Binding of daunorubicin to human serum albumin using molecular modeling and its analytical application

Systematic interaction of plasma albumin with the efficacy of chemotherapeutic drugs

Albumin, as the most abundant plasma protein, plays an integral role in the transport of a variety of exogenous and endogenous ligands in the bloodstream and extravascular spaces. For exogenous drugs, especially chemotherapeutic drugs, binding to and being delivered by albumin can significantly affect their efficacy. Meanwhile, albumin can also bind to many endogenous ligands, such as fatty acids, with important physiological significance that can affect tumor proliferation and metabolism. In this review, we summarize how albumin with unique properties affects chemotherapeutic drugs efficacy from the aspects of drug outcome in blood, toxicity, tumor accumulation and direct or indirect interactions with fatty acids, plus application of albumin-based carriers for anti-tumor drug delivery.

Interactions of the Rad51 inhibitor DIDS with human and bovine serum albumins: Optical spectroscopy and isothermal calorimetry approaches

Rad51 is a key protein in DNA repair by homologous recombination and an important target for development of drugs in cancer therapy. 4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) has been used in clinic during the past 30 years as an inhibitor of anion transporters and channels. Recently DIDS has been demonstrated to affect Rad51-mediated homologous pairing and strand exchange, key processes in homologous recombination. Consequently, DIDS has been considered as a potential revertant of radio- and chemo-resistance of cancer cells, the major causes of therapy failure. Here, we have investigated the behavior of DIDS towards serum albumins. The effects of environmental factors, primarily, solvent polarity, on DIDS stability were evaluated, and the mechanisms of interaction of DIDS with human or bovine serum albumin were analyzed using isothermal calorimetry, circular dichroism and fluorescence spectroscopies. DIDS interaction with both serum albumins have been demonstrated, and the interaction characteristics have been determined. By comparing these characteristics for several DIDS derivatives, we have identified the DIDS moiety essential for the interaction. Furthermore, site competition data indicate that human albumin has two DIDS-binding sites: a high-affinity site in the IIIA subdomain and a low-affinity one in the IB subdomain. Molecular docking has revealed the key molecular moieties of DIDS responsible for its interactions in each site and shown that the IB site can bind two ligands. These findings show that binding of DIDS to serum albumin may change the balance between the free and bound DIDS forms, thereby affecting its bioavailability and efficacy against Rad51.

Ag-4-ATP-MWCNT electrode modified with dsDNA as label-free electrochemical sensor for the detection of daunorubicin anticancer drug

This paper describes the synthesis of Ag-4-ATP-MWCNT nanocomposite and its use as a modifier of working electrode. The surface of the electrochemical Ag-4-ATP-MWCNT electrode was modified with a double-stranded DNA (dsDNA) to detect daunorubicin-DNA interactions. Differential pulse voltammetry was applied to develop an electroanalytical procedure for the determination of daunorubicin and evaluate its interaction with dsDNA immobilized on the electrode surface. After the optimization of operational parameters, the linear dependence of the peak current on the daunorubicin concentration was observed in the range of 0.10×10^-8 to 1.00×10^-5molL^-1, with the detection and quantification limits of 3.00×10^-10 and 1.00×10^-9molL^-1, respectively. The proposed biosensor was successfully applied to validate its capability for the determination of daunorubicin in human serum and urine samples.

Multi-spectroscopic and molecular modeling studies of interaction between two different angiotensin I converting enzyme inhibitory peptides from gluten hydrolysate and human serum albumin

The present study was carried out to characterize Angiotensin-converting enzyme (ACE) inhibitory peptides which are released from the trypsin hydrolysate of wheat gluten protein. The binding of two inhibitory peptide (P₄ and P₆) to human serum albumin (HSA) under physiological conditions has been investigated by multi-spectroscopic in combination with molecular modeling techniques. Time-resolved and quenching fluorescence spectroscopies results revealed that the quenching of HSA fluorescence by P₄ and P₆ in the binary and ternary systems caused HSA-peptides complexes formation. The results indicated that both peptides quenched the fluorescence intensity of HSA through a static mechanism. The binding affinities and number of binding sites were obtained for the HSA-peptides complexes. The circular dichroism (CD) data revealed that the presence of both peptides increased the α-helix content of HSA and induced the remarkable folding of the polypeptide of the protein. Therefore, the CD data determined that the protein structure has been stabilized in the percent of ACE inhibitory peptides in binary and ternary systems. The binding distances between HSA and both peptides were estimated by the Forster theory, and it was revealed that nonradiative energy transfer from HSA to peptides occurred with a high probability. ITC experiments reveal that, in the absence and presence of P₆, the dominant forces are electrostatic in binary and ternary systems. Furthermore, molecular modeling studies confirmed the experimental results. Molecular modeling investigation suggested that P₄ bound to the site IA and IIA of HSA in binary and ternary systems, respectively. This study on the interaction of peptides with HSA should prove helpful for realizing the distribution and transportation of food compliments and drugs in vivo, elucidating the action mechanism and dynamics of food compliments and drugs at the molecular level. It should moreover be of great use for understanding the pharmacokinetic and pharmacodynamic mechanism of the food compliments and drugs.

Synthesis and study on the binding of thiazol-2(3H)-ylidine derivative with human serum albumin using spectroscopic and molecular docking methods

In this article, a facile and convenient synthesis of thiazol-2(3H)-ylidine derivatives of fatty acid (3a-c) is described. The binding of N'-(4,5-dimethyl-3-penylthiazol-2(3H)-ylidine)octadec-9-enehydrazide (3a) with human serum albumin (HSA) is explored using various spectral methods and molecular docking. Fluorescence quenching results show that 3a induces conformational changes in HSA and the polarity around the tryptophan residues is increased. Stern-Volmer quenching plots at different temperatures (298, 305 and 312 K) show that the fluorescence quenching mechanism is static quenching. Synchronous fluorescence, 3D fluorescence spectra, circular dichroism and Fourier transform infrared spectroscopy are used to determine the structural change in HSA on interaction with 3a. Förster resonance energy transfer analysis shows that the binding distance (r₀  = 2.78 nm) between HSA (Trp214) and 3a is within the of range 2-8 nm for quenching to occur. The molecular docking study also confirms that 3a is located in subdomain IIA (site I) of HSA and is stabilized by hydrogen bonding and hydrophobic forces.

Spectroscopic and molecular modeling study on the separate and simultaneous bindings of alprazolam and fluoxetine hydrochloride to human serum albumin (HSA): with the aim of the drug interactions probing

The objective of the present research is to study the interaction of separate and simultaneous of alprazolam (ALP) and fluoxetine hydrochloride (FLX) with human serum albumin (HSA) in phosphate buffer (pH 7.4) using different kinds of spectroscopic, cyclic voltammetry and molecular modeling techniques. The absorbance spectra of protein, drugs and protein-drug showed complex formation between the drugs and HSA. Fluorescence analysis demonstrated that ALP and FLX could quench the fluorescence spectrum of HSA and demonstrated the conformational change of HSA in the presence of both drugs. Also, fluorescence quenching mechanism of HSA-drug complexes both separately and simultaneously was suggested as static quenching. The analysis of UV absorption data and the fluorescence quenching of HSA in the binary and ternary systems showed that FLX decreased the binding affinity between ALP and HSA. On the contrary, ALP increased the binding affinity of FLX and HSA. The results of synchronous fluorescence and three-dimensional fluorescence spectra indicated that the binding of drugs to HSA would modify the microenvironment around the Trp and Tyr residues and the conformation of HSA. The distances between Trp residue and the binding sites of the drugs were estimated according to the Förster theory, and it was demonstrated that non-radiative energy transfer from HSA to the drugs occurred with a high probability. Moreover, according to CV measurements, the decrease of peak current in the cyclic voltammogram of the both drugs in the presence of HSA revealed that they interacted with albumin and binding constants were calculated for binary systems which were in agreement with the binding constants obtained from UV absorption and fluorescence spectroscopy. The prediction of the best binding sites of ALP and FLX in binary and ternary systems in molecular modeling approach was done using of Gibbs free energy.

Thermodynamic characterization of the interaction between a peptide-drug complex and serum proteins

The interaction between a peptide-based drug delivery system and two serum proteins, bovine serum albumin (BSA) and immunoglobulin G (IgG), is investigated using fluorescence quenching and calorimetric techniques. An ionic-complementary self/co-assembling peptide, EAR8-II, is employed to encapsulate the hydrophobic anticancer drug pirarubicin (THP) and stabilize it in protein environments. Self/co-assembling properties of the peptide-drug complex (EAR8-II-THP) are shown to be different while interacting with serum proteins compared with the properties of the isolated complex. The results from thermodynamic studies suggest that the drug delivery system has a strong binding affinity (K(SV) 1689 M(-1)), exothermic and enthalpy-driven interaction, with BSA and a relatively weak affinity with IgG (K(SV) 295.2 M(-1)). In the presence of salt ions, the enthalpy and binding affinity remain unchanged, implying other interactions such as hydrogen bonding and Van der Waals interactions are present that are not affected by reduced polarity. This work forms the basis for further studies of EAR8-II-THP complexes in the presence of important proteins and for further evaluation of the complexes' immune response and anticancer activity.

Binding and conformational changes of human serum albumin upon interaction with 4-aminoantipyrine studied by spectroscopic methods and cyclic voltammetry

The interactions of 4-aminoantipyrine (AAP) with human serum albumin (HSA) have been studied by UV-visible spectroscopy, fluorescence spectroscopy and cyclic voltammetry. The binding of 4-aminoantipyrine quenches the HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 10(5) M(-1). The experimental results showed that AAP effectively quenched the intrinsic fluorescence of HSA via dynamic type of quenching. In addition, according to the synchronous fluorescence spectra of HSA in presence of 4-aminoantipyrine, the tryptophan residue of the proteins are most perturbed by the binding process. The number of binding sites, the binding constant, site probe study, some common metal ions effect and the thermodynamic parameters were calculated.

Administration of chromium(III) and manganese(II) as a potential protective approach against daunorubicin-induced cardiotoxicity: in vitro and in vivo experimental evidence

Daunorubicin (DNR) is a widely used antitumor drug, but its application is limited because of its cardiotoxic side effects. The present study was designed to investigate the interaction between DNR and cardiac myosin (CM) in the presence of chromium(III) (Cr(3+)) and manganese(II) (Mn(2+)) using fluorescence spectrometry under simulative physiological conditions with the aim of exploring the influence of metal ion on DNR-CM complex and finding out an aggressive approach to abrogate of DNR-induced cardiotoxicity. In detail, the quenching and binding constant of ternary system, including metal ion, DNR, and CM, were measured and compared with the DNR-CM. The data from in vitro experiments indicate that the presence of Cr(3+) or Mn(2+) distinctly decreased the binding force between DNR and CM, and alleviated the cardiac toxicity caused by DNR. In addition, the variations in mice body weight and myocardial enzyme level were examined by in vivo experiments. Animals receiving Cr(3+) or Mn(2+) supplementation of DNR showed preservation of the normal pattern of the heart, especially 2.0 mg Cr(3+)/kg body wt or 50.0 mg Mn(2+)/kg body wt exhibited an obviously protective effect accompanied with body weight raise when compared with the mice treated with DNR alone, decreased the ratio of heart to body weight (BW) and the ratio of left ventricular mass to BW to the normal levels, and inhibited the leak of myocardial enzyme caused by DNR. As a result, this study suggests that pretreatment of lower dose of Cr(3+) (2 mg/kg wt) and moderate dose of Mn(2+) (50 mg/kg wt) might be useful and play an important role in ameliorating the cardiotoxicity of DNR treatment in cancer patients.

Biophysical characterization of in vitro bound Streptomyces peucetius daunorubicin-serine protease complex

A serine protease of Streptomyces peucetius is found in association with daunorubicin in the culture filtrate and co-purifies as a complex as reported earlier by us (Dubey et al., 2013). The same protease was purified without drug attachment from dpsA(-) mutant of S. peucetius, which does not produce daunorubicin. Drug-protein complex was made in vitro by mixing daunorubicin and the protease. Spectral analysis and circular dichroism (CD) analysis were employed to determine the interaction between daunorubicin and the protease. Our study showed that interaction of daunorubicin with the protease affects the spectral characteristics of the drug and changes the secondary structure of the protein. Thin layer chromatography (TLC) analysis showed that the drug-protein interaction results in partial conversion of the drug to aglyconic form. The complex formation implies sequestration of the drug when it attains potentially lethal level in the extracellular milieu of S. peucetius culture.

Interaction of 3'-azido-3'-deamino daunorubicin with human serum albumin: investigation by fluorescence spectroscopy and molecular modeling methods

In this Letter, the binding of 3'-azido-3'-deamino daunorubicin (ADNR) to human serum albumin (HSA) was investigated at different temperatures by fluorescence spectroscopy at pH 7.4. The binding constant was determined according to Stern-Volmer equation based on the fluorescence quenching of HSA in the presence of ADNR. The thermodynamic parameters, ΔH and ΔS, were calculated according to the dependence of enthalpy change on the temperature to be -21.01 kJ mol(-1) and 24.71 J K(-l) mol(-l), respectively. The results revealed that ADNR had a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The hydrophobic force played a major role in the interaction of ADNR with HSA, which was in good agreement with the results of molecular modeling study. The effect of various metal ions on the binding constants of ADNR with HSA was also investigated. All the experimental results and theoretical data indicated that ADNR could bind to HSA and be effectively transported and eliminated in body, which might be a useful guideline for further drug design.

Interaction of an anthracycline disaccharide with ctDNA: Investigation by spectroscopic technique and modeling studies

This study was designed to examine the interaction of an anthracycline disaccharide, 4'-O-(beta-L-oleandrosyl) daunorubicin (DNR-D2), with calf thymus deoxyribonucleic acid (ctDNA) by UV-vis in combination with fluorescence spectroscopy and molecular modeling techniques under physiological conditions (Britton-Robinson buffer solutions, pH 7.4). By the analysis of UV-vis and fluorescence spectrum, it was observed that the binding mode between DNR-D2 and ctDNA might be intercalation, and fluorescence quenching mechanism of DNR-D2 by ctDNA was a static quenching type. Upon binding to ctDNA, the anthraquinone chromophore of DNR-D2 could slide into the C-G rich region of ctDNA. Hydrogen bonding forces may play an essential role in the binding of DNR-D2 to ctDNA. Furthermore, the results obtained from computational modeling corroborated the experimental results obtained from spectroscopic investigations. These studies are valuable for a better understanding the datailed mode of DNR-D2-DNA interaction, which should be important in deeper insight into the therapeutic efficiency of DNR-D2.

Interaction of anthracycline disaccharide with human serum albumin: investigation by fluorescence spectroscopic technique and modeling studies

Anthracyclines are considered to be some of the most effective anticancer drugs for cancer therapy. However, drug resistance and cardiotoxicity of anthracyclines limit their clinical application. An 3'-azido disaccharide analogue of daunorubicin, 7-[4-O-(2,6-dideoxy-3-O-methyl-alpha-l-arabino-hexopyranosyl)-3-azido-2,3,6-trideoxy-alpha-l-lyxo-hexopyranosyl]daunorubicinone (ADNR-3), was shown to exhibit 10-fold better activity than parent compound daunorubicin against the drug-resistant cells and completely overcomes the drug resistance with same IC(50) in both drug-resistant and drug-sensitive cells. In this paper, the interactions between ADNR-3 and human serum albumin (HSA) have been studied by spectroscopic techniques. By the analysis of fluorescence spectrum and fluorescence intensity, it was observed that the ADNR-3 has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The association constants of ADNR-3 with HSA were determined at different temperatures based on fluorescence quenching results. The negative DeltaH and positive DeltaS values in case of ADNR-3-HSA complexes showed that both hydrogen bonds and hydrophobic interactions play a role in the binding of ADNR-3 to HSA. Furthermore, synchronous fluorescence spectroscopy data and UV-vis absorbance spectra have suggested that the association between ADNR-3 and HSA changed the molecular conformation of HSA and the hydrophobic interactions play a major role in ADNR-3-HSA association. Moreover, the study of computational modeling indicated that ADNR-3 could bind to the site I of HSA and hydrophobic interaction was the major acting force for the second type of binding site, which was in agreement with the thermodynamic analysis. The distance, r, between donor (HSA) and acceptor (ADNR-3) was obtained according to the Förster's theory of non-radiation energy transfer. In addition, the effects of common ions on the binding constants of ADNR-3-HSA complexes were also investigated.

Effect of zinc and copper on the interaction of daunorubicin with cardiac myosin

Daunorubicin (DNR) is an anthracyline antibiotic which induces a well-described but incompletely understood cardiac toxicity. In this study, a direct action of DNR on the major contractile protein, cardiac myosin (CM), was described utilizing the fluorescence spectroscopy. The quenching mechanism was suggested to be static quenching according to the fluorescence measurement. In particular, the effects of common ions on the binding constants of DNR with CM were also investigated under physiological conditions, and the quenching constant K(SV) and binding constant K(LB) were obtained at room temperature. These data proved that Zn2+ and/or Cu2+ potentiated quenching fluorescence intensity of DNR-CM complex. Moreover, the normal ratio of Zn2+ to Cu2+ was able to competitively inhibit the binding interaction of DNR with CM, which might contribute to exert the most significant cardioprotective effect and guarantee the contractile machinery of cardiac muscle.