Presence Of Human Serum Albumin Research Articles

Enzalutamide-human serum albumin interaction: Electrochemical exploration of complex formation and binding parameters

This research investigation employed electrochemical methods to explore the interaction between the anti-cancer drug Enzalutamide (ENZ) and Human Serum Albumin (HSA). Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV), and Electrochemical Impedance Spectroscopy (EIS) techniques were used via a glassy carbon electrode (GCE) substrate. The interaction between ENZ and HSA was examined based on the changes in the electrochemical behavior of [Fe(CN)6]3−/4− redox species under physiological pH conditions. Electrochemical and kinetic parameters of the redox probe in the presence of HSA, ENZ, and the ENZ-HSA complex were calculated. The results showed significant differences in these parameters due to the formation of an electro-inactive complex between the protein and the drug. Binding parameters of ENZ-HSA, such as the binding constant and complex stoichiometry, were found, revealing the formation of a robust drug-albumin complex with a binding constant value of 2.7 × 108 M−1. A molecular docking study was conducted to examine the possible binding mode of ENZ and its interactions with HSA. This research provides valuable insights and can serve as a reference for future studies to enhance drug delivery systems.

Multi-spectroscopic and theoretical analysis on the interaction between human serum albumin and Cm-E2O2-Cm gemini surfactants

Human serum albumin (HSA) is among the blood plasma proteins crucial for transporting various natural and pharmaceutical substances throughout the body. This research examined how the structure of HSA changes when exposed to Cm-E2O2-Cm gemini surfactants, which possess various advantageous properties, utilizing a combination of multispectral analysis and computational modeling techniques. The aggregation behavior of gemini surfactants in the presence of HSA was also investigated to demonstrate the HSA-Cm-E2O2-Cm complexation. The intrinsic fluorescence findings showed that gemini surfactants caused HSA fluorescence to diminish due to static quenching. The binding constants (Kb) for HSA-Cm-E2O2-Cm at varying temperatures were around 103 M−1, with approximately one binding site detected. In addition, the effect of gemini surfactants on the conformation of HSA was analyzed by performing UV–vis, extrinsic, synchronous, RRS and 3-D fluorescence, and CD experiments. The interactions’ binding sites and driving forces (also spontaneity) were calculated using molecular docking analysis, which agrees with site marker studies and thermodynamic parameter value results.

Iron-carbohydrate complexes treating iron anaemia: Understanding the nano-structure and interactions with proteins through orthogonal characterisation

Intravenous (IV) iron-carbohydrate complexes are widely used nanoparticles (NPs) to treat iron deficiency anaemia, often associated with medical conditions such as chronic kidney disease, heart failure and various inflammatory conditions. Even though a plethora of physicochemical characterisation data and clinical studies are available for these products, evidence-based correlation between physicochemical properties of iron-carbohydrate complexes and clinical outcome has not fully been elucidated yet. Studies on other metal oxide NPs suggest that early interactions between NPs and blood upon IV injection are key to understanding how differences in physicochemical characteristics of iron-carbohydrate complexes cause variance in clinical outcomes. We therefore investigated the core-ligand structure of two clinically relevant iron-carbohydrate complexes, iron sucrose (IS) and ferric carboxymaltose (FCM), and their interactions with two structurally different human plasma proteins, human serum albumin (HSA) and fibrinogen, using a combination of cryo-scanning transmission electron microscopy (cryo-STEM), x-ray diffraction (XRD), small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS). Using this orthogonal approach, we defined the nano-structure, individual building blocks and surface morphology for IS and FCM. Importantly, we revealed significant differences in the surface morphology of the iron-carbohydrate complexes. FCM shows a localised carbohydrate shell around its core, in contrast to IS, which is characterised by a diffuse and dynamic layer of carbohydrate ligand surrounding its core. We hypothesised that such differences in carbohydrate morphology determine the interaction between iron-carbohydrate complexes and proteins and therefore investigated the NPs in the presence of HSA and fibrinogen. Intriguingly, IS showed significant interaction with HSA and fibrinogen, forming NP-protein clusters, while FCM only showed significant interaction with fibrinogen. We postulate that these differences could influence bio-response of the two formulations and their clinical outcome. In conclusion, our study provides orthogonal characterisation of two clinically relevant iron-carbohydrate complexes and first hints at their interaction behaviour with proteins in the human bloodstream, setting a prerequisite towards complete understanding of the correlation between physicochemical properties and clinical outcome.

The weakened physiological functions of human serum albumin in presence of polystyrene nanoplastics

Due to the widespread presence of nanoplastics (NPs) in daily essentials and drinking water, the potential adverse effects of NPs on human health have become a global concern. Human serum albumin (HSA), the most abundant and multi-functional protein in plasma, has been chosen to understand the biological effects of NPs after entering the blood. The esterase activity and the transport of bisphenol A in the presence of polystyrene nanoplastics (PSNPs) under physiological conditions (pH 4.0 and 7.4) have been investigated to evaluate the possible biological effects. The interactions between PSNPs and HSA have also been systematically studied by multispectral methods and dynamic light scattering techniques. The esterase activity of HSA presented a decreased trend with increasing PSNPs; conversely, higher permeabilities are accompanied by higher amounts of PSNPs. Compared with the unchanged hydrodynamic diameter and weaker interactions at pH 7.4, stronger binding between HSA and PSNPs at pH 4.0 led to a significant increase in the particle size of the PSNPs-HSA complex. The quenching mechanism belonged to the static quenching type. The electrostatic force is proposed to be the dominant factor for PSNPs binding to HSA. The work provides some information about the toxicity of NPs when exposed to humans.

Exploring weak ligand-protein interactions by relaxometry of long-lived spin order.

Relaxation times of nuclear spins often serve as a valuable source of information on the dynamics of various biochemical processes. Measuring relaxation as a function of the external magnetic field turned out to be extremely useful for the studies of weak ligand-protein interactions. We demonstrate that observing the relaxation of the long-lived spin order instead of longitudinal magnetization extends the capability of this approach. We studied the field-dependent relaxation of the longitudinal magnetization and the singlet order (SO) of methylene protons in alanine-glycine dipeptide and citrate in the presence of human serum albumin (HSA). As a result, SO relaxation proved to be more sensitive to ligand-protein interaction, providing higher relaxation contrast for various HSA concentrations. To assess the parameters of the binding process in more details, we utilized a simple analytical relaxation model to fit the experimental field dependences for both SO and T1 relaxation. We also tested the validity of our approach in the experiments with trimethylsilylpropanoic acid (TSP) used as a competitor in ligand binding with HSA.

Seeking for Innovation with Magnetic Resonance Imaging Paramagnetic Contrast Agents: Relaxation Enhancement via Weak and Dynamic Electrostatic Interactions with Positively Charged Groups on Endogenous Macromolecules.

Gd-L1 is a macrocyclic Gd-HPDO3A derivative functionalized with a short spacer to a trisulfonated pyrene. When compared to Gd-HPDO3A, the increased relaxivity appears to be determined by both the higher molecular weight and the occurrence of an intramolecularly catalyzed prototropic exchange of the coordinated OH moiety. In water, Gd-L1 displayed a relaxivity of 7.1 mM-1 s-1 (at 298 K and 0.5 T), slightly increasing with the concentration likely due to the onset of intermolecular aggregation. A remarkably high and concentration-dependent relaxivity was measured in human serum (up to 26.5 mM-1 s-1 at the lowest tested concentration of 0.005 mM). The acquisition of 1H-nuclear magnetic relaxation dispersion (NMRD) and 17O-R2 vs T profiles allowed to get an in-depth characterization of the system. In vitro experiments in the presence of human serum albumin, γ-globulins, and polylysine, as well as using media mimicking the extracellular matrix, provided strong support to the view that the trisulfonated pyrene fosters binding interactions with the exposed positive groups on the surface of proteins, responsible for a remarkable in vivo hyperintensity in T1w MR images. The in vivo MR images of the liver, kidneys, and spleen showed a marked contrast enhancement in the first 10 min after the i.v. injection of Gd-L1, which was 2-6-fold higher than that for Gd-HPDO3A, while maintaining a very similar excretion behavior. These findings may pave the way to an improved design of MRI GBCAs, for the first time, based on the setup of weak and dynamic interactions with abundant positive groups on serum and ECM proteins.

Modeling the deformation of the semiconductor quantum dot with a multilayer shell in a living cell

The model of the semiconductor quantum dot with a multilayer shell and the quantum dot-human serum albumin bionanocomplex, which are contained in a living cell, was constructed. The regularities of changes in deformation of materials of the CdSe-core / ZnS/CdS/ZnS-shell quantum dot with changes in cell elasticity (comprehensive modulus) at different core radii, thicknesses of individual shell layers, and surface concentration of albumin molecules were investigated. It is shown that the presence of human serum albumin on the surface of the quantum dot significantly increases its sensitivity to pressure caused by the surrounding medium (living cell). The obtained results indicate the prospect of using the core-shell quantum dot-human serum albumin bionanocomplexes for the diagnosis of cancer diseases in the early stages. This is due to the fact that such diseases are accompanied by a sharp change in the elasticity of the cell (its elastic constants).

Exploring the impact of novel thiazole-pyrazole fused benzo-coumarin derivatives on human serum albumin: Synthesis, photophysical properties, anti-cholinergic activity, and interaction studies

Derivatives of thiazole-pyrazole fused benzo-coumarin compounds were successfully synthesized and characterized, followed by a comprehensive spectroscopic investigation on various photophysical properties in different media. The multipronged approach using steady state and time resolved fluorescence spectroscopy pointed out the impact of substitution in the estimated spectroscopic and other physicochemical properties of the systems. Further, the evaluation of anti-acetylcholinesterase (anti-AChE) activity yielded significant insight into the therapeutic potential of the synthesized coumarinyl compounds for the treatment of Alzheimer's disease (AD). The findings revealed a non-competitive mode of inhibition mechanism, with an estimated IC50 value of 67.72 ± 2.00 nM observed for one of the investigated systems as AChE inhibitor. Notably, this value is even lower than that of an FDA-approved AD drug Donepezil (DON), indicating the enhanced potency of the coumarin derivatives in inhibiting AChE. Interestingly, significant diminution in inhibition was observed in presence of human serum albumin (HSA) as evidenced by the relative increase in IC50 value by 8 ∼ 39 % in different cases, which emphasized the role of albumin proteins to control therapeutic efficacies of potential medications. In-depth spectroscopic and in-silico analysis quantified the nature of interactions of the investigated systems with HSA and AChE. Overall, the outcomes of this study provide significant understanding into the biophysical characteristics of novel thiazole-pyrazole fused benzo-coumarin systems, which could aid in the development of new cholinergic agents for the treatment of AD and materials based on coumarin motifs.

Long-Acting Nanohybrid Hydrogel Induces Persistent Immunogenic Chemotherapy for Suppressing Postoperative Tumor Recurrence and Metastasis.

Despite the continuous advancement of surgical resection techniques, postoperative tumor recurrence and metastasis remain a huge challenge. Here, we constructed an injectable curcumin/doxorubicin-loaded nanoparticle (NanoCD) hydrogel, which could effectively inhibit tumor regrowth and metastasis via reshaping the tumor immune microenvironment (TIME) for highly effective postsurgical cancer treatment. NanoCD was prepared by the controlled assembly of curcumin (CUR) and doxorubicin (DOX) via π-π stacking and hydrogen bonding in the presence of human serum albumin. To facilitate prolonged treatment of postsurgical tumors, NanoCD was further incorporated into the temperature-sensitive Poloxamer 407 gel (NanoCD@Gel) for intracavity administration. Mechanistically, DOX induced the generation of intracellular reactive oxygen species (ROS) and CUR reduced the ROS metabolism by inhibiting thioredoxin reductase (TrxR). The synergy of DOX and CUR amplified intracellular ROS levels and thus resulted in enhanced immunogenic cell death (ICD) of tumor cells. Upon being injected into the tumor cavity after resection, the in situ-generated NanoCD@Gel allowed the local release of CUR and DOX in a controlled manner to induce local chemotherapy and persistently activate the antitumor immune response, thereby achieving enhanced immunogenic chemotherapy with reduced systemic toxicity. Our work provides an elegant strategy for persistently stimulating effective antitumor immunity to prevent postsurgical tumor recurrence and metastasis.

Gd3+ Complexes for MRI Detection of Zn2+ in the Presence of Human Serum Albumin: Structure-Activity Relationships.

Zn2+-responsive magnetic resonance imaging (MRI) contrast agents are typically composed of a Gd chelate conjugated to a Zn2+-binding moiety via a linker. They allow for Zn2+ detection in the presence of human serum albumin (HSA). In order to decipher the key parameters that drive their Zn2+-dependent MRI response, we designed a pyridine-based ligand, PyAmC2mDPA, and compared the properties of GdPyAmC2mDPA to those of analogue complexes with varying Gd core, Zn-binding moiety, or linker sizes. The stability constants determined by pH potentiometry showed the good selectivity of PyAmC2mDPA for Gd3+ (log KGd = 16.27) versus Zn2+ (log KZn = 13.58), proving that our modified Zn2+-binding DPA moiety prevents the formation of previously observed dimeric species. Paramagnetic relaxation enhancement measurements indicated at least three sites that are available for GdPyAmC2mDPA binding on HSA, as well as a 2-fold affinity increase when Zn2+ is present (KD = 170 μM versus KDZn = 60 μM). Fluorescence competition experiments provided evidence of the higher affinity for site II vs site I, as well as the importance of both the Zn-binding part and the Gd core in generating enhanced HSA affinity in the presence of Zn2+. Finally, an analysis of nuclear magnetic relaxation dispersion (NMRD) data suggested a significantly increased rigidity for the Zn2+-bound system, which is responsible for the Zn2+-dependent relaxivity response.

PEROXIDASE-LIKE ACTIVITY OF MAGNETIC NANOPARTICLES IN THE PRESENCE OF BLOOD PROTEINS

The generation of hydroxyl radicals from hydrogen peroxide in aqueous solutions containing magnetic nanoparticles (MNPs), hemoglobin (Hb), immunoglobulin G (IgG), and human serum albumin (HSA) has been determined. The dependence of the rate of formation of the oxidized product of o-phenylenediamine (o-PDA) on the concentration of MNPs in solution, as well as on the concentration of proteins, was obtained. The peroxidase-like activity of MNPs was shown to decrease in the presence of HSA and IgG, while the addition of Hb to the reaction mixture was leading to its decrease and increase depending on protein concentration. The obtained effects can be used in the development of systems based on MNPs for theranostics, in particular, for suppression of tumor growth, and in predicting the ability of particles to catalyze the generation of reactive oxygen species (ROS) in vivo.

Derivatization of the Peptidic Xxx-Zzz-His Motif toward a Ligand with Attomolar CuII Affinity under Maintaining High Selectivity and Fast Redox Silencing.

Cu chelation in biological systems is of interest as a tool to study the metabolism of this essential metal or for applications in the case of diseases with a systemic or local Cu overload, such as Wilson's or Alzheimer's disease. The choice of the chelating agent must meet several criteria. Among others, affinities and kinetics of metal binding and related metal selectivity are important parameters of the chelators to consider. Here, we report on the synthesis and characterization of Cu-binding properties of two ligands, L1 and L2, derivatives of the well-known peptidic CuII-binding motif Xxx-Zzz-His (also called ATCUN), where CuII is bound to the N-terminal amine, two amidates, and the imidazole. In either L, the N-terminal amine was replaced with a pyridine, and for L2, one amide was replaced with an amine compared to Xxx-Zzz-His. In particular, L2 showed several interesting features, including a CuII-binding affinity with a log KDapp = -16.0 similar to that of EDTA and stronger than all reported ATCUN peptides. L2 showed high selectivity for CuII over ZnII and other essential metal ions, even under the challenging conditions of the presence of human serum albumin. Further, L2 showed fast and efficient CuII redox silencing qualities and CuII-L2 was stable in the presence of mM GSH concentrations. Benefitting the fact that L2 can be easily elongated on its peptide part by standard SPPS to add other functions, L2 has attractive properties as a CuII chelator for application in biological systems.

Introducing a new perspective for the electrochemical detection of cardiac troponin I in the presence of human serum albumin (HSA), cardiac troponin C (cTnC) and C-reactive protein (CRP) based on molecular modeling and electrocatalytic activity towards ascorbic acid

Cardiac troponin I (cTnI) is a specific biomarker of myocardial damage. Several techniques have been reported for cTnI detection, which is based on immunoaffinity, aptamers, and molecular imprinting polymers. Using computational methods, we introduced a novel chemical receptor for cTnI, named tetrabromophenol blue (TBPB), which interacted with cTnI selectivity in the presence of human serum albumin (HSA), cardiac troponin C (cTnC) and C reactive protein (CRP). Employing TBPB as a chemical receptor, a novel electrochemical sensor was constructed for the electrochemical sensing of cTnI. A glassy carbon electrode surface was modified with layered double hydroxide nanostructures (LDHNS) and TBPB. The modified electrode showed electrocatalytic activity toward ascorbic acid (AA) in a phosphate buffer solution (pH 7.4). The results revealed that using AA as a signal enhancer for cTnI detection could be a good idea. The linear range (50.00–3.50 × 105 pM) and detection limit (2.77 pM) were calculated using differential pulse voltammetry to measure cTnI at the TBPB/meso-Fe/CoLDHNS/GCE in a pH 7.40 buffer solution containing 1 mM of AA. Firstly, based on our docking studies, TBPB showed a very low tendency towards HSA, cTnC, and CRP. Additionally, the selectivity of TBPB/meso-Fe/CoLDHNS/GCE for cTnI was studied electrochemically in the presence of HSA, cTnC, and CRP.

High cancer selectivity and improving drug release from mesoporous silica nanoparticles in the presence of human serum albumin in cisplatin, carboplatin, oxaliplatin, and oxalipalladium treatment

In this project, drug release was examined based on the adsorption of cisplatin, carboplatin, oxaliplatin, and oxalipalladium on aminated mesoporous silica nanoparticles (N-HMSNs) and human serum albumin (HSA). These compounds were characterized by different techniques where three clinical Pt-drugs, cisplatin, carboplatin, oxaliplatin, plus oxalipalladium were loaded and investigated for release. Based on loading analysis, the loading ability of the mentioned metallodrug on N-HMSNs was dependent on the nature of the drug structure as well as hydrophobic or hydrophilic interactions. Different adsorption and release profiles were observed for all mentioned compounds via dialysis and ICP method analysis. Although the maximum to minimum loading occurred for oxalipalladium, cisplatin, and oxaliplatin to carboplatin, respectively, release from a surface with greater control belonged to carboplatin to cisplatin systems in the absence and presence of HSA to 48 h due to weak interaction for carboplatin drug. The quick release of all mentioned compounds from the protein level at high doses of the drug during chemotherapy occurred very fast within the first 6 h. In addition, the cytotoxic activity of both free drugs and drug-loaded@N-HMSNs samples on cancerous MCF-7, HCT116, A549, and normal HFF cell lines was evaluated by MTT assay. It was found that free metallodrugs exhibited more active cytotoxic behavior on both cancerous and normal cell lines than drug-loaded@N-HMSNs. Data demonstrated that the Cisplatin@N-HMSNs with SI=6.0 and 6.6 for MCF7 and HCT116 cell lines, respectively, and Oxaliplatin@N-HMSNs with SI=7.4 for HCT116 cell line can be good candidates as an anticancer drug with minimal side effects by protecting cytotoxic drugs as well as controlled release and high selectivity.

A self-assembled nanoprobe for detecting HSA based on hydrazide Schiff base: Its applications in diseases diagnosis and lysosome targeting imaging

Human serum albumin (HSA) is considered to be a diagnostic index of numerous diseases, and detecting HSA in subcellular environments is of great importance. In this work, we successfully synthesized a fluorescent probe NDIC based on hydrazide Schiff base, which can self-assemble into nanospheres in aqueous solution and produce distinct fluorescence signal in the presence of HSA. NDIC showed advantages including good sensitivity (LOD = 8.44 nM), high selectivity and anti-interference (over different coexisting proteins, amino acids, cations and anions). Job's plot, CD spectra, HSA destruction, site binding replacement and molecular docking provided reliable evidence for the fact that NDIC could combine at drug site I of HSA. Non-toxic probe NDIC could be applied to quantitatively detect HSA contents in urine, and achieve cancer identification by HSA imaging in cancer cells. More importantly, successful confocal experiment proved that NDIC possessed the lysosome selective imaging ability with the aid of HSA. These results showed the probe NDIC met the requirements of biological applications and was expected to explore HSA at the subcellular levels.

The Iron Content of Human Serum Albumin Modulates the Susceptibility of Acinetobacter baumannii to Cefiderocol.

The mortality rates of patients infected with Acinetobacter baumannii who were treated with cefiderocol (CFDC) were not as favorable as those receiving the best available treatment for pulmonary and bloodstream infections. Previous studies showed that the presence of human serum albumin (HSA) or HSA-containing fluids, such as human serum (HS) or human pleural fluid (HPF), in the growth medium is correlated with a decrease in the expression of genes associated with high-affinity siderophore-mediated iron uptake systems. These observations may explain the complexities of the observed clinical performance of CFDC in pulmonary and bloodstream infections, because ferric siderophore transporters enhance the penetration of CFDC into the bacterial cell. The removal of HSA from HS or HPF resulted in a reduction in the minimal inhibitory concentration (MIC) of CFDC. Concomitant with these results, an enhancement in the expression of TonB-dependent transporters known to play a crucial role in transporting iron was observed. In addition to inducing modifications in iron-uptake gene expression, the removal of HSA also decreased the expression of β-lactamases genes. Taken together, these observations suggest that environmental HSA has a role in the expression levels of select A. baumannii genes. Furthermore, the removal of iron from HSA had the same effect as the removal of HSA upon the expression of genes associated with iron uptake systems, also suggesting that at least one of the mechanisms by which HSA regulates the expression of certain genes is through acting as an iron source.

Experimental and Computational Characterisation of the Molecular Interactions between 1‐Butyl‐1‐methyl‐pyrrolidin‐1‐ium bis(trifluoromethanesulphonyl)imide and Human Serum Albumin

AbstractRecently, ionic liquids (ILs) have emerged as a therapeutic agent for industrial‐based pharmacology. In this regard, the current study highlights the key aspects of IL, (1‐butyl‐1‐methyl‐pyrrolidine‐1‐ium bis(trifluoromethanesulphonyl)imide), [Pyr C4 NTf3−] such as pharmacodynamics and pharmacokinetics. We performed a detailed experimental and computational analysis of [Pyr C4 NTf3−] with human serum albumin (HSA) using various spectroscopic techniques viz. UV‐vis, steady‐state fluorescence, synchronous fluorescence, time‐resolved fluorescence, steady‐state anisotropy and tensiometry study along with molecular docking. Absorption and emission spectral studies revealed the complex formation between [Pyr C4 NTf3−] and HSA where the binding constant (Kb) was found to be 5.5×103 Lmol−1. Thermodynamic parameters, Gibb's free energy change (ΔG), molar enthalpy change (ΔH), and molar entropy change (ΔS) revealed that the complex formation process is spontaneous, and enthalpy driven where involvement of hydrogen bond and van der Waal forces play a major role. Further, CD spectroscopy and ANS experiment showed the stability of HSA in presence of [Pyr C4 NTf3−]. A site marker study suggested that the binding of [Pyr C4 NTf3−] occurred at site II in HSA which is well supported by a molecular docking study. Also, MD simulation was done which revealed the stability of the complex formed between HSA and [Pyr C4 NTf3−]. The study might help in utilizing [Pyr C4 NTf3−], IL as a therapeutic agent in the pharmaceutical industries.

Singlet oxygen and radical-mediated mechanisms in the oxidative cellular damage photosensitized by the protease inhibitor simeprevir.

Hepatitis C, a liver inflammation caused by the hepatitis C virus (HCV), is treated with antiviral drugs. In this context, simeprevir (SIM) is an NS3/4A protease inhibitor used in HCV genotypes 1 and 4. It is orally administered and achieves high virological cure rates. Among adverse reactions associated with SIM treatment, photosensitivity reactions have been reported. In the present work, it is clearly shown that SIM is markedly phototoxic, according to the in vitro NRU assay using BALB/c 3T3 mouse fibroblast. This result sheds light on the nature of the photosensitivity reactions induced by SIM in HCV patients, suggesting that porphyrin elevation in patients treated with SIM may not be the only mechanism responsible for SIM-associated photosensitivity. Moreover, lipid photoperoxidation and protein photooxidation assays, using human skin fibroblasts (FSK) and human serum albumin (HSA), respectively, reveal the capability of this drug to promote photodamage to cellular membranes. Also, DNA photo lesions induced by SIM are noticed through comet assay in FSK cells. Photochemical and photobiological studies on the mechanism of SIM-mediated photodamage to biomolecules indicate that the key transient species generated upon SIM irradiation is the triplet excited state. This species is efficiently quenched by oxygen giving rise to singlet oxygen, which is responsible for the oxidation of lipids and DNA (Type II mechanism). In the presence of HSA, the photobehavior is dominated by binding to site 3 of the protein, to give a stable SIM@HSA complex. Inside the complex, quenching of the triplet excited state is less efficient, which results in a longer triplet lifetime and in a decreased singlet oxygen formation. Hence, SIM-mediated photooxidation of the protein is better explained through a radical (Type I) mechanism.

New Synthetic Quinoline (Qui) Derivatives as Novel Antioxidants and Potential HSA's Antioxidant Activity Modulators-Spectroscopic Studies.

The antioxidant activity of drugs, as well as the influence of drugs on the activity of endogenous antioxidant mechanisms in the human body is of great importance for the course of the disease and the treatment process. Due to the need to search for new therapeutic methods, the study of newly synthesized substances with potential therapeutic activity is necessary. This study aimed to designate some properties and characteristic parameters of new, synthetic quinoline three derivatives-1-methyl-3-allylthio-4-(4'-methylphenylamino)quinolinium bromide (Qui1), 1-methyl-3-allylthio-4-(3'-hydroxyphenylamino)quinolinium bromide (Qui2) as well as 1-methyl-3-allylthio-4-(4'-hydroxyphenylamino)quinolinium bromide (Qui3), including their antioxidant properties, as well as to analyse their activity as the potential modulators of Human Serum Albumin (HSA) antioxidant activity. In order to achieve the goal of the study, spectroscopic methods such as UV-Vis and circular dichroism (CD) spectroscopy have been used and based on the obtained data only slight and probably some surface interaction of quinoline derivatives (Qui1-Qui3) with HSA have been observed. The effect of Qui1-Qui3 on the HSA secondary structure was also insignificant. All analysed quinine derivatives have antioxidant activity against ABTS cation radical, in turn against DPPH radical, only Qui3 has noticeable antioxidant potential. The highest reduction potential by Qui3 as well as (Qui3 + HSA)complex has been shown. Qui3 mixed with HSA has mostly the synergistic effect against DPPH, ABTS and FRAP, while Qui1 and Qui2 in the presence of HSA mostly have a synergistic and additive effect towards ABTS, respectively. Based on the obtained results it can be concluded that Qui2 and Qui3 can be considered potential modulators of HSA antioxidant activity.

Time-Resolved Study on Self-Assembling Behavior of PEGylated Gold Nanoparticles in the Presence of Human Serum Albumin: A System for Nanomedical Applications

Time-Resolved Study on Self-Assembling Behavior of PEGylated Gold Nanoparticles in the Presence of Human Serum Albumin: A System for Nanomedical Applications