Acid Buffer Solution Research Articles

Quantitative determination of human serum testosterone via isotope dilution ultra‑performance liquid chromatography tandem mass spectrometry.

Quantification of testosterone serves an important role in the differential diagnosis of androgen-related endocrine diseases. Mass spectrometry exhibits higher accuracy and lower variability than immunoassays, especially at low testosterone concentrations. The present study developed and validated an isotope dilution ultra-performance liquid chromatography tandem mass spectrometry method for determination of human serum testosterone. The serum was equilibrated with an isotopic internal standard and treated with acidic buffer to release hormones from their binding proteins. Testosterone was extracted via two serial liquid-liquid extractions. In the first stage, the lipid fractions from an acidic buffer solution were isolated using ethyl acetate and n-hexane. The organic phase was evaporated and reconstituted in a basic buffer solution. In the second stage, the polar impurities of n-hexane extraction were removed. Total testosterone in serum was quantified via ultra-performance liquid chromatography tandem mass spectrometry in multiple reaction monitoring mode with positive electrospray ionization. The coefficient of variation of the method for intra- and inter-assay was 2.13% (1.40–2.77%) and 3.44% (3.06–3.66%), respectively. The recovery ranged from 94.32 to 108.60% for different samples. The limit of detection was 0.50 ng/dl and the linear range was from 1.00 to 1,000.00 ng/dl. In addition, the extraction efficiency in three different levels of quality control of the serum ranged from 85.02 to 93.29%. Moreover, structural analogues were investigated and were not indicated to affect the quantification of testosterone. The present method may enable quantification of testosterone in a clinical setting with high precision and accuracy.

Electronic coupling between molybdenum disulfide and gold nanoparticles to enhance the peroxidase activity for the colorimetric immunoassays of hydrogen peroxide and cancer cells

Peroxidase nanoenzymes exhibit a specific affinity toward substrates, thereby demonstrating application potential for realizing the colorimetric immunoassays of hydrogen peroxide (H2O2), which can be further used as a probe for imaging cancer cells. To enhance the intrinsic peroxidase activity of molybdenum sulfide (MoS2) nanomaterials, gold (Au) nanoparticles with an average diameter of approximately 2.1 nm were modified on a MoS2/carbon surface (denoted as MoS2/C-Au600) via ascorbic acid reduction. MoS2/C-Au600 can oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to generate a blue oxidation product in the presence of H2O2; this product exhibits peroxidase-like activities, superior to those of most existing MoS2-based nanoenzymes. Furthermore, MoS2/C-Au600 exhibits a high detection capability for H2O2 in the range of 1 × 10−5 to 2 × 10−4 mol/L (R2 = 0.99), and the lowest detection limit is 1.82 µmol/L in a sodium acetate and acetic acid buffer solution. Steady state kinetics studies indicate that the catalytic mechanism is consistent with the ping-pong mechanism. Given its strong absorption peak at 652 nm in the visible region, MoS2/C-Au600 can be used to image cancer cells due to the enhanced permeability and retention effect. Our findings demonstrate that the synergistic electronic coupling between multiple components can enhance the peroxidase activity, which can facilitate the development of an effective, facile, and reliable method to perform colorimetric immunoassays of H2O2 and cancer cells.

Immune function and serum vitamin D in shelter dogs: A case-control study

This study sought to establish a baseline understanding of immune function and its association with serum vitamin D in shelter dogs. Ten apparently healthy shelter dogs housed in the Arizona Humane Society for ≥7 days and 10 apparently healthy, age, breed, and sex-matched control dogs were included. Serum 25-hydroxyvitamin D (25[OH]D), the major circulating vitamin D metabolite, was measured using high performance liquid chromatography. Whole blood samples were stimulated with lipopolysaccharide (LPS), lipoteichoic acid, or phosphate buffer solution, and tumor necrosis factor (TNF)-ɑ, interleukin (IL)-6, and IL-10 were measured using a canine-specific multiplex bead-based assay. Phagocytosis of opsonized-Escherichia coli and E. coli-induced oxidative burst were evaluated with flow cytometry.Shelter dogs had decreased percentages of granulocytes and monocytes (GM) that had phagocytized opsonized-E coli (P = 0.019) and performed E. coli-induced oxidative burst (P = 0.011). There were no significant differences in TNF-α, IL-6, IL-10, or 25(OH)D concentrations between shelter and control dogs. Serum 25(OH)D concentrations had a weak positive association with the intensity of GM E. coli-induced oxidative burst (r2 = 0.23, P = 0.03). There was a moderate inverse association between serum 25(OH)D concentration and LPS-stimulated TNF-ɑ production in shelter dogs (r2 = 0.40, P = 0.04). These results demonstrate immune dysregulation in vitro in shelter dogs housed for ≥7 days when compared to age, breed, and sex-matched control dogs. While serum 25(OH)D concentrations did not differ between shelter and control dogs, significant associations between 25(OH)D concentration and immune function parameters in vitro were identified.

Mannoside-Modified Branched Gold Nanoparticles for Photothermal Therapy to MDA-MB-231 Cells.

Recently, gold nanoparticles (Au NPs) have been used to study the treatment of malignant tumors due to their higher biocompatibility and lesser toxicity. In addition, they can be excited through a specific wavelength to produce oscillating plasmonic photothermal therapy (PPTT) on the basis of the localized surface plasma resonance (LSPR) effect. Au NPs can be heated to kill cancer cells in specific parts of the body in a noninvasive manner. In this study, branched gold nanoparticles (BAu NPs) were prepared by mixing HAuCl4 in a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution in a molar ratio of 1:2000. The UV–vis absorption peak was detected in the range of 700–1000 nm. Subsequently, BAu NPs were chemically linked to a thiol-modified mannoside molecule via a stable sulfur–Au covalent bond (Man@BAu NPs). Due to the presence of abundant mannose receptors on human-breast-cancer cells, MDA-MB-231, Man@BAu NPs were found to be abundant inside cancer cells. After irradiating the Man@BAu NP-laden MDA-MB231 switch with a near-infrared (NIR) laser at 808 nm wavelength, the photothermal-conversion effect raised the surface temperature of Man@BAu NPs, thus inducing cell death. Our experiment results demonstrated the advantages of applying Man@BAu NPs in inducing cell death in MDA-MB-231.

Degradation mechanism of sludge organic matter treated in alkaline/acidic solution and its effect on long-term strength

Sludge contains a little organic matter. Due to the action of microorganisms, organic matter was decomposed, and released humic acid. It can also affect lime or cement solidified sludge. Three categories of pH solution (pH = 4.0, 7.0, and 9.0) were prepared to soaking sludge. The organic matter and pH were observed for 78 days. The results showed that both acidic and alkaline buffer solutions can accelerate the consumption of organic matter, and change the molecule structure from tightness to loosening. In addition, the alkaline solution not only can promote humic acid releasing from organic matter, but also can consume it at the same time. This is a benefit to create alkaline pore water, and further improve the effect of lime or/and cement solidified sludge. The long-term strength indicated that solidified sludge without organic matter was almost unchanged throughout the curing time. From this view, pre-treatment organic matter with alkaline solution is an effective measurement for improving the long-term performance of cement/lime solidified sludge.

Electrochemical behaviour and analytical applications of a manganese porphyrin – silica hybrid film prepared by pulsed laser deposition

Hybrid nanomaterials can have superior properties in comparison with individual components, sometimes greatly improving their optoelectronic activity. For this reason, modified carbon electrodes were obtained using a hybrid material composed of 5,10,15,20-tetra(4-tolyl)porphyrinato manganese (III) chloride (MnTTP) embedded in a silica matrix. The laser ablation deposition technique (PLD) has been used to immobilize the manganese porphyrin–silica hybrid on the surface of the carbon electrodes. The successful transfer of the manganese-porphyrin was evidenced by UV–Vis absorption spectroscopy. The PLD-deposited hybrid film was characterized using AFM and electrochemical methods (cyclic voltammetry and square wave voltammetry). The viability of this hybrid nanomaterial film as a redox mediator for the anodic oxidation and sensitive voltammetric determination of ascorbic acid in buffer solution (pH = 6.5) is described. The recorded anodic process is attributed to its oxidation to dehydroascorbic acid, with satisfactory catalytic current response and low non-Faradaic current.

Tests on the Influence on Electro-Osmotic Effect of Drainage by Adding Humic Acid Buffer Solution to the Cathode Region

Tests on the Influence on Electro-Osmotic Effect of Drainage by Adding Humic Acid Buffer Solution to the Cathode Region

In vitro antibacterial activity and cytocompatibility of magnesium-incorporated poly(lactide-co-glycolic acid) scaffolds

BackgroundBone defects are often combined with the risk of infection in the clinic, and artificial bone substitutes are often implanted to repair the defective bone. However, the implant materials are carriers for bacterial growth, and biofilm can form on the implant surface, which is difficult to eliminate using antibiotics and the host immune system. Magnesium (Mg) was previously reported to possess antibacterial potential.MethodsIn this study, Mg was incorporated into poly(lactide-co-glycolic acid) (PLGA) to fabricate a PLGA/Mg scaffold using a low-temperature rapid-prototyping technique. All scaffolds were divided into three groups: PLGA (P), PLGA/10 wt% Mg with low Mg content (PM-L) and PLGA/20 wt% Mg with high Mg content (PM-H). The degradation test of the scaffolds was conducted by immersing them into the trihydroxymethyl aminomethane–hydrochloric acid (Tris–HCl) buffer solution and measuring the change of pH values and concentrations of Mg ions. The antibacterial activity of the scaffolds was investigated by the spread plate method, tissue culture plate method, scanning electron microscopy and confocal laser scanning microscopy. Additionally, the cell attachment and proliferation of the scaffolds were evaluated by the cell counting kit-8 (CCK-8) assay using MC3T3-E1 cells.ResultsThe Mg-incorporated scaffolds degraded and released Mg ions and caused an increase in the pH value. Both PM-L and PM-H inhibited bacterial growth and biofilm formation, and PM-H exhibited higher antibacterial activity than PM-L after incubation for 24 and 48 h. Cell tests revealed that PM-H exerted a suppressive effect on cell attachment and proliferation.ConclusionsThese findings demonstrated that the PLGA/Mg scaffolds possessed favorable antibacterial activity, and a higher content of Mg (20%) exhibited higher antibacterial activity and inhibitory effects on cell attachment and proliferation than low Mg content (10%).

Experimental study on interactions occurring between Pluronics and leflunomide in solution

The influence of Pluronics L64, F68, F88 and F127 on the solubility and membrane permeability of leflunomide (LEF) in acidic and alkaline buffer solutions with physiological pHs was revealed. A noticeable increase of LEF solubility in the presence of Pluronics was revealed. It was demonstrated that the structure of Pluronics has influence on the manifestation of a solubilizing effect. Namely, more efficient solubilizers for LEF were found to be L64 and F127, having the lowest content of ethylene oxide groups in the structure and lower HLB indices in comparison with F68 and F88. The binding of LEF with the core of Pluronic micelles was proposed on the basis of the obtained 1Н NMR data. Permeability of LEF through an artificial Permeapad barrier composed of phospholipids was measured using the Franz diffusion cell. Decrease of the LEF permeability in the presence of all investigated Pluronics was detected. The location of hydrophobic fragment of LEF molecule inside the micelle leads to a decrease in the non-polar surface area and the ability of the drug to pass through the lipophilic layer of the membrane.

Horseradish peroxidase-catalyzed oxidative polymerization of aniline in bicontinuous microemulsion stabilized by AOT/SDS

A bicontinuous microemulsion system consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), sodium dodecylsulfate (SDS), an aqueous solution (a 0.1 M disodium hydrogenphosphate/citric acid buffer solution of pH = 4.3), and decane was investigated in detail for applications as reaction medium for the horseradish peroxidase (HRP)/hydrogen peroxide-mediated synthesis of the conductive form of polyaniline (PANI). To formulate the optimal single-phase microemulsion with the phase inversion temperature being close to room temperature, the T-γ fishlike phase diagram of the AOT/SDS-buffer-decane pseudoternary system was determined. The effects of the surfactant concentration (γ), the oil-to-water ratio (α) and the temperature (T) on the conductivity of the resulting PANI and the underlying mechanism were investigated using UV–vis-NIR, ESR and small-angle X-ray scattering (SAXS) techniques. Results show that the bicontinuous microemulsion plays a template role in the PANI biosynthesis, and the PANI conductivity also depends on the activity and stability of the solubilized HRP, which are determined by the microdomain size of the microemulsions and the reaction temperature. As far as γ is concerned, it is found that as γ increases, the microdomain size of the bicontinuous microemulsion as well as the activity of the solubilized HRP decreases significantly, leading to a great decrease of the PANI conductivity. Compared with γ, the change of α has small effect on the PANI conductivity. As the α-dependent microdomain size changes little with increasing α, the small change of the PANI conductivity should be ascribed mainly to the HRP activity. For T, over the range of 20 °C–35 °C, it has a slight effect on the microdomain size of the bicontinuous microemulsion, but it has a marked effect on the enzymatic properties of HRP. As the temperature increases, the activity of HRP increases, but its thermal stability decreases greatly. Therefore, the thermal stability of HRP is the major factor causing that the PANI conductivity decreases significantly with increasing T. The present work deepens the understanding of the template effect of anionic surfactant aggregates in the biosynthesis of conducting PANI. To the best of our knowledge, this work is the first study of the use of bicontinuous microemulsions as reaction media for the enzymatic synthesis of a conducting polymer.

Effect of rosemary extract on lipid oxidation of cooked pork during simulated gastric digestion.

Oxidation of food lipids occurs in the gastrointestinal tract, resulting in potential adverse health effects. Rosemary extract (RE), as one of the most popular naturally sourced antioxidants, is widely used in the food industry. However, the effect of RE on lipid oxidation during gastrointestinal digestion has not been well investigated. Therefore, this study aimed to evaluate the effect of RE on lipid oxidation of cooked pork during simulated gastric digestion. Results showed that RE at 12.5, 25, 50, and 100 mg kg-1 pork effectively decreased the formation of malondialdehyde during simulated gastric digestion of cooked pork. RE also effectively mitigated the decline of fatty acids during the simulated gastric digestion of pork. The total phenolic content in RE was calculated to be 170.67 mg gallic acid equivalent (GAE) g-1 . RE dissolved in distilled water (pH 6.5) or potassium hydrogen phthalate-hydrochloric acid buffer solution (0.2 mol L-1 , pH 3.0) both exhibited strong 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activities as well as ferric reducing capacity. The inhibitory effects of RE on lipid oxidation of cooked pork during simulated gastric digestion may be attributed to the phenolic compounds with antioxidant properties. The results lend support to the possible application of rosemary or RE as a rich source of natural antioxidants to inhibit the oxidation of food lipids during gastrointestinal digestion. © 2019 Society of Chemical Industry.

SDS-PAGE for Monitoring the Dissolution of Zinc Oxide Bactericidal Nanoparticles (Zinkicide) in Aqueous Solutions.

Zinkicide is a systemic bactericidal formulation containing protein-size fluorescent zinc oxide-based nanoparticles (nano-ZnO). Previous studies have shown that Zinkicide is effective in controlling citrus diseases. Its field performance as an antimicrobial agent has been linked to the bioavailability of zinc ions (Zn2+) at the target site. It is therefore important to monitor Zn2+ release from Zinkicide so that application rates and frequency can be estimated. In this study, we present a simplistic approach designed to monitor Zinkicide nanoparticle dissolution rates in water and acidic buffer solutions using traditional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The evolution of nano-ZnO in the polyacrylamide gel scaffolds was studied by exciting the sample with UV light and detecting the fluorescence of nano-ZnO. Fluorescence intensities measured with this assay allowed for quantitative analysis of molecular weight changes of nano-ZnO in citrate buffer, a surrogate of citrus juice. Our results demonstrated that citrate buffer induced the greatest degradation of Zinkicide. Fluorescence intensity fluctuations were observed over time, indicating interactions of citrate with the surface of nano-ZnO. These findings provide a new approach to quantify the dissolution of nanoparticles in simulated environments, even when other analytical methods lack sensitivity because of the small size of the system (≈4 nm).

New polyazamacrocyclic 3-hydroxy-4-pyridinone based ligands for iron depletion antitumor activity.

Iron depletion is an efficient strategy for the development of anticancer agents. In an effort to develop efficient chelators, two new 3-hydroxy-4-pyridinone based polyazamacrocycles 1e and 2e were designed and synthesized. A preliminary study of the ligands was carried out to investigate their iron chelating capability and anti-tumor activity. Chelating kinetics revealed that the ligands exhibited excellent iron depletion capacity in neutral and acidic NH4OAc buffer solutions. Moreover, MTT assay showed that the new ligands displayed potent inhibitory activity in the proliferation of HepG2 cells. The attachment of hydroxypyridione units on the polyazamacrocycles promoted iron chelating capability and improved the anti-tumor activity by offering additional chelating sites and lipophilicity. These results indicate that two novel compounds may possess the therapeutic potential in the treatment of cancer through depleting cellular iron.

Surface and morphology analyses, and voltammetry studies for electrochemical determination of cerium(iii) using a graphene nanobud-modified-carbon felt electrode in acidic buffer solution (pH 4.0 ± 0.05).

Trace determination of radioactive waste, especially Ce3+, by electrochemical methods has rarely been attempted. Ce3+ is (i) a fluorescence quencher, (ii) an antiferromagnet, and (iii) a superconductor, and it has been incorporated into fast scintillators, LED phosphors, and fluorescent lamps. Although Ce3+ has been utilized in many industries due to its specific properties, it causes severe health problems to human beings because of its toxicity. Nanomaterials with fascinating electrical properties can play a vital role in the fabrication of a sensor device to detect the analyte of interest. In the present study, surfactant-free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) with nanobud (NB) morphology were utilized for the determination of Ce3+ through electrochemical studies. The working electrode, graphene nanobud (GNB)-modified-carbon felt (CF), was developed by a simple drop-coating method for the sensitive detection of Ce3+ in acetate buffer solution (ABS, pH 4.0 ± 0.05) at a scan rate of 50 mV s−1 using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. CV and DPV studies validated the existence of distinctive peaks at approximately +0.20 and +0.93 V (vs. SCE), respectively, with a limit of detection of approximately 2.60 μM. Furthermore, electrochemical studies revealed that the GNB-modified-CF electrode was (i) stable even after fifteen cycles, (ii) reproducible, (iii) selective towards Ce3+, (iv) strongly pH-dependent, and (v) favored Ce3+ sensing only at pH 4.0 ± 0.05. Impedance spectroscopy results indicated that the GNB-modified-CF electrode was more conductive (1.38 × 10−4 S m−1) and exhibited more rapid electron transfer than bare CF, which agrees with the attained Randles equivalent circuit. Microscopy (AFM, FE-SEM, and HR-TEM), spectroscopy (XPS and Raman), XRD, and energy-dispersive X-ray (EDX) analyses of the GNB-modified-CF electrode confirmed the adsorption of Ce3+ onto the electrode surface and the size of the electrode material. Ce3+ nanobuds increased from 35–40 to 50–55 nm without changing their morphology. The obtained results provide an insight into the determination of Ce3+ to develop an electrochemical device with low sensitivity.

Smart wound dressing for infection monitoring and NIR-triggered antibacterial treatment.

Wound infection is a major challenge in the clinic that greatly hinders the wound healing process. It is highly important to develop smart wound dressings that can sense bacterial infection at early stages and provide on-demand treatment. In this work, a smart hydrogel-based wound dressing capable of monitoring bacterial infection via a pH-responsive fluorescence resonance energy transfer (FRET) transition of Cyanine3 (Cy3) and Cyanine5 (Cy5) in a bacterial environment and providing on-demand treatment of infection via near infrared (NIR) light-triggered antibiotic release was developed. The smart hydrogel was prepared by physical crosslinking of polyvinyl alcohol (PVA) and an ultraviolet (UV)-cleavable polyprodrug (GS-Linker-MPEG), in which Cy3 and Cy5-modified silica nanoparticles (SNP-Cy3/Cy5) were loaded and acted as a pH-responsive fluorescent probe to detect bacterial infection based on the FRET effect between Cy3 and Cy5. Also, up-conversion nanoparticles (UCNP) were loaded into the hydrogels to cleave the UV-responsive GS-Linker-MPEG and achieve NIR-responsive release of GS in the bacterial environment. The in vitro studies proved that the smart hydrogels present good water absorption ability and excellent mechanical properties as well as good biocompatibility, which are necessary for their application in wound dressings. Moreover, the hydrogels showed obvious FRET transitions in both acidic buffer and bacteria solution. Upon irradiating the hydrogels with NIR light, UCNP were able to convert NIR light to UV light to trigger the release of GS from the hydrogels for antibacterial treatment. This research is expected to provide a new strategy for self-reporting and effective treatment of wound infection.

Development of Rhodamine 6G-Based Fluorescent Chemosensors for Al3+-Ion Detection: Effect of Ring Strain and Substituent in Enhancing Its Sensing Performance.

Four rhodamine 6G-based chemosensors (H3L1–H3L4) are designed for selective detection of Al3+ ion. They are characterized using various spectroscopic techniques and X-ray crystallography. All absorption and emission spectral studies have been performed in 10 mM N-(2-hydroxyethyl)piperazine-N′-ethanesulfonic acid (HEPES) buffer solution at pH 7.4 in H2O/MeOH (9:1, v/v) at 25 °C. In absorption spectra, chemosensors exhibit an intense band around 530 nm in the presence of Al3+ ion. Chemosensors (H3L1–H3L4) are nonfluorescent when excited around 490 nm. The presence of Al3+ ion enhances the emission intensity (555 nm) many times. The formation of complexes 1–4 is established with the aid of different spectroscopic techniques. The limit of detection value obtained in the nanomolar range confirms the high sensitivity of the probes toward Al3+ ion. It has been observed that the presence of aliphatic spacers in the diamine part and different halogen substituents in the salicylaldehyde part strongly influences the selectivity of the chemosensors toward Al3+ ion. The propensity of the chemosensors to identify intracellular Al3+ ions in triple-negative human breast cancer cell line MDA-MB-468 by fluorescence imaging is also examined in this study.

Improving Topical Skin Delivery of Monocrotaline Via Liposome Gel-based Nanosystems.

In this study, a liposomal gel based on a pH-gradient method was used to increase the skin-layer retention of monocrotaline (MCT) for topical administration. Using the Box-Behnken design, different formulations were designed to form liposome suspensions with optimal encapsulation efficiency (EE%) and stability factor (KE). In order to keep MCT in liposomes and accumulate in skin slowly and selectively, MCT liposome suspensions were engineered into gels. A pH-gradient method was used to prepare liposome suspensions. The optimal formulation of liposome suspensions (encapsulation efficiency: 83.10 ± 0.21%) was as follows: MCT 12 mg, soybean phosphatidyl choline (sbPC) 200 mg, cholesterol (CH) 41 mg, vitamin E (VE) 5 mg, and citric acid buffer solution (CBS) 4.0 10 mL (pH 7.0). The final formulation of liposomal gels consisted of 32 mL liposome suspensions, 4.76 mL deionized water, 0.40 g Carbopol-940, 1.6 g glycerol, 0.04 g methylparaben, and a suitable amount of triethanolamine for pH value adjustment. The results of in vitro drug release showed that MCT in liposomal gels could be released in 12 h constantly in physiological saline as a Ritger-Peppas model. Compared with plain MCT in gel form, liposomal MCT in gel had higher skin retention in vitro. In this study, liposomal gels were formed for greater skin retention of MCT. It is potentially beneficial for reducing toxicities of MCT by topical administration with liposomal gel.

Preclinical pharmacokinetics of M10 after intragastrical administration of M10-H and M10-Na in Wistar rats

As a myricetin derivative, M10 is a potent agent of anti-chronic colonic inflammation. It has better activity than myricetin in preventing azoxymethane/dextran sulfate sodium - induced ulcerative colitis. Here, we introduce a sensitive quantification method based on ultra performance liquid chromatography-tandem mass spectrometry for the determination of M10-H and M10-Na in Wistar rat plasma. Samples were treated with L - ascorbic acid and phosphate buffer solution to maintain stability and with acetonitrile to remove the proteins in the plasma. The supernatant was separated with BEH C18 column and eluted with ultrapure water and acetonitrile both containing 0.1% formic acid. The detection was performed by a triple quadrupole mass spectrometer with positive electrospray ionization mode in multiple reactive monitoring. This method was validated for the carryover effect, selectivity, accuracy, precision, matrix effect, stability, and recovery. A linear correlation was established between concentration and response by the calibration curves over 10–2000 ng·mL−1 (r > 0.99). This method was applied to a pharmacokinetic study of intragastrical administration of M10-H and M10-Na in Wistar rats. In addition, the relative bioavailability of M10-H to M10-Na in Wistar rats was 60 ± 19%, calculated by the ratio of area under concentration (AUC) of M10-H to M10-Na after intragastrical administration of a single dose (100 mg·kg−1 for M10-H and M10-Na, respectively) in Wistar rats.

Non-hybridization single nucleotide polymorphism detection and genotyping assay through direct discrimination of single base mutation by capillary electrophoretic separation of single-stranded DNA.

The significant demands for single nucleotide polymorphism detection and genotyping assays have grown. Most common assays are based on the recognition of the target sequence by the hybridization with its specific probe having the complementary sequence of the target. Herein, a simple, label-free, and economical non-hybridization assay was developed for single nucleotide polymorphism detection and genotyping, based on the direct discrimination of single base mutation by simple capillary electrophoresis separation for single-stranded DNA in an acidic electrophoretic buffer solution containing urea. Capillary electrophoresis separation of single-base sequential isomers of DNA was achieved due to charge differences resulting from the different protonation properties of the DNA bases. Single nucleotide polymorphism detection and genotyping were achieved by discriminating the electropherogram pattern change, that is, peak number in the electropherogram, obtained by the proposed method. The successful practical application of the proposed method was demonstrated through single nucleotide polymorphism detection and genotyping on a known gene region of 84-mer, in which guanine to adenine single-base mutation is commonly observed, using a human hair sample in combination with genomic DNA extraction, polymerase chain reaction amplification, DNA purification from polymerase chain reaction products, and capillary electrophoresis separation.

Molecular Recognition of Pyrophosphate with Extended Bis(Zn(II)-DPA) Derivatives.

A series of pyrophosphate (PPi) receptors were synthesized, and their binding affinities toward both PPi and adenosine triphosphate were evaluated in N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid-buffered solution. The presence of two hydrogen bond donors slightly retarded the reaction rate of anionic guest exchange, while four had a significant retardation effect. A macrocyclic receptor, 17, exhibited superior selectivity toward PPi compared with acyclic receptors, presumably due to effective steric interactions. Isothermal titration calorimetry experiments and potentiometric titration experiments revealed the effect of the substituent structure on the degree of anion guest stabilization and the deprotonation of water molecules bound to zinc(II) ions, as well as the guest binding thermodynamics.