Probing the interaction of human serum albumin with bilirubin in the presence of aspirin by multi-spectroscopic, molecular modeling and zeta potential techniques: insight on binary and ternary systems

Dietary Probiotic Bacillus subtilis Strain fmbj Increases Antioxidant Capacity and Oxidative Stability of Chicken Breast Meat during Storage

This study was aimed to measure the dietary effects of probiotic Bacillus subtilis strain fmbj (BS fmbj) on antioxidant capacity and oxidative stability of chicken breast meat during storage. Treatment groups were fed the basal diet with BS fmbj at 0 g/kg (CON), 0.2 g/kg (BS-1), 0.3 g/kg (BS-2), or 0.4 g/kg (BS-3) doses without antibiotics. During 8 days of storage at 4°C, BS-2 group showed a significant improvement (P < 0.05) on meat quality (pH, Drip loss, Cooking loss, Shear force, color L*, a*, b*), free radical scavenging activity (DPPH, ABTS⁺, H₂O₂), tissues antioxidant enzyme capacity (SOD, CAT, GSH-Px, GSH, T-SH), mitochondria antioxidant enzyme capacity (MnSOD, GPx, GSH), mRNA expression of antioxidant genes (Nrf2, HO-1, SOD, CAT, GSH-Px) and mitochondrial function genes (avUCP, NRF1, NRF2, TFAM, PGC-1α), oxidative damage index (MDA, ROS, PC, 8-OHdG), and MMP level in chicken breast meat as compared to the CON group. These results indicate that dietary BS fmbj in broiler diets can protect breast meat against the storage-induced oxidative stress by improving their free radical scavenging capacity and antioxidant activity during 8 days of storage at 4°C.

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

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

In Vitro Antioxidant versus Metal Ion Chelating Properties of Flavonoids: A Structure-Activity Investigation

Natural flavonoids such as quercetin, (+)catechin and rutin as well as four methoxylated derivatives of quercetin used as models were investigated to elucidate their impact on the oxidant and antioxidant status of human red blood cells (RBCs). The impact of these compounds against metal toxicity was studied as well as their antiradical activities with DPPH assay. Antihemolytic experiments were conducted on quercetin, (+)catechin and rutin with excess of Fe, Cu and Zn (400 μM), and the oxidant (malondialdehyde, carbonyl proteins) and antioxidant (reduced glutathione, catalase activity) markers were evaluated. The results showed that Fe and Zn have the highest prooxidant effect (37 and 33% of hemolysis, respectively). Quercetin, rutin and (+)catechin exhibited strong antioxidant properties toward Fe, but this effect was decreased with respect to Zn ions. However, the Cu showed a weak antioxidant effect at the highest flavonoid concentration (200 μM), while a prooxidant effect was observed at the lowest flavonoid concentration (100 μM). These results are in agreement with the physico-chemical and antiradical data which demonstrated that binding of the metal ions (for FeNTA: (+)Catechin, K_LFeNTA = 1.6(1) × 10⁶ M^-1 > Rutin, K_LFeNTA = 2.0(9) × 10⁵ M^-1 > Quercetin, K_LFeNTA = 1.0(7) × 10⁵ M^-1 > Q35OH, K_LFeNTA = 6.3(8.7) × 10⁴ M^-1 > Quercetin3’4’OH and Quercetin 3OH, K_LFeNTA ~ 2 × 10⁴ M^-1) reflects the (anti)oxidant status of the RBCs. This study reveals that flavonoids have both prooxidant and antioxidant activity depending on the nature and concentration of the flavonoids and metal ions.

Human Serum Albumin (HSA) Suppresses the Effects of Glycerol Monolaurate (GML) on Human T Cell Activation and Function

Glycerol monolaurate (GML) is a monoglyceride with well characterized anti-microbial properties. Because of these properties, GML is widely used in food, cosmetics, and personal care products and currently being tested as a therapeutic for menstrual associated toxic shock syndrome, superficial wound infections, and HIV transmission. Recently, we have described that GML potently suppresses select T cell receptor (TCR)-induced signaling events, leading to reduced human T cell effector functions. However, how soluble host factors present in the blood and at sites of infection affect GML-mediated human T cell suppression is unknown. In this study, we have characterized how human serum albumin (HSA) affects GML-induced inhibition of human T cells. We found that HSA and other serum albumins bind to 12 carbon acyl side chain of GML at low micromolar affinities and restores the TCR-induced formation of LAT, PLC-γ1, and AKT microclusters at the plasma membrane. Additionally, HSA reverses GML mediated inhibition of AKT phosphorylation and partially restores cytokine production in GML treated cells. Our data reveal that HSA, one of the most abundant proteins in the human serum and at sites of infections, potently reverses the suppression of human T cells by GML. This suggests that GML-driven human T cell suppression depends upon the local tissue environment, with albumin concentration being a major determinant of GML function.

Interaction between the photosensitizer lumichrome and human serum albumin: effect of excipients

Lumichrome (Lc) is a photodegradation product of riboflavin that can be used as a photosensitizer (PS) in antibacterial photodynamic therapy (aPDT). The binding of Lc with plasma proteins such as human serum albumin (HSA) could affect its efficiency as PS. Excipients are necessary to prepare stable formulations to be used in aPDT and they may affect the PS-HSA binding. Hydroxypropyl (HP)-α, β, γ-cyclodextrin (CD), polyethylene glycol 400 (PEG400) and Pluronic^® F-127 (PF127) were selected as model excipients in this study. The intrinsic HSA fluorescence quenching and absorption and fluorescence spectroscopy were used to evaluate the Lc-HSA interaction in the absence and presence of excipients. Nano-differential scanning calorimetry (DSC) was used to determine the effect of excipients on HSA. The photostability of the samples was also evaluated. The combined results showed a modest interaction between Lc and HSA which was reduced mainly by HPβCD. No major alterations of the HSA nano-DSC thermogram were observed after addition of excipients. HSA did enhance Lc photodegradation. The presence of PF127 did also induce photochemical destabilization of Lc independent of HSA. In conclusion, HPαCD, HPγCD and PEG400 seemed to be the excipients more suitable for use in topical preparations containing Lc.

Anthracycline Drugs on Modified Surface of Quercetin-Loaded Polymer Nanoparticles: A Dual Drug Delivery Model for Cancer Treatment

Polymer nanoparticles are vehicles used for delivery of hydrophobic anti-cancer drugs, like doxorubicin, paclitaxel or chemopreventors like quercetin (Q). The present study deals with the synthesis and characterisation of nano formulations (NFs) from Q loaded PLGA (poly lactic-co-glycolic acid) nano particles (NPs) by surface modification. The surface of Q-loaded (NPs) is modified by coating with biopolymers like bovine serum albumin (BSA) or histones (His). Conventional chemotherapeutic drugs adriamycin (ADR) and mitoxantrone (MTX) are bound to BSA and His respectively before being coated on Q-loaded NPs to nano formulate NF1 and NF2 respectively. The sizes of these NFs are in the range 400–500 nm as ascertained by SEM and DLS measurements. Encapsulation of Q in polymer NPs is confirmed from shifts in FT-IR, TGA and DSC traces of Q-loaded NPs compared to native PLGA and Q. Surface modification in NFs is evidenced by three distinct regions in their TEM images; the core, polymer capsule and the coated surface. Negative zeta potential of Q-loaded NPs shifted to positive potential on surface modification in NF1 and NF2. In vitro release of Q from the NFs lasted up to twenty days with an early burst release. NF2 is better formulation than NF1 as loading of MTX is 85% compared to 23% loading of ADR. Such NFs are expected to overcome multi-drug resistance (MDR) by reaching and treating the target cancerous cells by virtue of size, charge and retention.

Review on the delivery of steroids by carrier proteins

Due to the poor solubility of steroids in aqueous solution, delivery of these biomaterials is of major biomedical importance. We have reviewed the conjugation of testosterone and it aliphatic dimer and aromatic dimer with several carrier proteins, human serum albumin (HSA), bovine serum albumin (BSA) and milk beta-lactoglobulin (b-LG) in aqueous solution at physiological pH. The results of multiple spectroscopic methods, transmission electron microscopy (TEM) and molecular modeling were compared here. Steroid-protein bindings are via hydrophilic and H-bonding contacts. HSA forms more stable conjugate than BSA and b-LG. The stability of steroid-protein conjugates is testosterone>dimer-aromatic>dimer-aliphatic. Encapsulation of steroids by protein is shown by TEM images. Modeling showed the presence of H-bonding, which stabilized testosterone-protein complexes with the free binding energy of -12.95 for HSA and -11.55 for BSA and -8.92kcal/mol for b-LG conjugates. Steroid conjugation induced major perturbations of serum protein conformations. Serum proteins can transport steroids to the target molecules.

Probing the interaction of lysozyme with ciprofloxacin in the presence of different-sized Ag nano-particles by multispectroscopic techniques and isothermal titration calorimetry

The binding of ciprofloxacin to lysozyme in the presence of three Ag nano-particles of varying sizes was for the first time investigated by multispectroscopic and isothermal titration calorimetry techniques at pH 7.4. The results indicated that ciprofloxacin quenched the fluorescence intensity of lysozyme through a static mechanism but in the presence of size-II Ag nano-particles, there were two kinds of interaction behaviors. The interaction between ciprofloxacin and lysozyme occurred via a second type of binding site, whereas in the presence of the Ag nano-particles, some changes occurred. The secondary structure of lysozyme-ciprofloxacin in the presence of Ag nano-particles was determined by circular dichroism. The thermodynamic parameters of the interaction between ciprofloxacin and lysozyme in the presence of Ag nano-particles were measured according to the van't Hoff equation. The enthalpy (ΔH(○)) and entropy (ΔS(○)) changes were calculated to be -49.7 (kJ mol(-1)) and -20.1 (J mol(-1) K(-1)), respectively, which indicated that the interaction of ciprofloxacin with lysozyme was driven mainly by van der Waals forces and hydrogen bonding. In the presence of the three different-sized Ag nano-particles, the enthalpic and the entropic changes were both negative which indicated that hydrogen bonding with van der Waals forces played major roles in the binding between ciprofloxacin and lysozyme. Recent developments in nano-materials offer new pathways for controlling the protein behavior through surface interactions. These data indicate that the recent research on nano-particle/protein interactions will emphasize the importance of such interactions in biological systems with applications including the diagnosis and treatment of human diseases.

Investigation on the interaction between cyclophosphamide and lysozyme in the presence of three different kind of cyclodextrins: determination of the binding mechanism by spectroscopic and molecular modeling techniques

The interactions between cyclophosphamide (CYC) and lysozyme (LYZ) in the presence of different cyclodextrins (CDs) were investigated by UV absorption, fluorescence spectroscopy, circular dichroism (CD), and molecular modeling techniques under imitated physiological conditions. The UV absorption results showed the formation of complexes between CYC and LYZ in the presence of different CDs. Fluorescence data show that CYC has a stronger quenching effect on LYZ, and the red shifts suggested that the microenvironment of Trp residues was changed and became more hydrophilic. The interaction of CYC with LYZ and quenching properties of the complexes caused strong static fluorescence quenching in binary and ternary systems. The binding affinities as well as the number of binding sites were obtained from interaction between CYC and LYZ in the presence of different CDs as binary and ternary systems by modified Stern-Volmer plots. The Resonance Light Scattering (RLS) technique was utilized to investigate the effect of drug and CDs on conformational changes of LYZ as separate and simultaneous. The results suggested that the enhancement of RLS intensity was attributed to the formation of a complex between drug and protein in absence and presence of CDs. The effect of CYC and cyclodextrins on the conformation of LYZ was analyzed using synchronous fluorescence spectroscopy. Our results revealed that the fluorescence quenching of LYZ originated from the Trp and Tyr residues, and demonstrated conformational changes of LYZ with the addition of CYC and CDs. The molecular distances between the donor (LYZ) and acceptor (CYC and CDs) in binary and ternary systems were estimated according to Forster’s theory and showed static quenching for protein with CYC in the presence of CDs. The CD spectra indicated that the binding of the CYC induced secondary structural changes in LYZ in binary and ternary systems. Molecular modeling suggested the binding sites of CYC in the ternary systems differ from those in the binary systems. estimated the distance between CYC and Trp residues in binary and ternary systems in the presence of CDs and confirmed the experimental results.

Investigation on the site-selective binding of bovine serum albumin by erlotinib hydrochloride

The purpose of this study was to investigate the site-selective binding of erlotinib hydrochloride (ET), a targeted anticancer drug, to bovine serum albumin (BSA) through 1H NMR, spectroscopic, thermodynamic, and molecular modeling methods. The fluorescence quenching of BSA by ET was a result of the formation of BSA-ET complex with high binding affinity. The site marker competition study combined with isothermal titration calorimetry experiment revealed that ET binds to site II of BSA mainly through hydrogen bond and van der Waals force. Molecular docking was further applied to define the specific binding site of ET to BSA. The conformation of BSA was changed in the presence of ET, revealed by synchronous fluorescence, circular dichroism, and three-dimensional fluorescence spectroscopy results. Further, NMR analysis of the complex revealed that the binding capacity contributed by the aromatic protons in the binding site of BSA might be greater than the aliphatic protons. An animated interactive 3D complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:26.