Nm For Acid Research Articles

Inhibition behavior of Tragia involucrata L. phenolic compounds against acidic medium corrosion in low carbon steel surface

Abstract The antioxidant and anticorrosive effect of Tragia involucrate L. (T. involucrate L.) was evaluated to aid in finding new compounds which can be used for various purposes. The total phenolic (TPC) and flavonoid content (TFC), antioxidant activity (DPPH, reducing potential and phosphomolybdenum), and electrochemical measurements, Fourier transform infrared (FT-IR), UV–visible (UV–vis) spectral analysis, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM–EDX) and atomic force microscopy (AFM) were done to analyze the potency and also the inhibition efficiency of T. involucrate L. against 1 mol·L−1 HCl on low carbon steel. The TPC (145.21 mg GAE·g−1), TFC (52.32 mg QCE·g−1) and antioxidant activities were found to be significant. The electrochemical studies performed by AC impedance measurements showed significant changes in impedance spectra without causing any change in Nyquist plots. An increase in charge transfer resistance (Rct) values, a blockage in active sites exhibiting cathodic and anodic inhibition shows the action of inhibitor on low carbon steel. This was later confirmed by FT-IR and UV–vis which showed variation in absorption band at 270 nm and 273 nm (before immersion) and 208 and 281 nm (after immersion). The same was tested again by SEM–EDX through altered strength of iron and oxygen bands and using AFM by analyzing the change in average roughness values of low carbon steel before (61.65 nm) and after (97.87 nm) exposure to blank acid without inhibitor, while it was shifted to 81.58 nm in acid with inhibitor. All these results showed strong evidence adding values to T. involucrate L. plant extract in inhibiting corrosion on low carbon steel and by promoting antioxidant importance of the extract which helps in scavenging free radicals.

A two-photon fluorescent probe records the intracellular pH through ‘OR’ logic operation via internal calibration

Mapping the intracellular location and concentration of hydronium ions (H3O+) and their dynamics could be a useful diagnostic tool in modern clinical science. Current needs motivated us to develop a molecular pH probe 1, operating as a logic gate, and its analogue 2. The pyridyl moiety in 1 played a significant role in proton capture and release, in acidic to alkaline pH environments. In contrast, 2 failed to show a similar spectroscopic behavior. 1 shows emission maximum at 450 nm that is independent on the pH, with excitation at 353 nm or 410 nm in acid and alkaline pH, respectively. 1 was employed to provide input-dependent (excitation wavelength) fluorescence images in a cellular milieu to detect pH changes in cellular organelles such as lysosomes and mitochondria. Furthermore, 1 provided information on the variation of the pH in the presence of cellular ROS. 1 was also found to enable the real-time monitoring of cell acidification due to nutrient starvation, which is closely associated with mitochondrial malfunction, fusion and mitophagy processes. We envision that in due course 1 can open up new research avenues in the diagnostic sector for validating the pH in the cellular milieu.

Study by cyclic voltammetry and potential-modulated reflectance spectroscopy of the electroadsorption of methanol and ethanol on a rhodium electrode in acid and alkaline media

The electroadsorption of methanol and ethanol on rhodium was studied by cyclic voltammetry, using a flow cell, and by potential-modulated reflectance spectroscopy (PMRS), a technique with which chemisorbed CO can be easily identified in situ. It was found that in alkaline medium and at an admission potential of 0.07 V, both methanol and ethanol physisorb on rhodium, a fact which apparently had not been reported before. The peak potential of electro-oxidation of these physisorbed alcohols coincides with that of hydrogen desorption, approximately 0.2 V vs. RHE. Dissociative chemisorption of methanol or ethanol on rhodium yields a chemisorbed species, probably CO, both in acid and alkaline media. The hydrogen coverage does not show the usual dependence on the chemisorbed residue upon increasing the admission potential of the alcohol: with increasing amounts of chemisorbed CO the hydrogen coverage does not decrease, or decreases less than expected. We attribute this behaviour to the production of molecular hydrogen at low admission potentials. The chemisorbed residue of the adsorption of methanol or ethanol on rhodium produces a maximum in the PMR spectrum, whose wavelength lies at 290–310 nm in acid, and at 283–328 nm in base, depending on the measurement potential and on previous potential excursions. These wavelength shifts could perhaps be due to differences in the CO coverage and/or the background PMR spectrum.

Study of the electrooxidation of carbon monoxide on rhodium in acid and alkaline media by UV - visible potential-modulated reflectance spectroscopy and cyclic voltammetry

The chemisorption of CO on a Rh electrode in 0.5 M HClO 4 and 1 M NaOH was studied by cyclic voltammetry and UV-Visible Potential-Modulated Reflectance Spectroscopy (PMRS). Electrooxidation of dissolved CO on Rh is negligible in acid. On the contrary, the stationary current in base reaches ∼- 1 5 of the diffusion-limited value. We report a voltammetric peak due to the oxidation of dissolved CO in base, which can be observed only for CO admission potentials < 0.1 V vs. RHE, and which precedes the sharp peak for oxidation of (chemisorbed and dissolved) CO. The potential of this sharp peak in base is independent of the admission potential up to E adm = 0.47 V, but for higher values the peak potential increases linearly with E adm, probably due to the formation of a rhodium oxide prior to CO admission. The amount of CO chemisorbed on Rh in base is independent of the presence on the electrode surface of a thick layer of electrochromic oxide previously grown by potential cycling, which we attribute to CO chemisorption continuing to take place on the unoxidized Rh surface. The PMR spectrum of Rh on which CO is chemisorbed shows a well-defined maximum, which appears at 265 and 295 nm in acid and base, respectively. This PMRS maximum is due to an electric field effect, since its height is independent of the modulation frequency, and grows linearly with the modulation amplitude. Reflectograms recorded at the wavelength of the PMRS maximum during a slow potential sweep prove conclusively that it originates in the chemisorbed CO. The PMRS maximum at 265 nm is attributed to linearly chemisorbed CO, and that at 295 nm to bridged CO.

In-situ spectroscopic study of the adsorption of carbon monoxide on a polycrystalline ruthenium electrode by EMIRS and PMRS

The adsorption of CO on polycrystalline ruthenium was studied by cyclic voltammetry and by in-situ infrared (EMIRS) and UV-visible (PMRS = potential-modulated reflectance spectroscopy) techniques both in 0.5 M HClO 4 and in 1 M NaOH. Hydrogen adsorption was blocked by chemisorbed CO in both media, as is usually observed. Steady-state currents of CO electro-oxidation were observed in acid but not in alkaline media. The lack of electrocatalytic activity in base was not due to poisoning by a chemisorbed species, but was attributed to the presence on the surface of an inactive ruthenium oxide. An EMIRS bipolar band was seen in CO-saturated solution at 2040 cm − in acid and at 1970 cm − in base. It was due to the stretching vibration of CO chemisorbed on Ru, in the linear and bridged form, respectively. Similarly, a PMRS maximum was observed at a wavelength of 265 nm in acid and 285 nm in base, which were also attributed to linear and bridged CO, respectively. At the wavelength of the maximum, the PMRS signal intensity increased linearly with the modulation amplitude, and changed little with the modulation frequency, which shows that the PMRS signal is an electric field effect.

The inhibitory effect of acetaminophen on the myeloperoxidase-induced antimicrobial system of the polymorphonuclear leukocyte

Acetaminophen binds via its acetamido side chain to purified myeloperoxidase in a pH-dependent manner and maximum binding occurred around pH6. The H 2O 2-dependent myeloperoxidase-catalysed polymerization products of acetaminophen had excitation maxima at 304 nm and 334 nm in acid and alkaline solutions, respectively, and an intense blue fluorescence maximum at 426 nm. Acetaminophen can compete effectively with Cl − as myeloperoxidase substrate and thus HOCl formation is suppressed while HOCl, nevertheless present, can be scavenged by the drug. In this way the microbicidal action of the myeloperoxidase- H 2O 2-Cl − system can be seriously limited in the presence of high concentrations of acetaminophen. To study the effect of acetaminophen on peptide bond splitting in the myeloperoxidase antimicrobial system, thyroglobulin was used as a model peptide. Peptide bond splitting was inhibited at acetaminophen concentrations below the accepted toxic range for plasma values.

Dibucaine fluorescence and lifetime in aqueous media as a function of pH.

Abstract— The absorption and fluorescence spectra and fluorescence lifetimes of the local anesthetic dibucaine (2‐butoxy‐N‐[2‐(diethylamino) ethyl]‐4‐quinoline carboxamide) are reported as a function of pH in aqueous media. The fluorescence emission maxima are at 400 nm in neutral solution, 397 nm in alkali, and 454 nm in acid. The fluorescence is strongest and has the longest lifetime in neutral solution; the quantum yields are 0.25, 0.033, and 0.032, and the lifetimes (determined by the phase shift method) are 3.29, 0.60, and 1.37 ns, for the neutral, alkaline, and acid solutions, respectively. The pKoi the tertiary amine group was determined by fluorescence intensity and lifetime measurements to be 8.95, and the pK of the aromatic nitrogen was found to be 1.80 ± 0.03 by absorption and fluorescence intensity measurements. Phase and modulation lifetimes differed in the manner expected for a two lifetime system in the pH titration range of the tertiary amine, but gave anomalous results in the titration range of the aromatic nitrogen.

Myeloperoxidase of human neutrophilic granulocytes as chlorinating enzyme.

Two pH‐dependent spectral forms of myeloperoxidase have been described. Their absorption maxima in the Soret region were at 432 nm and 426 nm for acid and neutral pH, respectively. Chloride exerts an influence on the spectrum of peroxidase, mainly in acidic medium. Dissociation constants for the myeloperoxidase chloride complex and Km values for chloride in the chlorination reaction catalyzed by myeloperoxidase were determined. It was found that the affinity of chloride ions to the enzyme decreases with an increase of pH.Catalytic activity of myeloperoxidase in the reaction of incorporation of 36Cl into aliphatic amino compounds such as taurine, β‐alanine, ethanolamine and diethanolamine was investigated. Primary amino groups were chlorinated to N‐mono‐ or dichloramines, depending on the pH of the medium. The method of determination of 36Cl‐labelled chlorocompounds in the presence of excess Na36Cl was described.The role of myeloperoxidase as chlorinating enzyme in the mechanism of the bactericidal effect on bacteria phagocytized by neutrophilic granulocytes is discussed.

Optical rotatory dispersion and circular dichroism. Part LXX. The circular dichroism of some less common amino-acids

C.d. curves have been recorded at pH 1 and at pH 6 for fifty-five of the less common amino-acids. In most cases positive carboxy-group Cotton effects are observed at about 200 nm in water and 208–210 nm in acid. These results confirm the absolute configuration Ls previously allotted to these compounds by other methods.