Soil pH is probably the single most informative measurement that can be made to determine soil characteristics. At a single glance, pH tells much more about a soil than merely indicating whether it is acidic or basic. For example, availability of essential nutrients and toxicity of other elements can be estimated because of their known relationship with pH. The term pH was "invented" by the Swedish scientist Sorensen (1909) in order to obtain more convenient numbers and the idea quickly caught on. Gillespie and Hurst (1918) seem to have been among the earliest to determine pH (or PH, as it was then called) electrometrically using a platinum-palladium blackhydrogen gas electrode, a calomel reference electrode and a fairly cumbersome potentiometer and galvanometer system. At that period, it was still much more common to use colorimetric methods with indicator dyes than the electrometric method. This changed rapidly, however. Sharp and Hoagland (1919) used a similar but less involved method than Gillespie and Hurst (1918) and Healy and Karraker (1922) used a commercially available platinum-hydrogen gas electrode, potentiometer and galvanometer which had been designed by Clark (1920). The decade of the 1920s saw the development of the quinhydrone electrode which was less fragile and much less expensive than the hydrogen-platinum electrode. But, it was the development of the glass electrode in the 1930s that brought the determination of pH very rapidly to its present importance and convenience. The Beckman Model G pH meter (circa 1931) was practically indestructible and could be used as a portable as well as a laboratory instrument. Although it was cumbersome by today's standards, it was virtually foolproof (except for the constantly failing batteries) and many are still capable of operating if not actually operating today. As recently as two decades ago, the use of the small, handheld portable pH meters then available to determine pH in the field was a very imprecise and hazardous undertaking because both electrodes and meters were subject to sudden failures but this has changed rather abruptly in the last few years. Microcircuitry and plastic have contributed to rugged pH meters and electrodes that withstand
Higor V. M. Ferreira, Nelson H. T. Lemes, Yara L. Coelho
et al.
The application of surface plasmon resonance (SPR) has transformed the field of study of interactions between a ligand immobilized on the surface of a sensor chip, designated as $L_S$, and an analyte in solution, referred to as $A$. This technique enables the real-time measurement of interactions with high sensitivity. The dynamics of adsorption-desorption process, $A+L_S \rightarrow AL_S$, can be expressed mathematically as a set of coupled integer-order differential equations. However, this approach has limited ability to acoount for temperature distribution, diffusion and transport effects involved in the reaction process. The fractional kinetic model provides a methodology for incorporating non-local effects into the problem. In this study, the proposed model was applied to analyze data to the interaction between Immobilized Baru Protein (IBP) and Congo Red dye (CR) at concentrations ranging from $7.5$ to $97.5$ $μM$, at pH $7.4$ and $16^o$ C. The variation in the kinetic constants was studied, and it was demonstrated that the integer-order model is unable to adequately represent the experimental data. This work has shown that the fractional-order model is capable of capturing the complexity of the adsorption-desorption process involved in the SPR data.
Tiziana Mancini, Nicole Luchetti, Salvatore Macis
et al.
The SARS-CoV-2 pandemic has led to a significant emergence of highly mutated forms of viruses with a great ability to adapt to the human host. Some mutations resulted in changes in the amino acid sequences of viral proteins, including the Spike glycoproteins, affecting protein physico-chemical properties and functionalities. Here, we propose, for the first time to the best of our knowledge, a systematic and comparative study of the monomeric spike protein subunits 1 of three SARS-CoV-2 variants at pH 7.4, combining both an experimental approach, taking advantage of Attenuated Total Reflection Infrared and Circular Dichroism spectroscopies, and a computational approach via Molecular Dynamics simulations. Experimental data in combination with Molecular Dynamics and Surface polarity calculations provide a comprehensive understanding of variants proteins in terms of their secondary structure content, 3D conformational structure and order and interaction with the solvent. The present structural investigation clarifies which kind of changes in conformation and functionalities occurred as long as mutations appeared in amino acids sequences. This information is essential for preventive targeted actions, drug design, and biosensing applications.
Microbially Induced Carbonate Precipitation (MICP) is a biocementation technique that modifies the hydraulic and mechanical properties of porous materials using bacterial solutions. This study evaluates the efficiency of various MICP protocols under different environmental conditions, utilizing two bacterial strains: S. pasteurii and S. aquimarina, to optimize soil strength. Results indicate that bacterial strain and cementation solution concentration significantly affect biochemical outcomes, while temperature is the primary environmental factor. The efficiency of S. pasteurii's chemical conversion ranged from 40% to 80%, compared to only about 20% for S. aquimarina. MICP treatment with S. pasteurii produced CaCO3 content between 5% and 7%, whereas S. aquimarina yielded 0.5% to 1.5%. An optimized cementation solution concentration of 0.5 M was critical for maximum efficiency. The ideal operational temperature is between 20 and 35C, with salinity and oxygen levels having minimal effects. Although salinity influences carbonate crystal characteristics, its impact on Unconfined Compressive Strength (UCS) of treated soil is minor. Samples from a one-phase treatment at pH 6.0 to 7.5 showed UCS strength approximately half that of a two phase treatment. These findings suggest promising applications for MICP in enhancing strength in both terrestrial and marine environments.
Jingfang Shangguan, Dinggeng He, Xiaoxiao He
et al.
Measuring pH in living cells is of great importance for better understanding cellular functions as well as providing pivotal assistance for early diagnosis of diseases. In this work, we report the first use of a novel kind of label-free carbon dots for intracellular ratiometric fluorescence pH sensing. By simple one-pot hydrothermal treatment of citric acid and basic fuchsin, the carbon dots showing dual emission bands at 475 and 545 nm under single-wavelength excitation were synthesized. It is demonstrated that the fluorescence intensities of the as-synthesized carbon dots at the two emissions are pH-sensitive simultaneously. The intensity ratio (I475 nm/I545 nm) is linear against pH values from 5.2 to 8.8 in buffer solution, affording the capability as ratiometric probes for intracellular pH sensing. It also displays that the carbon dots show excellent reversibility and photostability in pH measurements. With this nanoprobe, quantitative fluorescence imaging using the ratio of two emissions (I475 nm/I545 nm) for the detection of intracellular pH were successfully applied in HeLa cells. In contrast to most of the reported nanomaterials-based ratiometric pH sensors which rely on the attachment of additional dyes, these carbon-dots-based ratiometric probes are low in toxicity, easy to synthesize, and free from labels.
Evgeniya Usenko, Alexander Glamazda, Anastasiia Svidzerska
et al.
TiO$_{2}$ nanoparticles (NPs) have unique photocatalytic properties, which are used in food industries, medicine, biosensorics, and solar energy conversion. Since the toxic properties of TiO$_{2}$ NPs have been insufficiently studied, additional information on the molecular mechanisms of their biological action on the structure and stability of biological macromolecules is needed, especially concerning DNA. In this work exploiting the differential UV-visible spectroscopy, the effect of the heating (from 20 till 90 $^0$C) and concentration of TiO$_{2}$ NPs ((1-3)$\times$10$^-$$^4$ M) on a conformation of native DNA adsorbed on TiO$_{2}$ NPs in a buffer solution (pH 5) is studied. Analysis of dynamic light scattering (DLS) data for the DNA:TiO$_{2}$ NPs suspension revealed that when the temperature increases the separated DNA:TiO$_{2}$ NP nanoassemblies form nanoaggregates. Correlation between the thermal dependency of the DLS data and thermal DNA denaturation measurements indicated that the appearance of the single-stranded unwound regions in double-stranded DNA in the suspension with temperature rise promotes the effective formation of the DNA:TiO$_{2}$ NPs nanoaggregates.
The microflora condition in the small intestine of weaning rabbits hasn’t developed yet. The use of acidifiers in rabbit feed aims to suppress harmful microorganisms and digestive disorders, especially in weaning rabbits. This research used different levels of acidifier as feed additives for weaning rabbits given on pellet feed. The acidifier addition level was control (T0), 0.1% (T1), 0.2% (T2) and 0.3% (T3). The parameter measured was the pH of the different parts of the small intestine. The research used 64 weaning rabbits (35 days old) which were kept for 6 weeks. Parameter measured was the pH of the parts of the small intestine consisting of the duodenum, jejunum and ileum. This research used a randomized group design with 4 treatments and 8 replications. The results showed that the addition of acidifiers had no significant difference effect (P>0.05) on pH of the duodenum and ileum, but there was a trend to decrease pH in all parts of intestine. While, the effect of acidifiers showed significant differences (P<0.05) on pH of jejunum. The conclusion is that the use of acidifier with a level of 0.3% gives the best effect to decrease of intestine pH of New Zealand White Rabbits.