Protopine and Allocryptopine Interactions with Plasma Proteins.

A comprehensive study of the interactions of human serum albumin (HSA) and α-1-acid glycoprotein (AAG) with two isoquinoline alkaloids, i.e., allocryptopine (ACP) and protopine (PP), was performed. The UV-Vis spectroscopy, molecular docking, competitive binding assays, and circular dichroism (CD) spectroscopy were used for the investigations. The results showed that ACP and PP form spontaneous and stable complexes with HSA and AAG, with ACP displaying a stronger affinity towards both proteins. Molecular docking studies revealed the preferential binding of ACP and PP to specific sites within HSA, with site 2 (IIIA) being identified as the favored location for both alkaloids. This was supported by competitive binding assays using markers specific to HSA's drug binding sites. Similarly, for AAG, a decrease in fluorescence intensity upon addition of the alkaloids to AAG/quinaldine red (QR) complexes indicated the replacement of the marker by the alkaloids, with ACP showing a greater extent of replacement than PP. CD spectroscopy showed that the proteins' structures remained largely unchanged, suggesting that the formation of complexes did not significantly perturb the overall spatial configuration of these macromolecules. These findings are crucial for advancing the knowledge on the natural product-protein interactions and the future design of isoquinoline alkaloid-based therapeutics.

Binding mechanism of pentamidine derivatives with human serum acute phase protein α1-acid glycoprotein.

Drug binding and interactions with plasma proteins play a crucial role in determining the efficacy of drug delivery, thus significantly impacting the overall pharmacological effect. AGP, the second most abundant plasma protein in blood circulation, has the unique capability to bind drugs and transport various compounds. In our present study, for the first time, we investigated whether AGP, a major component of the acute phase lipocalin in human plasma, can bind with pentamidine derivatives known for their high activity against the fungal pathogen Pneumocystis carinii. This investigation was conducted using integrated spectroscopic techniques and computer-based approaches. According to the results, it was concluded that compounds having heteroatoms (-NCH3) in the aliphatic linker and the addition of a Br atom and a methoxy substituent at the C-2 and C-6 positions on the benzene ring, exhibit strong interactions with the AGP binding site. These compounds are identified as potential candidates for recognition by this protein. MD studies indicated that the tested analogues complexed with AGPs reach an equilibrium state after 60 ns, suggesting the stability of the complexes. This observation was further corroborated by experimental results. Therefore, exploring the interaction mechanism of pentamidine derivatives with plasma proteins holds promise for the development of bis-benzamidine-designed pharmaceutically important drugs.

In vitro investigation of the binding characteristics of dacomitinib to human α 1-acid glycoprotein: Multispectral and computational modeling.

Dacomitinib is a highly selective second-generation tyrosine kinase inhibitor that can irreversibly bind to tyrosine kinase and is mainly used in the treatment of lung cancer. The binding characteristics of dacomitinib with human α 1-acid glycoprotein (HAG) were analyzed by multispectral and computational simulation techniques. The fluorescence spectra showed that dacomitinib can quench the fluorescence of HAG by forming the HAG-dacomitinib complex with a molar ratio of 1:1 (static quenching). At the temperature similar to that of the human body, the affinity of dacomitinib to HAG (8.95 × 106 M-1) was much greater than that to BSA (3.39 × 104 M-1), indicating that dacomitinib will give priority to binding onto HAG. Thermodynamics parameters analysis and driving force competition experiments showed that hydrogen bonding and hydrophobic forces were the major sources for keeping the complex of HAG-dacomitinib stable. The experimental outcomes also showed that the binding of dacomitinib can lead to the loosening of the skeleton structure of HAG, which led to a slight change in the secondary structure, and also reduces the hydrophobicity of the microenvironment of Trp and Tyr residues. The binding sites of dacomitinib on HAG and the contribution of key amino acid residues to the binding reaction were determined by molecular docking and molecular dynamics (MD) simulation. In addition, it was found that there was a synergistic effect between dacomitinib and Mg2+ and Co2+ ions. Mg2+ and Co2+ could increase the Kb of dacomitinib to HAG and prolong the half-life of dacomitinib.

Insight into intermolecular binding mechanism of apatinib mesylate and human alpha-1-acid glycoprotein: combined multi-spectroscopic approaches with in silico.

Apatinib mesylate (APM), an oral tyrosine kinase inhibitor, has a good anti-tumor activity in the treatment of various cancers, particularly in advanced non-small cell lung cancer. In this study, the intermolecular binding mechanism between APM and human alpha-1-acid glycoprotein (HAG) was investigated by combining multi-spectroscopic approaches with in silico techniques. The findings revealed that APM gave rise to the fluorescence quenching of HAG by forming a ground-state complex between APM and HAG with a stoichiometric ratio of 1:1, and APM has a moderate affinity for HAG as the binding constant of APM and HAG of approximately 105 M-1, which was larger than the APM-HAG complex. The findings from thermodynamic parameter analysis indicated that the dominant driving forces for the formation of the APM-HAG complex were van der Waals forces, hydrogen bonding and hydrophobic interactions, which were also verified with site-probe studies and molecular docking. The findings from in silico study indicated that APM inserted into the opening of the hydrophobic cavity of HAG, leads to a slight conformational change in the HAG, which was verified by circular dichroism (CD) measurements, that was, the beta sheet level of HAG decreased. Additionally, the results of synchronous and 3D fluorescence spectroscopies confirmed the decline in hydrophobicity of the microenvironment around Trp and Tyr residues. Moreover, some common metal ions such as Cu2+, Mg2+, Fe3+, Ca2+, and Zn2+ could cause the alteration in the binding constant of APM with HAG, leading to the change in the efficacy of APM. It will be expected that these study findings are to provide useful information for further understanding pharmacokinetic and structural modifications of APM.Communicated by Ramaswamy H. Sarma.

Conformational dynamics of α-1 acid glycoprotein (AGP) in cancer: A comparative study of glycosylated and unglycosylated AGP.

α-1 acid glycoprotein (AGP) is one of the most abundant plasma proteins. It fulfills two important functions: immunomodulation, and binding to various drugs and receptors. These different functions are closely associated and modulated via changes in glycosylation and cancer missense mutations. From a structural point of view, glycans alter the local biophysical properties of the protein leading to a diverse ligand-binding spectrum. However, glycans can typically not be observed in the resolved X-ray crystallography structure of AGP due to their high flexibility and microheterogeneity, so limiting our understanding of AGP's conformational dynamics 70 years after its discovery. We here investigate how mutations and glycosylation interfere with AGP's conformational dynamics changing its biophysical behavior, by using molecular dynamics (MD) simulations and sequence-based dynamics predictions. The MD trajectories show that glycosylation decreases the local backbone flexibility of AGP and increases the flexibility of distant regions through allosteric effects. We observe that mutations near the glycosylation site affect glycan's conformational preferences. Thus, we conclude that mutations control glycan dynamics which modulates the protein's backbone flexibility directly affecting its accessibility. These findings may assist in the drug design targeting AGP's glycosylation and mutations in cancer.

Investigation on the binding behavior of human α1-acid glycoprotein with Janus Kinase inhibitor baricitinib: Multi-spectroscopic and molecular simulation methodologies.

Baricitinib is a Janus Kinase (JAK) inhibitor that is primarily used to treat moderately to severely active rheumatoid arthritis in adults and has recently been reported for the treatment of patients with severe COVID-19. This paper describes the investigation of the binding behavior of baricitinib to human α1-acid glycoprotein (HAG) employing a variety of spectroscopic techniques, molecular docking and dynamics simulations. Baricitinib can quench the fluorescence from amino acids in HAG through a mix of dynamic and static quenching, according to steady-state fluorescence and UV spectra observations, but it is mainly static quenching at low concentration. The binding constant (Kb) of baricitinib to HAG at 298 K was at the level of 104 M-1, indicating a moderate affinity of baricitinib to HAG. Hydrogen bonding and hydrophobic interactions conducted the main effect, according to thermodynamic characteristics, competition studies between ANS and sucrose, and molecular dynamics simulations. For the change in HAG conformation, the results of multiple spectra showed that baricitinib was able to alter the secondary structure of HAG as well as increase the polarity of the microenvironment around the Trp amino acid. Furthermore, the binding behavior of baricitinib to HAG was investigated by molecular docking and molecular dynamics simulations, which validated experimental results. Also explored is the influence of K+, Co2+, Ni2+, Ca2+, Fe3+, Zn2+, Mg2+ and Cu2+plasma on binding affinity.

Enantioselective binding of carvedilol to human serum albumin and alpha-1-acid glycoprotein.

Carvedilol, a highly protein-bound beta-blocker, is used in therapy as a racemic mixture of its two enantiomers that exhibit different pharmacological activity. The aim of this study was to evaluate the stereoselective nature of its binding to the two major plasma proteins: albumin and alpha-1-acid glycoprotein. The determination of the plasma protein-binding degree for carvedilol and its enantiomers was achieved using ultrafiltration for the separation of the free fraction, followed by LC-MS/MS quantification, using two different developed and validated methods in terms of stationary phase: achiral C18 type and chiral ovomucoid type. Furthermore, molecular docking methods were applied in order to investigate and to better understand the mechanism of protein-binding for S-(-)- and R-(+)-carvedilol. A difference in the binding behavior of the two enantiomers to the plasma proteins was observed when taken individually, with R-(+)-carvedilol having a higher affinity for albumin and S-(-)-carvedilol for alpha-1-acid glycoprotein. However, in the case of the racemic mixture, the binding of the S enantiomer to alpha-1-acid glycoprotein seemed to be influenced by the presence of its antipode, although no such influence was observed in the case of albumin. The results raise the question of a binding competition between the two enantiomers for alpha-1-acid glycoprotein.

Comprehending binding features between ibrutinib and Human Alpha-1 acid glycoprotein: Combined experimental approaches and theoretical simulations.

Human alpha-1 acidic glycoprotein (HAG) is one of the proteins widely present in the blood, and the level of HAG in patients with cancer and inflammation is significantly increased. As one of transport proteins in the blood, the ability of HAG to bind with a drug, especially alkaline drugs, affects significantly the drug content at the target site, which in turn affects the efficacy of the drug. In this study, the interaction mechanism between HAG and the first generation Bruton's tyrosine kinase (BTK) inhibitor namely ibrutinib was explored by a combination of multi-spectroscopic techniques and theoretical calculations. The findings revealed that the quenching and binding constants of the HAG-ibrutinib system both reduced as the temperature rose, demonstrating that ibrutinib quenched the intrinsic fluorescence of HAG in a static manner. It was confirmed that HAG and ibrutinib formed a 1:1 complex with moderate affinity due to the binding constant of around 105 M-1 and accompanied by Förster resonance energy transfer. It was verified by thermodynamic parameter analysis and competition assays as well as molecular simulation that the existence of hydrogen bonds, van der Waals forces, and hydrophobic forces in the complexation of HAG and ibrutinib.The findings from theoretical calculations including molecular docking and theoretical calculation simulation confirmed that ibrutinib bound to the barrel hydrophobic pocket of HAG with a binding energy of -41.9 kJ∙mol-1, and the the binding constant of around 105 M-1 and the contribution of each residue in the complexation of ibrutinib and HAG. Additionally, it can be confirmed that metal ions affected the binding interaction of ibrutinib with HAG, among them, some promoted binding while others inhibited it.

The structural basis for high affinity binding of α1-acid glycoprotein to the potent antitumor compound UCN-01.

The α1-acid glycoprotein (AGP) is an abundant blood plasma protein with important immunomodulatory functions coupled to endogenous and exogenous ligand-binding properties. Its affinity for many drug-like structures, however, means AGP can have a significant effect on the pharmokinetics and pharmacodynamics of numerous small molecule therapeutics. Staurosporine, and its hydroxylated forms UCN-01 and UCN-02, are kinase inhibitors that have been investigated at length as antitumour compounds. Despite their potency, these compounds display poor pharmokinetics due to binding to both AGP variants, AGP1 and AGP2. The recent renewed interest in UCN-01 as a cytostatic protective agent prompted us to solve the structure of the AGP2-UCN-01 complex by X-ray crystallography, revealing for the first time the precise binding mode of UCN-01. The solution NMR suggests AGP2 undergoes a significant conformational change upon ligand binding, but also that it uses a common set of sidechains with which it captures key groups of UCN-01 and other small molecule ligands. We anticipate that this structure and the supporting NMR data will facilitate rational redesign of small molecules that could evade AGP and therefore improve tissue distribution.

Optimization and application of silver staining of non-glycosylated and glycosylated proteins and nucleic acids for agarose native gel electrophoresis.

Electrophoresis is one of the major techniques to analyze macromolecular structure and interaction. Its capability depends on the sensitivity and specificity of the staining methods. We have here examined silver staining of proteins and nucleic acids separated by agarose native gel electrophoresis. By comparing five commercial kits, we identified Silver Stain Plus from Bio-Rad most adequate, as it provided little background staining and reasonable band staining. One of the disadvantages of the Silver Stain Plus kit is its variable staining of glycoproteins as tested with several model samples, including hen egg white proteins, α1-acid glycoprotein and SARS-CoV-2 Spike protein. One of the advantages of silver staining is its ability to stain nucleic acids as demonstrated here for a model nucleic acid with two kits. It was then used to monitor the removal of nucleic acids from the affinity-purified maltose binding protein and monoclonal antibody. It also worked well on staining proteins on agarose gels prepared in the vertical mode, although preparation of the vertical agarose gels required technological modifications described in this report. With the silver staining method optimized here, it should be possible in the future to analyze biological samples that may be available in limited quantity.

Glycoprotein analysis using lectin microcolumns and capillary electrophoresis: Characterization of alpha1-acid glycoprotein by combined separation methods.

Separations based on combinations of 2.1 mm I.D. high-performance affinity microcolumns and capillary electrophoresis were developed and used to characterize the glycoforms of an intact glycoprotein. Human alpha1-acid glycoprotein (AGP) was used as a model analyte due to its heterogeneous glycosylation resulting from variations in its degree of branching, fucosylation, and number of sialic acids. Three separation formats were examined based on microcolumns that contained the lectins concanavalin A (Con A) or Aleuria aurantia lectin (AAL). These microcolumns were used with one another or in combination with capillary electrophoresis. N-Glycan analysis of the non-retained and retained AGP fractions was carried out by using PNGase F digestion and nanoflow electrospray ionization mass spectrometry. Con A microcolumns were found to selectively enrich AGP that contained bi-antennary N-glycans, while AAL microcolumns retained AGP with fucose-containing N-glycans. Results from these separation methods indicated that fucosylation of the N-linked glycans was more abundant when a high degree of branching was present in AGP. Sialic acid residues were more abundant when higher degrees of branching and more fucose residues were present in AGP. The separation and analysis methods that were developed could be used with relatively small amounts of AGP and can be adapted for use with other intact glycoproteins.

Diffusion and Relaxation Edited Proton NMR Spectroscopy of Plasma Reveals a High-Fidelity Supramolecular Biomarker Signature of SARS-CoV-2 Infection.

We have applied nuclear magnetic resonance spectroscopy based plasma phenotyping to reveal diagnostic molecular signatures of SARS-CoV-2 infection via combined diffusional and relaxation editing (DIRE). We compared plasma from healthy age-matched controls (n = 26) with SARS-CoV-2 negative non-hospitalized respiratory patients and hospitalized respiratory patients (n = 23 and 11 respectively) with SARS-CoV-2 rRT-PCR positive respiratory patients (n = 17, with longitudinal sampling time-points). DIRE data were modelled using principal component analysis and orthogonal projections to latent structures discriminant analysis (O-PLS-DA), with statistical cross-validation indices indicating excellent model generalization for the classification of SARS-CoV-2 positivity for all comparator groups (area under the receiver operator characteristic curve = 1). DIRE spectra show biomarker signal combinations conferred by differential concentrations of metabolites with selected molecular mobility properties. These comprise the following: (a) composite N-acetyl signals from α-1-acid glycoprotein and other glycoproteins (designated GlycA and GlycB) that were elevated in SARS-CoV-2 positive patients [p = 2.52 × 10-10 (GlycA) and 1.25 × 10-9 (GlycB) vs controls], (b) two diagnostic supramolecular phospholipid composite signals that were identified (SPC-A and SPC-B) from the -+N-(CH3)3 choline headgroups of lysophosphatidylcholines carried on plasma glycoproteins and from phospholipids in high-density lipoprotein subfractions (SPC-A) together with a phospholipid component of low-density lipoprotein (SPC-B). The integrals of the summed SPC signals (SPCtotal) were reduced in SARS-CoV-2 positive patients relative to both controls (p = 1.40 × 10-7) and SARS-CoV-2 negative patients (p = 4.52 × 10-8) but were not significantly different between controls and SARS-CoV-2 negative patients. The identity of the SPC signal components was determined using one and two dimensional diffusional, relaxation, and statistical spectroscopic experiments. The SPCtotal/GlycA ratios were also significantly different for control versus SARS-CoV-2 positive patients (p = 1.23 × 10-10) and for SARS-CoV-2 negatives versus positives (p = 1.60 × 10-9). Thus, plasma SPCtotal and SPCtotal/GlycA are proposed as sensitive molecular markers for SARS-CoV-2 positivity that could effectively augment current COVID-19 diagnostics and may have value in functional assessment of the disease recovery process in patients with long-term symptoms.

Tracking of Glycans Structure and Metallomics Profiles in BRAF Mutated Melanoma Cells Treated with Vemurafenib.

Nearly half of patients with advanced and metastatic melanomas harbor a BRAF mutation. Vemurafenib (VEM), a BRAF inhibitor, is used to treat such patients, however, responses to VEM are very short-lived due to intrinsic, adaptive and/or acquired resistance. In this context, we present the action of the B-Raf serine-threonine protein kinase inhibitor (vemurafenib) on the glycans structure and metallomics profiles in melanoma cells without (MeWo) and with (G-361) BRAF mutations. The studies were performed using α1-acid glycoprotein (AGP), a well-known acute-phase protein, and concanavalin A (Con A), which served as the model receptor. The detection of changes in the structure of glycans can be successfully carried out based on the frequency shifts and the charge transfer resistance after interaction of AGP with Con A in different VEM treatments using QCM-D and EIS measurements. These changes were also proved based on the cell ultrastructure examined by TEM and SEM. The LA-ICP-MS studies provided details on the metallomics profile in melanoma cells treated with and without VEM. The studies evidence that vemurafenib modifies the glycans structures and metallomics profile in melanoma cells harboring BRAF mutation that can be further implied in the resistance phenomenon. Therefore, our data opens a new avenue for further studies in the short-term addressing novel targets that hopefully can be used to improve the therapeutic regiment in advanced melanoma patients. The innovating potential of this study is fully credible and has a real impact on the global patient society suffering from advanced and metastatic melanomas.

Interaction of silver nanoparticles with plasma transport proteins: A systematic study on impacts of particle size, shape and surface functionalization.

Metallic nanoparticles are an important and widely used materials in development of nano-enabled medicine. For that reason, their interaction with biological molecules has to be systematically examined, as use of nanoparticles can lead to altered biological functions. In this study, we evaluated the interaction between silver nanoparticles (AgNPs) and two important plasma transport proteins - albumin and α-1-acid glycoprotein. To investigate comprehensively how different physico-chemical properties impact interaction of proteins with nanosurface, AgNPs of different size, shape and surface coating was prepared. The study was conducted using UV-Vis absorption, fluorescence, inductively coupled plasma mass spectrometry, circular dichroism spectroscopy, transmission electron microscopy, dynamic and electrophoretic light scattering techniques. The results showed significant complexities of the nano-bio interface and binding affinities of proteins onto surface of different AgNPs, which were affected by both AgNPs and protein properties. The most significant role on AgNPs-protein interaction had the coating agents used for AgNPs surface stabilization. Our findings should improve safe-by-design approach to development of the metallic nanomaterials for medical use.

Sequential modifications of glycans by linkage-specific alkylamidation of sialic acids and permethylation.

Permethylation is useful for glycosidic linkage analysis, but is often accompanied by a large proportion of by-products, especially for glycans containing sialic acids (Sia). Unlike hydroxyl groups of glycans, which are converted to stable methyl ethers by permethylation, the carboxylic acids on Sia are converted to methyl esters, which are easily reversible to carboxylate under alkaline conditions. To overcome this problem, we used linkage-specific alkylamidation to protect Sia prior to the permethylation. This method not only decreased the levels of by-products, but also enabled us to distinguish isomers of α2,3- and α2,6-Sia while simultaneously determining other glycosidic linkages.

Serum Levels and Glycosylation Changes of Alpha-1-Acid Glycoprotein According to Severity of Breast Cancer in Korean Women.

Elevated serum levels of alpha-1-acid glycoprotein (AGP) are known to be associated with several types of cancer. In addition, some reports have indicated that changes in glycosylation of AGP are associated with cancer progression. However, changes in AGP levels of serum and changes in glycosylation of AGPs in breast cancer have not been specifically studied. In the present study, serum AGP levels in benign (BN) cancer and breast cancer stage I (BC I), BC IIA, BC IIB, and BC III in Korean women were measured using an enzyme-linked immunosorbent assay (ELISA). AGP was purified from individual sera by hot phenol extraction and then subjected to AGP glycosylation analysis. Three types of AGP glycosylation (fucosylation, high-mannose-type and sialylation) were detected using enzyme-linked lectin assays (ELLAs). Serum AGP levels were higher in BC I, BC IIA, BC IIB, and BC III, than in the BN group, and the level in BC I and BC IIA was high enough to be distinguished from BN. Meanwhile, terminal fucosylation and high-mannose-type glycans appeared to be lowest in BC I. The glycosylation levels of BC I provide sensitivity and specificity that make BC I clearly distinguishable from BC IIA, BC IIB, and BC III as well as BN. Therefore, determination of serum AGP or AGP glycosylation level could be useful for detecting the early stages of breast cancer.

Insights on the interaction mechanism of brigatinib to human α-1-acid glycoprotein: Experimental and computational approaches.

Brigatinib, a multi-target kinase inhibitor, is primarily used to treat anaplastic lymphoma kinase (ALK)-positive patients with advanced non-small cell lung cancer (NSCLC) who have previously received crizotinib or are resistant to crizotinib. In this study, we focused on elucidating the interaction mechanism between brigatinib and human alpha-1-acid glycoprotein (HAG) through experimental and computational approaches. Steady-state fluorescence and UV-vis spectroscopy measurements revealed that brigatinib could quench the intrinsic fluorescence of HAG in a static quenching manner and formed the brigatinib-HAG complex with the stoichiometric ratio of 1:1. The findings revealed that brigatinib had a stronger affinity on HAG due to higher binding constant of 2.91 × 105 M-1 at 298 K. It can be proved from thermodynamic parameter analysis that brigatinib spontaneously bound to HAG in the means of enthalpy driven, the main forces for stabilizing brigatinib-HAG complexes were hydrogen bonding and hydrophobic interactions. The experimental results also indicated that the binding interaction induced micro-environmental changes around tryptophan residues and the alteration in secondary structure of HAG. The presence of metal ions like Mg2+, Zn2+, Ca2+, Ni2+ and Co2+ affects the binding interaction and thus change the therapeutic efficacy of brigatinib. Molecular docking results suggested that brigatinib was embedded to the hydrophobic cavity of HAG. The experimental and computational results certified that hydrogen bonding and hydrophobic interaction as well as electrostatic energy and van der Waals forces plays a leading role in the binding process.

Characterization of the mechanism of interaction between α1 -acid glycoprotein and lipid membranes by vacuum-ultraviolet circular-dichroism spectroscopy.

α1 -Acid glycoprotein (AGP) interacts with lipid membranes as a peripheral membrane protein so as to decrease the drug-binding capacity accompanying the ß→α conformational change that is considered a protein-mediated uptake mechanism for releasing drugs into membranes or cells. This study characterized the mechanism of interaction between AGP and lipid membranes by measuring the vacuum-ultraviolet circular-dichroism (VUVCD) spectra of AGP down to 170 nm using synchrotron radiation in the presence of five types of liposomes whose constituent phospholipid molecules have different molecular characteristics in the head groups (e.g., different net charges). The VUVCD analysis showed that the α-helix and ß-strand contents and the numbers of segments of AGP varied with the constituent phospholipid molecules of liposomes, while combining VUVCD data with a neural-network method predicted that these membrane-bound conformations comprised several common long helix and small strand segments. The amino-acid composition of each helical segment of the conformations indicated that amphiphilic and positively charged helices formed at the N- and C-terminal regions of AGP, respectively, were candidate sites for the membrane interaction. The addition of 1 M sodium chloride shortened the C-terminal helix while having no effect on the length of the N-terminal one. These results suggest that the N- and C-terminal helices can interact with the membrane via hydrophobic and electrostatic interactions, respectively, demonstrating that the liposome-dependent conformations of AGP analyzed using VUVCD spectroscopy provide useful information for characterizing the mechanism of interaction between AGP and lipid membranes.

Insight into the binding behavior of ceritinib on human α-1 acid glycoprotein: Multi-spectroscopic and molecular modeling approaches.

Ceritinib is a second-generation anaplastic lymphoma kinase (ALK) inhibitor for mainly treating non-small cell lung cancer (NSCLC). This investigation focused on to clarify in detail the binding behavior between human α-1 acid glycoprotein (HAG) and ceritinib by means of multi-spectroscopic and molecular modeling approaches. Fluorescence data obtained at four different temperatures indicated ceritinib quenched the endogenous fluorescence of HAG by a static quenching mechanism. Based on the Kb value at 105 M-1 level, it can be inferred that the binding affinity between both is strong. From findings of thermodynamic parameter analysis, the competitive experiments with ANS and sucrose as well as molecular dynamic (MD) simulation, it can be inferred that hydrophobicity, hydrogen bonding, van der Waals forces as well as electrostatic interactions exist in the binding interaction between ceritinib and HAG. The findings from UV absorption, circular dichroism, and synchronous fluorescence spectroscopy indicated that the change in the microenvironment around the protein structure, secondary structure and tryptophan residues occurred after interaction with ceritinib. The data from FRET analysis confirmed that the non-radiative energy transfer between the two existed and the binding distance between the acceptor (ceritinib) and donor (HAG) was 2.11 nm. Meantime, the influence of Ca2+, Cu2+, Ni2+, Co2+, and Zn2+ ions on the binding interaction of ceritinib with HAG were obvious, especially Zn2+ ion.

Study of the binding affinity between imatinib and α-1 glycoprotein using nuclear spin relaxation and isothermal titration calorimetry.

Imatinib is a selective tyrosine kinase inhibitor, successfully used for the treatment of chronic myelogenous leukaemia and gastrointestinal stromal tumors. Binding of drugs to proteins influence their pharmacokinetic and pharmacodynamics action. In the blood, the drug is distributed in the body in the free form or bound to plasma protein. Albumin and α-1 glycoprotein (AGP) are plasma proteins with the highest affinity for drug substances. Drugs which are weak acids mainly bind to plasma albumin, while drugs that are bases have affinity for α-1 glycoprotein. The main goal of this study is to quantitatively evaluate the interaction between imatinib mesylate (IMT) and α-1 glycoprotein to characterize the nature and forces underlying the formation of a molecular complex. Relaxation experiments provide quantitative information about the relationship between the binding affinity and structure of IMT. Thus, association constant was determined as Ka = 873.36 M-1. The ITC data revealed that the binding was an entropy driven process and the association constant Ka = 3.22 × 103 M-1, with a 1:1 stoichiometry. The results obtained by NMR and ITC were complemented with a molecular docking study.