Higher pHs Research Articles

Acidic polymers reversibly deactivate phages due to pH changes.

Bacteriophages are promising as therapeutics and biotechnological tools, but they also present a problem for routine and commercial bacterial cultures, where contamination must be avoided. Poly(carboxylic acids) have been reported to inhibit phages' ability to infect their bacterial hosts and hence offer an exciting route to discover additives to prevent infection. Their mechanism and limitations have not been explored. Here, we report the role of pH in inactivating phages to determine if the polymers are unique or simply acidic. It is shown that lower pH (=3) triggered by either acidic polymers or similar changes in pH using HCl lead to inhibition. There is no inhibitory activity at higher pHs (in growth media). This was shown across a panel of phages and different molecular weights of commercial and controlled-radical polymerization-derived poly(acrylic acid)s. It is shown that poly(acrylic acid) leads to reversible deactivation of phage, but when the pH is adjusted using HCl alone the phage is irreversibly deactivated. Further experiments using metal binders ruled out ion depletion as the mode of action. These results show that polymeric phage inhibitors may work by unique mechanisms of action and that pH alone cannot explain the observed effects whilst also placing constraints on the practical utility of poly(acrylic acid).

Adsorption of Fluoride Ions Using Si–Al–Mg Layered Double Hydroxides

ABSTRACT Removal of fluoride ions from water environments has become a research topic because high concentrations of fluoride ions in drinking water are harmful to the human body. The adsorption of fluoride ions by a Si – Al – Mg layered double hydroxide (LDH) was investigated in this study. The prepared adsorbent had a hydrotalcite-like LDH structure, which was decomposed by calcination and reconstructed upon contacting water. The adsorption process followed pseudo-second-order kinetics. Granulation of the adsorbent for application to chromatographic operation decreased the adsorption rate constant. Adsorption of fluoride ions was high at 7 < pHeq <10 and decreased at higher pHs. The adsorption mechanism involved ion exchange between the fluoride ions in aqueous solution and chloride ions in the adsorbent as well as physisorption via van der Waals forces. The adsorbent was selective towards fluoride ions over nitrate and sulfate ions, although the adsorption of fluoride ions was suppressed in the presence of chloride, carbonate, and phosphate ions. Chromatographic operation using the granulated adsorbent with an alumina-based binder was characterized by slow kinetics, necessitating a low flow rate for the feed solution. The prepared adsorbent was also used to selectively adsorb fluoride ions from simulated wastewater produced by the semiconductor manufacturing process.

Self-Assembly of Three-Dimensional Hyperbranched Magnetic Composites and Application in High-Turbidity Water Treatment.

In order to improve dispersibility, polymerization characteristics, chemical stability, and magnetic flocculation performance, magnetic Fe3O4 is often assembled with multifarious polymers to realize a functionalization process. Herein, a typical three-dimensional configuration of hyperbranched amino acid polymer (HAAP) was employed to assemble it with Fe3O4, in which we obtained three-dimensional hyperbranched magnetic amino acid composites (Fe3O4@HAAP). The characterization of the Fe3O4@HAAP composites was analyzed, for instance, their size, morphology, structure, configuration, chemical composition, charged characteristics, and magnetic properties. The magnetic flocculation of kaolin suspensions was conducted under different Fe3O4@HAAP dosages, pHs, and kaolin concentrations. The embedded assembly of HAAP with Fe3O4 was constructed by the N-O bond according to an X-ray photoelectron energy spectrum (XPS) analysis. The characteristic peaks of -OH (3420 cm-1), C=O (1728 cm-1), Fe-O (563 cm-1), and N-H (1622 cm-1) were observed in the Fourier transform infrared spectrometer (FTIR) spectra of Fe3O4@HAAP successfully. In a field emission scanning electron microscope (FE-SEM) observation, Fe3O4@HAAP exhibited a lotus-leaf-like morphological structure. A vibrating sample magnetometer (VSM) showed that Fe3O4@HAAP had a relatively low magnetization (Ms) and magnetic induction (Mr); nevertheless, the ferromagnetic Fe3O4@HAAP could also quickly respond to an external magnetic field. The isoelectric point of Fe3O4@HAAP was at 8.5. Fe3O4@HAAP could not only achieve a 98.5% removal efficiency of kaolin suspensions, but could also overcome the obstacles induced by high-concentration suspensions (4500 NTU), high pHs, and low fields. The results showed that the magnetic flocculation of kaolin with Fe3O4@HAAP was a rapid process with a 91.96% removal efficiency at 0.25 h. In an interaction energy analysis, both the UDLVO and UEDLVO showed electrostatic repulsion between the kaolin particles in the condition of a flocculation distance of <30 nm, and this changed to electrostatic attraction when the separation distance was >30 nm. As Fe3O4@ HAAP was employed, kaolin particles could cross the energy barrier more easily; thus, the fine flocs and particles were destabilized and aggregated further. Rapid magnetic separation was realized under the action of an external magnetic field.

Successful application of photocatalytic recycled TiO2-GO membranes for the removal of trace organic compounds from tertiary effluent

Photocatalytic membranes are a promising technology for water and wastewater treatment. Towards circular economy, extending the lifetime of reverse osmosis (RO) membranes for as long as possible is extremely important, due to the great amount of RO modules discarded every year around the world. Therefore, in the present study, photocatalytic membranes made of recycled post-lifespan RO membrane (polyamide thin-film composite), TiO2 nanoparticles and graphene oxide are used in the treatment tertiary-treated domestic wastewater to remove trace organic compounds (TrOCs). The inclusion of dopamine throughout the surface modification process enhanced the stability of the membranes to be used as long as 10 months of operation. We investigated TrOCs removal by the membrane itself and in combination with UV-C and visible light by LED. The best results were obtained with integrated membrane UV-C system at pH 9, with considerable reductions of diclofenac (92%) and antipyrine (87%). Changes in effluent pH demonstrated an improvement in the attenuation of TrOCs concentration at higher pHs. By modifying membranes with nanocomposites, an increase in membrane hydrophilicity (4° contact angle reduction) was demonstrated. The effect of the lamp position on the light fluence that reaches the membrane was assessed, and greater values were found in the middle of the membrane, providing parameters for process optimization (0.29 ± 0.10 mW cm−2 at the center of the membrane and 0.07 ± 0.03 mW cm−2 at the right and left extremities). Photocatalytic recycled TiO2-GO membranes have shown great performance to remove TrOCs and extend membrane lifespan, as sustainable technology to treat wastewater.

Effect of extraction method on the calcium binding capacity of faba bean globulin fractions at various pH

Faba bean ingredients are rich in proteins and good sources of calcium (Ca), although containing phytic acid (PA) molecules. PA, a polyphosphate compound, can affect the bioavailability of minerals/proteins through complex formation. This study evaluates the impact of two extraction processes, Alkaline Extraction-IsoElectric Precipitation (AE-IEP) and Sequential Extraction (SE), on the ability of faba bean globulin systems to bind added calcium ions. Increasing concentrations of CaCl2 were introduced into 2.5% (w/v) protein dispersions at pHs 4.5, 5.5, 6.5, and 7.5, and free Ca monitored. Near the isoelectric point of globulin (pH ∼ 4–5), Ca binding capacity was found to be low. At higher pHs, significant Ca chelation occurred, initially attributed to free PA binding sites, resulting in the formation of insoluble complexes and subsequent protein precipitation. The AE-IEP globulin fraction exhibited a higher Ca binding capacity than the SE globulin, attributed to its higher PA and lower initial Ca concentrations.

3D printed and smart alginate wound dressings with pH-responsive drug and nanoparticle release

The pH of a wound site can undergo a significant change from its normal range of 5.4–5.6 to a more alkaline environment of 7.2–8.9 after being infected by microorganisms. Therefore, the development of a smart material that can respond to this shift in pH and release antimicrobial agents for effective treatment of wound infections holds great promise for the future of wound care. In the present work, we produced 3D printed alginate wound dressings doped with calcium phosphate nanoparticles (CaP NPs), referred to as alginate-CaP nanocomposites hereafter. The CaP NPs enabled pH-responsive switching of the degradation and drug release of 3D-printed alginate-based wound dressings. Three sizes of rod-shaped CaP NPs were synthesised, including small NPs (62 × 18 nm), medium NPs (197 × 49 nm), and large NPs (496 × 143 nm). The addition of CaP NPs significantly increased both the tensile strength and elongation at the break of the alginate dressings. Additionally, the degradation rate of the alginate-CaP nanocomposite dressings increased with pH, potentiating pH responsive drug delivery from the dressing. Alginate nanocomposites with 1 mg/mL of medium-sized CaP NPs were found to elicit the strongest pH responsiveness. The release rates of rhodamine B, the antibiotic peptide bacitracin, and antimicrobial selenium nanoparticles were assessed, and showed faster release at higher pHs. These results illustrate that CaP NPs can be easily used as a pH-responsive switch to effectively control the degradation and drug release of alginate based wound dressings, enabling increased antimicrobial release at the pH of infected wounds.

THE DEPENDENCE OF ACID-BASE EQUILBRIA AND ACIDITY CONSTANTS OF CONGO RED IN BUFFER SOLUTIONS ON THE IONIC STRENGTH

In this study, the spectrophotometric studies of aqueous ethanol solution of Congo red in various buffers solutions at room temperature 25oC and at different ionic strength of 0.05, 0.1, 0.3, and 0.5 KCl mol L-1 were investigated. The acidity constants of Congo red were estimated by three different methods. The two protonation stages were observed in pH range 2 - 4 and 4 - 6 as result as protonation of amino group and azo groups. The dependence of absorption spectra of Congo red on the ionic strength of solutions which exhibited blue shift with increases ionic strength in addition the shape and intensity were varied. Therefore, the acid-base equilibria shifted toward the higher pHs with the rise in ionic strength. Also, the acidity constants were affected by the ionic strength which the acidity constants decrease with increasing ionic strength of solution because the electrostatic interaction force increased.

Relation of bubble size, grade and recovery in the copper flotation systems

In recent years, studies have shown that bubble structure, which is affected by reagent types, dosages, and particle size, is closely related to flotation performance. In contrast to two-phase systems, there is very limited information regarding bubble size in three-phase systems. To this aim, we investigated the relationship between bubble size and flotation performance with two different copper ores. Firstly, the surface tension and bubble size measurements were carried out in two-phase systems with Methyl isobutyl carbinol, and Polypropylene glycol methyl ether. Then the bubble size measurements were performed in three-phase systems at laboratory and industrial scales. The results showed that surface tension decreased with higher frother amounts and higher pHs. Although remarkable decreases in bubble size were observed with increasing frother amount, a direct relationship between surface tension and bubble size was not observed. However, pH affected the behavior of the frother, resulting in smaller bubble sizes at pH 12 compared to pH 7. Similarly, the three-phase laboratory tests showed that higher amount of frother caused a reduction in the bubble size and the copper grade. Increasing the amount of collector also caused the bubble size and copper grade to decrease, but the frothers were more effective in bubble size reduction. Compared to the two-phase, in the three-phase study bubble size was notably bigger due to the presence of a collector and solid. In the plant scale, smaller bubble size and higher grade were obtained compared with the laboratory scale due to presence of cleaning circuit measurements. The froth phase properties were also affected by the ore types due to properties such as size and hydrophobicity of the various mineral species present.

Effect of temperature on the dissolution of the lead (II) carbonate hydrocerussite for varying pH and dissolved inorganic carbon conditions

The effect of temperature on the solubility of lead-bearing solid phases in water distribution systems for different water chemistry conditions remains unclear although lead concentrations are known to vary seasonally. The study objective is to explore the effect of temperature on the solubility of the lead(II) carbonate hydrocerussite under varying pH and DIC conditions. This is achieved through batch dissolution experiments conducted at multiple pHs (6–10) and DIC concentrations (20–200 mg CL−1) at temperatures ranging from 5 to 40 °C. A thermodynamic model was also applied to evaluate the model’s ability to predict temperature effects on lead(II) carbonate solubility including solid phase transformations. In general, increasing temperature increased total dissolved lead at high pHs and the effect of temperature was greater for high DIC conditions, particularly for pH > 8. Temperature also influenced the pH at which the dominant lead(II) solid phase switched from hydrocerussite to cerussite (occurred between pH 7.25 to 10). Finally, the model was able to capture the overall trends observed despite thermodynamic data limitations. While this study focuses on a simple lead solid-aqueous system, findings provide important insights regarding the way in which temperature and water chemistry interact to affect lead concentrations.

High-pressure processing (HPP) of phycocyanin extract solutions: Enhancing stability through molecular interactions

C-Phycocyanin (PC) has been proposed as a replacement for synthetic colors in foods. However, C-PC stability is adversely affected during food processing due to exposure to high temperature, pressure, oxygen concentration or extreme pHs. This study assessed the degradation mechanisms of C-PC under a nonthermal pasteurization technology, i.e., High-Pressure Processing (HPP), and identified potential processing protocols to arrest C-PC instability at low pH. Aqueous C-PC solutions (pH:4–6) were subject to HPP (500–600 MPa) for 1–5 min. C-PC stability was monitored based on changes in the photophysical properties of its fluorophores (phycocyanobilin chromophore and aromatic amino acid residues) and particle size. pH significantly affected C-PC's stability towards HPP (<stability at < pH). Sharper hypsochromic (blue) shifts, lower intensity, and higher anisotropy were observed as pressure and treatment time increased, which suggested conformational changes in C-PC's polypeptides, followed by aggregation. pH adjustment after HPP treatments resulted in a significant reduction in color loss and aggregation, possibly due to partial stabilization of the polypeptide subunits' conformation.

Effect of an NHE3 inhibitor in combination with an NPT2b inhibitor on gastrointestinal phosphate absorption in Rodent models.

Many of the pathological consequences of chronic kidney disease can be attributed to an elevation in serum phosphate levels. Current therapies focused on decreasing intestinal phosphate absorption to treat hyperphosphatemia are inadequate. The most effective therapeutic strategy may be to target multiple absorptive pathways. In this study, the ability of a novel inhibitor of the intestinal sodium hydrogen exchanger 3 (NHE3), LY3304000, which inhibits paracellular, diffusional uptake of phosphate, to work in combination with an inhibitor of the active transporter, sodium dependent phosphate cotransporter 2b (NPT2b), LY3358966, was explored. LY3304000 modestly inhibited the acute uptake of phosphate into plasma of rats, while surprisingly, it doubled the rate of phosphate uptake in mice, an animal model dominated by NPT2b mediated acute phosphate uptake. In rats, LY3004000 and LY3358966 work in concert to inhibit acute phosphate uptake. On top of LY3358966, LY3304000 further decreased the acute uptake of phosphate into plasma. Studies measuring the recovery of radiolabeled phosphate in the intestine demonstrated LY3304000 and LY3358966 synergistically inhibited the absorption of phosphate in rats. We hypothesize the synergism is because the NHE3 inhibitor, LY3304000, has two opposing effects on intestinal phosphate absorption in rats, first it decreases diffusion mediated paracellular phosphate absorption, while second, it simultaneously increases phosphate absorption through the NPT2b pathway. NHE3 inhibition decreases proton export from enterocytes and raises the cell surface pH. In vitro, NPT2b mediated phosphate transport is increased at higher pHs. The increased NPT2b mediated transport induced by NHE3 inhibition is masked in rats which have relatively low levels of NPT2b mediated phosphate transport, by the more robust inhibition of diffusion mediated phosphate absorption. Thus, the inhibition of NPT2b mediated phosphate transport in rats in the presence of NHE3 inhibition has an effect that exceeds its effect in the absence of NHE3 inhibition, leading to the observed synergism on phosphate absorption between NPT2b and NHE3 inhibition.

Silicon ameliorates iron deficiency in sour orange seedlings grown under different pHs

Iron (Fe) is an essential element for all plants while silicon (Si) is non-essential but has some beneficial roles for reducing iron deficiency stresses in plants. Soil pH affect iron solubility and availability and thus plant Fe nutrition however, little is known on how high or low pHs affect Si efficiency in alleviating Fe deficiency stress. In this research the interactive effects of root zone pH and Si nutrition on the alleviation of Fe deficiency in sour orange (Citrus aurantium) seedlings were investigated. Citrus seedlings were grown for three months in Fe-sufficient (control), Fe-deficient and Fe-zero media supplied with or without Si (0.7 mM), adjusted to pHs 6.5 and 8.0 and analyzed subsequently. Fe deficiency resulted in declined tissue Fe, proteins, chlorophylls, carotenoids and the activities of catalase, soluble and cell wall peroxidase associated with increased hydrogen peroxide and lipid peroxidation. Higher pH compromised plant growth associated with depleted tissue Fe in both Fe-deficient and Fe-sufficient plants and imposed chlorophylls and soluble proteins reduction. Si nutrition increased plant growth in Fe-deficient and Fe-sufficient plants under both pH treatments. It also improved tissue Fe content, soluble proteins, chlorophylls, carotenoids and the activities of antioxidant enzymes while decreased tissue hydrogen peroxide and lipid peroxidation levels. These results suggest that Si nutrition can reduce the harmful effects of soil Fe deficiency and higher pHs in sour orange plants via increase of Fe content and reduction of oxidative stress; however, in the absence of Fe, the applied Si cannot mitigate plant nutrient stress symptoms.

Enhancing electrochemical production of peroxophosphates using new boron doped diamond coatings

Two boron doped ultrananocristallyne diamond (UNC) electrodes were manufactured and compared with a standard microcrystalline commercial electrode, to clarify how their differences may affect to the production of oxidants in the electrolysis of solutions containing phosphoric acid or phosphate salts. Effects of the current density and electrolyte pH were evaluated. Significant differences were found in the production of oxidants, being the production of oxidants favored, at high current densities and alkaline pHs. The effect of the pH was explained in terms of the higher stability of the peroxodiphosphate anion in comparison with the monoperoxyphosphate acid produced at low pHs. As well, because of the improved electrostatic attraction of the anion with the anode. Despite not exhibiting the largest electrochemical surface area, the flat UNC electrode shows the best performance for this process, except for the operation at low current densities and alkaline pHs in which the porous UNC outperforms it. Better efficiencies are obtained operating at mild current densities which was explained in terms of the great significance of direct processes in the production of oxidants by electrolysis of phosphoric acid or phosphate solutions

Polyamidoamine Dendrimers Functionalized with ZnO-Chitosan Nanoparticles as an Efficient Surface for L-asparaginase Immobilization.

In this study, the third-generation polyamidoamine dendrimer was functionalized with a 5-amino-1H-tetrazole heterocycle to load the synthesis enzyme and its surface groups. Then, chitosan was attached to the dendrimer by a suitable linker, and finally, zinc oxide nanoparticles were inserted into dendrimer cavities to increase loading. FTIR, FESEM, TEM, and DLS analysis showed that this new dendrimer has specific branches, and ZnO nanoparticles were spread between the branches and connected with the branches and chitosan biopolymer. Also proved the presence of stabilized L-asparaginase enzyme and ZnO nanoparticles in the designed system. Furthermore, the extent of L-asparaginase enzyme loading and release was investigated in the laboratory with a dialysis bag. Examining the toxicity of the new third-generation polyamidoamine (PAMAM) dendrimeric nanocarrier based on chitosan-zinc oxide biopolymer (PAMAM-G3@ZnO-Cs nanocarrier) on the Jurkat cell line (human acute lymphoblastic leukemia) at pH 7.4 showed that this nanocarrier effectively encapsulates the drug L-asparaginase and slowly releases it and also preventing the growth of cancer cells. The activity of the loaded enzyme in the nanocarrier and the free enzyme was calculated. During the investigations, it was found that the enzyme attached to the nanocarrier is more stable than the free enzyme at optimal pH and temperature and at high temperatures, acidic and basic pHs. Vmax and Km values were lower for loaded enzymes. The synthesized PAMAM-G3@ZnO-Cs nanocarrier can be a promising candidate in the pharmaceutical industry and medical science for cancer treatment due to its biocompatibility, non-toxicity, stability, and slow release of L-asparaginase.

The growth of mercury-resistant bacterial consortium at different levels of pH, temperature, and C:N ratio

The study was conducted to investigate the growth of mercury-resistant bacterial consortium under the influence of different pHs, temperatures, and C:N ratios, as a part of mercury bioremediation research. The consortium consisted of five bacterial isolates selected due to their resistance to HgCl2 up to 100 ppm and was proven to effectively reduce mercury from the culture media. Consortium suspension was inoculated into two sets of media: 1) Tryptic soy broth (TSB) with pHs of 4.8, 6.1, 8.5, and 9.7; 2) Mineral salt with the addition of glucose and peptone to create C:N ratios of 20:1, 30:1, and 40:1 while the pH was set to 7.4. For comparison, a solution containing mercury-contaminated soil was added to the same set of media and regarded as a microbial community. The growth curves show that the bacterial consortium tended to grow better compared to the microbial community, especially in the TSB medium at incubation temperatures of 20 and 35 °C. In the same medium at a temperature of 45 °C, the growth of both consortium and community under high pHs (8.5 and 9.7) was higher than the one under lower pHs (4.8 and 6.1). Meanwhile, in the mineral salt medium, the influence of the inoculant was not remarkable except under an incubation temperature of 35 °C. Moreover, the C:N ratio did not affect the growth of either the bacterial consortium or the microbial community (p > 0.05). The variance analysis also indicated that the growths were significantly different only when the pH was 4.8.

Probing interfacial water structure induced by charge reversal and hydrophobicity of silica surface in the presence of divalent heavy metal ions using sum frequency generation spectroscopy

HypothesisAdsorption of divalent heavy metal ions (DHMIs) at the mineral–water interfaces changes interfacial chemical species and charges, interfacial water structure, Stern (SL), and diffuse (DL) layers. These molecular changes can be detected by probing changing orientation and hydrogen-bond network of interfacial water molecules in response to changing local charges and hydrophobicity. ExperimentsSum-frequency generation (SFG) spectroscopy was used to probe changes in vibrational resonances of interfacial OH vs. DHMI concentration and pH. SFG spectra were deconvoluted using the measured surface potential and maximum entropy method in conjunction with the electrical double-layer theory for the SL and DL structures and correlated by hydrophobicity. FindingsThree surface charge reversals (CRs) were detected at low (CR1), medium (CR2), and high (CR3) pHs. Unlike CR1, SFG signals were minimized at CR2 and CR3 for DHMIs-silica systems highlighting considerable alterations in the structure of interfacial waters due to the inner-sphere sorption of metal hydroxo complexes. SFG results showed “hydrophobic-like” stretching modes at > 3600 cm−1 for Pb-, Cu-, and Zn-treated silica. However, contact angle measurements revealed the hydrophobization of silica only in the presence of Pb(II), as confirmed by an in-depth SFG analysis of the hydrogen-bond network of the interfacial water molecules in the SL.

Biochemical and Spectroscopic Characterization of a Recombinant Laccase from Thermoalkaliphilic Bacillus sp. FNT with Potential for Degradation of Polycyclic Aromatic Hydrocarbons (PAHs)

Laccases are industrially relevant enzymes that are known for the wide variety of substrates they can use. In recent years, fungal laccases have been progressively replaced by bacterial laccases in applied contexts due to their capacity to work on harsh conditions including high temperatures, pHs, and chloride concentrations. The focus of researchers has turned specifically towards enzymes from extremophilic organisms because of their robustness and stability. The recombinant versions of enzymes from extremophiles have shown to overcome the problems associated with growing their native host organisms under laboratory conditions. In this work, we further characterize a recombinant spore-coat laccase from Bacillus sp. FNT, a thermoalkaliphilic bacterium isolated from a hot spring in a geothermal site. This recombinant laccase was previously shown to be very active and thermostable, working optimally at temperatures around 70–80 °C. Here, we showed that this enzyme is also resistant to common inhibitors, and we tested its ability to oxidize different polycyclic aromatic hydrocarbons, as these persistent organic pollutants accumulate in the environment, severely damaging ecosystems and human health. So far, the enzyme was found to efficiently oxidize anthracene, making it a compelling biotechnological tool for biocatalysis and a potential candidate for bioremediation of aromatic contaminants that are very recalcitrant to degradation.

PH-equilibration of human hair: Kinetics and pH-dependence of the partition ratios for H+ − and OH− -ions based on a Freundlich isotherm

Hair is an insoluble, fibrous, α-keratinous, protein composite material, providing outer coverage, e.g., for mammals. In the context of a wider study on the effects of pH on human hair properties, we investigated the time-dependence of pH-equilibration study across the acid and the basic pH-range, using appropriate pure solutions of hydrochloric acid and sodium hydroxide. The results show that pH-equilibration follows essentially equal 1st-order kinetics across the pH-range. The characteristic process time does not change significantly and is in the range of 2.5–5 h. The analysis enables to determine the equilibrium uptakes of H+- and OH− -ions. These follow the expected U-shaped path across the pH-range. For both acidic and alkaline conditions, data are well described by two very similar sorption isotherms of the Freundlich-type. In consequence, partition ratios for both ions are highest near neutrality (pH 7: >6000) and drop off strongly towards low and high pHs (<50). Hair is thus a very strong ‘sink’ for H+ and OH−. This observation fundamentally challenges traditional views of limited ion uptake, namely, in the mid-pH-range due to hindered diffusion. It also does not support considerations on special roles of certain pHs, specific groups of amino acids, or morphological components. Our analysis thus suggests that established views of the interaction of hair and pH need to be reconsidered, The Freundlich isotherm approach appears to provide a versatile tool to refine our understanding of the interactions of hair and possibly other keratinous materials (horn, nail, feathers) with acids and bases.

Two different alanine dehydrogenases from Geobacillus kaustophilus: Their biochemical characteristics and differential expression in vegetative cells and spores

Two putative alanine dehydrogenase (AlaDH) genes (GK2752 and GK3448) were found in the genome of a thermophilic spore-forming bacterium, Geobacillus kaustophilus. The amino acid sequences deduced from the two genes showed mutually high homology (71%), and the phylogenetic tree based on the amino acid sequences of the two putative AlaDHs and the homologous proteins showed that the two putative AlaDH genes (GK2752 and GK3448) belong to different groups. Both of the recombinant gene products exhibited high NAD+-dependent AlaDH activity and were purified to homogeneity and characterized in detail. Both enzymes showed high stability against low and high pHs and high temperatures (70 °C). Kinetic analyses showed that the activities of both enzymes proceeded according to the same sequentially ordered Bi-Ter mechanism. X-ray crystallographic analysis showed the two AlaDHs to have similar homohexameric structures. Notably, GK3448-AlaDH was detected in vegetative cells of G. kaustophilus but not spores, while GK2752-AlaDH was present only in the spores. This is the first report showing the presence of two AlaDHs separately expressed in vegetative cells and spores.

Simple and complex coacervation methods for the nanoencapsulation of Rosa damascena mill L. anthocyanin in zein/potato starch: A new approach to enhance antioxidant and thermal properties.

The structure and antioxidant properties of zein and potato starches as well as the stability of anthocyanins strongly depend on the pH. However, due to the stability of anthocyanins in at acidic medium, their encapsulation has been limited to low pHs. In the present work, an encapsulation of anthocyanins extracted from Rosa damascena mill L. (as a model) into zein, starch, and their binary mixtures by simple and complex coacervation methods over a wide range of pH (especially higher pHs), and different encapsulating agent doses and different initial volumes of anthocyanin were studied in order to obtain new conditions for the preservation of anthocyanins and to improve the antioxidant activities of zein and potato starches. High levels of antioxidant activity and encapsulation efficiency for zein/starch/anthocyanin nanocapsules and maximum antioxidant activity for zein/starch nanocapsules (without anthocyanin) were obtained at pHs 8 and 2, respectively. Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray powder diffraction, and thermal gravimetric analysis techniques were used to analyze simple and complex coacervates biopolymer interactions, morphology, and thermal stability. The size of zein nanocapsules (283-366nm) decreased in the range of 50-175nm after the encapsulation of anthocyanin (pH 8), which makes them suitable for drug delivery processes. The prepared nanocapsules showed a high scavenging ability.