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1.
J Cell Biochem ; 120(2): 2642-2656, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30242891

RESUMO

Amyloid fibrillation is associated with several human maladies, such as Alzheimer's, Parkinson's, Huntington's diseases, prions, amyotrophic lateral sclerosis, and type 2 diabetes diseases. Gaining insights into the mechanism of amyloid fibril formation and exploring novel approaches to fibrillation inhibition are crucial for preventing amyloid diseases. Here, we hypothesized that ligands capable of stabilizing the native state of query proteins might prevent protein unfolding, which, in turn, may reduce the propensity of proteins to form amyloid fibrils. We demonstrated the efficient inhibition of amyloid formation of the human serum albumin (HSA) (up to 85%) and human insulin (up to 80%) by a nonsteroidal anti-inflammatory drug, ibuprofen (IBFN). IBFN significantly increases the conformational stability of both HSA and insulin, as confirmed by differential scanning calorimetry (DSC). Moreover, increasing concentration of IBFN boosts its amyloid inhibitory propensity in a linear fashion by influencing the nucleation phase as assayed by thioflavin T fluorescence, transmission electron microscopy, and dynamic light scattering. Furthermore, circular dichroism analysis supported the DSC results, showing that IBFN binds to the native state of proteins and almost completely prevents their tendency to lose secondary and tertiary structures. Cell toxicity assay confirms that species formed in the presence of IBFN are less toxic to neuronal cells (SH-SY5Y). These results demonstrate the feasibility of using a small molecule to stabilize the native state of proteins, thereby preventing the amyloidogenic conformational changes, which appear to be the common link in several human amyloid diseases.

2.
J Cell Biochem ; 119(5): 3945-3956, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29350433

RESUMO

Protein misfolding and aggregation lead to amyloid generation that in turn may induce cell membrane disruption and leads to cell apoptosis. In an effort to prevent or treat amyloidogenesis, large number of studies has been paying attention on breakthrough of amyloid inhibitors. In the present work, we aim to access the effect of two drugs, that is, acetylsalicylic acid and 5-amino salicylic acid on insulin amyloids by using various biophysical, imaging, cell viability assay, and computational approaches. We established that both drugs reduce the turbidity, light scattering and fluorescence intensity of amyloid indicator dye thioflavin T. Premixing of drugs with insulin inhibited the nucleation phase and inhibitory potential was boosted by increasing the concentration of the drug. Moreover, addition of drugs at the studied concentrations attenuated the insulin fibril induced cytotoxicity in breast cancer cell line MDA-MB-231. Our results highlight the amino group of salicylic acid exhibited enhanced inhibitory effects on insulin fibrillation in comparison to acetyl group. It may be due to presence of amino group that helps it to prolong the nucleation phase with strong binding as well as disruption of aromatic and hydrophobic stacking that plays a key role in amyloid progression.


Assuntos
Amiloide , Insulina , Mesalamina/química , Ácido Salicílico/química , Amiloide/química , Amiloide/farmacologia , Animais , Bovinos , Linhagem Celular Tumoral , Humanos , Insulina/química , Insulina/farmacologia
3.
Biochim Biophys Acta Proteins Proteom ; 1866(4): 549-557, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29496560

RESUMO

Protein aggregation and amyloid fibrillation are responsible for several serious pathological conditions (like type II diabetes, Alzheimer's and Parkinson's diseases etc.) and protein drugs ineffectiveness. Therefore, a molecule that can inhibit the amyloid fibrillation and potentially clear amyloid fibrils is of great therapeutic value. In this manuscript, we investigated the antiamyloidogenic, fibril disaggregating, as well as cell protective effect of an anti-tuberculosis drug, Capreomycin (CN). Aggregation kinetics data, as monitored by ThT fluorescence, inferred that CN retards the insulin amyloid fibrillation by primarily targeting the fibril elongation step with little effect on lag time. Increasing the dose of CN boosted its inhibitory potency. Strikingly, CN arrested the growth of fibrils when added during the elongation phase, and disaggregated mature insulin fibrils. Our Circular Dichroism (CD) results showed that, although CN is not able to maintain the alpha helical structure of protein during fibrillation, reduces the formation of beta sheet rich structure. Furthermore, Dynamic Light Scattering (DLS) and Transmission Electronic Microscopy (TEM) analysis confirmed that CN treated samples exhibited different size distribution and morphology, respectively. In addition, molecular docking results revealed that CN interacts with insulin through hydrophobic interactions as well as hydrogen bonding, and the Hemolytic assay confirmed the non-hemolytic activity of CN on human RBCs. For future research, this study may assist in the rational designing of molecules against amyloid formation.


Assuntos
Amiloide/química , Capreomicina/química , Insulina/química , Simulação de Acoplamento Molecular , Agregados Proteicos , Amiloide/ultraestrutura , Animais , Capreomicina/farmacologia , Bovinos , Humanos
4.
J Mol Recognit ; 30(8)2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28295815

RESUMO

Nowadays, understanding of interface between protein and drugs has become an active research area of interest. These types of interactions provide structural guidelines in drug design with greater clinical efficacy. Thus, structural changes in catalase induced by clofazimine were monitored by various biophysical techniques including UV-visible spectrometer, fluorescence spectroscopy, circular dichroism, and dynamic light scattering techniques. Increase in absorption spectra (UV-visible spectrum) confers the complex formation between drug and protein. Fluorescence quenching with a binding constants of 2.47 × 104  M-1 revealed that clofazimine binds with protein. Using fluorescence resonance energy transfer, the distance (r) between the protein (donor) and drug (acceptor) was found to be 2.89 nm. Negative Gibbs free energy change (ΔG°) revealed that binding process is spontaneous. In addition, an increase in α-helicity was observed by far-UV circular dichroism spectra by adding clofazimine to protein. Dynamic light scattering results indicate that topology of bovine liver catalase was slightly altered in the presence of clofazimine. Hydrophobic interactions are the main forces between clofazimine and catalase interaction as depicted by molecular docking studies. Apart from hydrophobic interactions, some hydrogen bonding was also observed during docking method. The results obtained from the present study may establish abundant in optimizing the properties of ligand-protein mixtures relevant for numerous formulations.


Assuntos
Catalase/química , Clofazimina/química , Fígado/química , Simulação de Acoplamento Molecular , Animais , Sítios de Ligação , Catalase/isolamento & purificação , Bovinos , Cristalografia por Raios X , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Fígado/enzimologia , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Análise Espectral/métodos , Termodinâmica
5.
Int J Biol Macromol ; 273(Pt 2): 133083, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38866289

RESUMO

In recent decades, there has been a concerning and consistent rise in the incidence of cancer, posing a significant threat to human health and overall quality of life. The transferrin receptor (TfR) is one of the most crucial protein biomarkers observed to be overexpressed in various cancers. This study reports on the development of a novel voltammetric immunosensor for TfR detection. The electrochemical platform was made up of a glassy carbon electrode (GCE) functionalized with gold nanoparticles (AuNPs), on which anti-TfR was immobilized. The surface characteristics and electrochemical behaviors of the modified electrodes were comprehensively investigated through scanning electron microscopy, XPS, Raman spectroscopy FT-IR, electrochemical cyclic voltammetry and impedance spectroscopy. The developed immunosensor exhibited robust analytical performance with TfR fortified buffer solution, showing a linear range (LR) response from 0.01 to 3000 µg/mL, with a limit of detection (LOD) of 0.01 µg/mL and reproducibility (RSD <4 %). The fabricated sensor demonstrated high reproducibility and selectivity when subjected to testing with various types of interfering proteins. The immunosensor designed for TfR detection demonstrated several advantageous features, such as being cost-effective and requiring a small volume of test sample making it highly suitable for point-of-care applications.

6.
Bioelectrochemistry ; 153: 108493, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37392576

RESUMO

C-reactive protein (CRP) is produced by the liver in response to systemic inflammation caused by bacterial infection, trauma and internal organ failures. CRP serves as a potential biomarker in the precise diagnosis of cardiovascular risk, type-2 diabetes, metabolic syndrome, hypertension and various types of cancers. The pathogenic conditions indicated above are diagnosed by an elevated CRP level in the serum. In this study, we successfully fabricated a highly sensitive and selective carbon nanotube field-effect transistor (CNT-FET) immunosensor for the detection of CRP. The CNTs were deposited on the Si/SiO2 surface, between source-drain electrodes, afterwards modified with well-known linker PBASE and then anti-CRP was immobilized. This anti-CRP functionalized CNT-FET immunosensor exhibits a wide dynamic detection range (0.01-1000 µg/mL) CRP detection, rapid response time (2-3 min) and low variation (<3 %) which can be delivered as a low-cost and rapid clinical detection technology for the early diagnosis of coronary heart disease (CHD). For the clinical applications, our sensor was tested using CRP fortified serum samples and sensing performance was validated using enzyme-linked immune-sorbent assay (ELISA). This CNT-FET immunosensor will be helpful in taking over the complex laboratory-based expensive traditional CRP diagnostic procedures practiced in the hospitals.


Assuntos
Técnicas Biossensoriais , Nanotubos de Carbono , Proteína C-Reativa/análise , Imunoensaio/métodos , Técnicas Biossensoriais/métodos , Dióxido de Silício , Biomarcadores
7.
J Biomol Struct Dyn ; 37(6): 1390-1401, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-29669491

RESUMO

Alpha1-acid glycoprotein (AAG) is a major acute phase protein of human plasma. Binding of clofazimine to AAG is investigated using optical spectroscopy and molecular docking tools. We found significant quenching of intrinsic fluorescence of AAG upon the binding of clofazimine, binding mode is static with binding constant of 3.52 × 104at 298 K. The Gibbs free energy change is found to be negative for the interaction of clofazimine with AAG indicating spontaneity of the binding process. Binding of clofazimine induced ordered structure in protein and lead to molecular compaction. Molecular docking results indicate the binding site is located in the central beta barrel, hydrogen bonding and hydrophobic interactions are main bonding forces between AAG-clofazimine.


Assuntos
Fenômenos Biofísicos , Clofazimina/química , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Orosomucoide/química , Sítios de Ligação , Clofazimina/metabolismo , Humanos , Estrutura Molecular , Orosomucoide/metabolismo , Ligação Proteica , Análise Espectral , Relação Estrutura-Atividade , Termodinâmica
8.
Int J Biol Macromol ; 112: 217-229, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29374532

RESUMO

The newly synthesized unfolded polypeptide attains its functional and unique three-dimensional conformation through the process of protein folding for which several models have been proposed. The protein misfolding diseases include Alzheimer's, Parkinson's and Cataract which are result of formation of amyloid or amorphous aggregates, respectively. The distinction in morphology shows relation with the melting temperature (Tm). The temperatures near or slightly higher than Tm induces amyloids while much higher or low temperature mediate amorphous aggregation. The aggregation is not always deleterious rather it also performs several important cellular functions essential for survival wide range of organisms called as functional amyloids. Protein gets modulated by several modulators which mediate the aggregation, acceleration, delay, transformations, inhibition and disaggregation of protein aggregates. The exclusive properties of inhibition and disaggregation displayed by various molecules can be employed to treat the life threatening disorders.


Assuntos
Proteínas Amiloidogênicas/química , Peptídeos/química , Agregação Patológica de Proteínas/genética , Dobramento de Proteína , Proteínas Amiloidogênicas/metabolismo , Amiloidose/genética , Amiloidose/patologia , Humanos , Peptídeos/metabolismo , Conformação Proteica , Deficiências na Proteostase/genética , Deficiências na Proteostase/patologia
9.
Int J Biol Macromol ; 106: 1115-1129, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28890370

RESUMO

This review article summarises the possible mechanisms of the protein-ligand interaction, folding, misfolding, aggregation and inhibition of protein aggregates. Under certain stressed condition the folding process deviates from its path and results into misfolding and aggregation of proteins. So aggregates have to be inhibited in order to cure the diseases. In some cases of protein-ligand interaction studies we have seen that the interaction of a protein with more than one ligand may show both type of quenching mechanisms i.e. dynamic as well as static quenching rather than single type of quenching mechanism, that result can be entirely different by the result of binding study utilising single ligand. So, likewise it is hypothesized that if the aggregates are inhibited by using more than one inhibitor may give more fruitful results rather than application of single inhibitor in inhibition and disaggregation of the preformed aggregates. Therefore, we have hypothesized mechanisms for the inhibition of protein aggregates that may assist in curing the neurodegenerative diseases. Thus, besides the mechanism of protein-ligand interaction, folding, misfolding and aggregation; the hypothesized mechanisms for the inhibition of protein aggregates may show new route to researchers either directly or indirectly in treating the diseases.


Assuntos
Doenças Neurodegenerativas/metabolismo , Agregados Proteicos , Agregação Patológica de Proteínas/metabolismo , Proteínas/química , Humanos , Ligantes , Doenças Neurodegenerativas/etiologia , Doenças Neurodegenerativas/patologia , Agregação Patológica de Proteínas/patologia , Dobramento de Proteína , Proteínas/metabolismo
10.
J Biomol Struct Dyn ; 36(10): 2543-2557, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28768117

RESUMO

Protein aggregation into oligomers and mature fibrils are associated with more than 20 diseases in humans. The interactions between cationic surfactants dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB) with varying alkyl chain lengths and bovine liver catalase (BLC) were examined by various biophysical approaches. The delicate coordination of electrostatic and hydrophobic interactions with protein, play imperative role in aggregation. In this article, we have reconnoitered the relation between charge, hydrophobicity and cationic surfactants DTAB and TTAB on BLC at pH 7.4 and 9.4 which are two and four units above pI, respectively. We have used techniques like turbidity, Rayleigh light scattering, far-UV CD, ThT, ANS, Congo red binding assay, DLS, and transmission electron microscopy. The low concentration ranges of DTAB (0-600 µM) and TTAB (0-250 µM) were observed to increase aggregation at pH 9.4. Nevertheless, at pH 7.4 only TTAB was capable of inducing aggregate. DTAB did not produce any significant change in secondary structure at pH 7.4 suggestive of the role of respective charges on surfactants and protein according to the pI and alkyl chain length. The morphology of aggregates was further determined by TEM, which proved the existence of a fibrillar structure. The surfactants interaction with BLC was primarily electrostatic as examined by ITC. Our work demystifies the critical role of charge as well as hydrophobicity in amyloid formation.


Assuntos
Fenômenos Biofísicos , Catalase/química , Tensoativos/química , Animais , Benzotiazóis/metabolismo , Calorimetria , Catalase/ultraestrutura , Cátions , Bovinos , Dicroísmo Circular , Difusão Dinâmica da Luz , Hidrodinâmica , Concentração de Íons de Hidrogênio , Nefelometria e Turbidimetria , Compostos de Amônio Quaternário/química , Espectrometria de Fluorescência , Termodinâmica , Compostos de Trimetil Amônio/química
11.
J Biomol Struct Dyn ; 36(5): 1261-1273, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28399705

RESUMO

The aggregation phenomenon (amyloid and amorphous) is associated with several pathological complications in human, such as Alzheimer's, Parkinson's, Huntington, Cataract diseases, and Diabetes mellitus type 2. In the present study we are offering evidence and breaking the general belief with regard to the polyphenols action as protein aggregate inhibitors. Herein we confirm that tannic acid (TA) is not only an amyloid inducer, but also it switches one type of conformation, ultimately morphology, into another. We ascertain based on our findings that aggregates are not rigid structures and the stability can be challenged under certain conditions. This study also confirms that unfolded and amorphous aggregates can serve as precursors of amyloids and TA interactions with unordered aggregates (amorphous) bringing orderliness in the conformation via amyloidosis. The shifting of unordered conformation toward orderliness is governed by the modulation in surface hydrophobic patches in Concanavalin A (ConA). Hence, a degree of exposed hydrophobic cluster can be claimed as a strong parameter to detect and distinguish the native, amorphous and both types of amyloids. Turbidity and Rayleigh light scattering measurements followed similar pattern while Thioflavin T and 1-anilino-8-naphthalene sulfonate fluorescence assays of the binding with amorphous and amyloid followed an inverse relation. Electron microscopic studies revealed the morphological variation in the ConA at 65°C as amorphous while the ConA treated with TA followed by heat treatment at 65°C was defined as amyloid in nature. Interestingly for the first time we are reporting the slight agglutination activity by the ConA amyloids.


Assuntos
Amiloide/química , Fenômenos Biofísicos , Concanavalina A/química , Conformação Proteica , Taninos/química , Amiloide/metabolismo , Amiloide/ultraestrutura , Benzotiazóis/química , Agregados Proteicos/efeitos dos fármacos , Análise Espectral , Taninos/farmacologia
12.
Int J Biol Macromol ; 107(Pt B): 2450-2464, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29102789

RESUMO

Numerous phenolic compounds have been reported in the last decade that have a good antioxidant property and interaction affinity towards mammalian serum albumins. In the present study, we have utilized mammalian serum albumins as a model protein to examine their comparative interaction property with polyphenolic compound tannic acid (TA) by using various spectroscopic and calorimetric methods We have also monitored the esterase and antioxidant activity of mammalian serum albumins in the absence and presence of TA. The obtain results recommended that the TA have a good binding affinity (∼104 to 106M-1) towards mammalian serum albumins and shows double sequential binding sites, which depends on the concentration of TA that induced the conformational alteration which responsible for the thermal stability of proteins. Binding affinity, structural transition and thermodynamic parameters were calculated from spectroscopic and calorimetric method reveals that non-covalent interaction causes partial conformational alteration in the secondary structure of protein ie.; increase in α-helical content with decrease in ß-sheet, random coil and other structure. Meanwhile, we have found that esterase activities of serum albumins were also stabilized against hydrolysis and shows higher antioxidant activity in the presence of TA because albumins its self have an immense antioxidant activity beside TA.


Assuntos
Polifenóis/química , Ligação Proteica , Albumina Sérica/química , Taninos/química , Animais , Sítios de Ligação , Fenômenos Biofísicos , Bovinos , Dicroísmo Circular , Humanos , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Estrutura Secundária de Proteína , Albumina Sérica/ultraestrutura , Termodinâmica
13.
Int J Biol Macromol ; 94(Pt A): 290-300, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27744055

RESUMO

Under physical or chemical stress, proteins tend to form aggregates either highly ordered (amyloid) or unordered (amorphous) causing many pathological disorders in human and loss of proteins functionality in both laboratory conditions and industries during production and storage at commercial level. We investigated the effect of increasing temperature on Conalbumin (CA) and induced aggregation at 65°C. The enhanced Thioflavin T (ThT) and ANS (1-anilinonaphtalene 8-sulfonic acid) fluorescence intensity, show no shift on Congo red binding, additionally, transmission and scanning electron microscopy (TEM) (SEM) reveal amorphous morphology of the aggregate. Our investigation clearly demonstrated that polyols namely Glycerol (GL) and Ethylene glycol (EG) are so staunch to inhibit amorphous aggregates via restoring secondary conformation. Addition of polyols (15% GL and 35% EG) significantly decrease the turbidity, Rayleigh scattering ThT and ANS fluorescence intensity. The dynamic light scattering (DLS) data show that hydrodynamic radii (Rh) of the aggregates is ∼20 times higher than native CA while nearly similar for GL and EG protected CA due to condensation of core size with little difference.


Assuntos
Conalbumina/química , Etilenoglicol/química , Glicerol/química , Benzotiazóis , Dicroísmo Circular , Difusão Dinâmica da Luz , Metaloproteases/química , Agregados Proteicos , Estrutura Secundária de Proteína , Tiazóis/química
14.
J Biomol Struct Dyn ; 35(7): 1407-1419, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-27141925

RESUMO

Neurodegenerative disorders are mainly associated with amyloid fibril formation of different proteins. Stem bromelain (SB), a cysteine protease, is known to exist as a molten globule state at pH 10.0. It passes through the identical surrounding (pH 10.0) in the gut epithelium of intestine upon oral administration. Protein-surfactant complexes are widely employed as drug carriers, so the nature of surfactant toward protein is of great interest. The present work describes the effect of cationic surfactants (CTAB & DTAB) and their hydrophobic behavior toward amyloidogenesis behavior of SB at pH 10.0. Multiple approaches including light scattering, far UV-CD, turbidity measurements, and dye binding assay (ThT, Congo red and ANS) were performed to measure the aggregation propensity of SB. Further, we monitored the hydrodynamic radii of aggregates formed using dynamic light scattering technique. Structure of fibrils was also visualized through fluorescence microscopy as well as TEM. At pH 10.0, low concentration of CTAB (0-200 µM) induced amyloid formation in SB as evident from a prominent increase in turbidity and light scattering, gain in ß-sheet content, and enhanced ThT fluorescence intensity. However, further increase in CTAB concentration suppressed the fibrillation phenomenon. In contrast, DTAB did not induce fibril formation at any concentration used (0-500 µM) due to lower hydrophobicity. Net negative charge developed on protein at high pH (10.0) might have facilitated amyloid formation at low concentration of cationic surfactant (CTAB) due to electrostatic and hydrophobic interactions.


Assuntos
Amiloide/química , Bromelaínas/química , Compostos de Cetrimônio/química , Compostos de Amônio Quaternário/química , Tensoativos/química , Amiloide/ultraestrutura , Naftalenossulfonato de Anilina/química , Benzotiazóis , Cetrimônio , Corantes/química , Vermelho Congo/química , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica de Transmissão , Microscopia de Fluorescência , Agregados Proteicos , Ligação Proteica , Eletricidade Estática , Tiazóis/química
15.
J Pharm Biomed Anal ; 135: 106-115, 2017 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-28012306

RESUMO

The binding interaction between clofarabine, an important anticancer drug and two important carrier proteins found abundantly in human plasma, Human Serum Albumin (HSA) and α-1 acid glycoprotein (AAG) was investigated by spectroscopic and molecular modeling methods. The results obtained from fluorescence quenching experiments demonstrated that the fluorescence intensity of HSA and AAG is quenched by clofarabine and the static mode of fluorescence quenching is operative. UV-vis spectroscopy deciphered the formation of ground state complex between anticancer drug and the two studied proteins. Clofarabine was found to bind at 298K with both AAG and HSA with the binding constant of 8.128×103 and 4.120×103 for AAG and HSA, respectively. There is stronger interaction of clofarabine with AAG as compared to HSA. The Gibbs free energy change was found to be negative for the interaction of clofarabine with AAG and HSA indicating that the binding process is spontaneous. Binding of clofarabine with HSA and AAG induced ordered structures in both proteins and lead to molecular compaction. Clofarabine binds to HSA near to drug site II. Hydrogen bonding and hydrophobic interactions were the main bonding forces between HSA-clofarabine and AAG-clofarabine as revealed by docking results. This study suggests the importance of binding of anticancer drug to AAG spatially in the diseases like cancers where the plasma concentration of AAG increases many folds. Design of drug dosage can be adjusted accordingly to achieve optimal treatment outcome.


Assuntos
Nucleotídeos de Adenina/análise , Nucleotídeos de Adenina/metabolismo , Arabinonucleosídeos/análise , Arabinonucleosídeos/metabolismo , Simulação de Acoplamento Molecular/métodos , Albumina Sérica/análise , Albumina Sérica/metabolismo , Nucleotídeos de Adenina/química , Arabinonucleosídeos/química , Clofarabina , Humanos , Ligação Proteica/fisiologia , Estrutura Secundária de Proteína , Albumina Sérica/química , Espectrofotometria Ultravioleta/métodos
16.
Int J Biol Macromol ; 105(Pt 3): 1572-1580, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28414112

RESUMO

Erucic acid (EA) is one of the key fatty acids usually found in canola oil, mustard oil and rapeseed oil. Consumption of EA in primates was found to cause myocardial lipidosis and cardiac steatosis. To have an insight of the effect of EA in humans, we performed in vitro interaction studies of EA with the primary plasma protein, human serum albumin (HSA). Spectroscopic (UV-vis and fluorescence) analysis of the HSA-EA interaction revealed a static mode of quenching with binding constant Kb ∼104 reflecting high affinity of EA for HSA. The negative value of ΔG° for binding of EA to HSA in the fluorescence studies indicates the process to be spontaneous. Thermodynamic signatures of the HSA-EA interaction in the complex reflect dominance of hydrogen bonds. Despite predominance of hydrogen bonds, hydrophobic interactions in the HSA-EA complex were found acting as a contributing factor in the binding of EA to HSA, observed as structural change in the far-UV CD spectra. Förster's resonance energy transfer of the EA-HSA complex revealed a distance of 3.2nm between acceptor molecules (EA) and the donor Trp residue of HSA. To have a deeper insight of the structural dependence of the HSA-EA interaction in the complex, thermodynamic study was supplemented with molecular docking. The molecular docking analysis further highlighted the EA binding in the subdomain IIIA (Sudlow site II) of HSA. The information generated in the study reflects greater pharmacological significance of EA and highlights its importance in the clinical medicine.


Assuntos
Ácidos Erúcicos/metabolismo , Simulação de Acoplamento Molecular , Albumina Sérica Humana/metabolismo , Sítios de Ligação , Transferência de Energia , Humanos , Ligação Proteica , Estrutura Secundária de Proteína , Albumina Sérica Humana/química , Análise Espectral , Termodinâmica
17.
Int J Biol Macromol ; 94(Pt A): 301-308, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27744056

RESUMO

Studying amyloid associated neurodegenerative diseases is an active area of research. Cure for these diseases are still to be discovered. In the present study we have performed comprehensive biophysical and computational experiments showing levodopa not only significantly inhibits heat induced fibrillization of human serum albumin but also disaggregates preformed fibrils. Thioflavin T (ThT) binding assay was used to monitor the fibrillation process of human serum albumin (HSA) at 65°C in the presence and absence of levodopa. Binding of levodopa was studied using isothermal titration calorimetry (ITC), binding constant was found to be 3.6×103M-1. Thermal stabilization effect of levodopa on HSA was studied using differential scanning calorimetry (DSC). Microscopic imaging techniques were employed to analyze the morphology of aggregates and effect of levodopa on aggregation. Further, molecular docking study was also utilized to decipher the amino acid residues involved in the binding interaction of levodopa with HSA. Levodopa interferes in the Fibrillogenesis of HSA by interacting with the amino acid residues near to drug binding site II on the HSA with the binding constant of the order of 103 and stabilizes the protein. The results are indicative of the potential use of levodopa as a therapeutic agent for the treatment of amyloid diseases.


Assuntos
Amiloide/química , Antiparkinsonianos/química , Levodopa/química , Albumina Sérica/química , Sítios de Ligação , Varredura Diferencial de Calorimetria , Humanos , Simulação de Acoplamento Molecular , Ligação Proteica , Estabilidade Proteica , Termodinâmica
18.
Int J Biol Macromol ; 93(Pt A): 1174-1182, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27693336

RESUMO

Quaternary amine of diethylaminoethyl rosin ester (QRMAE), chemically synthesized by rosin modified biocompatible cationic surfactant, has various biological applications in the field of pharmacy as well as used as food product additive. Here, we report biophysical insights in to the interaction mechanism of thymoquinone (TQ), copper nanoparticles (Cu-NPs) and QRMAE with bovine serum albumin (BSA) individually and also in complexes forms to determine their competitive binding affinity. We have also studied the aggregation-inhibition effects of Cu-NPs and TQ individually, as well as in complexes form in the presence of QRMAE surfactant which is responsible for induction of amorphous aggregates in BSA within hours of incubation at 65°C and physiological pH. The formation of aggregates was established by using various spectroscopic methods and dye binding assay. The circular dichroism (CD) spectroscopy showed that QRMAE significantly altered the secondary structure of BSA. However, the presence of TQ and Cu-NPs restricted the aggregation process which was observed to be more efficient when TQ and Cu-NPs were present together. This study provides very significant competitive binding results of QRMAE, Cu-NPs, TQ and protein aggregation behavior at higher temperature which was induced by rosin surfactant QRMAE, and protein aggregation process was inhibited by Cu-NPs, TQ individually and together. Therefore, our finding suggested that rosin surfactant QRMAE has high propensity to induce amorphous aggregation in BSA which was favored at elevated temperature and higher concentration of the protein. When BSA-QRMAE sample was incubated in the presence Cu-NPs under similar condition, the aggregation propensity reduced, and drastically inhibited by TQ and Cu-NPs together.


Assuntos
Benzoquinonas/química , Benzoquinonas/farmacologia , Fenômenos Biofísicos , Cobre/química , Nanopartículas Metálicas/química , Agregados Proteicos/efeitos dos fármacos , Animais , Ligação Competitiva , Bovinos , Concentração de Íons de Hidrogênio , Resinas Vegetais/química , Soroalbumina Bovina/química , Temperatura
19.
J Biomol Struct Dyn ; 34(7): 1545-60, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26309154

RESUMO

In the present work, we have examined the binding parameters, thermodynamics, and stability of human serum albumin (HSA) isoforms at pH 7.4 and 9.0, using spectroscopic, calorimetric, and molecular docking methods in the presence of water-soluble camptothecin analog irinotecan hydrochloride (CPT-11). We observed that CPT-11 binds to HSA through a static quenching procedure of ground-state complex formation with N-isoform and B-isoform. Hydrogen bond and hydrophobic interactions are the major governing forces that participating in the formation of protein-drug complex. To determine the binding site of CPT-11 within HSA molecules, we also have performed molecular docking experiments. We explored the CPT-11-mediated stability and modulation of HSA by performing dynamic light scattering (DLS) and differential scanning calorimetry (DSC) experiments. DLS and DSC techniques are used to determine the size and the melting point (Tm) of HSA, which was decreased in the presence of CPT-11. Therefore, CPT-11 plays an important role in HSA stability and protein-ligand interactions. The present study provides valuable information in the field of pharmacokinetics, pharmaco-dynamics, and drug discovery.


Assuntos
Camptotecina/análogos & derivados , Simulação de Acoplamento Molecular , Albumina Sérica/química , Termodinâmica , Camptotecina/química , Camptotecina/metabolismo , Humanos , Irinotecano , Cinética , Conformação Molecular , Simulação de Dinâmica Molecular , Estrutura Molecular , Ligação Proteica , Estabilidade Proteica , Albumina Sérica/metabolismo , Análise Espectral
20.
Int J Biol Macromol ; 78: 417-28, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25900857

RESUMO

Here we have used five non-fluorinated cosolvents (acetonitrile, ethanol, methanol, sec-butanol and ter-butanol) at increasing concentrations and analyzed their aggregation inducing behavior on interaction with conalbumin (CA). The aggregates were identified as amorphous by performing spectroscopic experiments like circular dichroism and dye binding assay. The amorphous aggregate contains rich ß-sheet content, show insignificant increment in Thioflavin-T (ThT) fluorescence intensity but strong 1-anilino-8-napthalene sulfonate (ANS) binding with enhanced fluorescence intensity. We also performed transmission electron microscope (TEM) and scanning electron microscope (SEM) imaging of the aggregates which made the result more informative. The morphology appeared on TEM imaging shows aggregates but there is no exhibition of fibril formation, as was observed in amyloid induced by 2,2,2-trifuoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-propan-2-ol (HFIP). SEM imaging also gives the similar results indicating the formation of amorphous aggregates. Web based tools (Waltz and AGGRESCAN) predicted aggregation prone regions in CA which are accountable for the aggregation.


Assuntos
Conalbumina/química , Metaloproteases/química , Solventes/química , Animais , Benzotiazóis , Cinética , Modelos Moleculares , Agregados Proteicos/efeitos dos fármacos , Ligação Proteica , Conformação Proteica , Solventes/farmacologia , Análise Espectral/métodos , Tiazóis/química
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