8-methoxypsoralene enabling transdermal diffusion of the guest

PAMAM dendrimers form host–guest complexes with 8-methoxypsoralene (8-MOP) – the photosensitizer for PUVA therapy. The stoichiometry of complexes was studied by 1H NMR spectroscopy in solution and by differential scanning calorimetry in neat mixtures containing 8-MOP and dendrimers of generations G2.5, G3, G3.5, and G4. The dendrimers showed solubilization effect for 8-MOP resulting in increase of 8-MOP concentration in methanol up to 15 molecules of 8-MOP per G2.5 and G3 and 30 molecules of 8-MOP per G3.5, and G4. Isolation of oily host–guest complexes containing 3 or 7 molecules of 8-MOP per G3 and G4, respectively corroborate well with DSC results; glass transition temperature of neat host–guest complexes increases with number of host molecules in comparison with G3 or G4, until the capacity of host is exceeded. The oily host–guest complexes of stoichiometry 3:1 and 7:1 of 8-MOP to G3 and G4, respectively are well soluble in water. The 3:1 host–guest complexes diffused slowly through polyvinyldifluoride and pig ear skin membranes, when released from o/w emulsion. The host–guest complex 8-MOP- G3 was proposed as convenient formulation for psoralene skin administration in PUVA therapy.

Modulation of the activity of cytosolic phospholipase A2α (cPLA2α) by cellular sphingolipids and inhibition of cPLA2α by sphingomyelin

We examined the effect of the cellular sphingolipid level on the release of arachidonic acid (AA) and activity of cytosolic phospholipase A2alpha (cPLA2alpha) using two Chinese hamster ovary (CHO)-K1-derived mutants deficient in sphingolipid synthesis: LY-B cells defective in the LCB1 subunit of serine palmitoyltransferase for de novo synthesis of sphingolipid species, and LY-A cells defective in the ceramide transfer protein CERT for SM synthesis. When LY-B and LY-A cells were cultured in Nutridoma medium and the sphingolipid level was reduced, the release of AA stimulated by the Ca(2+) ionophore A23187 increased 2-fold and 1.7-fold, respectively, compared with that from control cells. The enhancement in LY-B cells was decreased by adding sphingosine and treatment with the cPLA2alpha inhibitor. When CHO cells were treated with an acid sphingomyelinase inhibitor to increase the cellular SM level, the release of AA induced by A23187 or PAF was decreased. In vitro studies were then conducted to test whether SM interacts directly with cPLA2alpha. Phosphatidylcholine vesicles containing SM reduced cPLA2alpha activity. Furthermore, SM disturbed the binding of cPLA2alpha to glycerophospholipids. These results suggest that SM at the biomembrane plays important roles in regulating the cPLA2alpha-dependent release of AA by inhibiting the binding of cPLA2alpha to glycerophospholipids.

Photoactivable sphingosine as a tool to study membrane microenvironments in cultured cells

Human fibroblasts from normal subjects and Niemann-Pick A (NPA) disease patients were fed with two labeled metabolic precursors of sphingomyelin (SM), [(3)H]choline and photoactivable sphingosine, that entered into the biosynthetic pathway allowing the synthesis of radioactive phosphatidylcholine and SM, and of radioactive and photoactivable SM ([(3)H]SM-N(3)). Detergent resistant membrane (DRM) fractions prepared from normal and NPA fibroblasts resulted as highly enriched in [(3)H]SM-N(3). However, lipid and protein analysis showed strong differences between the two cell types. After cross-linking, different patterns of SM-protein complexes were found, mainly associated with the detergent soluble fraction of the gradient containing most cell proteins. After cell surface biotinylation, DRMs were immunoprecipitated using streptavidin. In conditions that maintain the integrity of domain, SM-protein complexes were detectable only in normal fibroblasts, whereas disrupting the membrane organization, these complexes were not recovered in the immunoprecipitate, suggesting that they involve proteins belonging to the inner membrane layer. These data suggest that differences in lipid and protein compositions of these cell lines determine specific lipid-protein interactions and different clustering within plasma membrane. In addition, our experiments show that photoactivable sphingolipids metabolically synthesized in cells can be used to study sphingolipid protein environments and sphingolipid-protein interactions.

Effects of cholesteryl ester transfer protein inhibition on apolipoprotein A-II-containing HDL subspecies and apolipoprotein A-II metabolism

This study was designed to establish the mechanism responsible for the increased apolipoprotein (apo) A-II levels caused by the cholesteryl ester transfer protein inhibitor torcetrapib. Nineteen subjects with low HDL cholesterol (<40 mg/dl), nine of whom were also treated with 20 mg of atorvastatin daily, received placebo for 4 weeks, followed by 120 mg of torcetrapib daily for the next 4 weeks. Six subjects in the nonatorvastatin cohort participated in a third phase, in which they received 120 mg of torcetrapib twice daily for 4 weeks. At the end of each phase, subjects underwent a primed-constant infusion of [5,5,5-(2)H(3)]L-leucine to determine the kinetics of HDL apoA-II. Relative to placebo, torcetrapib significantly increased apoA-II concentrations by reducing HDL apoA-II catabolism in the atorvastatin (-9.4%, P < 0.003) and nonatorvastatin once- (-9.9%, P = 0.02) and twice- (-13.2%, P = 0.02) daily cohorts. Torcetrapib significantly increased the amount of apoA-II in the alpha-2-migrating subpopulation of HDL when given as monotherapy (27%, P < 0.02; 57%, P < 0.003) or on a background of atorvastatin (28%, P < 0.01). In contrast, torcetrapib reduced concentrations of apoA-II in alpha-3-migrating HDL, with mean reductions of -14% (P = 0.23), -18% (P < 0.02), and -18% (P < 0.01) noted during the atorvastatin and nonatorvastatin 120 mg once- and twice-daily phases, respectively. Our findings indicate that CETP inhibition increases plasma concentrations of apoA-II by delaying HDL apoA-II catabolism and significantly alters the remodeling of apoA-II-containing HDL subpopulations.

Analysis of lectin binding to glycolipid complexes using combinatorial glycoarrays

Glycolipids are major components of the plasma membrane, interacting with themselves, other lipids, and proteins to form an array of heterogeneous domains with diverse biological properties. Considerable effort has been focused on identifying protein binding partners for glycolipids and the glycan specificity for these interactions, largely achieved through assessing interactions between proteins and homogenous, single species glycolipid preparations. This approach risks overlooking both the enhancing and attenuating roles of heterogeneous glycolipid complexes in modulating lectin binding. Here we report a simple method for assessing lectin-glycolipid interactions. An automatic thin-layer chromatography sampler is employed to create easily reproducible arrays of glycolipids and their heterodimeric complexes immobilized on a synthetic polyvinyl-difluoride membrane. This array can then be probed with much smaller quantities of reagents than would be required using existing techniques such as ELISA and thin-layer chromatography with immuno-overlay. Using this protocol, we have established that the binding of bacterial toxins, lectins, and antibodies can each be attenuated, enhanced, or unaffected in the presence of glycolipid complexes, as compared with individual, isolated glycolipids. These findings underpin the wide-ranging influence and importance of glycolipid-glycolipid cis interactions when the nature of protein-carbohydrate recognition events is being assessed.

Induction of Pyruvate Dehydrogenase Kinase-3 by Hypoxia-inducible Factor-1 Promotes Metabolic Switch and Drug Resistance

The switch of cellular metabolism from mitochondrial respiration to glycolysis is the hallmark of cancer cells and associated with tumor malignancy. However, the mechanism of this metabolic switch remains largely unknown. Herein, we reported that hypoxia-inducible factor-1 (HIF-1) induced pyruvate dehydrogenase kinase-3 (PDK3) expression leading to inhibition of mitochondrial respiration. Promoter activity assay, small interference RNA knockdown assay, and chromatin immunoprecipitation assay demonstrated that hypoxia-induced PDK3 gene activity was regulated by HIF-1 at the transcriptional level. Forced expression of PDK3 in cancer cells resulted in increased lactic acid accumulation and drugs resistance, whereas knocking down PDK3 inhibited hypoxia-induced cytoplasmic glycolysis and cell survival. These data demonstrated that increased PDK3 expression due to elevated HIF-1alpha in cancer cells may play critical roles in metabolic switch during cancer progression and chemoresistance in cancer therapy.