Manufacture of Toman Fish Protein (Channa micropeltes) Isolate with Different pH Methods using Star Fruit (Averrhoa bilimbi) Acid

Toman fish (Channa micropeltes) is a type of freshwater fish that belongs to the genus Channa which is the largest size compared to the others and has high protein. This study aims to obtain the isolate of toman fish protein (Channa micropeltes) by the method of pH regulation using star fruit acid. Wuluh star fruit acid is used as a substitute for HCl in making fish protein isolates to reduce pH. This research method uses a Completely Randomized Design (CRD). The treatments consisted of (P1 = pH 4, P2 = pH 5, P3 = pH 6). The results showed that star fruit acid can replace HCl as a protein precipitant and P1 (pH 4) obtained the most isolates, namely an average protein content of 91.64% (db), a moisture content of 1.67%, ash content of 2.06 % (db), fat content of 2.74% (db), yield of 88.46%, and total amino acid composition of 61.30%, where the type of amino acid that dominates is glutamic acid (12.30%). Glutamic acid amino acid is the one that influences a lot in giving pH isoelectric point, in the treatment of P1 with pH 4 making isolates of toman fish protein to be the best treatment, because glutamic acid has an isoelectric point of 3.22 which is the closest to pH 4 plus also the pH of isoelectric point from other amino acids.

Expanded perlite: potential for removing antibiotics from water

This work aims to study the potential of expanded perlite (EP) for amoxicillin (AMX) removal in aqueous solution. For this purpose, chemical, morphological, and textural characteristics of the EP were evaluated, in addition to AMX removal by the adsorption process. The kinetic, isothermal, and thermodynamic parameters were also assessed. The EP presented an isoelectric point of 6.5 and a surface with hydroxyl bands, which favour the adsorption process. Air bubbles were sealed and randomly connected with each other, increasing the surface area relative to the adsorption sites. These non-porous or macro-porous sites demonstrate efficiency in the mechanisms of mass transfer. AMX removal was determined to be a pseudo-second-order process since the adsorption velocity was proportional to the square of the available adsorption sites and indicates heterogeneity in the surface interactions between the adsorbed molecules. Also, the interactions were considered multilayer for low concentrations and monolayer for high concentrations (Sips isotherm). The adsorption process was endothermic and utilised a physical adsorption mechanism. Considering that no modification treatment was applied to the EP, and due to its neutral isoelectric point, macropores, amorphous and dipole induction force (physical adsorption) characteristics, favourable affinity between EP and AMX was observed.

Virtual 2D mapping of the viral proteome reveals host-specific modality distribution of molecular weight and isoelectric point

A proteome-wide study of the virus kingdom based on 1.713 million protein sequences from 19,128 virus proteomes was conducted to construct an overall proteome map of the virus kingdom. Viral proteomes encode an average of 386.214 amino acids per protein with the variation in the number of protein-coding sequences being host-specific. The proteomes of viruses of fungi hosts (882.464) encoded the greatest number of amino acids, while the viral proteome of bacterial host (210.912) encoded the smallest number of amino acids. Viral proteomes were found to have a host-specific amino acid composition. Leu (8.556%) was the most abundant and Trp (1.274%) the least abundant amino acid in the collective proteome of viruses. Viruses were found to exhibit a host-dependent molecular weight and isoelectric point of encoded proteins. The isoelectric point (pI) of viral proteins was found in the acidic range, having an average pI of 6.89. However, the pI of viral proteins of algal (pI 7.08) and vertebrate (pI 7.09) hosts was in the basic range. The virtual 2D map of the viral proteome from different hosts exhibited host-dependent modalities. The virus proteome from algal hosts and archaea exhibited a bimodal distribution of molecular weight and pI, while the virus proteome of bacterial host exhibited a trimodal distribution, and the virus proteome of fungal, human, land plants, invertebrate, protozoa, and vertebrate hosts exhibited a unimodal distribution.

High Purity of α-Lactalbumin from Binary Protein Mixture by Charged UF Membrane Far from the Isoelectric Point to Limit Fouling

Separation and high recovery factor of proteins similar in molecular mass is a challenging task, and heavily studied in the literature. In this work, a systematic study to separate a binary protein mixture by charged ultrafiltration membranes without affecting membrane performance was carried out. α-lactalbumin (ALA, 14.4 kDa) and β-lactoglobulin (BLG, 18.4 kDa) were used as a binary model system. These two proteins are the main proteins of whey, a very well-known byproduct from the dairy industry. Initially, a systematic characterization of individual proteins was carried out to determine parameters (protein size and aggregation, zeta potential) which could influence their passage through a charged membrane. Then, the influence of operating parameters (such as initial protein concentration, pH, and critical pressure) on the UF process was investigated, so as to identify conditions that limit membrane fouling whilst maximizing protein recovery factor and purity. The study permitted to identify process conditions able to fully separate ALA from BLG, with high purity (95%) and recovery factor (80%), in a single UF step. Compared to studies reported in literature, here, the main approach used was to carry out a charged UF process far from proteins isoelectric point (pI) to limit protein aggregation and membrane fouling.

Influence of the isoelectric point of gelatin on its adsorption on nanosilica surface

The joint efforts of chemists, physicians and technologists conducting researches to create new medical sorbents and combined drugs based on nanosilica, which have not only a detoxifying effect, but also antibacterial, wound healing, hemostatic and other important properties. One of the stages of such a research is developing regulatory documentation. To control the quality of the sorbent, the method of point measurements is most often used, according to it, the amount of adsorption of the marker substance at the single point of the adsorption curve is determined. The suitability of sorbents based on nanosilicа for using is determined by the value of the adsorption capacity concerning to medical gelatin. No other requirements for the process of test adsorption of gelatin by the sorbent are given. although it is known that the adsorption of proteins depends on the pH of the solution. Its maximum value is reached at a pH value corresponding to the isoelectric point (pI) of the protein. Each protein can be characterized by its own isoelectric point. Domestic and foreign standards give only the value of “pH of aqueous solutions” of gelatin and do not contain the indicator “isoelectric point”. The aim of the work is to study the influence of the isoelectric point of gelatin on its adsorption on nanosilica surface at different pH to appreciate the suitability of conditions for determining the adsorption activity of medical sorbents based on nanosilica. The adsorption of three samples of gelatin was examined in the work: A – edible gelatin (pI = 4.3–4.8); B – that from the catalog “Merck” (pI = 4.3–4.8) and C – that from the catalog “Fluka” (pI = 7.5–7.7) on nanosilica surface in the pH range from 3 to 8. It has been shown that for samples A and B the dependence has a maximum at pH ~ 4.5–5; and for sample C, the adsorption increases monotonically with increasing pH. It was noted that at pH ~ 5 the adsorption values for all gelatin samples were approximately equal. The adsorption activity of nanosilica concerning to proteins determined from the isotherms and the method of point measurements is compared. It has been found that the adsorption value of gelatin A onto the nanosilica at Cinitial = 700 mg/100 ml is equal to the Aave value determined by the Langmuir isotherms. This fact verifies the applicability of the method of point measurements for nanosilica/gelatin system to characterize the pharmacological activity of nanosilica based sorbents.

EFFECT OF ELECTROLYTES ON ELECTROSURFACE PROPERTIES OF MICROCRYSTALLINE CELLU-LOSE PARTICLES

The electrical surface properties (specific surface charge of particles - σ0, point of zero charge – pHPZC, electrokinetic potential - ζ and position of isoelectric point - pHIEP) of dispersions of microcrystalline cellulose (MCC) in aqueous solutions of H2SO4, NaOH, Na2SO4 and TiOSO4 were investigated. Significant effects of specific adsorption of anions and cations on pHPZC and pHIEP have been demonstrated. The isoelectric point of the MCC particles in the H2SO4 solution is at pH 2.0, while the zero charge point in 5·10-4 M solution Na2SO4 at pH 5.6. An explanation of the observed effects is given. Possible schemes of the structure of the electrical double layer at different pH values, taking into account specific adsorption of ions in the Stern layer, are given. The introduction of TiOSO4 (10-5 mol/dm3) shifts the position of IEP to a less acidic region (pHIEP 4.5) due to the specific adsorption of positively charged TiOSO4 hydrolysis products particles.

Approaches to increasing the heat stability of whey proteins

В работе обобщаются новейшие теоретические подходы к регулированию термических реакций денатурации и агрегации сывороточных белков, включая физические, химические, ферментативные, а также комбинации различных методов. Описывается поведение модифицированных сывороточных белков во время термической обработки. Среди физических способов модификации приведены существующие технологии обработки сывороточных белков с использованием ультразвука, а также обработки белка под высоким давлением в сочетании с предварительным нагревом. В обзоре подчеркивается, что любая химическая модификация сывороточных белков осуществляется посредством нарушения структуры белка за счет блокирования свободных сульфгидрильных групп. Приводятся такие способы повышения термостойкости, как создание белково-полисахаридных комплексов, которые при pH, близких к изоэлектрической точке, проявляют характеристики псевдопластических жидкостей. В обзоре отмечается способность реакции гликирования также повышать термическую стойкость сывороточных белков. Подчеркивается перспективность ферментативной модификации сывороточных белков в пищевой промышленности, способствующей повышению как термостабильности, так и растворимости белков в кислых значениях pH из-за потери вторичной структуры. Отмечается возможность применения продуктов гидролиза, обладающих растворимостью вблизи изоэлектрической точки, в технологии напитков. Представляет интерес повышение эффективности ферментативного гидролиза сывороточных белков за счет фракционирования гидролизатов молочной сыворотки с использованием ультрафильтрации. Как следствие продукты фракционирования, а именно пермеат с низкомолекулярными пептидными фракциями, прогнозируемо являются потенциальными ингредиентами в технологии напитков. Практический интерес представляет производство термостойких напитков, содержащих высокий уровень сывороточных белков. The article summarizes the latest theoretical approaches to the regulation of thermal reactions of denaturation and aggregation of whey proteins, including physical, chemical, enzymatic, as well as combinations of various methods. Describes the behavior of modified whey proteins during heat treatment. Among the methods of physical modification, the existing technologies for processing whey proteins using ultrasound, as well as processing proteins under high pressure in combination with preheating are given. The review emphasizes that any chemical modification of whey proteins is carried out by disrupting the protein structure by blocking free sulfhydryl groups. Methods for increasing thermal stability are presented, such as the creation of protein-polysaccharide complexes that exhibit the characteristics of pseudoplastic fluids at a pH close to the isoelectric point. The review notes the ability of the glycation reaction to also increase the thermal stability of whey proteins. The prospects for enzymatic modification of whey proteins in the food industry are emphasized, which contribute to an increase in both thermal stability and solubility of proteins at acidic pH values due to the loss of secondary structure. The possibility of using hydrolysis products with a solubility close to the isoelectric point in the technology of beverage production is noted. It is of interest to increase the efficiency of enzymatic hydrolysis of whey proteins due to fractionation of whey hydrolysates using ultrafiltration. Fractionation products, namely permeate with low molecular weight peptide fractions, are predictable potential ingredients in beverage technology. Of practical interest is the production of heat-resistant drinks with a high content of whey proteins.

Isoelectric Point of Proteins at Hydrophobic Interfaces

Structural and colloidal stability of proteins at different surfaces and interfaces is of great importance in many fields including medical, pharmaceutical, or material science. Due to their flexibility, proteins tend to respond to their environmental conditions and can undergo structural and conformational changes. For instance, alterations in physiological factors such as temperature, ions concentration, or pH as well as the adsorption to an interface can initiate protein aggregation. Therefore, at different surfaces and interfaces the characterization of the structural and colloidal stability of proteins, which is mainly influenced by their electrostatic and hydrophobic interactions, is of fundamental importance. In this study, we utilized sum frequency generation (SFG) spectroscopy to assess the role of solution pH on the polarity and magnitude of the electric field within the hydration shell of selected model proteins adsorbed to a hydrophobic surface. We used polystyrene (PS) as a model hydrophobic surface and determined the isoelectric point (IEP) of four structurally different model proteins. Comparing the measured IEP of proteins at the PS/solution or air/solution interface with that determined in the bulk solution via zeta potential measurement, we found significant similarities between the IEP of surface adsorbed proteins and those in the bulk aqueous phase. The pH dependence behavior of proteins was correlated to their amino acid composition and degree of hydrophobicity.

Single-Particle Characterization of SARS-CoV-2 Isoelectric Point and Comparison to Variants of Interest

SARS-CoV-2, the cause of COVID-19, is a new, highly pathogenic coronavirus, which is the third coronavirus to emerge in the past 2 decades and the first to become a global pandemic. The virus has demonstrated itself to be extremely transmissible and deadly. Recent data suggest that a targeted approach is key to mitigating infectivity. Due to the proliferation of cataloged protein and nucleic acid sequences in databases, the function of the nucleic acid, and genetic encoded proteins, we make predictions by simply aligning sequences and exploring their homology. Thus, similar amino acid sequences in a protein usually confer similar biochemical function, even from distal or unrelated organisms. To understand viral transmission and adhesion, it is key to elucidate the structural, surface, and functional properties of each viral protein. This is typically first modeled in highly pathogenic species by exploring folding, hydrophobicity, and isoelectric point (IEP). Recent evidence from viral RNA sequence modeling and protein crystals have been inadequate, which prevent full understanding of the IEP and other viral properties of SARS-CoV-2. We have thus experimentally determined the IEP of SARS-CoV-2. Our findings suggest that for enveloped viruses, such as SARS-CoV-2, estimates of IEP by the amino acid sequence alone may be unreliable. We compared the experimental IEP of SARS-CoV-2 to variants of interest (VOIs) using their amino acid sequence, thus providing a qualitative comparison of the IEP of VOIs.

The Isoelectric Point of an Exotic Oxide: Tellurium (IV) Oxide

The pH-dependent surface charging of tellurium (IV) oxide has been studied. The isoelectric point (IEP) of tellurium (IV) oxide was determined by microelectrophoresis in various 1-1 electrolytes over a concentration range of 0.001–0.1 M. In all electrolytes studied and irrespective of their concentration the zeta potential of TeO2 was negative over the pH range 3–12. In other words the IEP of TeO2 is at pH below 3 (if any). TeO2 specifically adsorbs ionic surfactants, and their presence strongly affects the zeta potential. In contrast the effect of multivalent inorganic ions on the zeta potential of TeO2 is rather insignificant (no shift in the IEP). In this respect TeO2 is very different from metal oxides.