pH-dependent Growth Research Articles

Antimicrobial Activity of Positively Charged Oligopeptides with Theoretical High α-Helix Content against Cutibacterium acnes.

Cutibacterium acnes is abundant and commonly exists as a superficial bacteria on human skin. Recently, the resistance of C. acnes to antimicrobial agents has become a serious concern, necessitating the development of alternative pharmaceutical products with antimicrobial activity against C. acnes. To address this need, we evaluated the antimicrobial activity of CKR-13-a mutant oligopeptide of FK-13 with increased net charge and theoretical α-helical content-against C. acnes in modified Gifu Anaerobic Medium broth by determining the minimum inhibitory concentration (MIC). CKR-13 exerted greater antimicrobial activity against C. acnes than FK-13 in the broth at pH 7.0. The antimicrobial activity of CKR-13 with RXM against C. albicans was pH-dependent. The ionization of CKR-13 and pH-dependent growth delay of C. albicans was suggested to be associated with the increase in CKR-13 antimicrobial activity.

PH-dependent growth of alumina nanorods with a high aspect ratio for enhanced propane dehydrogenation performance

Controllable synthesis of porous alumina is always challenging due to the diversity of precursors and the complexity of the growth process. In this work, alumina nanorods with adjustable aspect ratios were synthesized by precipitation to investigate the morphology evolution mechanism related to aging pH, and the structure–activity relationship of alumina. The evolution path of precursors ammonium aluminum carbonate hydroxide (NH4Al(OH)2CO3, AACH) was established by tracking the variation in electrical charges and nitrate concentration during the growth process. It was revealed that the anisotropic adsorption of ions on the AACH crystal facets can modulate the axial and radial growth rates of the microcrystalline rods, regulating the one-dimensional oriented assembly of AACH. Alumina synthesized at pH 9.5 exhibited more exposition of (100) facets due to its higher aspect ratio, resulting in an aluminum content of up to 30% in the five-coordinated state. Due to the presence of strong metal-support interactions, the corresponding PtSn/Al2O3 catalyst demonstrated good propane dehydrogenation activity and stability, with propylene formation with 99% selectivity within 30 h of reaction. This study highlighted the significance of pH regulation in the growth environment of AACH, enabling the selective exposure of crystal facets in the alumina support, and providing an effective pathway to obtain highly active and stable catalysts.

Antibodies toward Na+,HCO3--cotransporter NBCn1/SLC4A7 block net acid extrusion and cause pH-dependent growth inhibition and apoptosis in breast cancer.

Na+,HCO3--cotransporter NBCn1/Slc4a7 accelerates murine breast carcinogenesis. Lack of specific pharmacological tools previously restricted therapeutic targeting of NBCn1 and identification of NBCn1-dependent functions in human breast cancer. We develop extracellularly-targeted anti-NBCn1 antibodies, screen for functional activity on cells, and evaluate (a) mechanisms of intracellular pH regulation in human primary breast carcinomas, (b) proliferation, cell death, and tumor growth consequences of NBCn1 in triple-negative breast cancer, and (c) association of NBCn1-mediated Na+,HCO3--cotransport with human breast cancer metastasis. We identify high-affinity (KD ≈ 0.14 nM) anti-NBCn1 antibodies that block human NBCn1-mediated Na+,HCO3--cotransport in cells, without cross-reactivity towards human NBCe1 or murine NBCn1. These anti-NBCn1 antibodies abolish Na+,HCO3--cotransport activity in freshly isolated primary organoids from human breast carcinomas and lower net acid extrusion effectively in primary breast cancer tissue from patients with macrometastases in axillary lymph nodes. Inhibitory anti-NBCn1 antibodies decelerate tumor growth in vivo by ~50% in a patient-derived xenograft model of triple-negative breast cancer and pH-dependently reduce colony formation, cause G2/M-phase cell cycle accumulation, and increase apoptosis of metastatic triple-negative breast cancer cells in vitro. Inhibitory anti-NBCn1 antibodies block net acid extrusion in human breast cancer tissue, particularly from patients with disseminated disease, and pH-dependently limit triple-negative breast cancer growth.

Water assisted self-assembly of Cu(II)(pyridine-3-carboxylate)2(H2O)4 coordination complexes and pH dependent growth of microtubes around the crystals – X-ray crystallographic, FESEM, spectroscopic and DFT studies

Water assisted self-assembly of the Cu(II)(pyridine-3-carboxylate)2(H2O)4 coordination complex has been characterized through the X-ray crystallographic structural analysis and density functional theoretical studies. The pH dependent growth of microtubes around the crystal was observed within seven days after the formation of the parent crystal. The shape and morphology of the micro-rods obtained at difference pH values have been investigated using FESEM analysis. Fourier transform infrared (FTIR) spectroscopy, UV–Vis spectroscopy and Raman Spectroscopy have been carried out to characterize the synthesized compound.

Optimizing growth, linear and 3rd order nonlinear optical traits of potassium aluminium sulfate (KAS) crystal by tuning pH for photonic device applications

Grown crystals, optical transparency and z-scan plots in open and close aperture conditions of KAS. • Novel pH dependent crystal growth of KAS was done. • PXRD confirmed improved crystallinity with decrease in pH. • Optical transmittance enhanced with decrease in pH. • 3rd order nonlinear optical properties were tuned by change in pH. This investigation is first to report the optimized crystal growth of potassium aluminium sulfate (KAS) at different pH. The well-defined single KAS crystals have been grown at pH 3, 5 and 7 engaging the slow evaporation process. Crystal structure and lattice parameters of grown KAS crystals have been determined using the powder X-ray diffraction technique. The impact of pH on optical transparency of KAS crystal is studied within 200–1000 nm through UV–visible optical analysis. He-Ne laser assisted Z-scan method is used to analyse third order nonlinear optical (TONLO) attributes of KAS crystal grown at alike pH. TONLO phase modification in refraction of grown crystals is inferred by Z-scan in close aperture configuration while the nonlinear absorption nature was sightseen by open orifice Z-scan. The Z-scan data has been used for comparative evaluation of TONLO refraction (n 2 ), susceptibility (χ 3 ) and absorption (β) coefficient of KAS crystals.

Controllable synthesis of Sn:ZnO/SnO2 nanorods: pH-dependent growth for an ethanol gas sensor

Tin-doped zinc oxide/tin oxide nanorod (Sn:ZnO/SnO2 NR) films were successfully synthesized using a solution immersion method by manipulating the pH concentration of the solutions to fabricate an ethanol gas sensor. Sn:ZnO/SnO2 NR films were prepared at constant Sn:ZnO solution pH (5.5), while the pH of the SnO2 solutions was varied between 4.5 and 6.5. In this study, the structural, morphological, and optical properties of Sn:ZnO/SnO2 NR films were investigated. The diameter and thickness of Sn:ZnO/SnO2 NR films were found to increase with the SnO2 pH. Interestingly, the Sn:ZnO/SnO2 NR sample that was prepared at SnO2 solution pH 5.5 showed the highest relative peak intensity along the c-axis plane orientation, which enhanced the sensor performance due to the shorter carrier pathway. In addition, this sample indicated a higher level of surface donor-related defects, which are favorable for sensing device performance. The samples were exposed to ethanol gas to measure their gas-sensing properties. Sn:ZnO/SnO2 NR films prepared at SnO2 solution pH 5.5 showed the highest sensing performance with short response/recovery times.

Interaction between the yeast RAVE complex and Vph1-containing Vo sectors is a central glucose-sensitive interaction required for V-ATPase reassembly

The yeast vacuolar H+-ATPase (V-ATPase) of budding yeast (Saccharomyces cerevisiae) is regulated by reversible disassembly. Disassembly inhibits V-ATPase activity under low-glucose conditions by releasing peripheral V1 subcomplexes from membrane-bound Vo subcomplexes. V-ATPase reassembly and reactivation requires intervention of the conserved regulator of H+-ATPase of vacuoles and endosomes (RAVE) complex, which binds to cytosolic V1 subcomplexes and assists reassembly with integral membrane Vo complexes. Consistent with its role, the RAVE complex itself is reversibly recruited to the vacuolar membrane by glucose, but the requirements for its recruitment are not understood. We demonstrate here that RAVE recruitment to the membrane does not require an interaction with V1 Glucose-dependent RAVE localization to the vacuolar membrane required only intact Vo complexes containing the Vph1 subunit, suggesting that the RAVE-Vo interaction is glucose-dependent. We identified a short conserved sequence in the center of the RAVE subunit Rav1 that is essential for the interaction with Vph1 in vivo and in vitro Mutations in this region resulted in the temperature- and pH-dependent growth phenotype characteristic of ravΔ mutants. However, this region did not account for glucose sensitivity of the Rav1-Vph1 interaction. We quantitated glucose-dependent localization of a GFP-tagged RAVE subunit to the vacuolar membrane in several mutants previously implicated in altering V-ATPase assembly state or glucose-induced assembly. RAVE localization did not correlate with V-ATPase assembly levels reported previously in these mutants, highlighting both the catalytic nature of RAVE's role in V-ATPase assembly and the likelihood of glucose signaling to RAVE independently of V1.

Associations between the vaginal microbiome and Candida colonization in women of reproductive age

The composition of bacteria within the vaginal microbiome has garnered a lot of recent attention and has been associated with reproductive health and disease. Despite the common occurrence of yeast (primarily Candida) within the vaginal microbiome, there is still an incomplete picture of relationships between yeast and bacteria (especially lactobacilli), as well as how such associations are governed. Such relationships could be important to a more holistic understanding of the vaginal microbiome and its connection to reproductive health. The objective of the study was to perform molecular characterization of clinical specimens to define associations between vaginal bacteria (especially Lactobacillus species) and Candida colonization. Invitro studies were conducted to test the 2 most common dominant Lactobacillus species (Lactobacillus crispatus and Lactobacillus iners) in their ability to inhibit Candida growth and to examine the basis for such inhibition. A nested cross-sectional study of reproductive-age women from the Contraceptive CHOICE Project was conducted. Vaginal swabs from 299 women were selected to balance race and bacterial vaginosis status, resulting in a similar representation of black and white women in each of the 3 Nugent score categories (normal [0-3], intermediate [4-6], and bacterial vaginosis [7-10]). Sequencing of the 16S ribosomal gene (V4 region) was used to determine the dominant Lactobacillus species present (primarily Lactobacillus iners and Lactobacillus crispatus), defined as >50% of the community. Subjects without dominance by a single Lactobacillus species were classified as Diverse. A Candida-specific quantitative polymerase chain reaction targeting the internally transcribed spacer 1 was validated using vaginal samples collected from a second cohort of women and used to assess Candida colonization. Two hundred fifty-five nonpregnant women with sufficient bacterial biomass for analysis were included in the final analysis. Generalized linear models were used to evaluate associations between Lactobacillus dominance, sociodemographic and risk characteristics, and vaginal Candida colonization. In separate invitro studies, the potential of cell-free supernatants from Lactobacillus crispatus and Lactobacillus iners cultures to inhibit Candida growth was evaluated. Forty-two women (16%) were vaginally colonized with Candida. Microbiomes characterized as Diverse (38%), Lactobacillus iners-dominant (39%), and Lactobacillus crispatus-dominant (20%) were the most common. The microbiome, race, and Candida colonization co-varied with a higher prevalence of Candida among black women and Lactobacillus iners-dominant communities compared with white womenand Lactobacillus crispatus-dominant communities. Lactobacillus iners-dominant communities were more likely to harbor Candida than Lactobacillus crispatus-dominant communities (odds ratio, 2.85, 95%confidence interval, 1.03-7.21; Fisher exact test, P= .048). Invitro,Lactobacillus crispatus produced greater concentrations of lactic acid and exhibited significantly more pH-dependent growth inhibition of Candida albicans, suggesting a potential mechanism for the clinical observations. In nonpregnant women, Lactobacillus iners-dominant communities were significantly more likely to harbor Candida than Lactobacillus crispatus-dominant communities, suggesting that Lactobacillus species have different relationships with Candida. Invitro experiments indicate that Lactobacillus crispatus may impede Candida colonization more effectively than Lactobacillus iners through a greater production of lactic acid.

Characterization of pH Dependent Growth Response of Agriculturally Important Microbes for Development of Plant Growth Promoting Bacterial Consortium

Characterization of pH Dependent Growth Response of Agriculturally Important Microbes for Development of Plant Growth Promoting Bacterial Consortium

A novel investigation of the growth and lipid production of the extremophile microalga Coccomyxa melkonianii SCCA 048 under the effect of different cultivation conditions: Experiments and modeling

In the present study, the effect of nitrogen manipulation on the growth of the extremophile microalgal strain Coccomyxa melkonianii SCCA 048 was investigated for the first time to study its ability to produce marketable products, such as lipids. To identify the best strategies for cultivating this alga in large scale systems, the nitrate- and pH-dependent growth kinetics and the corresponding kinetic parameters were first evaluated in a multiwell screening. Subsequently, the effects of initial nitrogen concentration on the growth rate, nitrate uptake, as well as the synthesis of lipids and their corresponding quality, were investigated in batch photobioreactors. The experimental results were then successfully interpreted by a simple, albeit novel and exhaustive, mathematical model which takes into account the effects of light intensity, nitrate concentration and pH on the growth and lipid synthesis of this strain. By assessing the pH-dependent kinetics, it was confirmed that Coccomyxa melkonianii is extremophile as far as pH conditions are concerned. Moreover, the obtained growth rates and lipid productivities were high enough to permit sustainable cultivation at large scale. In particular, a quite interesting lipid content (about 40 %wt) was achieved under nitrogen starvation conditions. The fatty acids obtained by transesterification of the extracted lipids might be potentially exploited in different industrial sectors. In addition, the proposed model represents a first step towards the development of a useful tool for the optimization and the design of raceway-type bioreactor where Coccomyxa melkonianii would be cultivated.

Dual functionalized, stable and water dispersible CdTe quantum dots: Facile, one-pot aqueous synthesis, optical tuning and energy transfer applications

We report a facile one-pot synthesis of aqueously dispersible CdTe quantum dots (QDs) with tunable optical properties by using dual capping agents namely MPA and Citric acid. Optimum precursor ratio and pH > 8 at 80 °C facilitated particle size tunability and exceptional optical properties. QDs are ∼3.7 nm as seen from HR-TEM image; highly-luminescent showing absolute quantum-yield up to 54% and bear good photostability. CdTe QDs are highly stable in water with large negative Zeta potential. Optimum ratio of Cd2+:MPA:TeO32−:NaBH4:citric acid was 1:2:0.2:3.2:5.2, respectively. The pH dependent nucleation and growth of QDs subsequently lead to quasi CdTe/CdS structure as indicated by XRD, FTIR and particle size analysis. QDs showed excitation independent emission with tunable peak width. QDs can be stored over 6-months at 4 °C without causing agglomeration. Interaction of QDs with Rhodamine-6G and plasmonic silver nanoparticles via resonance energy transfer (RET) imply their suitability for sensors and biomedical applications.

Evaluation of CO2 gas supply of large open algae ponds

In this study it is evaluated how large open algae ponds can be supplied with sufficient CO2. Therefore, a 2.2 acre and a 10 acre pond are simulated over a one-year operating period. The ponds are operated with two different kinds of algae that achieve a yearly yield of 8 gm2d and 25 gm2d. The algae consume CO2, which is fed into the ponds as CO2 gas injected into sumps.The algae ponds have such long channels that the CO2 has to be injected at multiple points along the channel to keep the pH value in the pond within a specified operating range. The necessary number of injection points is determined for different operating pH ranges. Furthermore, the influence of multiple injection points on algae showing a pH dependent growth is evaluated.The investigations show that it is possible to supply such large ponds with sufficient CO2 by injecting CO2 gas whose volume flow is controlled by a proportional control algorithm. Large ponds that have long channels require more than one injection point along the channel. In some scenarios, even a high number of injection points cannot prevent the pH value from violating the lower limit of the operating range.

NH₄OH-Oriented and pH-Dependent Growth of ZnO Nanostructures via Microwave-Assisted Growth Method.

We proffer NH4OH-oriented and pH-dependent growth of ZnO nanostructures via a microwaveassisted growth method. The fabrication of ZnO nanorods (ZNRs), nanoflowers (ZNFs), nanostars (ZNSs), and nanotetrapods (ZNTs) is presented. NH4OH was used as a mineralizer to change the solution pH for nanostructure growth, where temperature and other variables were fixed. Because of an efficient heat transfer and facile growth of nanostructures, a domestic microwave oven was used to facilitate the nanostructure growth in the span of just 10-15 min. The results showed that the growth of ZnO nanostructures was dependent upon the number of growth units and ZnO nuclei present in the solution, which ultimately depend upon the pH of the solution. At the outset, without the addition of NH4OH, the pH of the solution was ~6.8 and the ZNRs were formed in the solution or on a seeded substrate which persisted in the pH range of ~6.8-9. An abrupt change in the shapes and the types of the nanostructures was observed when the pH was boosted beyond 10. A transition from ZNRs to ZNFs was observed at pH 10 and ZNFs were formed at pH 11. The solution gave birth to ZNSs and ZNTs when the pH was further raised to 12 and 13, respectively.

PH-Dependent growth of atomic Pd layers on trisoctahedral gold nanoparticles to realize enhanced performance in electrocatalysis and chemical catalysis.

In this work, the controlled epitaxial growth of ultrathin Pd shells of a few atomic layers (denoted as nL) on the surfaces of gold nanoparticle (Au NP) cores of different morphologies (trisoctahedral, cubic, and spherical shapes) in the presence of cetyltrimethylammonium chloride (CTAC) was achieved by regulating the pH value of the aqueous CTAC solution and finely tuning the amount of the Pd precursor. It was found that the critical shell thickness for epitaxial Pd growth at the optimal pH value was 4 atomic layers, taking {331}-faceted trisoctahedral (TOH) Au@PdnL NPs as an example, on the basis of the results of atomic-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images. Moreover, the resulting TOH Au@Pd1L NPs (100.9 m2 g-1, 13.2 A mgPd-1 and 13.1 mA cm-2) exhibited excellent electrocatalytic performance and long-term electrocatalytic activity for ethanol oxidation, around 4.8-fold, 66-fold, and 21.8-fold better than commercial Pd/C catalysts (31 m2 g-1, 0.2 A mgPd-1, and 0.6 mA cm-2). Furthermore, the resulting TOH Au@Pd1L NPs not only markedly enhance the chemical catalytic activity for the reduction of 4-nitrophenol (4-NP), but also allow the in situ surface-enhanced Raman spectroscopy (SERS) monitoring of the reaction process of the Pd-catalyzed reduction of 4-NTP. Thus, our work may provide a new way to fabricate core-shell (CS) bimetallic NPs with the merits of both metal outer shells (excellent catalytic performance in electrocatalysis and chemical catalysis) and Au NP cores (reaction process by in situ SERS monitoring).

Electrolyte pH dependent controlled growth of co-electrodeposited CZT films for application in CZTS based thin film solar cells

Understanding Cu–Zn–Sn co-electrodeposition is important from the view point of developing high quality CZTS (Cu2ZnSnS4) absorber layer for thin film solar cells. One of the major issue during electrodeposition is hydrogen evolution which can severely affect the growth of the depositing film. In the present study, the hydrogen evolution is controlled by systematically varying electrolyte pH during co-electrodeposition of Cu–Zn–Sn films. Cu–Zn–Sn metal precursor films were co-electrodeposited using electrolytic baths with pH varying from 4 to 8 and conditions for obtaining dense and stoichiometric Cu–Zn–Sn films were evaluated. Films electrodeposited with electrolyte pH of 6, 7 and 8 produced dense and continuous electrodeposited films in contrast to those deposited using electrolyte pH of 4 and 5. Films deposited with different electrolyte pH were sulphurized in Argon atmosphere and their physical characterization was carried out in order to find out conditions to obtain a dense and compact CZTS film having phase purity with appropriate stoichiometry resulting in a band gap of 1.45 eV.

PH-Dependent Single-Step Rapid Synthesis of CuO Nanoparticles and Their Optical Behavior

This paper reports the pH-dependent growth of copper oxide (CuO) nanoparticles by wet chemical precipitation method using pH value of the samples as the only variable parameter. The phase purity, morphology, optical behavior, and elemental analysis of synthesized nanoparticles are shown to be critically dependent on the pH of the samples. Scanning electron microscope (SEM) results shows that a higher pH results well-defined CuO nanoflakes. X-ray powder diffraction (XRD) results disclosed that the growth of pure CuO with monoclinic structure at higher pH 8, whereas mixed phase was formed at lower pH 7. The average crystallite size of samples prepared at pH 8 to 10 was varying from 23.36 to 25.78 nm. The infrared spectroscopy showed that the O–H stretching peaks become narrow with an increase in the pH value. Optical results revealed the existence of the sharp absorption edges with precise excitonic features and photoluminescence bands both located at visible and near infrared spectral region attributed to the excellent optical behavior and narrow size distribution of particles. The additional near infrared band in photoluminescence spectrum located at 860 nm is attributed the defect-related luminescence. The growth mechanism of CuO nanostructures was discussed in the light of our findings.

Bile salt assisted morphological changes of cationic gemini surfactant (12-4-12) micelles

pH and concentration dependent growth of gemini surfactant (12-4-12) micelles in the presence of bile salts.

Modeling the Role of pH on Baltic Sea Cyanobacteria.

We simulate pH-dependent growth of cyanobacteria with an ecosystem model for the central Baltic Sea. Four model components—a life cycle model of cyanobacteria, a biogeochemical model, a carbonate chemistry model and a water column model—are coupled via the framework for aquatic biogeochemical models. The coupled model is forced by the output of a regional climate model, based on the A1B emission scenario. With this coupled model, we perform simulations for the period 1968–2098. Our simulation experiments suggest that in the future, cyanobacteria growth is hardly affected by the projected pH decrease. However, in the simulation phase prior to 1980, cyanobacteria growth and N-fixation are limited by the relatively high pH. The observed absence of cyanobacteria before the 1960s may thus be explained not only by lower eutrophication levels, but also by a higher alkalinity.

PH induced tuning of size, charge and viscoelastic behavior of aqueous micellar solution of Pluronic ® P104–anthranilic acid mixtures: A scattering, rheology and NMR study

• SANS and rheology data for AA loaded P104 micelles at different pH are reported. • Uniaxial growth was seen with [AA] which suppressed in strongly acidic and alkaline pH. • The pH dependent growth in the presence of AA is accounted for charged micelles. • NOESY showed the location of AA in micelles at core–shell interface. A moderately hydrophilic ethylene oxide–propylene oxide triblock copolymer (EO 27 –PO 63 –EO 27 ) Pluronic ® P104 hereafter referred to as P104 forms spherical core–shell micelles in water. The pH dependence on the influence of anthranilic acid (AA) on P104 micelles was investigated by cloud point (CP), viscosity, dynamic light scattering (DLS), small angle neutron scattering (SANS), nuclear Overhauser enhancement spectroscopy (NOESY) and rheology. SANS results showed the remarkable effects on the structure of micelles and are discussed in terms of micellar growth and transition. NOESY revealed the location of AA close to the core–corona region of the micelle. These micelles develop ionic nature by changes in pH which affects micelle hydration and inter-micellar interaction. This was further supported by changes in viscosity, cloud point and DLS. The storage/loss modulus and other rheological parameters for selected viscoelastic solutions were evaluated and discussed.

Bbmsn2 acts as a pH-dependent negative regulator of secondary metabolite production in the entomopathogenic fungus Beauveria bassiana.

Fungal secondary metabolites are chemical compounds important for development, environmental adaptation and for potential biotechnological and pharmaceutical applications. Oosporein, a red-pigmented benzoquinone, produced by many fungal insect pathogenic Beauveria spp., shows remarkable functional diversity, displaying antimicrobial, antiviral and even anti-proliferative activities. A homologue of the msn2/seb1 transcription factor was identified in a Beauveria bassiana random T-DNA insertion library. Targeted gene-knockout of Bbmsn2 resulted in reduced growth and increased sensitivity to Calcofluor White, H2 O2 and Congo Red. However, when normalized to growth at 26°C, the ΔBbmsn2 mutant was more tolerant to high temperature (32°C) than the wild type parent. The ΔBbmsn2 mutant also displayed a pH-dependent growth phenotype, with little growth seen at pH < 5.0 but, better growth at alkaline conditions (pH > 8.0). Unexpectedly, a pH-dependent deregulation of a red pigment, identified as oosporein, was seen in the ΔBbmsn2 mutant. The ΔBbmsn2 strain was impaired in virulence in both topical and intrahaemocoel injection bioassays against Galleria mellonella. ΔBbmsn2 proliferation in the host haemolymph and conidiation on the host cadaver was reduced. These data indicate that Bbmsn2 acts as a negative regulator of oosporein production and contributes to virulence and growth in response to external pH in B. bassiana.