Study on the interaction between clozapine and bovine serum albumin

Characterization of the structural and molecular interactions of Ferulic acid ethyl ester with human serum albumin and Lysozyme through multi-methods

Ferulic acid ethyl ester (FAEE) is an essential raw material for the formulation of drugs for cardiovascular and cerebrovascular diseases and leukopenia. It is also used as a fixed aroma agent for food production due to its high pharmacological activity. In this study, the interaction of FAEE with Human serum albumin (HSA) and Lysozyme (LZM) was characterized by multi-spectrum and molecular dynamics simulations at four different temperatures. Additionally, the quenching mechanism of FAEE-HSA and FAEE-LZM were explored. Meanwhile, the binding constants, binding sites, thermodynamic parameters, molecular dynamics, molecular docking binding energy, and the influence of metal ions in the system were evaluated. The results of Synchronous fluorescence spectroscopy, UV-vis spectroscopy, CD, three-dimensional fluorescence spectrum, and resonance light scattering showed that the microenvironment of HSA and LZM and the protein conformation changed in the presence of FAEE. Furthermore, the effects of some common metal ions on the binding constants of FAEE-HSA and FAEE-LZM were investigated. Overall, the experimental results provide a theoretical basis for promoting the application of FAEE in the cosmetics, food, and pharmaceutical industries and significant guidance for food safety, drug design, and development.

Mechanistic study on inhibition of porcine pancreatic α-amylase using the flavonoids from dandelion

This study was designed to investigate quantitatively the inhibition and molecular mechanism of pancreatic α-amylase exhibited by flavonoids from dandelion to reveal its potential use in relieving postprandial hyperglycemia. The results show that the flavonoids reversibly inhibited the α-amylase in a non-competitive manner with Michaelis-Menten constant (K_m) and half-inhibitory concentration (IC₅₀) value of 10.51 and 0.0067 mg/mL, respectively. The flavonoids present a strong ability to quench the intrinsic fluorescence of α-amylase through static quenching by forming a complex. The values of the binding site (n) at different temperatures were found to be approximately the unity, indicating the presence of a single class of molecular binding of the dandelion flavonoids on α-amylase. The positive values of enthalpy and entropy change reveal that the binding was predominately driven by hydrophobic interactions. This study suggests a benefit of incorporating the dandelion flavonoids in making functional foods in managing the diet of the diabetes.

Study on the interaction between 4-(1H-indol-3-yl)-2-(p-tolyl)quinazoline-3-oxide and human serum albumin

An organic small-molecular drug, 4-(1H-indol-3-yl)-2-(p-tolyl)quinazoline-3-oxide 1a was synthesized. It was employed to investigate the binding interaction and mechanism with human serum albumin (HSA). The experimental results indicated that the fluorescence quenching of HSA by 1a is a static quenching process and formation 1a-HSA complex. The site competition experiments revealed that the combination of 1a on HSA are hydrophobic interactions in the IIA domain and hydrogen bonds in IIIA domain of HSA, and the hydrophobic interactions of 1a on HSA are stronger than that of hydrogen bonds. These results were also confirmed by molecular docking theoretic analysis and ANS-hydrophobic fluorescent probe experiment. Synchronous fluorescence experiments showed that the polarity of HSA microenvironment was increase in the interaction process of 1a with HSA. The results of binding distance explored indicated that the combination distance between 1a and HSA is 3.63 nm, which is between 0.5R₀ and 1.5R₀, revealing the energy transfer between HSA and 1a is non-radiative. These results are very helpful for people to screen out high efficient indoloquinazoline drugs.

Surface functionalized quantum dots as biosensor for highly selective and sensitive detection of ppb level of propafenone

Monodispersed CdTe quantum dots (QDs) were prepared by using thioglycolic acid as surfactants in aqueous solution. The thioglycolic acid was chemically adsorbed on the surface of CdTe QDs that enables the QDs positively charged. In week acidic media, propafenone is positively charged, which can combine with the CdTe QDs to form larger ion-association complex via electrostatic attraction and hydrogen bond. Moreover, the formed ion-association complex could increase the intensity of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling-scattering (FDS) of CdTe QDs, and quench the CdTe QDs fluorescence. Importantly, under optimal experimental conditions, the increased RRS, SOS and FDS intensity, and quenched fluorescence intensity of CdTe QDs were in direct proportion to the propafenone concentration in a certain range, respectively. Among them, the RRS method exhibited the highest sensitivity. In a wide concentration range of propafenone from 0.003 to 7.0 μg mL^-1, the detection limit could reach 0.96 ng mL^-1, which was much lower than previously reported methods. To simulate practical applications, the possible foreign interfering substances were also investigated, such as common ions, amino acid, and glucide. The proposed method here is rapid, sensitive and shows promising application for detection of ppb level of propafenone in human serum.

Effect of Toxic Metal Binding on Tax-Interacting Protein1 (TIP1): A Protein Related to Brain Diseases

Human tax-interacting protein1 (TIP1), also known as glutaminase-interacting protein (GIP), is a small globular protein containing a PDZ domain. PDZ domains are the most common protein-protein interaction modules present in eukaryotes. In humans, TIP1 plays a very important role in many cellular pathways including β-catenin-mediated Wnt signaling, Rho-activator rhotekin-mediated Rho signaling pathway, and glutamate signaling pathway for the normal activity of the central nervous system. TIP1 also regulates potassium channel expression in the plasma membrane and is a binding partner to many proteins including viral oncoproteins, HTLV-1 Tax and HPV16 E6. Since TIP1 is at a pivotal point in many cellular processes through its interaction with a growing list of partner proteins, any impact on the proper functioning of this protein can have severe consequences on the well-being of a living system. Although metals are essential for plants and animals in trace amounts, elevated levels of heavy metals such as arsenic, cadmium, zinc, and lead are toxic causing various health problems including cardiovascular disorders, neuronal damage, renal injuries, and cancer. Here, we report the effect of heavy metals, arsenic and cadmium, on TIP1 conformation using circular dichroism and fluorescence spectroscopy techniques. Our study revealed these metals have a significant impact on the structure of TIP1 even at very low levels.

Study on the interaction between carbonyl-fused N-confused porphyrin and bovine serum albumin by spectroscopic techniques

The interaction between carbonyl-fused N-confused porphyrin (CF-NCP) and bovine serum albumin (BSA) was investigated by fluorescence and ultraviolet-visible (UV-Vis) spectroscopy. The results indicated that CF-NCP has strong ability to quench the intrinsic fluorescence of BSA by forming complexes. The binding constants (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at three different temperatures. The results revealed that the binding process is spontaneous, and the acting force between CF-NCP and BSA were mainly electrostatic forces. According to Förster non-radiation energy transfer theory, the binding distance between CF-NCP and BSA was calculated to be 4.37nm. What is more, the conformation of BSA was observed from synchronous fluorescence spectroscopy.

Spectroscopic studies on the interaction of Phacolysin and bovine serum albumin

The interaction between Phacolysin (PCL) and bovine serum albumin (BSA) under imitated physiological conditions was investigated by spectroscopic (fluorescence, UV-Vis absorption and Circular dichroism) techniques. The experiments were conducted at different temperatures (294K, 302K, 306K and 310K) and the results showed that the PCL caused the fluorescence quenching of BSA through a static quenching procedure. The binding constant (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at different temperatures. The results revealed that the binding process was spontaneous and the acting force between PCL and BSA were mainly hydrogen bonding and van der Waals forces. According to Förster non-radiation energy transfer theory, the binding distance between PCL and BSA was calculated to be 2.41nm. What is more, both synchronous fluorescence and Circular dichroism spectra confirmed the interaction, which indicated the conformational changes of BSA.

The investigation of the interaction between Tropicamide and bovine serum albumin by spectroscopic methods

The fluorescence and ultraviolet-visible (UV-Vis) spectroscopy were explored to study the interaction between Tropicamide (TA) and bovine serum albumin (BSA) at three different temperatures (292, 301 and 310K) under imitated physiological conditions. The experimental results showed that the fluorescence quenching mechanism between TA and BSA was static quenching procedure. The binding constant (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at different temperatures. The results revealed that the binding process is spontaneous, hydrogen binds and vander Waals were the main force to stabilize the complex. According to Förster non-radiation energy transfer theory, the binding distance between TA and BSA was calculated to be 4.90 nm. Synchronous fluorescence spectroscopy indicated the conformation of BSA changed in the presence of TA. Furthermore, the effect of some common metal ions (Mg(2+), Ca(2+), Cu(2+), and Ni(2+)) on the binding constants between TA and BSA were examined.

Synthesis, anticonvulsant, antioxidant and binding interaction of novel N-substituted methylquinazoline-2,4(1H,3H)-dione derivatives to bovine serum albumin: a structure-activity relationship study

A novel class of N-substituted glycosmicine derivatives was synthesized, and their anticonvulsant, antioxidant activity and interaction with bovine serum albumin (BSA) were evaluated. The synthesized compounds 4a-j were examined for anticonvulsant activity by maximal electroshock induced seizures (MESs) test and their neurotoxic effects were determined by rotorod test in mice. The structure-activity relationships (SARs) of these compounds were also investigated. Compounds 4d, 4g, 4i and 4j were found to have good protective effect from seizure. The in vitro antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging assay. The interaction between novel N-substituted methylquinazoline-2,4(1H,3H)-dione (NMQ) and BSA was analyzed by fluorescence and ultraviolet spectroscopy at 304K under simulative physiological conditions. BSA fluorescence quenched by NMQ is discussed according to the Stern-Volmer equation. The binding constant and binding sites of NMQ with BSA were calculated. According to Forster non-radiation energy transfer theory, the binding distance (r) between NMQ and BSA was calculated.

Spectroscopic analyses on interaction of Naphazoline hydrochloride with bovine serum albumin

The fluorescence and ultraviolet spectroscopy were explored to study the interaction between Naphazoline hydrochloride (Naphcon) and bovine serum albumin (BSA) at three different temperatures (292, 301, and 310 K) under imitated physiological conditions. The quenching mechanism of BSA by Naphacon was interpreted using the Stern-Volmer mechanism, and a combined quenching (dynamic and static quenching). The binding constants, binding sites and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) of the interaction system were calculated at different temperatures. According to Förster non-radiation energy transfer theory, the binding distance between BSA and Naphcon was found to be 4.71 nm. Synchronous fluorescence spectroscopy showed the conformation of BSA changed in the presence of Naphacon. In addition, the effect of some common metal ions (Mg(2+), Ca(2+), Ni(2+), Cu(2+), and Fe(2+)) on the binding constant between Naphcon and BSA was examined.

Spectroscopic analysis of the interaction between thiazolo[2,3-b]pyrimidine analogues and bovine serum albumin

The interaction between thiazolo[2,3-b]pyrimidine (TZPM) analogues and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and UV-Vis spectroscopy at two different temperatures (299 and 307K) under imitated physiological conditions. The results indicate that both static quenching and dynamic quenching contribute to the fluorescence quenching of BSA by TZPM. The binding constant (K(a)) and binding sites (n) were calculated from the obtained spectra. Based on the Förster non-radiation energy transfer theory, the average binding distance between BSA and TZPM was estimated. The synchronous fluorescence spectra indicate that the conformation of BSA has been changed. The comparison of binding potency of TZPM and BSA suggests that the substituents on the benzene ring enhance the binding affinity of TZPM and BSA. We investigated the possible sub-domains on BSA that bind TZPM by displacement experiments. Furthermore, to explore the effect of molecular structure on the binding, a study on quantitative structure-property relationship (QSPR) was performed, the quantitative relationship equation of R(0), r and K(a) were obtained. We observed that R(0), r and K(a) between BSA and TZPM is connected with the margin of the highest and the lowest occupied orbital energy (ΔE), dipole moment (μ), Molar Volume (V(m)), Mole Mass (M).

Study on the interaction between novel spiro pyrrolidine and bovine serum albumin by spectroscopic techniques

Spiro pyrrolidines, which were proved with diverse and potent biological activities and they were discovered widespread in nature. In this paper, using fluorescence and ultraviolet spectroscopy, we investigated the interactions between novel spiro pyrrolidine (NSP) and bovine serum albumin (BSA) under the imitated physiological condition. The results show that the NSP binds to BSA molecules. Static quenching and non-radiation energy transfer are the main reasons for fluorescence quenching. We calculated the binding constant (K(a)) and binding sites (n) at different temperatures and obtained the binding distance between the tryptophan residue in BSA and the NSP based on the Förster theory of non-radiation energy transfer. In addition, using synchronous fluorescence spectra, we demonstrated conformation changes of BSA caused by NSP. The comparison of binding potency of NSP and BSA suggests that the substituent on the benzene ring influences the binding ability of NSP and BSA.

Spectroscopic and molecular modeling evidence of clozapine binding to human serum albumin at subdomain IIA

Various spectroscopy and molecular docking methods were used to examine the binding of Clozapine (CLZ) to human serum albumin (HSA) in this paper. By monitoring the intrinsic fluorescence of single Trp214 residue and performing Dansylamide (DNSA) displacement measurement, the specific binding of CLZ in the vicinity of Sudlow's Site I of HSA has been clarified. An apparent distance of 27.3 Å between the Trp214 and CLZ was obtained via fluorescence resonance energy transfer (FRET) method. In addition, the changes in the secondary structure of HSA after its complexation with CLZ ligand were studied with CD spectroscopy, which indicate that CLZ does not has remarkable effect on the structure of the protein. Moreover, thermal denaturation experiment shows that the HSA-CLZ complexes are conformationally more stable. Finally, the binding details between CLZ and HSA were further confirmed by molecular docking studies, which revealed that CLZ was bound at subdomain IIA through multiple interactions, such as hydrophobic effect, van der Waals forces and hydrogen bonding.

Study on the interaction between salvianic acid A sodium and bovine serum albumin by spectroscopic methods

The interaction between salvianic acid A sodium (SAS) and bovine serum albumin (BSA) was investigated using fluorescence and ultraviolet spectroscopy at different temperatures under imitated physiological conditions. The experimental results showed that the fluorescence of BSA was quenched by SAS through a static quenching procedure. The binding constants of SAS with BSA were 2.03, 1.17 and 0.71×10(5) L mol(-1) at 291, 298 and 305 K, respectively. Negative values of ΔG, ΔH, and ΔS indicate that the interaction between SAS and BSA is driven by hydrogen bonds and van der Waals forces. According to Förster non-radiation energy transfer theory, the binding distance between BSA and SAS was calculated to be about 2.92 nm. The effect of SAS on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. In addition, the effect of some metal ions Cu(2+), Ca(2+), Mg(2+), and Zn(2+) on the binding constant between SAS and BSA was examined.

Influences of urea and guanidine hydrochloride on the interaction of 6-thioguanine with bovine serum albumin

The interaction of 6-thioguanine (6-TG) and bovine serum albumin (BSA) in the absence and presence of denaturant (urea and Guanidine hydrochloride) was investigated by fluorescence spectroscopic techniques. Changes of fluorescence intensity both in F(304) and in F(348) of BSA reflected increasing participation of tyrosine fluorescence in the total emission with increasing denaturant, which indicated that energy transfer from tyrosyl residues to tryptophanyl residues became less efficient in the denatured tertiary protein structure. The quenching effects of 6-TG were shown not only on the native but also on the unfolded form of BSA. The quenching constants and binding constants were calculated from the fluorescence spectra of the BSA/6-TG complex both in the absence and presence of the denaturant. The data suggested that the quenching constants and binding constants of 6-TG for BSA decreased with increasing concentration of denaturant. The spectroscopic analysis also showed antidenaturant properties of 6-TG under both denaturant conditions.

Quantitative structure-property relationship study on the determination of binding constant by fluorescence quenching

Models to predict binding constant (logK) to bovine serum albumin (BSA) should be very useful in the pharmaceutical industry to help speed up the design of new compounds, especially as far as pharmacokinetics is concerned. We present here an extensive list of logK binding constants for thirty-five compounds to BSA determined by florescence quenching from the literature. These data have allowed us the derivation of a quantitative structure-property relationship (QSPR) model to predict binding constants to BSA of compounds on the basis of their structure. A stepwise multiple linear regression (MLR) was performed to build the model. The statistical parameter provided by the MLR model (R = 0.9200, RMS = 0.3305) indicated satisfactory stability and predictive ability for the model. Using florescence quenching spectroscopy, we also experimentally determined the binding constants to BSA for two bioactive components in traditional Chinese medicines. Using the proposed model it was possible to predict the binding constants for each, which were in good agreement with the experimental results. This QSPR approach can contribute to a better understanding of structural factors of the compounds responsible for drug-protein interactions, and be useful in predicting the binding constants of other compounds.

Fluorescence quenching study of quercetin interaction with bovine milk xanthine oxidase

Quercetin is a natural flavonoid with many important therapeutic properties. The interaction of this polyphenolic compound bovine milk xanthine oxidase as one of its major target proteins was studied using fluorescence quenching method for the first time. It was found that the fluorescence quenching of xanthine oxidase occurs through a static mechanism. The results revealed the presence of a single binding site on xanthine oxidase with the binding constant value equals to 1.153 x 10(4) l mol(-1) at 310 K and pH 7.4. The thermodynamic parameters were also calculated at different temperatures. The enthalpy and entropy changes were found as -10.661 kJ mol(-1) and +43.321 J mol(-1) K(-1) indicating that both hydrogen binding and hydrophobic are involved in the interaction of this polyphenolic natural compound with xanthine oxidase. The results may provide a ground for further studies with different flavonoids to find a safe alternative for allopurinol, the only xanthine oxidase inhibitor with clinical application.

Spectroscopic studies on the interaction between nicotinamide and bovine serum albumin

The interaction of nicotinamide (NA) and bovine serum albumin (BSA) was studied by fluorescence and absorption spectroscopy at different temperatures. The results revealed that NA caused the fluorescence quenching of BSA through a static quenching procedure. The binding constants K(A), and the number of binding sites n, corresponding thermodynamic parameters DeltaG, DeltaH, DeltaS between NA and BSA at different temperatures were calculated. The primary binding pattern between NA and BSA was interpreted as hydrophobic interaction. In addition, the effect of NA on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. The binding average distance, r between the donor (BSA) and acceptor (NA) was determined based on the Förster's theory and it was found to be 3.1 nm.

Study on the Interaction between Florasulam and Bovine Serum Albumin

In this paper, the interaction between florasulam (FU, 2',6',8-trifluoro-5-methoxy [Kragh-Hansen U, Molecular aspects of ligand binding to serum albumin. Pharmacol Rev 33(1):17-53 1981; Carter DC and Ho JX, Structure of serum albumin. Adv Protein Chem 45:153-203 1994; He XM, and Carter DC, Atomic structure and chemistry of human serum albumin. Nature 358(6383):209-215 1992] triazolo [1,5-c]pyrimidine-2-sulfonanilide) and bovine serum albumin (BSA) was investigated by fluorescence, ultraviolet absorption (UV) and Far-UV circular dichroism (CD) spectrometries. A strong fluorescence quenching was observed and the quenching mechanism was considered as static quenching. The binding constant of FU with BSA at 299 and 309 K were obtained as 1.5 x 10(4) and 7.1 x 10(3) l mol(-1), respectively. There was one binding site between FU and BSA. The thermodynamic parameters enthalpy change (DeltaH) and entropy change (DeltaS) were calculated as -57.89 kJ mol(-1) and -113.6 J mol(-1) K(-1), respectively, which indicated that the acting force between FU and BSA was mainly hydrogen bond and Van der Waals force. According to the Förster non-radiation energy transfer theory, the average binding distance between donor (BSA) and acceptor (FU) was obtained (r = 1.59 nm). The investigations of the UV/Vis and CD spectra of the system showed that the conformation of BSA was changed in presence of FU.