Foam fractionation of a dilute solution of bovine lactoferrin

Lactoferrin (Lf), a protein found in human and bovine milk, tears, blood, and other secretory fluids, has been used to prevent infection from potential microbial pathogens by its ability to bind with iron (Fe³⁺). Currently, bovine lactoferrin can be purified from milk using ion exchange resin, which is a costly procedure making lactoferrin expensive. The purpose of this work was to investigate a low-cost foam fractionation process as the first step in separating lactoferrin from milk.     

Antiviral properties of lactoferrin--a natural immunity molecule

Lactoferrin, a multifunctional iron binding glycoprotein, plays an important role in immune regulation and defence mechanisms against bacteria, fungi and viruses. Lactoferrin's iron withholding ability is related to inhibition of microbial growth as well as to modulation of motility, aggregation and biofilm formation of pathogenic bacteria. Independently of iron binding capability, lactoferrin interacts with microbial, viral and cell surfaces thus inhibiting microbial and viral adhesion and entry into host cells. Lactoferrin can be considered not only a primary defense factor against mucosal infections, but also a polyvalent regulator which interacts in viral infectious processes. Its antiviral activity, demonstrated against both enveloped and naked viruses, lies in the early phase of infection, thus preventing entry of virus in the host cell. This activity is exerted by binding to heparan sulphate glycosaminoglycan cell receptors, or viral particles or both. Despite the antiviral effect of lactoferrin, widely demonstrated in vitro studies, few clinical trials have been carried out and the related mechanism of action is still under debate. The nuclear localization of lactoferrin in different epithelial human cells suggests that lactoferrin exerts its antiviral effect not only in the early phase of surface interaction virus-cell, but also intracellularly. The capability of lactoferrin to exert a potent antiviral activity, through its binding to host cells and/or viral particles, and its nuclear localization strengthens the idea that lactoferrin is an important brick in the mucosal wall, effective against viral attacks and it could be usefully applied as novel strategy for treatment of viral infections.     

Lactoferrin: A Glycoprotein Involved in Immunomodulation,Anticancer, and Antimicrobial Processes

Lactoferrin is an iron binding glycoprotein with multiple roles in the body. Its participation in apoptotic processes in cancer cells, its ability to modulate various reactions of the immune system, and its activity against a broad spectrum of pathogenic microorganisms, including respiratory viruses, have made it a protein of broad interest in pharmaceutical and food research and industry. In this review, we have focused on describing the most important functions of lactoferrin and the possible mechanisms of action that lead to its function.     

Thiophilic interaction chromatography of mammalian and avian transferrins

Transferrins are a class of iron-binding proteins widely distributed in biological fluids. All transferrins possess two metal binding sites, each of which can bind a ferric iron. Transferrins play a major role in plasma iron transport and have anti-bacterial, anti-inflammatory, and immunological functions. Lactoferrin is an iron-binding bilobal protein of the transferrin family found in neutrophilic leukocytes and external secretion of mammals. In an earlier communication, we have shown that both human serum transferrin and lactoferrin bind to 3S-gel. Ovotransferrin, the major egg-white protein, is an avian transferrin. In this paper, the details of the binding of mammalian and avian transferrins to 2S gel is presented. Both, apo and holo ovotransferrin, bind to 2S T-gel. Holo and apo lactoferrin from other mammalian species such as cow, rabbit, dog, mouse, and rat bind to T-gel.     

Bacillibactin-mediated iron transport in Bacillus subtilis

The hexadentate triscatecholamide bacillibactin delivers iron to Bacillus subtilis and is structurally similar to enterobactin, although in a more oblate conformation. B. subtilis uses two partially overlapping permeases (1 and 2) to acquire iron from its endogenous siderophores (bacillibactin and itoic acid). Enterobactin and bacillibactin have opposite metal chiralities, different affinity for ferric ion, and dissimilar iron transport behaviors. The solution thermodynamic stability of ferric bacillibactin has been investigated through potentiometric and spectrophotometric titrations. The addition of a glycine to the catechol chelating arms causes a destabilization of the ferric complex of bacillibactin compared to ferric enterobactin. B. subtilis appears to express a separate receptor for enterobactin (permease 3), although enterobactin can also be transported through the permease for bacillibactin (permease 2).     

Structure and function of ferritin

Ferritin is the major iron storage protein of mammals and consists of up to 4500 atoms of ferric iron surrounded by a shell of protein subunits. The protein component, apoferritin, consists of 24 identical polypeptide chains each of molecular weight 18500. The function of ferritin is to store iron in a soluble form from which it can be readily mobilized. Recent results concerning the structure of the protein are reported, and progress in the elucidation of the mechanisms whereby iron is introduced into apoferritin and released from ferritin is reviewed.     

Dissociation Chemistry of Hydrogen-Deficient Radical Peptide Anions

The fragmentation chemistry of anionic deprotonated hydrogen-deficient radical peptides is investigated. Homolytic photodissociation of carbon–iodine bonds with 266 nm light is used to generate the radical species, which are subsequently subjected to collisional activation to induce further dissociation. The charges do not play a central role in the fragmentation chemistry; hence deprotonated peptides that fragment via radical directed dissociation do so via mechanisms which have been reported previously for protonated peptides. However, charge polarity does influence the overall fragmentation of the peptide. For example, the absence of mobile protons favors radical directed dissociation for singly deprotonated peptides. Similarly, a favorable dissociation mechanism initiated at the N-terminus is more notable for anionic peptides where the N-terminus is not protonated (which inhibits the mechanism). In addition, collisional activation of the anionic peptides containing carbon–iodine bonds leads to homolytic cleavage and generation of the radical species, which is not observed for protonated peptides presumably due to competition from lower energy dissociation channels. Finally, for multiply deprotonated radical peptides, electron detachment becomes a competitive channel both during the initial photoactivation and following subsequent collisional activation of the radical. Possible mechanisms that might account for this novel collision-induced electron detachment are discussed.     

Real-Time Observation of Pyoverdine Dissolving Ferric Hydroxide

Pyoverdine is one of the siderphores excreted by Pseudomonas aeruginosa that can help microbe to uptake iron in vitro. To determine the effect of pyoverdine chelating with iron, we purified the free pyoverdine and applied the dynamic laser light scattering (DLS) to detect the interaction between the pyoverdine and ferric hydroxide. The real-time DLS data analysis indicated that pyoverdine can directly combine with Fe(OH)₃ to form complexes and these substances are gradually degraded by themselves then completely disappeared. In our experiment, we have demonstrated that pyoverdine may not only chelate ferric ion but also availably dissolve ferric hydroxide which assists bacteria to survive in iron-deficient environments.     

Fouling mechanism of separator membranes for the iron/chromium redox battery

The NASA chromium/iron redox battery being developed for photovoltaic and load-levelling storage applications uses an anionic permselective membrane to keep the reactants separate while providing electrical continuity. The membrane resistance increases as a function of time when exposed to a ferric chloride solution. The resistance increase termed “fouling” is related to the ability of the ferric ion to form ferric chloride complexes which are not electrically repelled by the anionic membrane. Electron microprobe analyses show that fouling is associated with an uptake of iron that approaches a uniform distribution across the membrane thickness. Since the iron does not cause fouling by covering the surface of the membrane, alternative explanations were considered. The amount of water in the membrane was found to decrease when the membrane became fouled. Percolation theory was used to relate the resistance of fouled membranes to the volume fraction of water. The fit was excellent and the fitting parameters were physically reasonable. The water loss is caused by an osmotic effect from placing the membrane in a ionic solution and a displacement effect when the ferric chloride complex enters the membrane.     

水热法制备聚苯胺及其铁氧化物纳米复合材料

利用水热法与无模板自组装法相结合, 以三氯化铁为氧化剂、 掺杂剂和反应物, 制备了聚苯胺及其铁氧化物纳米复合材料. 结果表明, 通过改变三氯化铁的浓度可以调控产物的微观结构和组成. 当三氯化铁的浓度≤0.13 mol/L时, 产物组成为未掺杂的低聚苯胺与α-Fe₂O₃的复合纳米材料, 其微观结构为纳米颗粒组装成的椭球体和准立方体; 当三氯化铁的浓度≥0.20 mol/L时, 产物组成为掺杂态聚苯胺, 其微观结构为纳米片层结构组装成的微米级大丽花球; 并且产物的粒径随三氯化铁浓度的增大而增大. 利用扫描电子显微镜、 红外光谱、 紫外-可见光谱、 X光电子能谱及X射线衍射等手段对产物的微观结构和组成进行了表征, 并探讨了产物的形成机理.     

稀土离子与乳铁蛋白结合的光谱研究

用紫外示差光谱、荧光光谱及圆二色谱等方法研究了Tb³⁺和Eu³⁺在pH7.4的条件下与乳铁蛋白及脱铁乳铁蛋白的结合作用.结果表明,Tb³⁺及Eu³⁺可特异性地结合在脱铁乳铁蛋白的两个Fe³⁺结合部位,但不能从已经结合铁的乳铁蛋白中把铁置换出来.测得Tb³⁺ 与这两个部位结合的条件平衡常数为lgK₁=8.48±0.24和lgK₂=6.72±0.18(25℃,0.10mol/L NaCl, 0.10mol/LHepes,pH=7.4). Tb³⁺在这两个位点结合时,蛋白质的构象发生变化.在 Tb³⁺ 与蛋白质的浓度比低时,构象趋于紧缩,色氨酸残基进入疏水的环境;当Tb³⁺结合得较多时,构象转而开放,色氨酸残基转向亲水性环境.但无论哪种情况,Tb³⁺与脱铁乳铁蛋白的结合都不影响蛋白的二级结构.     

New Antibiotics for Multidrug-Resistant Bacterial Strains: Latest Research Developments and Future Perspectives

The present work aims to examine the worrying problem of antibiotic resistance and the emergence of multidrug-resistant bacterial strains, which have now become really common in hospitals and risk hindering the global control of infectious diseases. After a careful examination of these phenomena and multiple mechanisms that make certain bacteria resistant to specific antibiotics that were originally effective in the treatment of infections caused by the same pathogens, possible strategies to stem antibiotic resistance are analyzed. This paper, therefore, focuses on the most promising new chemical compounds in the current pipeline active against multidrug-resistant organisms that are innovative compared to traditional antibiotics: Firstly, the main antibacterial agents in clinical development (Phase III) from 2017 to 2020 are listed (with special attention on the treatment of infections caused by the pathogens Neisseria gonorrhoeae, including multidrug-resistant isolates, and Clostridium difficile), and then the paper moves on to the new agents of pharmacological interest that have been approved during the same period. They include tetracycline derivatives (eravacycline), fourth generation fluoroquinolones (delafloxacin), new combinations between one β-lactam and one β-lactamase inhibitor (meropenem and vaborbactam), siderophore cephalosporins (cefiderocol), new aminoglycosides (plazomicin), and agents in development for treating drug-resistant TB (pretomanid). It concludes with the advantages that can result from the use of these compounds, also mentioning other approaches, still poorly developed, for combating antibiotic resistance: Nanoparticles delivery systems for antibiotics.     

Control of Multidrug-Resistant Gene Flow in the Environment Through Bacteriophage Intervention

The spread of multidrug-resistant (MDR) bacteria is an emerging threat to the environment and public wellness. Inappropriate use and indiscriminate release of antibiotics in the environment through un-metabolized form create a scenario for the emergence of virulent pathogens and MDR bugs in the surroundings. Mechanisms underlying the spread of resistance include horizontal and vertical gene transfers causing the transmittance of MDR genes packed in different host, which pass across different food webs. Several controlling agents have been used for combating pathogens; however, the use of lytic bacteriophages proves to be one of the most eco-friendly due to their specificity, killing only target bacteria without damaging the indigenous beneficial flora of the habitat. Phages are part of the natural microflora present in different environmental niches and are remarkably stable in the environment. Diverse range of phage products, such as phage enzymes, phage peptides having antimicrobial properties, and phage cocktails also have been used to eradicate pathogens along with whole phages. Recently, the ability of phages to control pathogens has extended from the different areas of medicine, agriculture, aquaculture, food industry, and into the environment. To avoid the arrival of pre-antibiotic epoch, phage intervention proves to be a potential option to eradicate harmful pathogens generated by the MDR gene flow which are uneasy to cure by conventional treatments.     

Mecanisme de la fixation du fer ferrique sur un copolymere non ionisable d'ester carboxylique—III. Reactions de fixation du fer sur le copolymere

Fixation mechanisms for iron(III) on non-ionizable Hycar 4021 copolymer in hydrochloric acid are elucidated by simultaneous analysis of distribution and stoichiometric composition data. Several reactions are proposed depending on the amount of ferric iron in the copolymer and on the ethanol in the liquid phase. These reactions are similar to those dealing with liquid-liquid extraction of iron by organic solvents with carbon-oxygen bonds.     

铁基水处理材料除砷技术的研究进展

自然环境中的砷污染问题被认为是全球最严重的环境威胁之一,人类长期暴露于含砷饮用水环境中会引起各种疾病的发生,因此,开发经济有效的除砷技术一直是砷污染治理领域的研究热点。铁基水处理材料由于其对砷的良好亲和力、表面反应活性强、价廉易制、便于回收等特点,一直备受关注。本文综述了近年来不同铁基水处理材料如铁(氢)氧化物、纳米零价铁、铁基多金属氧化物复合材料除砷技术的研究进展,论述了铁基水处理材料对水相中砷去除的影响因素及机理;同时,对影响铁基水处理材料砷解吸的因素和毒性评估研究进行了总结;指出了目前铁基水处理材料砷污染去除技术研究中存在的主要问题,并对水相砷污染去除技术研究中值得关注的重要发展方向进行了展望。     

Structure, assembly, and topology of the G185R mutant of the fourth transmembrane domain of divalent metal transporter

The mammalian iron transporter, divalent metal transporter (DMT1), is a 12-transmembrane domain integral protein, responsible for dietary iron uptake in the duodenum and iron acquisition from transferrin in peripheral tissues. Two disease-causing mutants in animals have been found and attributed to the same missense mutation (G185R), which occurs within the putative transmembrane domain 4 (TM4) of DMT1. We have characterized a synthetic 24-mer peptide, corresponding to the sequence of the TM4 of DMT1 with G185R mutation using circular dichroism (CD) and NMR spectroscopy and show that the G185R peptide assumes mainly alpha-helical conformations in various membrane-mimetic environments. Solution structures derived from NMR and molecular dynamics/simulated annealing calculations demonstrate that the peptide exhibits a highly defined alpha-helix in its middle portion, flanked by a highly flexible N-terminus and a relatively ordered C-terminus. Both the folding and location of the C-terminus in SDS micelles are regulated by pH values. Paramagnetic broadening on peptide NMR signals by spin-labeled 5- and 16-doxylstearic acids and Mn(2+) ion suggests that both the N-terminus and the helical region of the peptide are embedded in SDS micelles. Surprisingly, self-association of the peptides for both the wild type and the G185R mutant studied by CD, electrospray ionization mass spectrometry, and NMR diffusion-ordered spectroscopy demonstrated that mutation of the Gly185 to a bulky and positively charged arginine causes a different self-assembly of the peptide, e.g., from a trimer to a hexamer, which implies that the quaternary structure of integral DMT1 may be crucial for its function in vivo.     

The Biochemical Mechanisms of Antimicrobial Photodynamic Therapy†

The unbridled dissemination of multidrug-resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose-dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by three different methods and showed a dose-dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community toward the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy.     

CuII binding sites located at His-96 and His-111 of the human prion protein: thermodynamic and spectroscopic studies on model peptides

The prion protein (PrP) is a Cu(2+)-binding cell-surface glycoprotein. Using PrP peptide fragments, by means of potentiometric, spectroscopic and thermodynamic techniques, we have shown that Cu(2+) ions bind to the region comprising His-96, His-111 and the octarepeat domain within residues 60-91. Cu(2+) may bind in different modes, which strongly depend both on His position within the peptide sequence and on the adjacent residues. We have used a series of protected oligopeptides having His at the C- or the N-terminus, inducing different binding modes to amide nitrogens around the His residue, either towards the N- or C-terminus. His imidazole acts as an anchoring site for Cu(2+) and then binding to ionized amide nitrogens follows. When it is directed towards the C-terminus the formation of a less stable seven-membered chelate ring with a {N(im), N(-)} binding mode occurs. When coordination goes towards the N-terminus the thermodynamically more stable six-membered chelate ring is formed. NMR data suggest that both the coordination modes are possible for the model peptides; however, the thermodynamic measurements show that they only slightly differ in energy and the influence of the adjacent amino acid residues can address the coordination toward the C- or the N-terminus.     

A radioactive tracer and radiation study of the stability of ferric and ferrous ions and ascorbic acid

A preliminary liquid-liquid extraction study of ferric and ferrous ions has been undertaken using the radioactive tracer technique with⁵⁹Fe as an indicator of iron. Various solvents were studied and suitable media and solvents were selected for the separation of the two oxidation states of iron. Such separation was used to study the effect of ascorbic acid and other reducing agents on the reduction of ferric ions. The oxidation of ferrous ions to the ferric state under the effect of gamma radiation from⁶⁰Co has also been investigated in the absence and presence of ascorbic acid, using spectrophotometry. In addition, a calculation of the amount of iron oxidized by gamma radiation is given with a discussion of its mechanism and possible effects on the metabolism of iron in the human body.