The Effect of Glucose on the Interaction of Bisphenol A and Bovine Hemoglobin Characterized by Spectroscopic and Molecular Docking Techniques

The interaction mechanism of hemoglobin (Hb) with bisphenol A (BPA) in diabetic patients and the difference with healthy people have been studied using spectroscopic and molecular docking techniques at several glucose (Glc) concentration, with bovine hemoglobin (BHb) instead of Hb. It is found that Glc can interact with BHb-BPA and affect its molecular structure, resulting in an altered microenvironment for tyrosine (Tyr) and tryptophan (Trp) in BHb-BPA. It is also found that Glc can bind to BHb alone, and its effect on the molecular structure of BHb is weaker than that on the structure of BHb in BHb-BPA complex. The results of circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) indicate that Glc causes an increase in the content of the α-helix and a decrease in that of the β-sheet of BHb-BPA by 1.5-1.9% and 3.1%, respectively. The results of molecular docking show that Glc binds to BHb-BPA through hydrogen and hydrophobic bonds, and the position of binding differs from that of Glc binding to BHb alone, which may be attributed to the fact that BPA affects the protein molecular structure of BHb and has an effect on the binding of BHb to Glc. This study provides some theoretical basis for the mechanism of BPA toxicity in vivo for people with different blood glucose levels.

Comparison of the Bioactive Properties of Human and Bovine Hemoglobin Hydrolysates Obtained by Enzymatic Hydrolysis: Antimicrobial and Antioxidant Potential of the Active Peptide α137-141

This study focuses on the enzymatic hydrolysis of hemoglobin, the main component of cruor that gives blood its red color in mammals. The antibacterial and antioxidant potentials of human hemoglobin hydrolysates were evaluated in comparison to bovine hemoglobin. The results showed strong antimicrobial activity of the peptide hydrolysates against six bacterial strains, independent of the initial substrate concentration level. The hydrolysates also showed strong antioxidant activity, as measured by four different tests. In addition, the antimicrobial and antioxidant activities of the human and bovine hemoglobin hydrolysates showed little or no significant difference, with only the concentration level being the determining factor in their activity. The results of the mass spectrometry study showed the presence of a number of bioactive peptides, the majority of which have characteristics similar to those mentioned in the literature. New bioactive peptides were also identified in human hemoglobin, such as the antibacterial peptides PTTKTYFPHF (α37-46), FPTTKTYFPH (α36-45), TSKYR (α137-141), and STVLTSKYR (α133-141), as well as the antioxidant TSKYR (α137-141). According to these findings, human hemoglobin represents a promising source of bioactive peptides beneficial to the food or pharmaceutical industries.

Potential of Human Hemoglobin as a Source of Bioactive Peptides: Comparative Study of Enzymatic Hydrolysis with Bovine Hemoglobin and the Production of Active Peptide α137-141

Cruor, the main component responsible for the red color of mammalian blood, contains 90% haemoglobin, a protein considered to be a rich source of bioactive peptides. The aim of the present study is to assess the potential of human hemoglobin as a source of bioactive peptides, compared with bovine hemoglobin, which has been extensively studied in recent years. More specifically, the study focused on the α137-141 fragment of bovine haemoglobin (TSKYR), a small (653 Da) hydrophilic antimicrobial peptide. In this work, the potential of human hemoglobin to contain bioactive peptides was first investigated in silico in comparison with bovine hemoglobin-derived peptides using bioinformatics tools. The blast results showed a high identity, 88% and 85% respectively, indicating a high similarity between the α and β chains. Peptide Cutter software was used to predict cleavage sites during peptide hydrolysis, revealing major conservation in the number and location of cleavage sites between the two species, while highlighting some differences. Some peptides were conserved, notably our target peptide (TSKYR), while others were specific to each species. Secondly, the two types of hemoglobin were subjected to similar enzymatic hydrolysis conditions (23 °C, pH 3.5), which showed that the hydrolysis of human hemoglobin followed the same reaction mechanism as the hydrolysis of bovine hemoglobin, the 'zipper' mechanism. Concerning the peptide of interest, α137-141, the RP-UPLC analyses showed that its identification was not affected by the increase in the initial substrate concentration. Its production was rapid, with more than 60% of the total α137-141 peptide production achieved in just 30 min of hydrolysis, reaching peak production at 3 h. Furthermore, increasing the substrate concentration from 1% to 10% (w/v) resulted in a proportional increase in α137-141 production, with a maximum concentration reaching 687.98 ± 75.77 mg·L-1, approximately ten-fold higher than that obtained with a 1% (w/v) concentration. Finally, the results of the UPLC-MS/MS analysis revealed the identification of 217 unique peptides in bovine hemoglobin hydrolysate and 189 unique peptides in human hemoglobin hydrolysate. Of these, 57 peptides were strictly common to both species. This revealed the presence of several bioactive peptides in both cattle and humans. Although some had been known previously, new bioactive peptides were discovered in human hemoglobin, such as four antibacterial peptides (α37-46 PTTKTYFPHF, α36-45 FPTTKTYFPH, α137-141 TSKYR, and α133-141 STVLTSKYR), three opioid peptides (α137-141 TSKYR,β31-40 LVVYPWTQRF,β32-40, VVYPWTQRF), an ACE inhibitor (β129-135 KVVAGVA), an anticancer agent (β33-39 VVYPWTQ), and an antioxidant (α137-141 TSKYR). To the best of our knowledge, these peptides have never been found in human hemoglobin before.

Probing the Bovine Hemoglobin Adsorption Process and its Influence on Interfacial Water Structure at the Air-Water Interface

*These authors contributed equally to this work.The molecular-level insight of protein adsorption and its kinetics at interfaces is crucial because of its multifold role in diverse fundamental biological processes and applications. In the present study, the sum frequency generation (SFG) vibrational spectroscopy has been employed to demonstrate the adsorption process of bovine hemoglobin (BHb) protein molecules at the air-water interface at interfacial isoelectric point of the protein. It has been observed that surface coverage of BHb molecules significantly influences the arrangement of the protein molecules at the interface. The time-dependent SFG studies at two different frequencies in the fingerprint region elucidate the kinetics of protein denaturation process and its influence on the hydrogen-bonding network of interfacial water molecules at the air-water interface. The initial growth kinetics suggests the synchronized behavior of protein adsorption process with the structural changes in the interfacial water molecules. Interestingly, both the events carry similar characteristic time constants. However, the conformational changes in the protein structure due to the denaturation process stay for a long time, whereas the changes in water structure reconcile quickly. It is revealed that the protein denaturation process is followed by the advent of strongly hydrogen-bonded water molecules at the interface. In addition, we have also carried out the surface tension kinetics measurements to complement the findings of our SFG spectroscopic results.

Investigation on the interaction between Ag+ and bovine hemoglobin using spectroscopic methods

Silver ions (Ag⁺) can be released by silver nanoparticles (AgNPs) which are widely used in diverse fields. Ag⁺ can exist inside cells to produce cytotoxicity. This report uses spectroscopic methods to reveal the interactions between Ag⁺ and bovine hemoglobin (BHb). The results of the quenching rate constant (K_q) and the fluorescence lifetime detection showed that the quenching mechanism of BHb by Ag⁺ was static. Thermodynamic investigations indicated that Ag⁺ can interact with BHb with one binding site to form complex mainly through van der Waals interactions and hydrogen bonds. The UV-vis absorption and synchronous fluorescence spectra showed that Ag⁺ changed the conformation of BHb, which may affect protein functions. This research is favorable for understanding the molecular toxic mechanism of Ag⁺ in vivo.

Bovine Hemoglobin Enzymatic Hydrolysis by a New Eco-Efficient Process-Part II: Production of Bioactive Peptides

Bovine cruor, a slaughterhouse waste, was mainly composed of hemoglobin, a protein rich in antibacterial and antioxidant peptides after its hydrolysis. In the current context of food safety, such bioactive peptides derived from enzymatic hydrolysis of hemoglobin represent potential promising preservatives for the food sector. In this work, the hemoglobin hydrolysis to produce bioactive peptides was performed in a regulated pH medium without the use of chemical solvents and by an eco-efficient process: electrodialysis with bipolar membrane (EDBM). Bipolar/monopolar (anionic or cationic) configuration using the H⁺ and OH^- generated by the bipolar membranes to regulate the pH was investigated. The aim of this study was to present and identify the bioactive peptides produced by EDBM in comparison with conventional hydrolysis and to identify their biological activity. The use of the EDBM for the enzymatic hydrolysis of hemoglobin has allowed for the production and identification of 17 bioactive peptides. Hydrolysates obtained by EDBM showed an excellent antimicrobial activity against six strains, antioxidant activity measured by four different tests and for the first time anti-fungal activities against five yeasts and mold strains. Consequently, this enzymatic hydrolysis carried out in regulated pH medium with bipolar membranes could provide bioactive peptides presenting antibacterial, antifungal and antioxidant interest.

Bovine Hemoglobin Enzymatic Hydrolysis by a New Ecoefficient Process-Part I: Feasibility of Electrodialysis with Bipolar Membrane and Production of Neokyotorphin (α137-141)

Neokyotorphin (α137-141) is recognized as an antimicrobial peptide and a natural meat preservative. It is produced by conventional enzymatic hydrolysis of bovine hemoglobin, a major component of cruor, a by-product of slaughterhouses. However, during conventional hydrolysis, chemical agents are necessary to adjust and regulate the pH of the protein solution and the mineral salt content of the final hydrolysate is consequently high. To produce this peptide of interest without chemical agents and with a low salt concentration, electrodialysis with bipolar membrane (EDBM), an electromembrane process recognized as a green process, with two different membrane configurations (cationic (MCP) and anionic (AEM) membranes) was investigated. Hydrolysis in EDBM showed the same enzymatic mechanism, “Zipper”, and allowed the generation of α137-141 in the same concentration as observed in conventional hydrolysis (control). EDBM-MCP allowed the production of hydrolysates containing a low concentration of mineral salts but with fouling formation on MCP, while EDBM-AEM allowed the production of hydrolysates without fouling but with a similar salt concentration than the control. To the best of our knowledge, this was the first time that EDBM was demonstrated as a feasible and innovative technology to produce peptide hydrolysates from enzymatic hydrolysis.

Fabrication of Yb3+-Immobilized Hydrophilic Phytic-Acid-Coated Magnetic Nanocomposites for the Selective Separation of Bovine Hemoglobin from Bovine Serum

In this work, Yb³⁺-immobilized hydrophilic phytic-acid-coated magnetic nanocomposites were prepared through a facile route and used to selectively separatrf bovine hemoglobin. Hydrophilic phytic acid (PA) was coated onto the magnetic Fe₃O₄-PEI via electrostatic interactions, followed by finally chelating with Yb³⁺ ions, which could produce specific protein binding sites at room temperature in water, and complex instrumentation was not necessary. The performance of as-prepared hybrids (Fe₃O₄-PEI-PA-Yb³⁺) was assessed by selectively isolating bovine hemoglobin (BHb). The obtained maximum binding capacity was 347.3 mg g^-1. The retained BHb could be eluted under simple elution via using 0.1 M of Na₂CO₃, giving a recovery of 83%. Moreover, the generation of nanocomposites was demonstrated. In addition, the PA and PEI could improve the hydrophilicity of nanoparticles and further reduce the nonspecific adsorption. Therefore, such nanocomposites were successfully employed to selectively bind and separate BHb from bovine serum as verified by SDS-PAGE and MALDI-TOF MS analysis, providing a new perspective for the isolation of heme proteins in proteomics.

Nitrogen and sulfur co-doped carbon nanodots toward bovine hemoglobin: A fluorescence quenching mechanism investigation

A deep understanding of the molecular interactions of carbon nanodots with biomacromolecules is essential for wider applications of carbon nanodots both in vitro and in vivo. Herein, nitrogen and sulfur co-doped carbon dots (N,S-CDs) with a quantum yield of 16% were synthesized by a 1-step hydrothermal method. The N,S-CDs exhibited a good dispersion, with a graphite-like structure, along with the fluorescence lifetime of approximately 7.50 ns. Findings showed that the fluorescence of the N,S-CDs was effectively quenched by bovine hemoglobin as a result of the static fluorescence quenching. The mentioned quenching mechanism was investigated by the Stern-Volmer equation, temperature-dependent quenching, and fluorescence lifetime measurements. The binding constants, number of binding sites, and the binding average distance between the energy donor N,S-CDs and acceptor bovine hemoglobin were calculated as well. These findings will provide for valuable insights on the future bioapplications of N,S-CDs.

HJH-1, a Broad-Spectrum Antimicrobial Activity and Low Cytotoxicity Antimicrobial Peptide

With the overuse of antibiotics, multidrug-resistant bacteria pose a significant threat to human health. Antimicrobial peptides (AMPs) are a promising alternative to conventional antibiotics. This study examines the antimicrobial and membrane activity of HJH-1, a cationic peptide derived from the hemoglobin α-subunit of bovine erythrocytes P3. HJH-1 shows potent antimicrobial activity against different bacterial species associated with infection and causes weaker hemolysis of erythrocytes, at least five times the minimum inhibitory concentration (MIC). HJH-1 has good stability to tolerance temperature, pH value, and ionic strength. The anionic membrane potential probe bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC₄(3)] and propidium iodide are used as indicators of membrane integrity. In the presence of HJH-1 (1× MIC), Escherichiacoli membranes rapidly depolarise, whereas red blood cells show gradual hyperpolarisation. Scanning electron microscopy and transmission electron micrographs show that HJH-1 (1× MIC) damaged the membranes of Escherichia coli, Staphylococcus aureus, and Candida albicans. In conclusion, HJH-1 damages the integrity of the bacterial membrane, preventing the growth of bacteria. HJH-1 has broad-spectrum antibacterial activity, and these activities are performed by changing the normal cell transmembrane potential and disrupting the integrity of the bacterial membrane.

Dual effects include antioxidant and pro-oxidation of ascorbic acid on the redox properties of bovine hemoglobin

The oxidation reactions have become the main obstacle of development of bovine hemoglobin-derivates products. Herein, the effects of vitamin C (Vc), a easily available natural antioxidant reagent, on the redox reaction of bovine hemoglobin were systematically investigated through methemoglobin (MetHb) formation and spectrophotometric analysis and oxygen affinity monitoring of hemoglobin. The results showed that Vc presented antioxidant effects in the initial stage of reaction and then could accelerated the MetHb content increasing by production of hydrogen peroxide, which can be indirectly characterized by the formation of choleglobin in the following side reactions. The dual effects of Vc include antioxidant and pro-oxidant effects could be confirmed by the spectrophotometric spectrums analysis in this research. The results of this research supplied the novel insight into understanding of redox properties of bovine hemoglobin and also revealed the main obstacle in exploration of Vc application in the future development of bovine hemoglobin-derivates products.

Molecular Imprinting Based Hybrid Ratiometric Fluorescence Sensor for the Visual Determination of Bovine Hemoglobin

We describe a simple and effective strategy to construct a molecular imprinting ratiometric fluorescence sensor (MIR sensor) for the visual detection of bovine hemoglobin (BHb) used as a model protein. The sensor was prepared by simply mixing the solution of green and red CdTe quantum dots (QDs), which were embedded in core-shell structured molecularly imprinted polymers and silica nanoparticles, respectively. The resultant hybrid MIR sensor can selectively bind with BHb and thus quench the fluorescence of the green QDs, while the red QDs wrapped with silica are insensitive to BHb with the fluorescence intensity unchanged. As a result, a continuous obvious fluorescence color change from green to red can be observed by naked eyes, with the detection limit of 9.6 nM. Moreover, the MIR sensor was successfully applied to determine BHb in bovine urine samples with satisfactory recoveries at three spiking levels ranging from 95.7 to 101.5%, indicating great potential application for detecting BHb in real samples. This strategy of using different fluorescence emission materials incorporated to construct a ratiometric fluorescence sensor is reasonable and convenient, which can be extended to the preparation of other ratiometric fluorescence systems for targeted analytes.

Bovine hemoglobin: a nontraditional approach to the management of acute anemia in a Jehovah's Witness patient with autoimmune hemolytic anemia

INTRODUCTION

Management of severe symptomatic anemia in critically ill Jehovah's Witness patients remains a challenge. The paucity of therapeutic alternatives to human red blood cells has prompted the use of blood substitutes.

CASE REPORT

A 19-year-old female Jehovah's Witness patient presented to the emergency department following several episodes of syncope. She was found to have a positive Coombs test and was diagnosed with warm-bodied autoimmune hemolytic anemia. Upon admission, her hemoglobin was 8.4 g/dL, then dropped to a nadir of 2.8 g/dL 4 days later. She received traditional management with corticosteroids, intravenous immune globulin, rituximab, and partial splenic artery embolization. Despite these therapies, hemoglobin levels failed to respond, and she experienced signs of marked ischemia. A decision was made to give 2 units of Hemopure, a bovine hemoglobin-based oxygen carrier, and the hemoglobin levels increased to 8.7 g/dL 10 days later. The patient's overall clinical condition improved leading to subsequent hospital discharge.

CONCLUSION

This case exemplifies the ingenuity that health care practitioners must use in critical situations involving the medical management of anemic Jehovah's Witness patients who refuse blood products. Hemopure was used as "bridging treatment" to help save a patient from the devastating effects of ischemia resulting from severe anemia.