scholarly journals ON PHOSPHOTUNGSTIC ACID STAINING. I

1971 ◽  
Vol 19 (11) ◽  
pp. 641-647 ◽  
Author(s):  
G. QUINTARELLI ◽  
R. ZITO ◽  
J. A. CIFONELLI
Keyword(s):  
Heavy Metal ◽  
Sialic Acid ◽  
Chondroitin Sulfate ◽  
Phosphotungstic Acid ◽  
Model Systems ◽  
Organic Cations ◽  
Hydroxyl Groups ◽  
Sublingual Gland ◽  
Ph Dependent ◽  
Positively Charged

In this study histochemical experiments have been carried out in order to understand the "staining mechanism" of phosphotungstic acid (PTA). One of the main objectives of this project was to investigate the mode of interaction of the heavy metal and to define the type of functional groups in the substrates responsible for PTA binding. Therefore, tissues containing known macromolecules were selected and utilized as model systems. Epiphyseal cartilage, rat sublingual glands, human bone and purified collagen were used to study the interaction of the polyacid with chondroitin sulfate (cartilage), sialic acid (sublingual gland) and collagen (purified collagen and bone). The results obtained suggested that PTA does not interact with chondroitin sulfate, with sialic acid or with the hydroxyl groups of the sugar moieties of these macromolecules. Rather, the binding appeared to be selective for positively charged groups. Since PTA interaction to organic cations was pH-dependent, it is suggested that the heavy metal binds by means of coulombic forces and that no hydrogen bonds are involved.

scholarly journals ON PHOSPHOTUNGSTIC ACID STAINING. II

1971 ◽  
Vol 19 (11) ◽  
pp. 648-653 ◽  
Author(s):  
G. QUINTARELLI ◽  
J. A. CIFONELLI ◽  
R. ZITO
Keyword(s):  
Amino Acids ◽  
Phosphotungstic Acid ◽  
Hydroxyl Groups ◽  
Amino Groups ◽  
Ionic Interaction ◽  
Neutral Sugars ◽  
Acidic Conditions ◽  
Heparin Oligosaccharides ◽  
Positively Charged ◽  
Acid Glycosaminoglycans

Phosphotungstic acid (PTA) used at different concentrations in water was combined with various compounds (amino acids, proteins, acid glycosaminoglycans, glycoproteins and simple sugars). The results obtained indicated that PTA interacts with positively charged groups, that the sugar-hydroxyls do not take part in the interaction and that the type of binding involves electrostatic forces. To substantiate these findings further, heparin and heparin oligosaccharides were N-desulfated, combined with PTA and the precipitates were analyzed. It was found that the interaction had taken place only between the metal and the desulfated hexosamine amino groups and that when the N-desulfated product was acetylated no PTA binding occurred. When PTA was used at higher concentrations and in extremely acidic conditions, a precipitation of proteins, amino acids, acid glycosaminoglycans and neutral sugars ensued. This complex formation was interpreted as due to ionic interaction between the polyacid and the protonated hydroxyl groups.

scholarly journals Humic + Fulvic acid mitigated Cd adverse effects on plant growth, physiology and biochemical properties of garden cress

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ertan Yildirim ◽  
Melek Ekinci ◽  
Metin Turan ◽  
Güleray Ağar ◽  
Atilla Dursun ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Adverse Effects ◽  
Plant Growth ◽  
Fulvic Acid ◽  
Pollution Level ◽  
Hydroxyl Groups ◽  
Cd Stress ◽  
Garden Cress ◽  
Cd Uptake ◽  
Fresh Leaf

AbstractCadmium (Cd) is a toxic and very mobile heavy metal that can be adsorbed and uptaken by plants in large quantities without any visible sign. Therefore, stabilization of Cd before uptake is crucial to the conservation of biodiversity and food safety. Owing to the high number of carboxyl and phenolic hydroxyl groups in their structure, humic substances form strong bonds with heavy metals which makes them perfect stabilizing agents. The aim of this study was to determine the effects of humic and fulvic acid (HA + FA) levels (0, 3500, 5250, and 7000 mg/L) on alleviation of Cadmium (Cd) toxicity in garden cress (Lepidium sativum) contaminated with Cd (CdSO4.8H2O) (0, 100, and 200 Cd mg/kg) under greenhouse conditions. Our results showed that, Cd stress had a negative effect on the growth of garden cress, decreased leaf fresh, leaf dry, root fresh and root dry weights, leaf relative water content (LRWC), and mineral content except for Cd, and increased the membrane permeability (MP) and enzyme (CAT, SOD and POD) activity. However, the HA + FA applications decreased the adverse effects of the Cd pollution. At 200 mg/kg Cd pollution, HA + FA application at a concentration of 7000 mg/L increased the leaf fresh, leaf dry, root fresh, root dry weights, stem diameter, leaf area, chlorophyll reading value (CRV), MP, and LRWC values by 262%, 137%, 550%,133%, 92%, 104%, 34%, 537%, and 32% respectively, compared to the control. Although the highest H2O2, MDA, proline and sucrose values were obtained at 200 mg/L Cd pollution, HA + FA application at a concentration of 7000 mg/L successfully alleviated the deleterious effects of Cd stress by decreasing H2O2, MDA, proline, and sucrose values by 66%, 68%, 70%, and 56%, respectively at 200 mg/kg Cd pollution level. HA + FA application at a concentration of 7000 mg/L successfully mitigated the negative impacts of Cd pollution by enhanced N, P, K, Ca, Mg, Fe, Mn, Cu, Mn, Zn, and B by 75%, 23%, 84%, 87%, 40%, 85%, 143%, 1%, 65%, and 115%, respectively. In addition, HA + FA application at a concentration of 7000 mg/L successfully reduced Cd uptake by 95% and Cl uptake by 80%. Considering the plant growth parameters, the best results were determined when HA + FA concentration was 7000 mg/L. We have shown that, it is critical to apply a humic substance with high percentage of FA, which was 10% in this study, to mitigate the adverse effects of heavy metal stress on plant growth. In conclusion, the application of HA + FA may be suggested as an effective solution for reducing the Cd uptake of the plants by stabilizing Cd in soil and preventing translocation of Cd from the roots of plant to its shoot and leaves.

scholarly journals Anchoring Water Soluble Phosphotungstic Acid by Hybrid Fillers to Construct Three-Dimensional Proton Transport Networks

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 536
Author(s):  
Shaojian He ◽  
Zhongrui Lu ◽  
Wenxu Dai ◽  
Kangning Yang ◽  
Yang Xue ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Composite Membrane ◽  
Proton Transport ◽  
Phosphotungstic Acid ◽  
Three Dimensional ◽  
Water Soluble ◽  
Hydroxyl Groups ◽  
Transport Networks ◽  
Hybrid Fillers ◽  
Speek Membrane

Phosphotungstic acid (HPW)-filled composite proton exchange membranes possess high proton conductivity under low relative humidity (RH). However, the leaching of HPW limits their wide application. Herein, we propose a novel approach for anchoring water soluble phosphotungstic acid (HPW) by polydopamine (PDA) coated graphene oxide and halloysite nanotubes (DGO and DHNTs) in order to construct hybrid three-dimensional proton transport networks in a sulfonated poly(ether ether ketone) (SPEEK) membrane. The introduction of PDA on the surfaces of the hybrid fillers could provide hydroxyl groups and secondary amine groups to anchor HPW, resulting in the uniform dispersion of HPW in the SPEEK matrix. The SPEEK/DGO/DHNTs/HPW (90/5/5/60) composite membrane exhibited higher water uptake and much better conductivity than the SPEEK membrane at low relative humidity. The best conductivity reached wass 0.062 S cm−1 for the composite membrane, which is quite stable during the water immersion test.

Polyoxometalates as sialidase mimics: selective and non-destructive removal of sialic acid from a glycoprotein promoted by phosphotungstic acid

2017 ◽  
Vol 53 (76) ◽  
pp. 10600-10603 ◽  
Author(s):  
Laura Sofia Van Rompuy ◽  
Tatjana N. Parac-Vogt
Keyword(s):  
Sialic Acid ◽  
Phosphotungstic Acid ◽  
Glycosidic Bond ◽  
Selective Hydrolysis ◽  
Fetuin A ◽  
Keggin Type ◽  
Terminal Sialic Acid ◽  
Non Destructive ◽  
Hydrolysis Of

The selective hydrolysis of the glycosidic bond between the terminal sialic acid and the penultimate sugar has been achieved in the alpha-2-HS-glycoprotein (Fetuin-A) in the presence of H3PW12O40, a Keggin type polyoxometalate.

scholarly journals Constructing Positively Charged Thin-Film Nanocomposite Nanofiltration Membranes with Enhanced Performance

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2526
Author(s):  
Wenyao Shao ◽  
Chenran Liu ◽  
Tong Yu ◽  
Ying Xiong ◽  
Zhuan Hong ◽  
...  
Keyword(s):  
Thin Film ◽  
Heavy Metal ◽  
Water Flux ◽  
Water Contact ◽  
Salt Rejection ◽  
Thin Film Composite ◽  
Charged Surfaces ◽  
Active Layers ◽  
Positively Charged ◽  
Thin Film Nanocomposite

Using polyethylenimine (PEI) as the aqueous reactive monomers, a positively charged thin-film nanocomposite (TFN) nanofiltration (NF) membrane with enhanced performance was developed by successfully incorporating graphene oxide (GO) into the active layer. The effects of GO concentrations on the surface roughness, water contact angle, water flux, salt rejection, heavy metal removals, antifouling property, and chlorine resistance of the TFN membranes were evaluated in depth. The addition of 20 ppm GO facilitated the formation of thin, smooth, and hydrophilic nanocomposite active layers. Thus, the TFN-PEI-GO-20 membrane showed the optimal water flux of 70.3 L·m−2·h−1 without a loss of salt rejection, which was 36.8% higher than the thin-film composite (TFC) blank membrane. More importantly, owing to the positively charged surfaces, both the TFC-PEI-blank and TFN-PEI-GO membranes exhibited excellent rejections toward various heavy metal ions including Zn2+, Cd2+, Cu2+, Ni2+, and Pb2+. Additionally, compared with the negatively charged polypiperazine amide NF membrane, both the TFC-PEI-blank and TFN-PEI-GO-20 membranes demonstrated superior antifouling performance toward the cationic surfactants and basic protein due to their hydrophilic, smooth, and positively charged surface. Moreover, the TFN-PEI-GO membranes presented the improved chlorine resistances with the increasing GO concentration.

scholarly journals pH-dependent pyridoxine transport by SLC19A2 and SLC19A3: Implications for absorption in acidic microclimates

2020 ◽  
Vol 295 (50) ◽  
pp. 16998-17008
Author(s):  
Takahiro Yamashiro ◽  
Tomoya Yasujima ◽  
Hamid M. Said ◽  
Hiroaki Yuasa
Keyword(s):  
Vitamin B1 ◽  
Hek293 Cells ◽  
Intestinal Epithelial ◽  
Madin Darby Canine Kidney ◽  
Mdckii Cells ◽  
Charge Selectivity ◽  
Acidic Conditions ◽  
Ph Dependent ◽  
Darby Canine Kidney ◽  
Positively Charged

SLC19A2 and SLC19A3, also known as thiamine transporters (THTR) 1 and 2, respectively, transport the positively charged thiamine (vitamin B1) into cells to enable its efficient utilization. SLC19A2 and SLC19A3 are also known to transport structurally unrelated cationic drugs, such as metformin, but whether this charge selectivity extends to other molecules, such as pyridoxine (vitamin B6), is unknown. We tested this possibility using Madin-Darby canine kidney II (MDCKII) cells and human embryonic kidney 293 (HEK293) cells for transfection experiments, and also using Caco-2 cells as human intestinal epithelial model cells. The stable expression of SLC19A2 and SLC19A3 in MDCKII cells (as well as their transient expression in HEK293 cells) led to a significant induction in pyridoxine uptake at pH 5.5 compared with control cells. The induced uptake was pH-dependent, favoring acidic conditions over neutral to basic conditions, and protonophore-sensitive. It was saturable as a function of pyridoxine concentration, with an apparent Km of 37.8 and 18.5 μm, for SLC19A2 and SLC19A3, respectively, and inhibited by the pyridoxine analogs pyridoxal and pyridoxamine as well as thiamine. We also found that silencing the endogenous SLC19A3, but not SLC19A2, of Caco-2 cells with gene-specific siRNAs lead to a significant reduction in carrier-mediated pyridoxine uptake. These results show that SLC19A2 and SLC19A3 are capable of recognizing/transporting pyridoxine, favoring acidic conditions for operation, and suggest a possible role for these transporters in pyridoxine transport mainly in tissues with an acidic environment like the small intestine, which has an acidic surface microclimate.

scholarly journals The role of N-acetylneuraminic (sialic) acid in the pH dependence of influenza virion fusion with planar phospholipid membranes.

1991 ◽  
Vol 97 (6) ◽  
pp. 1121-1140 ◽  
Author(s):  
W D Niles ◽  
F S Cohen
Keyword(s):  
Influenza Virus ◽  
Sialic Acid ◽  
Ph Dependence ◽  
Phospholipid Composition ◽  
Fusion Rate ◽  
Influenza Virion ◽  
Order Of Magnitude ◽  
Ph Dependent ◽  
Planar Membrane ◽  
Planar Membranes

It is known that fusion of influenza virus to host cell membranes is strongly promoted by acidic pH. We have determined conditions required to obtain pH-dependent fusion of influenza virus to planar bilayer membranes. The rate of viral fusion was determined from the flash rate of R18-labeled virions delivered to the surface of the planar membrane by pressure-ejection from a pipette. For a bilayer formed only of phospholipids and cholesterol, the fusion rate was independent of pH and unaffected by the phospholipid composition. When the gangliosides GD1a + GT1b were included in the planar membrane, however, the fusion rate varied steeply with pH. The rate at pH 7.4 in the presence of the gangliosides was about an order of magnitude less than in their absence. At pH less than approximately 5.5, the rate was about an order of magnitude greater in the presence of gangliosides than in their absence. The fusion rate with planar membranes containing globoside, a ceramide-backboned glycolipid, was also independent of pH, indicating that the pH dependence required sialic acid on the carbohydrate moiety of the glycolipid. The gangliosides GM1a and GM3, both of which possess sialic acid, produced the same pH-dependent fusion rate as seen with GD1a + GT1b, indicating that the presence, but not the location, of terminal sialic acids is critical. Incubating virus with soluble sialyllactose blocked fusion to both ganglioside-free and ganglioside-containing planar membranes. These results show that the pH dependence of influenza virion fusion arises from the interaction of the sialic acid receptor with the influenza hemagglutinin. A model for sialic acid-hemagglutinin interactions accounting for pH-dependent fusion is presented.

Synthesis of a novel biopolymer by means of Thiol-Ene Photopolymerization using diallyl sucrose and dithiotreitol as comonomers

2010 ◽  
Vol 1277 ◽  
Author(s):  
Ricardo Acosta Ortiz ◽  
Antelmo Yasser Ruiz Martinez ◽  
Aida E García Valdez ◽  
María Lydia Berlanga Duarte
Keyword(s):  
Allyl Bromide ◽  
Uv Light ◽  
Bulk Polymerization ◽  
Hydroxyl Groups ◽  
Flexible Material ◽  
Water As Solvent ◽  
Acidic Conditions ◽  
Ph Dependent ◽  
Kinetics Of ◽  
Water Absorbance

A novel biopolymer derived from diallyl sucrose (A2S) and dithiotreitol (DTT) was prepared by means of Thiol-Ene Photopolymerization. A2S was prepared by alkylating the sucrose with allyl bromide, using water as solvent. After purification by column chromatography, a fraction (F2A2S) with 94% diallyl sucrose (A2S), 4 % of triallyl sucrose (A3S) and 2 % of monoallyl sucrose (A1S) was obtained. This fraction was subsequently photopolymerized with Dithiothreitol (DTT) which is a difunctional thiol. Kinetics of photopolymerization were determined by means of Real-Time Infrared spectroscopy. It was found that the photocurable formulation with DTT and F2A2S, polymerized rapidly in the presence and absence of a photoinitiator, at low intensities of UV light. After bulk polymerization, a flexible material with high elastic modulus and a Tg of 30 °C was obtained. Besides, the polymer displayed moderate water absorbance properties as a result of the presence of multiple hydroxyl groups. This property was pH dependent with maximum absorbance at pH=14. The polymer degraded rapidly under acidic conditions

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