Interaction of aspirin and vitamin C with bovine serum albumin

Novel vanadyl complexes synthesis, characterization and interactions with bovine serum albumin-effects on STZ- diabetes rats

Drug-protein interactions are essential since most administered drugs bind abundantly and reversibly to serum albumin and are delivered mainly as a complex with protein. The nature and strength of drug-protein interactions have a big impact on how a drug works biologically. The binding parameters are useful in studying the pharmacological response of drugs and the designing of dosage forms. Serum albumin is regarded as optimal model for in vitro research on drug-protein interaction since it is the main protein that binds medicines and other physiological components. In this perspective, binary complex have been synthesized and characterized, from vanadium metal and acetylacetone(4,4,4-trifluoro-1-(2-theonyl)-1,3-butanedione). Imidazole, 2-Methyl-imidazole, and 2-Ethyl-imidazole auxiliary ligands were employed for the synthesis of ternary complexes. Additionally, UV absorption and fluorescence emission spectroscopy were used to examine the binding interactions between vanadium complexes and Bovine Serum Albumin. The outcomes of the binding studies and spectral approaches were in strong agreement with one another. These complexes upon inoculation into diabetes-induced Wistar rats stabilized their serum glucose levels within 3 days. From various studies, it was discovered that the ordering of glucose-lowering actions of these metal complexes were equivalent. The vanadium ternary metal complex derived from (4,4,4-trifluoro-1-(2-theonyl)-1,3-butanedione) and imidazole as ligands is the best among the other metal vanadium complexes.

Aminoquinoline-based Re(I) tricarbonyl complexes: Insights into their antiproliferative activity and mechanisms of action

In an effort to develop new potent anticancer agents, two Schiff base rhenium(I) tricarbonyl complexes, containing the ubiquitous aminoquinoline scaffold, were synthesized. Both aminoquinoline ligands and Re(I) complexes showed adequate stability over a 48-h incubation period. Furthermore, the cytotoxic activity of the precursor ligands and rhenium(I) complexes were evaluated against the hormone-dependent MCF-7 and hormone-independent triple negative MDA-MB-231 breast cancer cell lines. Inclusion of the [Re(CO)3Cl]+ entity significantly enhanced the cytotoxicity of the aminoquinoline Schiff base ligands against the tested cancer cell lines. Remarkably, the incorporation of the Schiff-base iminoquinolyl entity notably enhanced the cytotoxic activity of the Re(I) complexes, in comparison with the iminopyridyl entity. Notably, the quinolyl-substituted complex showed up to three-fold higher activity than cisplatin against breast cancer cell lines, underpinning the significance of the quinoline pharmacophore in rational drug design. In addition, the most active Re(I) complex showed better selectivity towards the breast cancer cells over non-tumorigenic FG-0 cells. Western blotting revealed that the complexes increased levels of γH2AX, a key DNA damage response protein. Moreover, apoptosis was confirmed in both cell lines due to the detection of cleaved PARP. The complexes show favourable binding affinities towards both calf thymus DNA (CT-DNA), and bovine serum albumin (BSA), and the order of their interactions align with their cytotoxic effects. The in silico molecular simulations of the complexes were also performed with CT-DNA and BSA targets.

Alleviating Aspirin-Induced Gastric Injury by Binding Aspirin to β-Lactoglobulin

Purpose

Gastric injury is a major issue for long-term administration of aspirin. In this work, we tried to explore the possibility of using BLG to alleviate aspirin-induced gastric injury, because of excellent abilities of BLG in loading drug molecules.

Methods

Various spectroscopic techniques and molecular docking methods were applied to investigate the interaction mechanism between BLG and aspirin. Animal experiments were performed to figure out the effects of taking aspirin-BLG on the stomach.

Results

Our results demonstrate that aspirin could bind with BLG to form stable aspirin-BLG complex (the binding constant K_b= 2.051 × 10³ M⁻¹). The formation process is endothermic (∆H>0) and the main acting force is hydrophobic force. Our data also show that the aspirin-BLG complex is formed with a higher affinity in simulated gastric fluid and could remain stable for several hours, which might arise from its special binding mode under acidic condition and the resistance of BLG to gastric digestion. Furthermore, animal models (rats with aspirin-induced gastric damage) were built. The results of animal experiments reveal that the oral administration of aspirin-BLG could cause less damage to gastric tissue, and it also hardly triggers obvious inflammatory responses.

Conclusion

This study would contribute to an in-depth understanding of the interaction mechanism between BLG and aspirin. It is reasonable to believe that using BLG to bind with aspirin would be a potential way to alleviate the aspirin-induced gastric injury.

Effect of ascorbic acid and citric acid on bioavailability of iron from Tegillarca granosa via an in vitro digestion/Caco-2 cell culture system

Iron deficiency anaemia (IDA) has been receiving worldwide attention. Developing safe and effective iron supplements is of great significance for IDA treatment. Tegillarca granosa (T. granosa), a traditional aquaculture bivalve species in China, is considered to be an excellent source of micronutrients, but the distribution and bioavailability of these minerals have yet to be investigated. The present research was conducted to determine the contents and in vitro enzymatic digestibility of minerals in T. granosa, using beef and wheat flour as reference foods. Meanwhile, two iron-binding proteins, hemoglobin and ferritin, were extracted from T. granosa, and their structures, iron accessibility and bioavailability were investigated. Moreover, the effects of ascorbic acid (AA) and citric acid (CA), two commonly applied dietary factors, on these parameters were evaluated. Our results indicated that the mineral levels varied significantly among different food matrices, with T. granosa showing the highest contents of the tested elements. Comparison of iron absorption of meat versus wheat flour and hemoglobin versus ferritin confirmed that heme iron exhibited higher bioavailability than non-heme iron. The addition of the two organic acids notably enhanced the cellular iron uptake of T. granosa-derived proteins. This could be because AA/CA weakened hydrogen bonds within proteins and caused disordered secondary structures, thereby improving their enzymatic digestibility and releasing more soluble iron to be available for absorption. The results of this study provided a basis for the development of T. granosa-derived protein-based iron supplements, promoting the diverse utilization of marine aquatic resources.

Experimental and theoretical study on the hydrogen bond interactions between ascorbic acid and glycine

Cyclic voltammetry, 1H nuclear magnetic resonance and quantum chemistry calculations were applied to explore the hydrogen bond interactions between ascorbic acid (AA) and glycine. The experimental results demonstrate the existence of hydrogen bonds in AA-glycine system, which has a significant effect on the oxidation peak potentials and currents of AA and the chemical shifts of glycine. The formation of hydrogen bonds between AA and glycine were further confirmed by the density functional theory, quantum theory of atoms in molecules and natural bond orbital analyses.

Interaction between aspirin and vitamin C with human serum albumin as binary and ternary systems

Foods generally contain special ingredients which easily to interact with drugs human intaking, thus affecting drug efficacy and excretion, and even cause adverse reactions. Vitamin C (Vit. C) is abundant in fresh fruits and vegetables. It plays a regulatory role in redox metabolism, and its absence can cause scurvy. Aspirin (ASP) can be used to treat many diseases, is the earliest, common and widely used as antipyretic, analgesic and antirheumatic medicine. Human serum albumin (HSA) is the most abundant protein in vertebrate plasma and has the property of combining and transporting endogenous and exogenous substances. In this paper, the effects of Vit. C on the combination of ASP and HSA were studied by multi-spectra and voltammetric approaches. Fluorescence spectra showed that the quenching mode between Vit. C and HSA is dynamic, and the main binding force is hydrophobic force. The quenching mode between ASP and HSA is static one, and the main binding force is hydrogen bond and van der Waals force. For ternary biological system of (HSA-ASP)-Vit. C, the binding constant decreases compared with HSA-Vit. C system. However, for (HSA-Vit. C)-ASP system, the binding constant does not change when compared with binary system of HSA-ASP. Based on the technology combination of voltammetry, infrared, three-dimensional fluorescence and circular dichroism (CD), it is proved that the existence of ASP will influence the binding process of Vit. C to HSA. It could be concluded that taking Vit. C first doesn't affect the absorption of ASP and may be good for health; in contrast, it is not good to take Vit. C immediately as one have just taken ASP, because the existence of ASP reduce the absorption of Vit. C for human body.

Sodium salicylate interferes with quorum-sensing-regulated virulence in chronic wound isolates of Pseudomonas aeruginosa in simulated wound fluid

Introduction. An important factor for delayed healing of chronic wounds is the presence of bacteria. Quorum sensing (QS), a cell density-dependent signalling system, controls the production of many virulence factors and biofilm formation in Pseudomonas aeruginosa.Aim. Inhibition by sodium salicylate (NaSa) of QS-regulated virulence expression was evaluated in QS-characterized clinical wound isolates of P. aeruginosa, cultured in serum-containing medium.Methodology. Fourteen clinical P. aeruginosa strains from chronic wounds were evaluated for the production of QS signals and virulence factors. Inhibition of QS by NaSa in P. aeruginosa clinical strains, wild-type PAO1 and QS reporter strains was evaluated using in vitro assays for the production of biofilm, pyocyanin, siderophores, alkaline protease, elastase and stapholytic protease.Results. Six clinical strains secreted several QS-associated virulence factors and signal molecules and two were negative for all factors. Sub-inhibitory concentrations of NaSa downregulated the expression of the QS-related genes lasB, rhlA and pqsA and reduced the secretion of several virulence factors in PAO1 and clinical strains cultured in serum. Compared to serum-free media, the presence of serum increased the expression of QS genes and production of siderophores and pyocyanin but decreased biofilm formation.Conclusions. Pseudomonas aeruginosa from chronic wound infections showed different virulence properties. While very few strains showed no QS activity, approximately half were highly virulent and produced QS signals, suggesting that the targeting of QS is a viable and relevant strategy for infection control. NaSa showed activity as a QS-inhibitor by lowering the virulence phenotypes and QS signals at both transcriptional and extracellular levels.

Cooking Chemistry Transforms Proteins into High-Strength Adhesives

In prior generations, proteins were taken from horses and other animals to make glues. Petroleum-derived polymers including epoxies and cyanoacrylates have since replaced proteins owing to improved performance. These modern materials come at a cost of toxicity as well as being derived from limited resources. Ideally, replacement adhesives will be made from benign, cheap, and renewable feedstocks. Such a transition to biobased materials, however, will not occur until similar or improved performance can be achieved. We have discovered that coupling of proteins and sugars gives rise to strong adhesives. An unexpected connection was made between adhesion and Maillard chemistry, known to be at the heart of cooking foods. Cross-linked proteins bonded metal and wood with high strengths, in some cases showing forces exceeding those withstood by the substrates themselves. Simple cooking chemistry may provide a route to future high-performance materials derived from low-cost, environmentally benign components.

EPR studies of intermolecular interactions and competitive binding of drugs in a drug-BSA binding model

Understanding intermolecular interactions between drugs and proteins is very important in drug delivery studies. Here, we studied different binding interactions between salicylic acid and bovine serum albumin (BSA) using electron paramagnetic resonance (EPR) spectroscopy. Salicylic acid was labeled with a stable radical (spin label) in order to monitor its mobilized (free) or immobilized (bound to BSA) states. In addition to spin labeled salicylic acid (SL-salicylic acid), its derivatives including SL-benzoic acid, SL-phenol, SL-benzene, SL-cyclohexane and SL-hexane were synthesized to reveal the effects of various drug binding interactions. EPR results of these SL-molecules showed that hydrophobic interaction is the main driving force. Whereas each of the two functional groups (-COOH and -OH) on the benzene ring has a minute but detectable effect on the drug-protein complex formation. In order to investigate the effect of electrostatic interaction on drug binding, cationic BSA (cBSA) was synthesized, altering the negative net charge of BSA to positive. The salicylic acid loading capacity of cBSA is significantly higher compared to that of BSA, indicating the importance of electrostatic interaction in drug binding. Moreover, the competitive binding properties of salicylic acid, ibuprofen and aspirin to BSA were studied. The combined EPR results of SL-salicylic acid/ibuprofen and SL-ibuprofen/salicylic acid showed that ibuprofen is able to replace up to ∼83% of bound SL-salicylic acid, and salicylic acid can replace only ∼14% of the bound SL-ibuprofen. This indicates that ∼97% of all salicylic acid and ibuprofen binding sites are shared. On the other hand, aspirin replaces only ∼23% of bound SL-salicylic acid, and salicylic acid replaces ∼50% of bound SL-aspirin, indicating that ∼73% of all salicylic acid and aspirin binding sites are shared. These results show that EPR spectroscopy in combination with the spin labeling technique is a very powerful method to investigate drug binding dynamics in detail.

Synthesis, structures and biomolecular interactions of new silver(i) 5,5-diethylbarbiturate complexes of monophosphines targeting Gram-positive bacteria and breast cancer cells

New silver(i) 5,5-diethylbarbiturate complexes exhibit very high antimicrobial activity against Gram-positive bacteria and kill MCF-7 cells, damaging mitochondria and DNA.

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.

Binding interaction of phosphorus heterocycles with bovine serum albumin: A biochemical study

Interaction between bovine serum albumin (BSA) and phosphorus heterocycles (PHs) was studied using multi-spectroscopic techniques. The results indicated the high binding affinity of PHs to BSA as it quenches the intrinsic fluorescence of BSA. The experimental data suggested the fluorescence quenching mechanism between PHs and BSA as a dynamic quenching. From the UV–vis studies, the apparent association constant (K_app) was found to be 9.25×10², 1.27×10⁴ and 9.01×10² L/mol for the interaction of BSA with PH-1, PH-2 and PH-3 respectively. According to the Förster's non-radiation energy transfer (FRET) theory, the binding distances between BSA and PHs were calculated. The binding distances (r) of PH-1, PH-2 and PH-3 were found to be 2.86, 3.03, and 5.12 nm, respectively, indicating energy transfer occurs between BSA and PHs. The binding constants of the PHs obtained from the fluorescence quenching data were found to be decreased with increase of temperature. The negative values of the thermodynamic parameters ΔH, ΔS and ΔG at different temperatures revealed that the binding process is spontaneous; hydrogen bonds and van der Waals interaction were the main force to stabilize the complex. The microenvironment of the protein-binding site was studied by synchronous fluorescence and circular dichroism (CD) techniques and data indicated that the conformation of BSA changed in the presence of PHs. Finally, we studied the BSA-PHs docking using Autodock and results suggest that PHs is located in the cleft between the domains of BSA.

•

The interaction between BSA and PHs by spectroscopic methods.

•

The fluorescence quenching mechanism is dynamic.

•

Van der Waals force and hydrogen bond are the main force for BSA-PHs interaction.

•

Docking of PHs-BSA interaction.

Synthesis of a novel trinuclear palladium complex: the influence of an oxime chelate ligand on biological evaluation towards double-strand DNA, BSA protein and molecular modeling studies

Synthesis of a novel cluster palladium complex containing an oxime ligand. Study of the ability of the complex to interact with DNA via groove mechanism. The molecular docking indicates high binding affinity between DNA and BSA with the Pd complex.

Bioactive and biocompatible copper containing glass-ceramics with remarkable antibacterial properties and high cell viability designed for future in vivo trials

The efficiency of 60SiO₂·(32 − x) CaO·8P₂O₅·xCuO (mol%) glass-ceramics were proved, and was determined the most appropriate composition for further in vivo trials.

Investigations into the Use of a Protein Sensor Assay for Metabolite Analysis

Rapid and definitive classification of biological samples has application in industrial, agricultural, and clinical settings. Considerable effort has been given to analytical methods to address such applications over the past 50 years, with the majority of successful solutions focusing on a single molecular target. However, in many cases, a single or even a few features are insufficient for accurate characterization or classification. Serum albumin (SA) proteins are a class of cargo-carrying proteins in blood that have evolved to transport a wide variety of metabolites and peptides in mammals. These proteins have up to seven binding sites which communicate allosterically to orchestrate a complex pick-up and delivery system involving a large number of different molecules at any time. The ability of SA proteins to bind multiple molecular species in a sophisticated manner inspired the development of assays to differentiate complex biological solutions. The combination of SA and high-resolution liquid chromatography mass spectrometry (LC-MS) is showing exciting promise as a protein sensor assay (PSA) for classification of complex biological samples. In this study, the PSA has been applied to cells undergoing and recovering from mild oxidative stress. Analysis using traditional LC-MS-based metabolomics failed to differentiate samples into treatment or temporal groups, whereas samples first treated with the PSA were cleanly classified into both correct treatment and temporal groups. The success of the PSA could be attributed to selective binding of metabolites, leading to a reduction in sample complexity and a general reduction in chemical noise. Metabolites important to successful sample classification were often enriched by 100-fold or more yet displayed a wide range of affinities for SA. The end result of PSA treatment is better classification of samples with a reduction in the number of features seen overall. Together, these results demonstrate how the use of a protein-based assay before LC-MS analysis can greatly improve separation and lead to more accurate and successful tracking of the metabolic state in an organism, suggesting potential application in a wide range of fields.

In vitro DNA and BSA-binding, cell imaging and anticancer activity against human carcinoma cell lines of mixed ligand copper(II) complexes

Binding studies of two water soluble copper(II) complexes of the type [Cu(phen-dion)(diimine)Cl]Cl, where phen-dione is 1,10-phenanthroline-5,6-dione and diimine is 1,10-phenanthroline (1) and 2,2'-bipyridine (2), with fish sperm DNA (FS-DNA) and bovine serum albumin (BSA) have been examined under physiological conditions by a series of experimental methods (UV-Vis absorption, fluorescence, viscosity, cyclic voltammetry (CV) and circular dichroism (CD) spectroscopic techniques). The experimental results indicate that the complexes interact with FS-DNA by electrostatic and partial insertion of pyridyl rings between the base stacks of double-stranded DNA. The complexes could quench the intrinsic fluorescence of BSA with the binding constants (Kbin) of 32×10(5) M(-1) (1) and 1.7×10(5) M(-1) (2) at 290 K. The quenching mechanism, thermodynamic parameters, the number of binding sites and the effect of the Cu(II) complexes on the secondary structure of BSA have been explored. The in vitro anticancer chemotherapeutic potential of two copper(II) complexes against the three human carcinoma cell lines (MCF-7, A-549, and HT-29) and one normal cell line (DPSC) were evaluated by MTT assay. The results of in vitro cytotoxicity indicate that the complex (1) has greater cytotoxicity activity against all of the cell lines, especially HT-29 with IC50 values of 1.8 μM. Based on the IC50 values, these complexes did not display an apparent cyto-selective profile, because it would appear that two complexes are toxic to all four model cell lines. The microscopic analyses of the cancer cells confirm results of cytotoxicity.

Arsenic trioxide binding to serum proteins

Arsenic trioxide (ATO) also known as Trisenox, is an anticancer chemotherapeutic drug which has been used in treating diagnosed and relapsed patients with acute promyelocytic leukemia (APL). Serum albumin is the most abundant of the proteins in blood plasma and is the major transporter for delivering several drugs in vivo. The current study was designed to evaluate the potential ability of human and bovine serum albumin for delivering arsenic trioxide. Therefore, interaction of arsenic trioxide with HSA and BSA was investigated in aqueous solution at physiological conditions using a constant protein concentration and various drug contents. FTIR and UV-Vis spectroscopic methods were used to analyze arsenic trioxide and protein binding modes, the binding constants and the effect of drug complexation on HSA and BSA stability and conformation. Results of this study showed that drug complexation altered protein conformation by major reduction of α-helix and increase of turn structure which is indicative of a partial protein destabilization. Structural analysis revealed that arsenic trioxide bind HSA and BSA with overall binding constants of KATO-HSA=1.07 (±0.01)×10(4) M(-1) and KATO-BSA=1.27(±0.02)×10(4) M(-1). It could be concluded that serum albumins can be considered as good carriers for delivering arsenic trioxide to target tissue.

A mononuclear Ni(II) complex with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine: DNA- and BSA-binding and anticancer activity against human breast carcinoma cells

DNA- and BSA-binding properties of a mononuclear Ni(II) complex, [Ni(dppt)2Cl2] (dppt = 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine), have been investigated under physiological conditions. The interaction of the complex with the fish sperm DNA (FS-DNA) has been studied by UV-Vis absorption, thermal denaturation, viscosity measurement, competitive DNA-binding studies with ethidium bromide (EB) by fluorescence, and gel electrophoresis technique. The experimental results indicate that the complex interacts with DNA by intercalative binding mode. The competitive study with ethidium bromide (EB) shows that the complex competes for the DNA-binding sites with EB and displaces the DNA-bound EB molecule. The interactions of the dppt ligand and the complex with BSA have been studied by UV-Vis absorption and fluorescence spectroscopic techniques. The values of Kb for the BSA-dppt and the BSA-complex systems at room temperature were calculated to be 0.14×10(4) M(-1) and 0.32×10(5) M(-1), respectively, indicating that the complex has stronger tendency to bind with BSA than the dppt ligand. The quenching constants (Ksv), binding constants (Kbin), and number of binding sites (n) at different temperatures, as well as the binding distance (r) and thermodynamic parameters (ΔH°, ΔS° and ΔG°) have been calculated for the BSA-dppt and the BSA-complex systems. The cytotoxicities of the dppt ligand and the complex have been also tested against the human breast adenocarcinoma (MCF-7) cell line using the MTT assay. The results indicate that the dppt ligand and the complex display cytotoxicity against human breast cancer cell lines (MCF-7) with the IC50 values of 17.35 μM and 13.00 μM, respectively. It is remarkable that the complex can introduce as a potential anticancer drug.

Controlling the self-assembly and optical properties of gold nanoclusters and gold nanoparticles biomineralized with bovine serum albumin

While the size-dependent optical properties of BSA-stabilized gold nanoclusters are well known, the time-dependent growth mechanism remains to be described.

Dissection of the binding ofl-ascorbic acid to trypsin and pepsin using isothermal titration calorimetry, equilibrium microdialysis and spectrofluorimetry

Clear and quantitative information on the nature ofl-ascorbic acid interaction with trypsin/pepsin should provide a firm base for its rational use in clinical practice.

Interaction of a novel platinum drug with bovine serum albumin: FTIR and UV-Vis spectroscopy analysis

Platinum-Blue docks at a hydrophobic cavity at low concentrations with a binding constant comparable to that of cisplatin.

Physiological concentrations of albumin favor drug binding

We exploit the direct measurements of spin labeled drugs to study drug binding to/release from protein using EPR spectroscopy.

Addressing the optimal silver content in bioactive glass systems in terms of BSA adsorption

Bioactive glasses doped with silver are aimed to minimize the risk of microbial contamination; therefore, the influence of silver on the bioactive properties is intensely investigated. However, information related to the role played by silver, when added to the bioactive glass composition, on biocompatibility properties is scarce. This aspect is essential as long as the silver content can influence blood protein adsorption onto the surface of the glass, thus affecting the material's biocompatibility. Therefore, from the perspective of the biocompatibility standpoint, the finding of an optimal silver content in a bioactive glass is an extremely important issue. In this study, silver-doped bioactive glasses were prepared by a melt-derived technique, which eliminates the pores' influence in the protein adsorption process. The obtained glasses were characterized by X-ray diffraction, UV-vis, X-ray photoelectron (XPS) and Fourier transform infrared (FT-IR) spectroscopy; afterwards, they were investigated in terms of protein adsorption. Both UV-vis and XPS spectroscopy revealed the presence of Ag⁺ ions in all silver containing samples. By increasing the silver content, metallic Ag⁰ appears, the highest amount being observed for the sample with 1 mol% AgO₂. Electron paramagnetic resonance measurements evidenced that the amount of spin-labeled serum albumin attached to the surface increases with the silver content. The results obtained by analyzing the information derived from atomic force microscopy and FT-IR measurements indicate that the occurrence of metallic Ag⁰ in the samples' structure influences the secondary structure of the adsorbed protein. Based on the results derived from the protein response upon interaction with the investigated glass calcium-phosphate based system, the optimal silver oxide concentration was determined for which the secondary structure of the adsorbed protein is similar with that of the free one. This concentration was found to be 0.5 mol%.

Morphological analysis and interaction of chlorophyll and BSA

Interactions between proteins and drugs, which can lead to formation of stable drug-protein complexes, have important implications on several processes related to human health. These interactions can affect, for instance, free concentration, biological activity, and metabolism of the drugs in the blood stream. Here, we report on the UV-Visible spectroscopic investigation on the interaction of bovine serum albumin (BSA) with chlorophyll (Chl) in aqueous solution under physiological conditions. Binding constants at different temperatures—obtained by using the Benesi-Hildebrand equation—were found to be of the same order of magnitude (~10⁴ M⁻¹) indicating low affinity of Chl with BSA. We have found a hyperchromism, which suggested an interaction between BSA and Chl occurring through conformational changes of BSA caused by exposition of tryptophan to solvent. Films from BSA and Chl obtained at different Chl concentrations showed fractal structures, which were characterized by fractal dimension calculated from microscopic image analysis.

DNA- and BSA-binding studies and anticancer activity against human breast cancer cells (MCF-7) of the zinc(II) complex coordinated by 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine

Binding studies of a mononuclear zinc(II) complex, [Zn(dppt)2Cl2] (dppt is 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine), with DNA and bovine serum albumin (BSA) have been investigated under physiological conditions. The binding properties of the complex with fish sperm DNA (FS-DNA) have been investigated by UV-Vis absorption, thermal denaturation, competitive DNA-binding studies with ethidium bromide (EB) by fluorescence, and gel electrophoresis techniques. The competitive study with (EB) shows that the complex can displace EB from the DNA-EB system and compete for the DNA-binding sites with EB, which is usually characteristic of the intercalative interaction of compounds with DNA. The value of the fluorescence quenching constant (Ksv) was obtained as 3.1×10(4)M(-1), indicating that this complex shows a high quenching efficiency and a significant degree of binding to DNA. Moreover, the intercalative binding mode has also been verified by the results of UV-Vis absorption, thermal denaturation and gel electrophoresis. The value of Kb at room temperature was calculated to be 1.97×10(5)M(-1), indicating that the complex possesses strong tendency to bind with DNA. This value is very greater than to the values obtained for other zinc(II) complexes. The interaction of the complex with BSA has been studied by UV-Vis absorption, fluorescence and circular dichroism (CD) spectroscopic techniques. The results indicate that the complex has a quite strong ability to quench the fluorescence of BSA and the binding reaction is mainly a static quenching process. The quenching constants (KSV), the binding constants (Kb), the number of binding sites at different temperatures, the binding distance between BSA and the complex (r), and the thermodynamic parameters (ΔH(o), ΔS(o) and ΔG(o)) between BSA and the complex were calculated. The complex exhibits good binding propensity to BSA showing relatively high binding constant values. The positive ΔH(o) and ΔS(o) values indicate that the hydrophobic interaction is main force in the binding of the complex to BSA. Moreover, to evaluate the anticancer properties, the cytotoxicity of the complex has been tested against the human breast adenocarcinoma (MCF-7) cell lines using the MTT assay. The results indicate that the parent complex displays cytotoxicity against human breast cancer cell lines (MCF-7) with an IC50 value of 10.44μM. It is remarkable that the complex can introduce as a potential anticancer drug.