Electrochemical behavior of ferritin at the polarized water|1,2-dichloroethane interface
Introduction
Ferritin is a well-known iron storage and detoxification protein, which is ubiquitous in animals, plants and bacteria. Ferritin forms a nanocage structure in which up to 4500 iron atoms can be accommodated [1]. The diameter and inner cavity are approximately 12 and 8 nm, respectively [2]. Ferritin is composed of 24 subunits of two types known as heavy (H) and light (L) chains, classified according to the subunit molecular weight, 21 and 19 kDa, respectively [1,2]. The nanocage structure reversibly assembles and disassembles depending on the pH conditions. The pH-dependent structures of ferritin have been investigated by synchrotron small-angle X-ray scattering (SAXS) [3]. It has been found that the intact hollow spherical ferritin was stable over the pH range 3.40–10.0, while stepwise disassembly of the hollow sphere takes place below pH 3.40. Since these unique features could play an important role in developing a molecular capsule or container, much attention has been paid to ferritin in fields including nanocomposite materials, semiconductors, drug delivery system (DDS) and so on [[4], [5], [6], [7]]. In fact ferritin forms a nanocage structure with several channels through which metal ions and/or organic molecules could pass in vivo, however, ferritin could function as an attractive molecular capsule if one can control the reversible assembly reaction.
The interface between two immiscible electrolyte solutions (ITIES) is a useful model for biomembrane systems in which charge transfer and adsorption processes are controlled as a function of the Galvani potential difference between two liquid phases [8,9]. The physicochemical study of bioactive species in biomimetic liquid–liquid systems is important since it is difficult to investigate in vivo the complicated pharmacokinetics involved in molecular association, acid-base equilibrium and distribution on or across a biomembrane [[10], [11], [12]]. Furthermore, electrochemical ion transfer at the ITIES offers an attractive label-free method of determining non-redox active species [13]. There are a number of studies of the electrochemical characterization and determination of small ionizable drugs [[14], [15], [16]], polyelectrolytes [17], macromolecules [18,19], and proteins [[20], [21], [22], [23]] at the ITIES. We have recently investigated the interfacial mechanism of dendritic polymers and their association behavior with anionic water-soluble porphyrins [24], ionizable drugs [25] and bioactive flavin species [26] through spectroelectrochemical techniques. In these works, it was demonstrated that NH2- and COOH-terminated polyamidoamine (PAMAM) dendrimers are useful molecular capsules and that hyperbranched polymers are pharmacokinetic modifiers of bioactive species.
In this study, the voltammetric behavior of ferritin was studied at the water|1,2-dichloroethane (DCE) interface prior to an application of ferritin as a molecular capsule for a functional DDS. The influence of pH, the concentration of ferritin and the organic supporting electrolyte, and the effect of repetitive sweeps on the voltammetric response were investigated.
Section snippets
Reagents
Ferritin from equine spleen (F4503) was purchased from Aldrich and used as received. The concentration of ferritin was calculated by using the molecular weight of the peptides (ca. 440 kDa). 1.0 × 10−2 mol dm−3 LiCl and 5.0 × 10−3 mol dm−3 bis(triphenylphosphoranylidene)ammonium tetrakis(pentafluorophenyl)borate (BTPPATPFB) were used as supporting electrolytes for the aqueous and organic phases, respectively. BTPPATPFB was prepared by metathesis of bis(triphenylphosphoranylidene)ammonium
Results and discussion
Typical cyclic voltammograms (CVs) measured for ferritin under various pH conditions are shown in Fig. 2a. CVs obtained under acidic conditions varied gradually depending on the repetitive sweeps (discussed later). Unless otherwise noted, therefore, the CVs obtained after 5 repetitive sweeps are used for the following discussion. No obvious voltammetric responses were observed in the potential window under neutral and alkaline conditions. However, at pH 2.1, anodic and cathodic peaks were
Conclusions
The voltammetric investigation revealed that the electrochemical behavior of ferritin at the polarized liquid|liquid interface was dependent on the pH. In acidic conditions where ferritin is disassembled to subunits, the current responses were drastically increased in the positive potential region. This result demonstrated that ferritin subunits have large positive charges. Ferritin subunits provided two distinguishable voltammetric responses during the forward and reverse sweeps. The
Conflict of interest
There is no conflict of interest.
Acknowledgements
The authors are grateful for valuable discussions with Mr. Ryota Kenmotsu of Okayama University of Science.
References (30)
- et al.
Molecular aspects of iron uptake and storage in ferritin
Coord. Chem. Rev.
(1995) - et al.
Ferritin, a novel vehicle for iron supplementation and food nutritional factors encapsulation
Trends Food Sci. Technol.
(2015) - et al.
Ionic partition diagrams of ionisable drugs: pH-lipophilicity profiles, transfer mechanisms and charge effects on solvation
J. Electroanal. Chem.
(1999) - et al.
Adsorption-desorption mechanism of a cationic polyelectrolyte based on dimethylaminoethyl polymethacrylates at the water/1,2-dichloroethane interface
Electrochim. Acta
(2014) - et al.
Electrochemical behaviour of haemoglobin at the liquid/liquid interface
Electrochim. Acta
(2008) - et al.
Ion transfer and adsorption behavior of ionizable drugs affected by PAMAM dendrimers at the water|1,2-dichloroethane interface
Electrochim. Acta
(2016) - et al.
Molecular association between flavin derivatives and dendritic polymers at the water|1,2-dichloroethane interface
J. Electroanal. Chem.
(2016) - et al.
Galvani potential scales for water-nitrobenzene and water-1,2-dichloroethane interfaces
Electrochim. Acta
(1990) - et al.
On ferritin heterogeneity: further evidence for heteropolymers
J. Biol. Chem.
(1978) - et al.
Counterion binding to protamine polyion at a polarised liquid-liquid interface
J. Electroanal. Chem.
(2007)
Spectroelectrochemical analysis of ion-transfer and adsorption of the PAMAM dendrimer at a polarized liquid|liquid interface
Electrochim. Acta
Ferritin: structure, gene regulation, and cellular function in animals, plants, and microorganisms
Annu. Rev. Biochem.
pH-dependent structures of ferritin and apoferritin in solution: disassembly and reassembly
Biomacromolecules
Ferritin: a versatile building block for bionanotechnology
Chem. Rev.
Protein nanoparticles for therapeutic protein delivery
Biomater. Sci.
Cited by (17)
Indirect detection of acid phosphatase at the macroscopic electrified liquid-liquid interface
2024, Electrochimica ActaInterfacial association of ferritin with anionic fluorescent probe at the 1,2-dichloroethane/water interface
2021, Journal of Electroanalytical ChemistryCitation Excerpt :On the other hand, the molecular association behavior between ionic species and dendritic polymers at ITIES has been elucidated through the spectroelectrochemical analysis, in which the interfacial reaction mechanisms of ionic species were reversibly controlled by the interaction with dendritic polymers under the appropriate potential [22–24]. Recently, we have reported the voltammetric behavior of ferritin at the polarized 1,2-dichloroethane (DCE)/water interface, suggesting its specific adsorption at the interface and the facilitated ion transfer of the organic anions [25]. In the present study, the spectroelectrochemical analysis of ferritin has been conducted by employing a fluorescent probe, 8-anilino-1-naphthalenesulfonate (ANS−), in order to elucidate the interfacial association of ferritin with anionic species in detail.
Electrochemistry of catalase at a liquid|liquid micro-interface array
2021, BioelectrochemistryCitation Excerpt :But at aqueous phase of pH 5.5 (the natural pH of 10 mM LiCl), no obvious CV response was observed (Fig. 1(b)), on comparison of CVs in the absence (black dashed line) and in the presence of 2 µM CAT (black solid line). In respect of this observed pH dependence, CAT behaves like other proteins at the ITIES, e.g. ferritin [43], insulin [44], lysozyme [44], myoglobin [29], haemoglobin [45], where below the pI of CAT (pI 5.4) [9], it is protonated and cationic in nature. But when the aqueous phase pH is higher than the pI of CAT, it is anionic in nature and no definite voltammetric response was found.
Co-deposition of silica and proteins at the interface between two immiscible electrolyte solutions
2020, BioelectrochemistryCitation Excerpt :Further polarization, together with the accumulated positive or negative charge within defined locus, facilitates the transfer of the organic phase background electrolyte anions or cations, respectively. This type of interfacial behaviour was reported for dendrimers (poly-L-lysine [13]; poly(propylamine) [14]; poly(amidoamine) [14,15] or carboxyl terminated-poly(amidoamine) [16]), polyelectrolytes (poly(diallyl dimethylammonium chloride) [17]; chitosan [18] protamine [19]; heparin [20]), proteins (e.g. ferritin [21] haemoglobin (Hb) [22,23]; myoglobin [24]; insulin [25]; cytochrome [26]) or DNA (thrombin binding aptamer [27]). Resulting deposits usually reside at the interface in a form of thin films.
Electrochemistry of proteins at the interface between two immiscible electrolyte solutions
2018, Current Opinion in ElectrochemistryCitation Excerpt :Electrochemical parameters indicate also that multi-layer films of adsorbed protein are formed at the interface. Systematic studies of pH with a range of proteins revealed that this indeed was the case (lysozyme [15], insulin [13], haemoglobin [12], cytochrome c [10,11], myoglobin [17], serum albumin [18]) and most recently, ferritin [19] and thrombin [20] have been shown to react exactly as predicted. Such behaviour has been summarised in a range of reviews/chapters [21,22].
Acid phosphatase behaviour at an electrified soft junction and its interfacial co-deposition with silica
2018, Electrochemistry CommunicationsCitation Excerpt :The interface between two immiscible electrolyte solutions (ITIES) emerges as a unique analytical platform with detection arising from interfacial charge transfer reactions including ions or electrons [4]. Proteins, when (positively) charged, can undergo potential-dependent adsorption to the ITIES, as has been found for haemoglobin [5], lysozyme [6], insulin [7], myoglobin [8], albumin [7] and ferritin [9], amongst others. Proteins and synthetic multi-charged macromolecules (e.g. polyelectrolytes [10], dendrimers [11]) can be considered to have similar interfacial charge-transfer characteristics.