Mechanistic insights into protein precipitation by alcohol

Boosting antigen-specific T cell activation with lipid-stabilized protein nanoaggregates

Vaccines based on protein antigens have numerous advantages over inactivated pathogens, including easier manufacturing and improved safety. However, purified antigens are weakly immunogenic, as they lack the spatial organization and the associated 'danger signals' of the pathogen. Formulating vaccines as nanoparticles enhances the recognition by antigen presenting cells, boosting the cell-mediated immune response. This study describes a nano-precipitation method to obtain stable protein nanoaggregates with uniform size distribution without using covalent cross-linkers. Nanoaggregates were formed via microfluidic mixing of ovalbumin (OVA) and lipids in the presence of high methanol concentrations. A purification protocol was set up to separate the nanoaggregates from OVA and liposomes, obtained as byproducts of the mixing. The nanoaggregates were characterized in terms of morphology, ζ-potential and protein content, and their interaction with immune cells was assessed in vitro. Antigen-specific T cell activation was over 6-fold higher for nanoaggregates compared to OVA, due in part to the enhanced uptake by immune cells. Lastly, a two-dose immunization with nanoaggregates in mice induced a significant increase in OVA-specific CD8+ T splenocytes compared to soluble OVA. Overall, this work presents for the first time the microfluidic production of lipid-stabilized protein nanoaggregates and provides a proof-of-concept of their potential for vaccination.

Pulsed Electric Field-Assisted Extraction of Inulin from Ecuadorian Cabuya (Agave americana)

Inulin is a carbohydrate that belongs to fructans; due to its health benefits, it is widely used in the food and pharmaceutical industries. In this research, cabuya (Agave americana) was employed to obtain inulin by pulsed electric field-assisted extraction (PEFAE) and FTIR analysis confirmed its presence. The influence of PEFAE operating parameters, namely, electric field strength (1, 3 and 5 kV/cm), pulse duration (0.1, 0.2 and 0.5 ms), number of pulses (10,000, 20,000 and 40,000) and work cycle (20, 50 and 80%) on the permeabilization index and energy expenditure were tested. Also, once the operating conditions for PEFAE were set, the temperature for conventional extraction (CE) and PEFAE were defined by comparing extraction kinetics. The cabuya meristem slices were exposed to PEFAE to obtain extracts that were quantified, purified and concentrated. The inulin was isolated by fractional precipitation with ethanol to be characterized. The highest permeabilization index and the lowest energy consumption were reached at 5 kV/cm, 0.5 ms, 10,000 pulses and 20%. The same extraction yield and approximately the same amount of inulin were obtained by PEFAE at 60 °C compared to CE at 80 °C. Despite, the lower amount of inulin obtained by PEFAE in comparison to CE, its quality was better because it is mainly constituted of inulin of high average polymerization degree with more than 38 fructose units. In addition, TGA analyses showed that inulin obtained by PEFAE has a lower thermal degradation rate than the obtained by CE and to the standard.

Optimization of High-Activity earthworm fibrinolytic enzyme extraction methods and protein component analysis

OBJECTIVE

Optimize the extraction process of earthworm fibrinolytic enzyme.

METHODS

Chinese common earthworms underwent a series of purification processes, including grinding, salting out, hydrophobic medium chromatography, ammonium sulfate precipitation, and ion exchange chromatography, to obtain purified earthworm fibrinolytic enzyme.

RESULTS

Utilizing Pheretima aspergillum as the starting material, we discovered that the specific activity of lumbrokinase extracted via ammonium sulfate precipitation was 58 U/mg, noticeably surpassing that achieved through heat precipitation and ethanol precipitation methods. After undergoing two rounds of chromatographic separations employing hydrophobic affinity chromatography and anion exchange chromatography, the specific activity of the lumbrokinase protein soared to 9267 U/mg, significantly exceeding the 3,178 U/mg specific activity attained through industrial extraction methods.

DISCUSSION

The development of a novel crude extraction method for lumbrokinase protein can significantly boost its activity and purity. The discovery of a high-efficiency purification method and the identification of protein components within highly active lumbrokinase pave the way for further investigations into these proteins.

Evaluation of Chemical and Physical Triggers for Enhanced Photosynthetic Glycerol Production in Different Dunaliella Isolates

The salt-tolerant marine microalgae Dunaliella tertiolecta is reported to generate significant amounts of intracellular glycerol as an osmoprotectant under high salt conditions. This study highlights the phylogenetic distribution and comparative glycerol biosynthesis of seven new Dunaliella isolates compared to a D. tertiolecta reference strain. Phylogenetic analysis indicates that all Dunaliella isolates are newly discovered and do not relate to the D. tertiolecta reference. Several studies have identified light color and intensity and salt concentration alone as the most inducing factors impacting glycerol productivity. This study aims to optimize glycerol production by investigating these described factors singularly and in combination to improve the glycerol product titer. Glycerol production data indicate that cultivation with white light of an intensity between 500 and 2000 μmol m-2 s-1 as opposed to 100 μmol m-2 s-1 achieves higher biomass and thereby higher glycerol titers for all our tested Dunaliella strains. Moreover, applying higher light intensity in a cultivation of 1.5 M NaCl and an increase to 3 M NaCl resulted in hyperosmotic stress conditions, providing the highest glycerol titer. Under these optimal light intensity and salt conditions, the glycerol titer of D. tertiolecta could be doubled to 0.79 mg mL-1 in comparison to 100 μmol m-2 s-1 and salt stress to 2 M NaCl, and was higher compared to singularly optimized conditions. Furthermore, under the same conditions, glycerol extracts from new Dunaliella isolates did provide up to 0.94 mg mL-1. This highly pure algae-glycerol obtained under optimal production conditions can find widespread applications, e.g., in the pharmaceutical industry or the production of sustainable carbon fibers.

Cross-linked enzyme aggregates of polyethylene terephthalate hydrolyse (PETase) from Ideonella sakaiensis for the improvement of plastic degradation

Polyethylene terephthalate (PET) is one of the most produced plastics globally and its accumulation in the environment causes harm to the ecosystem. Polyethylene terephthalate hydrolyse (PETase) is an enzyme that can degrade PET into its monomers. However, free PETase lacks operational stabilities and is not reusable. In this study, development of cross-linked enzyme aggregate (CLEA) of PETase using amylopectin (Amy) as cross-linker was introduced to solve the limitations of free PETase. PETase-Amy-CLEA exhibited activity recovery of 81.9 % at its best immobilization condition. Furthermore, PETase-Amy-CLEA exhibited 1.37-, 2.75-, 2.28- and 1.36-fold higher half-lives than free PETase at 50 °C, 45 °C, 40 °C and 35 °C respectively. Moreover, PETase-Amy-CLEA showed broader pH stability from pH 5 to 10 and could be reused up to 5 cycles. PETase-Amy-CLEA retained >70 % of initial activity after 40 days of storage at 4 °C. In addition, lower Km of PETase-Amy-CLEA indicated better substrate affinity than free enzyme. PETase-Amy-CLEA corroded PET better and products yielded was 66.7 % higher than free PETase after 32 h of treatment. Hence, the enhanced operational stabilities, storage stability, reusability and plastic degradation ability are believed to make PETase-Amy-CLEA a promising biocatalyst in plastic degradation.

N-acetyl amino acid amide solubility in aqueous 1,6-hexanediol solutions: Insights into the protein droplet deformation mechanism

Proteinaceous liquid droplets, generated by liquid-liquid phase separation, function as membraneless compartments that are essential for diverse biological functions. Studies addressing droplet generation have used 1,6-hexanediol (1,6-HD) as a droplet-discerning agent owing to its capacity to induce droplet deformation. Despite the empirical utility of 1,6-HD, the mechanism underlying 1,6-HD-induced droplet deformation remains unknown. In this study, the solubilities of N-acetyl amino acid amides, which correspond to proteinogenic amino acid residues, were examined in the presence of 1,6-HD at 25 °C. Other solvents included ethanol, 1-propanol, and amides. Remarkably, 1,6-HD effectively solubilized hydrophobic species (particularly aromatic species) and exhibited reduced efficacy in solubilizing hydrophilic species and peptide bond moieties. These solubilizing effects are reflected in changes in protein solubility and structure. Specifically, 1,6-HD primarily targets the hydrophobic regions of a protein, increasing protein solubility without causing substantial structural changes. This solubilization mechanism is essential for elucidating the role of 1,6-HD as a droplet-discerning agent and recognizing its potential limitations.

Development of a Highly Selective NAD+ -Dependent Glyceraldehyde Dehydrogenase and its Application in Minimal Cell-Free Enzyme Cascades

Anthropogenic climate change has been caused by over-exploitation of fossil fuels and CO2 emissions. To counteract this, the chemical industry has shifted its focus to sustainable chemical production and the valorization of renewable resources. However, the biggest challenges in biomanufacturing are technical efficiency and profitability. In our minimal cell-free enzyme cascade generating pyruvate as the central intermediate, the NAD+ -dependent, selective oxidation of D-glyceraldehyde was identified as a key reaction step to improve the overall cascade flux. Successive genome mining identified one candidate enzyme with 24-fold enhanced activity and another whose stability is unaffected in 10 % (v/v) ethanol, the final product of our model cascade. Semi-rational engineering improved the substrate selectivity of the enzyme up to 21-fold, thus minimizing side reactions in the one-pot enzyme cascade. The final biotransformation of D-glucose showed a continuous linear production of ethanol (via pyruvate) to a final titer of 4.9 % (v/v) with a molar product yield of 98.7 %. Due to the central role of pyruvate in diverse biotransformations, the optimized production module has great potential for broad biomanufacturing applications.

Identification, Biochemical Characterization, and In Vivo Detection of a Zn-Metalloprotease with Collagenase Activity from Mannheimia haemolytica A2

Respiratory diseases in ruminants are a main cause of economic losses to farmers worldwide. Approximately 25% of ruminants experience at least one episode of respiratory disease during the first year of life. Mannheimia haemolytica is the main etiological bacterial agent in the ruminant respiratory disease complex. M. haemolytica can secrete several virulence factors, such as leukotoxin, lipopolysaccharide, and proteases, that can be targeted to treat infections. At present, little information has been reported on the secretion of M. haemolytica A2 proteases and their host protein targets. Here, we obtained evidence that M. haemolytica A2 proteases promote the degradation of hemoglobin, holo-lactoferrin, albumin, and fibrinogen. Additionally, we performed biochemical characterization for a specific 110 kDa Zn-dependent metalloprotease (110-Mh metalloprotease). This metalloprotease was purified through ion exchange chromatography and characterized using denaturing and chaotropic agents and through zymography assays. Furthermore, mass spectrometry identification and 3D modeling were performed. Then, antibodies against the 110 kDa-Mh metalloprotease were produced, which achieved great inhibition of proteolytic activity. Finally, the antibodies were used to perform immunohistochemical tests on postmortem lung samples from sheep with suggestive histology data of pneumonic mannheimiosis. Taken together, our results strongly suggest that the 110-Mh metalloprotease participates as a virulence mechanism that promotes damage to host tissues.

Formulation of Edible Coatings from Alfalfa Saponins to Enhance the Postharvest Quality of Tomatoes

Tomatoes are a major crop for global exports and have significant nutritional benefits. However, their lifespan is limited due to various biotic and abiotic factors. This study aimed to formulate an edible coating using crude alfalfa saponins coupled with decaglycerol monolaurate (ML-750) and polyoxyethylene (20) sorbitan monolaurate (Tween 20), to enhance the postharvest quality and shelf life of tomatoes by preventing spoilage. The effectiveness of alfalfa saponins coatings, both alone, and with ML-750 and Tween 20, was evaluated by comparing their impact on color, texture, overall acceptability, and % weight loss at 4°C and 25°C for 7 days. Significant improvements were observed in the quality attributes of tomatoes, including firmness, aroma, color, texture, and overall acceptability. Crude alfalfa saponins in emulsified form with Tween 20 increased the shelf stability of tomatoes more effectively than uncoated and ML-750 combined coatings. The total soluble solids (TSS) and pH also play a crucial role in determining the quality of the fruits. The results indicated no significant changes in the TSS of tomatoes coated with encapsulated saponins. Subsequently, a gradual increase in the pH of the coated tomatoes was observed on days 5 and 7, respectively. The findings of this study revealed that alfalfa saponins coupled with synthetic emulsifiers may be a beneficial strategy for prolonging the shelf life and improving the postharvest quality of tomatoes.

Bacteriocin Production by Bacillus Species: Isolation, Characterization, and Application

Antibiotic resistance is a problem that has been increasing lately; therefore, it is important to find new alternatives to treat infections induced by pathogens that cannot be eliminated with available products. Small antimicrobial peptides (AMPs) known as bacteriocin could be an alternative to antibiotics because they have shown to be effective against a great number of multidrug-resistant microbes. In addition to its high specificity against microbial pathogens and its low cytotoxicity against human cells, most bacteriocin present tolerance to enzyme degradation and stability to temperature and pH alterations. Bacteriocins are small peptides with a great diversity of structures and functions; however, their mechanisms of action are still not well understood. In this review, bacteriocin produced by Bacillus species will be described, especially its mechanisms of action, culture conditions used to improve its production and state-of-the-art methodologies applied to identify them. Bacteriocin utilization as food preservatives and as new molecules to treat cancer also will be discussed.

Characteristics of the enzyme-induced release of bitter peptides from wheat gluten hydrolysates

Bitter peptides in the enzymatic hydrolysates were prepared and purified from wheat gluten using aqueous ethanol solutions and macroporous resin, which has opened a new road for the extraction and separation of bitter peptides. This report contains the release regularity of bitter peptides and the factors affecting the change of bitter intensity during enzymatic hydrolysis, providing a scientific basis for the research on debitterizing method. In this study, the effects of different degrees of hydrolysis (DH) and enzyme active sites on the bitter peptide content and bitter taste thresholds were discussed. The relationship between amino acid composition, molecular weight distribution, surface hydrophobicity and bitter taste thresholds was extensively researched. The results showed the exposure of hydrophobic amino acids and the bitterness intensity of the hydrolysates increased as the DH increased, and the bitterness of wheat gluten hydrolysates (WGHs) hydrolyzed by Alcalase was stronger than that of Trypsin. According to correlation analysis, the proportion of total hydrophobic amino acid is the first factor that affects the sensory properties of bitter peptide, and the release content of bitter peptides and the content of total bitter amino acids are the second, following by the content of peptide in the molecular weight range of 500–1,000 Da and the surface hydrophobicity. The amino acid sequence of bitter peptides from WGHs were identified and predicted using high performance liquid chromatography-mass spectrometry (HPLC-MS/MS) and bioinformatics. It was found that the molecular weight of most of the peptides was below 1,500 Da, and the Q value was higher than 5.86 kJ/mol.

A Rapid and Universal Workflow for Label-Free-Quantitation-Based Proteomic and Phosphoproteomic Studies in Cereals

Proteomics and phosphoproteomics are robust tools to analyze dynamics of post-transcriptional processes during growth and development. A variety of experimental methods and workflows have been published, but most of them were developed for model plants and have not been adapted to high-throughput platforms. Here, we describe an experimental workflow for proteome and phosphoproteome studies tailored to cereal crop tissues. The workflow consists of two parallel parts that are suitable for analyzing protein/phosphoprotein from total proteins and the microsomal membrane fraction. We present phosphoproteomic data regarding quantification coverage and analytical reproducibility for example preparations from maize root and shoot, wheat leaf, and a microsomal protein preparation from maize leaf. To enable users to adjust for tissue specific requirements, we provide two different methods of protein clean-up: traditional ethanol precipitation (PC) and a recently developed technology termed single-pot, solid-phase-enhanced sample preparation (SP3). Both the PC and SP3 methods are effective in the removal of unwanted substances in total protein crude extracts. In addition, two different methods of phosphopeptide enrichment are presented: a TiO₂ -based method and Fe(III)-NTA cartridges on a robotized platform. Although the overall number of phosphopeptides is stable across protein clean-up and phosphopeptide enrichment methods, there are differences in the preferred phosphopeptides in each enrichment method. The preferred protocol depends on laboratory capabilities and research objective. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Total protein crude extraction Basic Protocol 2: Total protein clean-up with ethanol precipitation Alternate Protocol 1: Total protein clean-up with SP3 method Basic Protocol 3: Microsomal fraction protein extraction Basic Protocol 4: Protein concentration determination by Bradford assay Basic Protocol 5: In-solution digestion with trypsin Basic Protocol 6: Phosphopeptide enrichment with TiO₂ Alternate Protocol 2: Phosphopeptide enrichment with Fe(III)-NTA cartridges Basic Protocol 7: Peptide desalting with C₁₈ material Basic Protocol 8: LC-MS/MS analysis of (phospho)peptides and spectrum matching.

Rapid Detection of Gram-Positive and -Negative Bacteria in Water Samples Using Mannan-Binding Lectin-Based Visual Biosensor

Waterborne bacterial infection is a health threat worldwide, making accurate and timely bacteria detection crucial to prevent waterborne disease outbreaks. Inspired by the intrinsic capability of mannan-binding lectin (MBL) in recognizing the pathogen-associated molecular patterns (PAMPs), a visual biosensor is developed here for the on-site detection of both Gram-positive and -negative bacteria. The biosensor was synthesized by immobilization of the MBL protein onto the blue carboxyl-functionalized polystyrene microparticles (PSM), which is then used in a two-step assay to detect bacterial cells in water samples. The first step involved a 20 min incubation following the MBL-PSM and calcium chloride solution addition to the samples. The second step was to add ethanol to the resultant blue mixture and observe the color change with the naked eye after 15 min. The biosensor had a binary (all-or-none) response, which in the presence of bacterial cells kept its blue color, while in their absence the color changed from blue to colorless. Testing the water samples spiked with four Gram-negative bacteria including Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa and two Gram-positive bacteria of Enterococcus faecalis and Staphylococcus aureus showed that the biosensor could detect all tested bacteria with a concentration as low as 10^1.5 CFU/ml. The performance of biosensor using the water samples from a water treatment plant also confirmed its capability to detect the pathogens in real-life water samples without the need for instrumentation.

Structural changes and exposed amino acids of ethanol-modified whey proteins isolates promote its antioxidant potential

Whey protein isolates (WPI) were treated with different ethanol level (20, 40, 60, and 80%, v/v) to promote structural unfolding and subsequent aggregation. In general, protein aggregation gradually increased with increasing ethanol level in a dose-dependent manner, which was implied by notably increased turbidity and gradually decreased solubility. The formation of aggregates, which were confirmed by the results of circular dichroism spectrum and total sulfhydryl content, were promoted mainly through disulfide bonds and intra-molecular hydrogen bonds. Moreover, ethanol treated WPI (E-WPI) had significantly enhanced antioxidant activities over native WPI, which was mainly attribute to the higher contents of specific amino acids (such as hydrophobic amino acids, aromatic amino acids, and sulfur-containing amino acids), and E-WPI prepared with moderate ethanol concentration (40% in our present study) exhibited the highest antioxidant activities. These results reveal that antioxidant activities of WPI can be increased by ethanol treatment and are possibly achieved through molecular unfolding of native WPI.

•

Ethanol treatment caused unfolding and aggregation of whey protein isolate (WPI).

•

Aggregation enhanced with increasing ethanol concentration (EC).

•

Medium EC (40%, v/v) rendered the highest antioxidant activities of WPI.

Effect of different dehydration methods on the properties of gelatin films

The properties of gelatin film fabricated by ethanol precipitation effect dehydration, Hofmeister effect dehydration and hot air drying dehydration were investigated. The results revealed that the mechanical properties were significantly improved by ethanol precipitation and Hofmeister effect. The tensile strength and elongation at break of the film prepared by ethanol precipitation were increased by 83.28% (20% gelatin concentration) and 122.42% (5% gelatin concentration) respectively compared with that of hot air-dried gelatin film. The water contact angle was increased and water solubility was reduced by ethanol precipitation, which could attribute to the formation of compact structure, more triple helix content, and non-covalent interactions. However, the water contact angle of Hofmeister effect fabricated films was decreased compared with that of hot air drying owing to the adhesion of ammonium sulfate. Moreover, ethanol precipitation effect improved the color difference and opacity due to the ethanol decolorization effect.

Skin irritation and potential antioxidant, anti-collagenase, and anti-elastase activities of edible insect extracts

This study aimed to investigate antioxidant, anti-aging, and irritation properties of Thai edible insect extracts, including Bombyx mori, Omphisa fuscidentalis, Euconocephalus sp., Patanga succincta, Acheta domesticus, and Lethocerus indicus. Insects were extracted by 2 different methods, including maceration using ethanol or hexane and digestion using DI water. Then the extracts were determined for protein content using bicinchoninic acid assay and antioxidant activities using 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl, ferric reducing antioxidant power, and ferric thiocyanate assays. Anti-aging activities were investigated by determination of collagenase and elastase inhibitory activities using spectrophotometric assay. Maceration by hexane yielded the highest extract content, whereas aqueous extract from digestion possessed the significantly highest protein content and biological activities (p < 0.05). Interestingly, aqueous extracts of A. domesticus possessed the significantly highest biological activities (p < 0.05) with Trolox equivalent antioxidant capacity value of 8.8 ± 0.1 mmol Trolox/mg, DPPH^· inhibition of 19.5 ± 3.8%, equivalent concentration of 12.1 ± 0.7 µM FeSO₄/mg, lipid peroxidation inhibition of 31.3 ± 2.4%, collagenase inhibition of 60.8 ± 2.1%, elastase inhibition of 17.0 ± 0.1%, and no irritation effect on chorioallantoic membrane and volunteers. Therefore, aqueous extract of A. domesticus would be suggested for further topical product development.

Interactions in protein solutions close to liquid-liquid phase separation: ethanol reduces attractions via changes of the dielectric solution properties

Ethanol is a common protein crystallization agent, precipitant, and denaturant, but also alters the dielectric properties of solutions. While ethanol-induced unfolding is largely ascribed to its hydrophobic parts, its effect on protein phase separation and inter-protein interactions remains poorly understood. Here, the effects of ethanol and NaCl on the phase behavior and interactions of protein solutions are studied in terms of the metastable liquid-liquid phase separation (LLPS) and the second virial coefficient B₂ using lysozyme solutions. Determination of the phase diagrams shows that the cloud-point temperatures are reduced and raised by the addition of ethanol and salt, respectively. The observed trends can be explained using the extended law of corresponding states as changes of B₂. The results for B₂ agree quantitatively with those of static light scattering and small-angle X-ray scattering experiments. Furthermore, B₂ values calculated based on inter-protein interactions described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential and considering the dielectric solution properties and electrostatic screening due to the ethanol and salt content quantitatively agree with the experimentally observed B₂ values.

Biochemical Characterization of Cassiopea andromeda (Forsskål, 1775), Another Red Sea Jellyfish in the Western Mediterranean Sea

Increasing frequency of native jellyfish proliferations and massive appearance of non-indigenous jellyfish species recently concur to impact Mediterranean coastal ecosystems and human activities at sea. Nonetheless, jellyfish biomass may represent an exploitable novel resource to coastal communities, with reference to its potential use in the pharmaceutical, nutritional, and nutraceutical Blue Growth sectors. The zooxanthellate jellyfish Cassiopea andromeda, Forsskål, 1775 (Cnidaria, Rhizostomeae) entered the Levant Sea through the Suez Canal and spread towards the Western Mediterranean to reach Malta, Tunisia, and recently also the Italian coasts. Here we report on the biochemical characterization and antioxidant activity of C. andromeda specimens with a discussion on their relative biological activities. The biochemical characterization of the aqueous (PBS) and hydroalcoholic (80% ethanol) soluble components of C. andromeda were performed for whole jellyfish, as well as separately for umbrella and oral arms. The insoluble components were hydrolyzed by sequential enzymatic digestion with pepsin and collagenase. The composition and antioxidant activity of the insoluble and enzymatically digestible fractions were not affected by the pre-extraction types, resulting into collagen- and non-collagen-derived peptides with antioxidant activity. Both soluble compounds and hydrolyzed fractions were characterized for the content of proteins, phenolic compounds, and lipids. The presence of compounds coming from the endosymbiont zooxanthellae was also detected. The notable yield and the considerable antioxidant activity detected make this species worthy of further study for its potential biotechnological sustainable exploitation.

Affinity Diversification of a Polymer Probe for Pattern-recognition-based Biosensing Using Chemical Additives

Pattern-recognition-based sensing has attracted attention as a promising alternative to conventional sensing methods that rely on selective recognition. Here, we report on novel strategy using chemical additives with the ability to modulate probe/analyte interactions to more easily construct pattern-recognition-based sensing systems for proteins and cells. The fluorescence of dansyl-modified cationic poly-L-lysine (PLL-Dnc) is enhanced upon binding to proteins in aqueous solution, while the addition of salts, inert polymers, or alcohols modulates the protein/PLL-Dnc interactions via a variety of mechanisms. Subsequent readout of the fluorescence changes produces response patterns that reflect the characteristics of the analytes. Multivariate analysis of the response patterns allowed for accurate identification of not only eight structurally similar albumin homologues, but also four mammalian cells. This strategy, which uses inexpensive and common additives, significantly improves the accessibility of pattern-recognition-based sensing, which will offer new opportunities for the detection of various bioanalytes.

An antibody-free LC-MS/MS method for the quantification of intact insulin-like growth factors 1 and 2 in human plasma

Insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) are important biomarkers in research and diagnosis of growth disorders. Quantitative analysis is performed using various ligand-binding assays or enzymatic digestion LC-MS/MS methods, whose widespread adoption is hampered by time-consuming sample preparation procedures. We present a simple and fast antibody-free LC-MS/MS method for the quantification of intact IGF-1 and IGF-2 in human plasma. The method requires 50 μL of plasma and uses fully ¹⁵N-labelled IGF-1 as internal standard. It features trifluoroethanol (TFE)-based IGF/IGF-binding protein complex dissociation and a two-step selective protein precipitation workflow, using 5% acetic acid in 80/20 acetone/acetonitrile (precipitation 1) and ice-cold ethanol (precipitation 2). Detection of intact IGF-1 and IGF-2 is performed by means of a Waters XEVO TQ-S triple quadrupole mass spectrometer in positive electrospray ionisation (ESI+) mode. Lower limits of quantification were 5.9 ng/mL for IGF-1 and 8.4 ng/mL for IGF-2. Intra-assay imprecision was below 4.5% and inter-assay imprecision was below 5.8% for both analytes. An excellent correlation was found between nominal and measured concentrations of the WHO reference standard for IGF-1. Comparison with the IDS-iSYS IGF-1 immunoassay showed good correlation (R² > 0.97), although a significant bias was observed with the immunoassay giving substantially higher concentrations. The LC-MS/MS method described here allows for reliable and simultaneous quantification of IGF-1 and IGF-2 in plasma, without the need for enzymatic digestion. The method can be readily implemented in clinical mass spectrometry laboratories and has the potential to be adapted for the analysis of different similarly sized peptide hormones.

Location and Conformation of the LKα14 Peptide in Water/Ethanol Mixtures

It is widely recognized that solvation is one of the major factors determining structure and functionality of proteins and long peptides, however it is a formidable challenge to address it both experimentally and computationally. For this reason, simple peptides are used to study fundamental aspects of solvation. It is well established that alcohols can change the peptide conformation and tuning of the alcohol content in solution can dramatically affect folding and, as a consequence, the function of the peptide. In this work, we focus on the leucine and lysine based LKα14 peptide designed to adopt an α-helical conformation at an apolar-polar interface. We investigate LKα14 peptide's bulk and interfacial behavior in water/ethanol mixtures combining a suite of experimental techniques (namely, circular dichroism and nuclear magnetic resonance spectroscopy for the bulk solution, surface pressure measurements and vibrational sum frequency generation spectroscopy for the air-solution interface) with molecular dynamics simulations. We observe that ethanol highly affects both the peptide location and conformation. At low ethanol content LKα14 lacks a clear secondary structure in bulk and shows a clear preference to reside at the air-solution interface. When the ethanol content in solution increases, the peptide's interfacial affinity is markedly reduced and the peptide approaches a stable α-helical conformation in bulk facilitated by the amphiphilic nature of the ethanol molecules.

Transformation of Pueraria candollei var. mirifica phytoestrogens using immobilized and free β-glucosidase, a technique for enhancing estrogenic activity

Pueraria candollei var. mirifica (PM) has a significant beneficial effect on postmenopausal symptoms associated with estrogen deficiency. However, the estrogenic activity and intestinal absorption of isoflavonoid glycosides derived from PM, such as daidzin and genistin, are significantly lower than those of their aglycones. To enhance the estrogenic activity of the PM extract, we developed β-glucosidase and its immobilized form to increase the PM aglycone content (daidzein and genistein). The enzyme immobilization was done by alginate beads, and the resulting β-glucosidase alginate beads have a diameter of about 0.20 cm. Response surface methodology (RSM) was used to optimize certain parameters, such as the pH, temperature, and ethanol concentration. The optimal conditions of β-glucosidase for daidzein and genistein production were pH of 4.8–4.9, a temperature in the range 46.3–49.1 °C, and ethanol concentration of 10.0–11.0%. The ANOVA results indicated that the design experiment involving free and immobilized β-glucosidase was the best fit by quadratic models, which had adjusted R² values between 0.8625 and 0.9318. Immobilized β-glucosidase can be reused up to nine times and maintained efficacy of greater than 90%. Treatment of the PM extract with β-glucosidase increased the estrogenic activity of the PM extract by 8.71- to 23.2-fold compared to that of the untreated extract. Thus, β-glucosidase has a high potential for enhancing the estrogenic activity of PM constituents, and it can be applied on an industrial scale to increase the utility of these natural products.

Transformation of Pueraria candollei var. mirifica phytoestrogens by β-glucosidase increases estrogenic activity.

Development and Application of a Modified Method to Determine the Encapsulation Efficiency of Proteins in Polymer Matrices

A modified method to determine protein encapsulation efficiency in polymer matrices has been developed and applied to two proteins and two polymers to demonstrate its wide range of applicability. This study was pursued due to the wide variation in reported protein encapsulation efficiency of polymer-based microcapsules, even when the protein, the polymer, and the microcapsule manufacturing method were consistent. Hemoglobin (Hb) and bovine serum albumin (BSA) were chosen as model proteins and ethylcellulose and poly(lactic-co-glycolic acid) (PLGA) as model polymers. The polymer of the microcapsule was dissolved in dichloromethane/ethanol or dichloromethane/ethyl acetate for ethylcellulose or PLGA microcapsules, respectively. Liberated proteins were simultaneously precipitated, pelleted by centrifugation, isolated by decanting the polymer solution, redissolved in 10% w/v sodium dodecyl sulfate in 0.8 N sodium hydroxide, and quantified using a modified Lowry assay. Blank microcapsules and exogenously added proteins demonstrated ≥ 93.8% recovery of proteins. The mean encapsulation efficiency of ethylcellulose or PLGA microcapsules was 52.4 or 76.9% for Hb and 86.4 or 74.7% for BSA, respectively. This demonstrates the effective use of centrifugation and the importance of an appropriate cosolvent system in the measure of encapsulation efficiency where one solvent dissolves the polymer while the other solvent quantitatively precipitates the liberated protein. It is evident that an alkaline solution of sodium dodecyl sulfate is efficient at quantitatively dissolving precipitated proteins. Remediation of problems observed with current methods and high reproducibility suggest that this modified method is generally applicable to the measure of protein encapsulation efficiency of polymer microcapsules.

Stability of tuna trypsin-loaded alginate-chitosan beads in acidic stomach fluid and the release of active enzyme in a simulated intestinal tract environment

Encapsulation properties of trypsin from tonggol tuna (Thunnus tonggol) spleen using different materials including alginate (AG), low and high molecular weight chitosan (LC and HC, respectively), and soy lecithin (SL) were studied. The highest encapsulation efficiency and greatest relative activity were found in AG/LC beads after simulated gastric phase (p < .05). AG/LC encapsulated trypsin was used in simulated in vitro gastrointestinal tract for hydrolysis of sodium caseinate, soy protein isolate and fish mince, in which all protein samples were hydrolyzed as indicated by the increased α-amino group content (p < .05). Higher degradation was attained when beads containing trypsin were added. When AG/LC beads packed in blister pack were stored for 8 weeks at refrigerated temperature, a 26% decrease in activity occurred. Therefore, encapsulated tonggol tuna spleen trypsin can be prepared using AG/LC to withstand structural breakdown in stomach, but be released as an active protease within intestinal tract. PRACTICAL APPLICATION: Spleen from tonggol tuna is a by-product, which can be used as a source of trypsin, a proteolytic enzyme. The trypsin that was encapsulated within alginate and low molecular weight chitosan beads was released in the intestinal phase and was retained proteolytic activity. Therefore, this encapsulated trypsin can be packaged in capsules and taken as a supplement to aid protein digestion in the gastrointestinal tract, especially for people that need such digestive aids.

Unraveling How Ethanol-Induced Conformational Changes Affect BSA Protein Adsorption onto Silica Surfaces

Protein adsorption at solid-liquid interfaces is highly relevant to a wide range of applications such as biosensors, drug delivery, and pharmaceuticals. Understanding how protein conformation in bulk solution impacts adsorption behavior is fundamentally important and could also lead to the development of improved protein-based coatings. To date, relevant studies have been conducted in aqueous solutions, while it remains largely unknown how organic solvents and more specifically solvent-induced conformational changes might influence protein adsorption. Herein, using the quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) techniques, we systematically investigated the real-time adsorption behavior of bovine serum albumin (BSA) protein onto silica surfaces in different water-ethanol mixtures ranging from 0 to 60% (v/v) ethanol. The results showed that there was greater protein adsorption at higher ethanol fractions in the 10-30% range, while more complex adsorption profiles were observed in the 40-60% range. The combination of QCM-D and LSPR measurements led us to further identify specific cases in water-ethanol mixtures where washing steps caused densification of the adsorbed protein layer as opposed to typical desorption of weakly adsorbed molecules in aqueous conditions. We discuss mechanistic factors that drive these overall adsorption trends by taking into account how ethanol fraction affects BSA conformation in bulk solution. Together, our findings demonstrate that BSA proteins can adsorb onto silica surfaces across a wide range of water-ethanol mixture conditions, while specific adsorption profiles depended on the ethanol fraction in a manner closely linked to solution-phase conformational properties.

Pigments Content (Chlorophylls, Fucoxanthin and Phycobiliproteins) of Different Commercial Dried Algae

Algae are a complex, polyphyletic group of organisms, affordable and naturally rich in nutrients, but also valuable sources of structurally diverse bioactive substances such as natural pigments. The aim of this work was to evaluate the polar and non-polar pigment contents of different commercial dried algae (brown: Himanthalia elongata, Undaria pinnatifida, Laminaria ochroleuca; red: Porphyra spp.; and a blue-green microalga: Spirulina spp.). The pigment extraction was carried out using different solvents (100% methanol, 100% methanol acid free, 100% ethanol, 90% acetone, N,N-dimethylformamide, dimethyl sulfoxide-water (4:1, v/v) and pH 6.8 phosphate buffer), selected according to their affinity for each class of pigments. Acetone proved to be an efficient solvent to extract chlorophylls from brown and red algae, but not from Spirulina spp. Porphyra spp. presented considerably higher levels of all pigments compared to brown algae, although Spirulina spp. presented significantly higher (p < 0.05) levels of chlorophylls, carotenoids and phycobiliproteins, compared to all macroalgae. The content of fucoxanthin extracted from the three brown algae was highly correlated to the carotenoid content. Within this group, Himanthalia elongata presented the highest fucoxanthin/total carotenoids ratio. Although the yield of extraction depended on the solvent used, the algae studied herein are an interesting source of pigments of great value for a wide range of applications.

Effect of Decontamination Treatments on Micro-Shear Bond Strength between Blood-Saliva-Contaminated Post-Etched Dentin Substrate and Composite Resin

Blood–saliva contamination negatively affects the bonding potential of adhesive agents. The study aimed to assess the effect of various cleaning protocols on micro-shear bond strength (μSBS) between blood–saliva-contaminated post-etched dentin and composite resin in total-etch and self-etch adhesives. The cleaning methods tested were water rinsing, 37.5% phosphoric acid (H3PO4) re-etching, 6% sodium hypochlorite (NaoCl), 2% chlorhexidine gluconate (CXG), isopropyl alcohol (IPA), and pumice. Nono-hybrid composite cylinders with a 3-mm diameter and 2-mm height were directly cured over the dentin substrate, stored for 24 h, and subjected to 12,000 thermocycles. The shear force was exerted with a 200-μm knife-edged chisel-shaped head from a universal testing machine. The type of failure was assessed with stereomicroscope magnified images. The obtained data were evaluated by Kruskal–Wallis and Mann–Whitney U post-hoc tests. Water-rinsed contaminated dentin surfaces showed substantially reduced μSBS in the total etch from 25.93 to 20.29 Mpa and the corresponding values for the one-step self-etch adhesive were 10.10 to 8.8. Re-etching with 37.5% H3Po4 resulted in a recovery of bonding potential in both total-etch (24.58 Mpa) and self-etch adhesive (9.23 Mpa). Alternately, NaoCl and pumice cleaning showed promising results for the total-etch (23.51 Mpa) and self-etch (7.79 Mpa).

Study of the polyribosyl-ribitol-phosphate precipitation mechanism by salts and organic solvents

Precipitation has been widely applied to purification and fractionation of biological macromolecules. Several physical-chemical factors contribute to the destabilization of those solutions, such as the nature of solvent employed, presence of salts, temperature, and concentration of the macromolecule. In the case of charged biopolymers, electrostatic forces are the major contributors to their stability in solution. However, the role of each variable and the exact mechanism of precipitation are not completely understood yet. The aim of this work was to study the precipitation of polyribosyl-ribitol-phosphate (PRP, a linear homogeneous anionic biopolymer) in presence of salts and non-solvents, in order to contribute to the elucidation of its precipitation mechanism. The solvents tested (acetone, ethanol, and isopropanol) presented distinct dielectric constants. The salts used (NH₄Cl, NaCl, KCl, MgCl₂, and CaCl₂) differ by their cations. For each salt concentration, the solvent fraction that induces precipitation was identified and the dielectric constant of the bulk solution was calculated. Precipitation always occurred at well-defined combinations of solvents and salts. At low concentration of monovalent salts, there was a linear correlation between the logarithm of the salt concentration and the inverse of the medium dielectric constant at a defined precipitation point. This is a strong indication that the stability of the solution depends almost exclusively on the balance of electrostatic forces. This behavior is compatible with the DLVO modeling of colloidal systems. When divalent salts were used, low concentrations of the counterion were sufficient to induce precipitation, due to a phenomenon called ionic condensation. Apparently, PRP precipitates when around 90% of its charges are neutralized, value that is similar to charge neutralization for DNA precipitation.

Transforming protein-polymer conjugate purification by tuning protein solubility

Almost all commercial proteins are purified using ammonium sulfate precipitation. Protein-polymer conjugates are synthesized from pure starting materials, and the struggle to separate conjugates from polymer, native protein, and from isomers has vexed scientists for decades. We have discovered that covalent polymer attachment has a transformational effect on protein solubility in salt solutions. Here, protein-polymer conjugates with a variety of polymers, grafting densities, and polymer lengths are generated using atom transfer radical polymerization. Charged polymers increase conjugate solubility in ammonium sulfate and completely prevent precipitation even at 100% saturation. Atomistic molecular dynamic simulations show the impact is driven by an anti-polyelectrolyte effect from zwitterionic polymers. Uncharged polymers exhibit polymer length-dependent decreased solubility. The differences in salting-out are then used to simply purify mixtures of conjugates and native proteins into single species. Increasing protein solubility in salt solutions through polymer conjugation could lead to many new applications of protein-polymer conjugates.

Protein extraction from agri-food residues for integration in biorefinery: Potential techniques and current status

The biorefinery concept is attracting scientific and policy attention as a promising option for enhancing the benefits of agri-food biomass along with a reduction of the environmental impact. Obtaining bioproducts based on proteins from agri-food residues could help to diversify the revenue stream in a biorefinery. In fact, the extracted proteins can be applied as such or in the form of hydrolyzates due to their nutritional, bioactive and techno-functional properties. In this context, the present review summarizes, exemplifies and discusses conventional extraction methods and current trends to extract proteins from residues of the harvesting, post-harvesting and/or processing of important crops worldwide. Moreover, those extraction methods just integrated in a biorefinery scheme are also described. In conclusion, a plethora of methods exits but only some of them have been applied in biorefinery designs, mostly at laboratory scale. Their economic and technical feasibility at large scale requires further study.

Egg Yolk Extracts as Potential Liposomes Shell Material: Composition Compared with Vesicles Characteristics

Our aim was to propose simple extraction process to obtain phospholipids along with yolk-derived vitamins and fats. Five extracts marked as ethanol/acetone, methanol-chloroform/acetone, hot ethanol, hexane, and cold ethanol were developed and compared. Extracts' compositions were analyzed in terms of phospholipid, polar and nonpolar fraction, cholesterol, carotenoids, and tocopherols content. Further, liposomes prepared from extracts were characterized. The highest extraction efficiency was achieved by a one-step hexane procedure. However, that sample, in contrast to the other four extracts, revealed distinctively lower permeability when used for liposomes membrane formation. Principal component analysis proved that major components contents were decisive for liposomes membranes permeability, whereas minor constituents' content controlled zeta potential and Z-average size.

PRACTICAL APPLICATION

Liposomes are nanocarriers widely used in pharmaceutical industry. Due to intravenous route of administration, they have to be produced from phospholipids of very fine purity. On the other hand, there is increasing interest in nanoencapsulation of labile, bioactive substances for manufacturing of health promoting food. Unfortunately, high-price pure phospholipids are prohibitive for food applications. The use of raw material obtained by simple extraction procedure instead of highly purified phospholipids could be an attractive alternative for food industry.

Nanostructured Mineral Coatings Stabilize Proteins for Therapeutic Delivery

Proteins tend to lose their biological activity due to their fragile structural conformation during formulation, storage, and delivery. Thus, the inability to stabilize proteins in controlled-release systems represents a major obstacle in drug delivery. Here, a bone mineral inspired protein stabilization strategy is presented, which uses nanostructured mineral coatings on medical devices. Proteins bound within the nanostructured coatings demonstrate enhanced stability against extreme external stressors, including organic solvents, proteases, and ethylene oxide gas sterilization. The protein stabilization effect is attributed to the maintenance of protein conformational structure, which is closely related to the nanoscale feature sizes of the mineral coatings. Basic fibroblast growth factor (bFGF) released from a nanostructured mineral coating maintains its biological activity for weeks during release, while it maintains activity for less than 7 d during release from commonly used polymeric microspheres. Delivery of the growth factors bFGF and vascular endothelial growth factor using a mineral coated surgical suture significantly improves functional Achilles tendon healing in a rabbit model, resulting in increased vascularization, more mature collagen fiber organization, and a two fold improvement in mechanical properties. The findings of this study demonstrate that biomimetic interactions between proteins and nanostructured minerals provide a new, broadly applicable mechanism to stabilize proteins in the context of drug delivery and regenerative medicine.