The interaction of human serum albumin with selected lanthanide and actinide ions: Binding affinities, protein unfolding and conformational changes

Thorium Alters Lung Surfactant Protein Expression in Alveolar Epithelial Cells: In Vitro and In Vivo Investigation

Thorium-232 (Th), the most abundant naturally occurring nuclear fuel, has been identified as a sustainable source of energy. In view of its large-scale utilization and human evidence of lung disorders and carcinogenicity, it is imperative to understand the effect of Th exposure on lung cells. The present study investigated the effect of Th-dioxide (1-100 μg/mL, 24-48 h) on expression of surfactant proteins (SPs) (SP-A, SP-B, SP-C, and SP-D, which are essential to maintain lung's surface tension and host-defense) in human lung cells (WI26 and A549), representative of alveolar cell type-I and type-II, respectively. Results demonstrated the inhibitory effect of Th on transcriptional expression of SP-A, SP-B, and SP-C. However, Th promoted the mRNA expression of SP-D in A549 and reduced its expression in WI26. To a significant extent, the effect of Th on SPs was found to be in accordance with their protein levels. Moreover, Th exposure altered the extracellular release of SP-D/A from A549, which remained unaltered in WI26. Our results suggested the differential role of oxidative stress and ATM and HSP90 signaling in Th-induced alterations of SPs. These effects of Th were found to be consistent in lung tissues of mice exposed to Th aerosols, suggesting a potential role of SPs in Th-associated lung disorders.

Mechanistic insights into Thorium-232 induced liver carcinogenesis: The driving role of Wnt/β-catenin signaling pathway

Thorium-232 (Th-232), a naturally-occurring radioactive element with high potential of nuclear fuel is now being utilized in advanced nuclear reactors for CO2-free energy generation. To achieve all-round capability in Th-fuel cycle for health and environment, understanding the biological effects of Th-232 at cellular and molecular level are extremely important. The present study investigated long-term effects (6 and 12 months) of Th-232 (4, 10 and 20 mg/kg) on gene expression in mice liver (major target organ). Analysis of differentially expressed genes (DEGs, ≥2.0 folds, p < 0.05) showed that with the increase of Th dose (4 to 20 mg/kg), the number of upregulated DEGs increased and the number of downregulated DEGs decreased significantly. A significant number of upregulated DEGs (10 genes in 6 months and 14 genes in 12 months) were found common between 4 and 20 mg/kg. Gene Ontology analysis revealed significant (Padj ~ 10-6-10-28) enrichment of upregulated DEGs for metabolic process, signal transduction, cell death, cell cycle and cell proliferation. KEGG pathway analysis showed DEGs significantly enriched in several cancer-related pathways including hepatocellular carcinoma (HCC). Protein-protein interaction analysis further revealed statistically significant functional interaction (p-value ~10-6-10-10) among the proteins of HCC, which identified β-catenin as one of the most significant signaling nodes in association with myc, an oncogene and p53, a tumor suppressor. Importantly, these results were corroborated by quantitative real time-polymerase chain reaction and western blotting in liver tissues of animals exposed to Th-232. This study insights Wnt/β-catenin signaling network attributable to drive Th-induced liver carcinogenesis, which may have significant implications for management of long-term effects of Th-232.

Binding of human serum albumin with uranyl ion at various pH: an all atom molecular dynamics study

Uranium is routinely handled in various stages of nuclear fuel cycle and its association with human serum albumin (HSA) has been reported in literature, however, their binding characteristics still remains obscure. The present study aims to understand interaction of uranium with HSA by employing all atom molecular dynamics simulation of the HSA-metal ion complex. His67, His247 and Asp249 residues constitute the major binding site of HSA, which capture the uranyl ion (UO22+). A total of six sets of initial coordinates are used for Zn2+-HSA and UO22+-HSA system at pH = 4, 7.4 and 9, respectively. Enhance sampling method, namely, well-tempered meta-dynamics (WT-MtD) is employed to study the binding and un-binding processes of UO22+ and Zn2+ ions. Potential of mean force (PMF) profiles are generated for all the six sets of complexes from the converged WT-MtD run. Various basins and barriers are observed along the (un)binding pathways. Hydrogen bond dynamics and short-range Coulomb interactions are evaluated from the equilibrium run at each basins and barriers for both the ions at all pH values. The binding of UO22+ ion with HSA is the result of the dynamical balance between UO22+-HSA and UO22+-water short range Coulomb interactions. Zn2+ ion interact more strongly than UO22+ at all pH through short range Coulomb interactions. PMF values further concludes that UO22+ cannot associate to the Zn2+ bound HSA protein but can be captured by free HSA at all pH values i.e. endosomal, alkaline and physiological pH.Communicated by Ramaswamy H. Sarma.

Biodistribution of Multimodal Gold Nanoclusters Designed for Photoluminescence-SPECT/CT Imaging and Diagnostic

Highly biocompatible nanostructures for multimodality imaging are critical for clinical diagnostics improvements in the future. Combining optical imaging with other techniques may lead to important advances in diagnostics. The purpose of such a system would be to combine the individual advantages of each imaging method to provide reliable and accurate information at the site of the disease bypassing the limitations of each. The aim of the presented study was to evaluate biodistribution of the biocompatible technetium-99m labelled bovine serum albumin-gold nanoclusters (^99mTc-BSA-Au NCs) as photoluminescence-SPECT/CT agent in experimental animals. It was verified spectroscopically that radiolabelling with ^99mTc does not influence the optical properties of BSA-Au NCs within the synthesized ^99mTc-BSA-Au NCs bioconjugates. Biodistribution imaging of the ^99mTc-BSA-Au NCs in Wistar rats was performed using a clinical SPECT/CT system. In vivo imaging of Wistar rats demonstrated intense cardiac blood pool activity, as well as rapid blood clearance and accumulation in the kidneys, liver, and urinary bladder. Confocal images of kidney, liver and spleen tissues revealed no visible uptake indicating that the circulation lifetime of ^99mTc-BSA-Au NCs in the bloodstream might be too short for accumulation in these tissues. The cellular uptake of ^99mTc-BSA-Au NCs in kidney cells was also delayed and substantial accumulation was observed only after 24-h incubation. Based on our experiments, it was concluded that ^99mTc-BSA-Au NCs could be used as a contrast agent and shows promise as potential diagnostic agents for bloodstream imaging of the excretory organs in vivo.

Stable Chelation of the Uranyl Ion by Acyclic Hexadentate Ligands: Potential Applications for 230U Targeted α-Therapy

Uranium-230 is an α-emitting radionuclide with favorable properties for use in targeted α-therapy (TAT), a type of nuclear medicine that harnesses α particles to eradicate cancer cells. To successfully implement this radionuclide for TAT, a bifunctional chelator that can stably bind uranium in vivo is required. To address this need, we investigated the acyclic ligands H₂dedpa, H₂CHXdedpa, H₂hox, and H₂CHXhox as uranium chelators. The stability constants of these ligands with UO₂²⁺ were measured via spectrophotometric titrations, revealing log β_ML values that are greater than 18 and 26 for the "pa" and "hox" chelators, respectively, signifying that the resulting complexes are exceedingly stable. In addition, the UO₂²⁺ complexes were structurally characterized by NMR spectroscopy and X-ray crystallography. Crystallographic studies reveal that all six donor atoms of the four ligands span the equatorial plane of the UO₂²⁺ ion, giving rise to coordinatively saturated complexes that exclude solvent molecules. To further understand the enhanced thermodynamic stabilities of the "hox" chelators over the "pa" chelators, density functional theory (DFT) calculations were employed. The use of the quantum theory of atoms in molecules revealed that the extent of covalency between all four ligands and UO₂²⁺ was similar. Analysis of the DFT-computed ligand strain energy suggested that this factor was the major driving force for the higher thermodynamic stability of the "hox" ligands. To assess the suitability of these ligands for use with ²³⁰U TAT in vivo, their kinetic stabilities were probed by challenging the UO₂²⁺ complexes with the bone model hydroxyapatite (HAP) and human plasma. All four complexes were >95% stable in human plasma for 14 days, whereas in the presence of HAP, only the complexes of H₂CHXdedpa and H₂hox remained >80% intact over the same period. As a final validation of the suitability of these ligands for radiotherapy applications, the in vivo biodistribution of their UO₂²⁺ complexes was determined in mice in comparison to unchelated [UO₂(NO₃)₂]. In contrast to [UO₂(NO₃)₂], which displays significant bone uptake, all four ligand complexes do not accumulate in the skeletal system, indicating that they remain stable in vivo. Collectively, these studies suggest that the equatorial-spanning ligands H₂dedpa, H₂CHXdedpa, H₂hox, and H₂CHXhox are highly promising candidates for use in ²³⁰U TAT.

Role of calcium ion channels and cytoskeletal proteins in Thorium-232 induced toxicity in normal human liver cells (WRL 68) and its validation in swiss mice

Hepatic disorders reported in humans exposed to Thorium-232 (Th-232) rationalizes the present study investigating the toxicological response of normal human liver cells (WRL 68) and its validation in Swiss mice. Cell count analysis of WRL 68 cells-treated with Th-nitrate (1-200 μM) estimated IC50 of ∼24 μM (at 24 h) and 35 μM (at 48 h). Analysis of cell viability (trypan blue assay) showed the IC50 of ∼172 μM. Phase contrast bright-field microscopy revealed Th-induced morphological changes and cell-released microvesicle-like structures in extracellular space. Th-estimation by ICP-MS (Inductively-coupled plasma mass-spectrometry) showed uptake of Th by cells as a function of concentration and incubation time. Employing DTPA as a chelating agent in cell harvesting solution, cell-internalized/strongly-bound Th was estimated to be ∼42% of total incubated Th. Th-uptake studies in the presence of ion-channel specific inhibitors (e.g. nifedipine, thapsigargin) revealed the role of plasma membrane calcium channels and cytoplasmic calcium in modulating the Th-uptake. Transmission electron microscopy of Th-treated cells showed cell-derived extracellular vesicles, alterations in the shape and size of nucleus and mitochondria as well as cytoplasmic inclusions. The order of Th accumulation in various sub-cellular protein fractions was found to be as cytoskeleton (43%) > cytoplasmic (15%) > chromatin (7%) > nuclear (5%) & membrane (5%). Immunofluorescence analysis of WRL 68 cells showed that Th significantly altered the expression of cytoskeleton proteins (F-actin and keratin), which was further validated in liver tissues of Swiss mice administered with Th-232. Findings herein highlight the role of calcium channels and cytoskeleton in Th-induced toxicity. Keywords: Thorium toxicity; Liver cells; Calcium channels; Sub-cellular targets, Cytoskeleton; Swiss Mice.

Engineering lanmodulin's selectivity for actinides over lanthanides by controlling solvent coordination and second-sphere interactions

Developing chelators that combine high affinity and selectivity for lanthanides and/or actinides is paramount for numerous industries, including rare earths mining, nuclear waste management, and cancer medicine. In particular, achieving selectivity between actinides and lanthanides is notoriously difficult. The protein lanmodulin (LanM) is one of Nature's most selective chelators for trivalent actinides and lanthanides. However, mechanistic understanding of LanM's affinity and selectivity for f-elements remains limited. In order to decipher, and possibly improve, the features of LanM's metal-binding sites that contribute to this actinide/lanthanide selectivity, we characterized five LanM variants, substituting the aspartate residue at the 9^th position of each metal-binding site with asparagine, histidine, alanine, methionine, and selenomethionine. Spectroscopic measurements with lanthanides (Nd³⁺ and Eu³⁺) and actinides (²⁴³Am³⁺ and ²⁴⁸Cm³⁺) reveal that, contrary to the behavior of small chelator complexes, metal-coordinated water molecules enhance LanM's affinity for f-elements and pH-stability of its complexes. Furthermore, the results show that the native aspartate does not coordinate the metal directly but rather hydrogen bonds to coordinated solvent. By tuning this first-sphere/second-sphere interaction, the asparagine variant nearly doubles LanM's selectivity for actinides versus lanthanides. This study not only clarifies the essential role of coordinated solvent for LanM's physiological function and separation applications, but it also demonstrates that LanM's preference for actinides over lanthanides can be further improved. More broadly, it demonstrates how biomolecular scaffolds possess an expanded repertoire of tunable interactions compared to most small-molecule ligands – providing an avenue for high-performance LanM-based actinide/lanthanide separation methods and bio-engineered chelators optimized for specific medical isotopes.

Nature’s most potent protein for f-elements, lanmodulin, relies on subtle first-sphere/second-sphere interactions to bind metal ions. Dissecting lanmodulin’s binding mechanism yielded variants with enhanced actinide/lanthanide selectivity.

Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment

Anthropogenic radionuclides, including long-lived heavy actinides such as americium and curium, represent the primary long-term challenge for management of nuclear waste. The potential release of these wastes into the environment necessitates understanding their interactions with biogeochemical compounds present in nature. Here, we characterize the interactions between the heavy actinides, Am³⁺ and Cm³⁺, and the natural lanthanide-binding protein, lanmodulin (LanM). LanM is produced abundantly by methylotrophic bacteria, including Methylorubrum extorquens, that are widespread in the environment. We determine the first stability constant for an Am³⁺-protein complex (Am₃LanM) and confirm the results with Cm₃LanM, indicating a ∼5-fold higher affinity than that for lanthanides with most similar ionic radius, Nd³⁺ and Sm³⁺, and making LanM the strongest known heavy actinide-binding protein. The protein's high selectivity over ²⁴³Am's daughter nuclide ²³⁹Np enables lab-scale actinide-actinide separations as well as provides insight into potential protein-driven mobilization for these actinides in the environment. The luminescence properties of the Cm³⁺-LanM complex, and NMR studies of Gd³⁺-LanM, reveal that lanmodulin-bound f-elements possess two coordinated solvent molecules across a range of metal ionic radii. Finally, we show under a wide range of environmentally relevant conditions that lanmodulin effectively outcompetes desferrioxamine B, a hydroxamate siderophore previously proposed to be important in trivalent actinide mobility. These results suggest that natural lanthanide-binding proteins such as lanmodulin may play important roles in speciation and mobility of actinides in the environment; it also suggests that protein-based biotechnologies may provide a new frontier in actinide remediation, detection, and separations.

Mechanism of thorium-nitrate and thorium-dioxide induced cytotoxicity in normal human lung epithelial cells (WI26): Role of oxidative stress, HSPs and DNA damage

Inhalation represents the most prevalent route of exposure with Thorium-232 compounds (Th-nitrate/Th-dioxide)/Th-containing dust in real occupational scenario. The present study investigated the mechanism of Th response in normal human alveolar epithelial cells (WI26), exposed to Th-nitrate or colloidal Th-dioxide (1-100 μg/ml, 24-72 h). Assessment in terms of changes in cell morphology, cell proliferation (cell count), plasma membrane integrity (lactate dehydrogenase leakage) and mitochondrial metabolic activity (MTT reduction) showed that Th-dioxide was quantitatively more deleterious than Th-nitrate to WI26 cells. TEM and immunofluorescence analysis suggested that Th-dioxide followed a clathrin/caveolin-mediated endocytosis, however, membrane perforation/non-endocytosis seemed to be the mode of Th internalization in cells exposed to Th-nitrate. Th-estimation by ICP-MS showed significantly higher uptake of Th in cells treated with Th-dioxide than with Th-nitrate at a given concentration. Both Th-dioxide and nitrate were found to increase the level of reactive oxygen species, which seemed to be responsible for lipid peroxidation, alteration in mitochondrial membrane potential and DNA-damage. Amongst HSPs, the protein levels of HSP70 and HSP90 were affected differentially by Th-nitrate/dioxide. Specific inhibitors of ATM (KU55933) or HSP90 (17AAG) were found to increase the Th- cytotoxicity suggesting prosurvival role of these signaling molecules in rescuing the cells from Th-toxicity.

Complexation of Cm(III) with blood serum proteins: recombinant human serum albumin (rHSA)

The complexation of Cm(III) with the recombinant human serum albumin (rHSA) (characterized by single deletion of residue Asp-1), is studied in dependence of pH and rHSA concentration using time-resolved laser fluorescence spectroscopy (TRLFS). A Cm(III) rHSA species is formed between pH 6.4 and 10.0 with the conditional stability constant being logK = 6.47 at pH = 7.4. Competition titration experiments with Cu(II) and Zn(II) confirm complexation at the N-terminal binding site (NTS) of rHSA and exclude the involvement of the Multi-Metal Binding Site (MBS). Comparison with a previous study on Cm(III) interaction with native albumin, HSA, points out, that residue Asp-1 is involved in Cm(III) binding to HSA but is not crucial for Cm(III) complexation at the NTS. The results are of major importance for a better understanding of fundamental actinide-protein interaction mechanisms which are highly required for the identification and characterization of relevant distribution pathways of incorporated radionuclides.

Detection and Quantification of Tightly Bound Zn2+ in Blood Serum Using a Photocaged Chelator and a DNAzyme Fluorescent Sensor

DNAzymes have emerged as a powerful class of sensors for metal ions due to their high selectivity over a wide range of metal ions, allowing for on-site and real-time detection. Despite much progress made in this area, detecting and quantifying tightly bound metal ions, such as those in the blood serum, remain a challenge because the DNAzyme sensors reported so far can detect only mobile metal ions that are accessible to bind the DNAzymes. To overcome this major limitation, we report the use of a photocaged chelator, XDPAdeCage to extract the Zn²⁺ from the blood serum and then release the chelated Zn²⁺ into a buffer using 365 nm light for quantification by an 8-17 DNAzyme sensor. Protocols to chelate, uncage, extract, and detect metal ions in the serum have been developed and optimized. Because DNAzyme sensors for other metal ions have already been reported and more DNAzyme sensors can be obtained using in vitro selection, the method reported in this work will significantly expand the applications of the DNAzyme sensors from sensing metal ions that are not only free but also bound to other biomolecules in biological and environmental samples.

Evaluation of parent and nano-encapsulated terbium(III) complex toward its photoluminescence properties, FS-DNA, BSA binding affinity, and biological applications

BACKGROUND

There is a crucial need for finding and developing new compounds as the anticancer and antimicrobial agents with better activity, specific target, and less toxic side effects.

OBJECTIVES

Base on the potential anticancer properties of lanthanide complexes, in the paper, the biological applications of terbium (Tb) complex, containing 2,9-dimethyl- 1,10-phenanthroline (Me2Phen) such as anticancer, antimicrobial, DNA cleavage ability, the interaction with FS-DNA (Fish-Salmon DNA) and BSA (Bovine Serum Albumin) was examined.

METHODS

The interaction of Tb-complex with BSA and DNA was studied by emission spectroscopy, absorption titration, viscosity measurement, CD spectroscopy, competitive experiments, and docking calculation. Also, the ability of this complex to cleave DNA was reported by gel electrophoresis. Tb-complex was concurrently screened for its antibacterial activities by different methods. Besides, the nanocarriers of Tb-complex (lipid nanoencapsulation (LNEP) and the starch nanoencapsulation (SNEP)), as active anticancer candidates, were prepared. MTT technique was applied to measure the antitumor properties of these compounds on human cancer cell lines.

RESULTS

The experimental and docking results suggest significant binding between DNA as well as BSA with terbium-complex. Besides, groove binding plays the main role in the binding of this compound with DNA and BSA. The competitive experiment with hemin demonstrated that the terbium complex was bound at site III of BSA, which was confirmed by the docking study. Also, Tb-complex was concurrently screened for its DNA cleavage, antimicrobial, and anticancer activities. The anticancer properties of LNEP and SNEP are more than the terbium compound.

CONCLUSIONS

Tb-complex can bond to DNA/BSA with high binding affinity. Base on biological applications of Tb-complex, it can be concluded that this complex and its nanocarriers can suggest as novel anticancer, antimicrobial candidates.

What do we know about actinides-proteins interactions?

Since the early 40s when the first research related to the development of the atomic bomb began for the Manhattan Project, actinides (An) and their association with the use of nuclear energy for civil applications, such as in the generation of electricity, have been a constant source of interest and fear. In 1962, the first Society of Toxicology (SOT), led by H. Hodge, was established at the University of Rochester (USA). It was commissioned as part of the Manhattan Project to assess the impact of nuclear weapons production on workers’ health. As a result of this initiative, the retention and excretion rates of radioactive heavy metals, their physiological impact in the event of acute exposure and their main biological targets were assessed. In this context, the scientific community began to focus on the role of proteins in the transportation and in vivo accumulation of An. The first studies focused on the identification of these proteins. Thereafter, the continuous development of physico-chemical characterization techniques has made it possible to go further and specify the modes of interaction with proteins from both a thermodynamic and structural point of view, as well as from the point of view of their biological activity. This article reviews the work performed in this area since the Manhattan Project. It is divided into three parts: first, the identification of the most affine proteins; second, the study of the affinity and structure of protein-An complexes; and third, the impact of actinide ligation on protein conformation and function.

Strong Uranium(VI) Binding onto Bovine Milk Proteins, Selected Protein Sequences, and Model Peptides

Hexavalent uranium is ubiquitous in the environment. In view of the chemical and radiochemical toxicity of uranium(VI), a good knowledge of its possible interactions in the environment is crucial. The aim of this work was to identify typical binding and sorption characteristics of uranium(VI) with both the pure bovine milk protein β-casein and diverse related protein mixtures (caseins, whey proteins). For comparison, selected model peptides representing the amino acid sequence 13-16 of β-casein and dephosphorylated β-casein were also studied. Complexation studies using potentiometric titration and time-resolved laser-induced fluorescence spectroscopy revealed that the phosphoryl-containing proteins form uranium(VI) complexes of higher stability than the structure-analog phosphoryl-free proteins. That is in agreement with the sorption experiments showing a significantly higher affinity of caseins toward uranium(VI) in comparison to whey proteins. On the other hand, the total sorption capacity of caseins is lower than that of whey proteins. The discussed binding behavior of milk proteins to uranium(VI) might open up interesting perspectives for sustainable techniques of uranium(VI) removal from aqueous solutions. This was further demonstrated by batch experiments on the removal of uranium(VI) from mineral water samples.

Thorium decorporation efficacy of rationally-selected biocompatible compounds with relevance to human application

During civil, nuclear or defense activities, internal contamination of actinides in humans and mitigation of their toxic impacts are of serious concern. Considering the health hazards of thorium (Th) internalization, an attempt was made to examine the potential of ten rationally-selected compounds/formulations to decorporate Th ions from physiological systems. The Th-induced hemolysis assay with human erythrocytes revealed good potential of tiron, silibin (SLB), phytic acid (PA) and Liv.52^® (L52) for Th decorporation, in comparison to diethylenetriaminepentaacetic acid, an FDA-approved decorporation drug. This was further validated by decorporation experiments with relevant human cell models (erythrocytes and liver cells) and biological fluid (blood) under pre-/post-treatment conditions, using inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM). Furthermore, density functional theory-based calculations and extended X-ray absorption fine structure (EXAFS) spectroscopy confirmed the formation of Th complex by these agents. Amongst the chosen biocompatible agents, tiron, SLB, PA and L52 hold promise to enhance Th decorporation for human application.

Interaction of Cm(III) with human serum albumin studied by time-resolved laser fluorescence spectroscopy and NMR

The complexation of Cm(III) with human serum albumin (HSA) was investigated using time-resolved laser fluorescence spectroscopy (TRLFS). The Cm(III) HSA species is dominating the speciation between pH 7.0 and 9.3. The first coordination sphere is composed by three to four H₂O molecules and five to six coordinating ligands from the protein. For the complex formation at pH 8.0 a conditional stability constant of logK = 6.16 ± 0.50 was determined. Furthermore, information on the Cm(III) HSA binding site were obtained. With increasing Cu(II) concentration the Cm(III) HSA complexation is suppressed whereas the addition of Zn(II) has no effect. This points to the complexation of Cm(III) at the N-terminal binding site (NTS) which is the primary Cu(II) binding site. NMR experiments with Cu(II), Eu(III) and Am(III) HSA show a decrease of the peak assigned to the His C2 proton of His 3, which is part of the NTS, with increasing metal ion concentration. This confirms the complexation of Eu(III) and Am(III) at the Cu(II) binding site NTS. The results presented in this study contribute to a better understanding of relevant biochemical reactions of incorporated actinides.

Captopril apparently increase and cisplatin apparently decrease human albumin concentration in artificial urinary solutions

BACKGROUND

Measurement of urinary albumin (HSA) is very important in diagnostic of kidney diseases. Much less is known about the possible impact of substances present in urine together with albumin on the results of measurements.

METHODS

We investigated the effect of the presence of captopril and cisplatin in the solution on the result of the determination of HSA by native polyacrylamide gel electrophoresis. Protein conformation in the absence and presence of the drugs was examined using Fourier Transform Infrared Spectroscopy (FTIR).

RESULTS

The presence of captopril apparently increases HSA concentration while cisplatin causes an apparent decrease in the HSA concentration. The presence of both drugs also influence the secondary structure forms of HSA albumin investigated by FTIR.

CONCLUSION

Both drugs tested in the concentration of human use can have an impact on the results of determination of albumin in urine which can influence clinical decision.

Investigating the Interaction of Fe Nanoparticles with Lysozyme by Biophysical and Molecular Docking Studies

Herein, the interaction of hen egg white lysozyme (HEWL) with iron nanoparticle (Fe NP) was investigated by spectroscopic and docking studies. The zeta potential analysis revealed that addition of Fe NP (6.45±1.03 mV) to HEWL (8.57±0.54 mV) can cause to greater charge distribution of nanoparticle-protein system (17.33±1.84 mV). In addition, dynamic light scattering (DLS) study revealed that addition of Fe NP (92.95±6.11 nm) to HEWL (2.68±0.37 nm) increases suspension potential of protein/nanoparticle system (51.17±3.19 nm). Fluorescence quenching studies reveled that both static and dynamic quenching mechanism occur and hydrogen bond and van der Waals interaction give rise to protein-NP system. Synchronous fluorescence spectroscopy of HEWL in the presence of Fe NP showed that the emission maximum wavelength of tryptophan (Trp) residues undergoes a red-shift. ANS fluorescence data indicated a dramatic exposure of hydrophobic residues to the solvent. The considerable reduction in melting temperature (T(m)) of HEWL after addition of Fe NP determines an unfavorable interaction system. Furthermore circular dichoroism (CD) experiments demonstrated that, the secondary structure of HEWL has not changed with increasing Fe NP concentrations; however, some conformational changes occur in tertiary structure of HEWL. Moreover, protein-ligand docking study confirmed that the Fe NP forms hydrogen bond contacts with HEWL.