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1.
Proteomics ; 21(6): e2000237, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33463023

RESUMO

Royal Jelly (RJ) is a gelatinous white-yellowish fluid, possessing a sour taste and a slight phenolic smell that is secreted by the hypopharyngeal and mandibular salivary glands of the nurse honeybees, and is used in nutrition of larvae and adult queens. Similar to other substances associated with the activities of honeybees, RJ not only contains nutritive components, such as carbohydrates, proteins, peptides, lipids, vitamins, and mineral salts, but also represents a natural ingredient with cosmetic and health-promoting properties. RJ is characterized by remarkable multifunctionality, possessing numerous biological activities. Although this multifunctionality of RJ can be considered as a consequence of its complex nature, many proteins and peptides in RJ are polyfunctional entities themselves. In this article, we show that RJ proteins contain different levels of intrinsic disorder, have sites of post-translational modifications, can be found in multiple isoforms, and many of them possess disorder-based binding sites, suggesting that the conformational ensembles of the RJ proteins might undergo change as a result of their interaction with specific binding partners. All these observations suggest that the multifunctionality of proteins and peptides from RJ is determined by their structural heterogeneity and polymorphism, and serve as an illustration of the protein structure-function continuum concept.


Assuntos
Ácidos Graxos , Proteoma , Animais , Abelhas , Sítios de Ligação , Ácidos Graxos/química , Processamento de Proteína Pós-Traducional
2.
Cell Mol Life Sci ; 76(23): 4635-4662, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31342121

RESUMO

Citrullination is a post-translation modification of proteins, where the proteinaceous arginine residues are converted to non-coded citrulline residues. The immune tolerance to such citrullinated protein can be lost, leading to inflammatory and autoimmune diseases. Citrullination is a chemical reaction mediated by peptidylarginine deiminase enzymes (PADs), which are a family of calcium-dependent cysteine hydrolase enzymes that includes five isotypes: PAD1, PAD2, PAD3, PAD4, and PAD6. Each PAD has specific substrates and tissue distribution, where it modifies the arginine to produce a citrullinated protein with altered structure and function. All mammalian PADs have a sequence similarity of about 70-95%, whereas in humans, they are 50-55% homologous in their structure and amino acid sequences. Being calcium-dependent hydrolases, PADs are inactive under the physiological level of calcium, but could be activated due to distortions in calcium homeostasis, or when the cellular calcium levels are increased. In this article, we analyze some of the currently available data on the structural properties of human PADs, the mechanisms of their calcium-induced activation, and show that these proteins contain functionally important regions of intrinsic disorder. Citrullination represents an important trigger of multiple physiological and pathological processes, and as a result, PADs are recognized to play a number of important roles in autoimmune diseases, cancer, and neurodegeneration. Therefore, we also review the current state of the art in the development of PAD inhibitors with good potency and selectivity.


Assuntos
Autoimunidade , Desiminases de Arginina em Proteínas/metabolismo , Animais , Cálcio/química , Cálcio/metabolismo , Morte Celular , Citrulina/metabolismo , Inibidores Enzimáticos/química , Inibidores Enzimáticos/metabolismo , Humanos , Isoenzimas/antagonistas & inibidores , Isoenzimas/química , Isoenzimas/metabolismo , Desiminases de Arginina em Proteínas/antagonistas & inibidores , Desiminases de Arginina em Proteínas/genética , Espécies Reativas de Oxigênio/metabolismo
3.
J Mol Recognit ; 28(12): 699-709, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26086855

RESUMO

The biological cells and extracellular matrix exhibit a highly crowded environment, called as macromolecular crowding. Crowding significantly influences protein structure and may lead to its aggregation. In the present study, buffalo heart cystatin (BHC), after purification from buffalo heart tissue, has been used as a model protein for studying effect of macromolecular crowding in the presence of high concentrations of bovine serum albumin (BSA), poly-ethylene glycol-1000 (PEG-1000), and poly-ethylene glycol-4000 (PEG-4000). Cystatins are thiol protease inhibitors and found to be involved in various important physiological processes. Functional inactivation of BHC was observed upon crowding, which varied as a function of concentration and molecular weight of crowding agents as well as incubation time. Structural changes of BHC at tertiary and secondary level were detected with the help of fluorescence and CD spectroscopy. CD analysis showed changes of α-helix to ß-sheet, which could be due to aggregation. The ANS-fluorescence study suggested the unfolding and presence of some partially folded intermediates. Increase in ThT-fluorescence and absorption of Congo red spectra with red shift, confirmed the amyloid type aggregation of BHC in the presence of various crowding agents. Finally, electron microscopy provided the physical evidence about the formation of amyloid fibrils. Results suggested that among the various crowding agents used, amyloidogenesis of BHC was maximal in case of BSA followed by PEG-4000 and least for PEG-1000. The present work makes an important contribution in crowding mediated protein aggregation, which can have implications of potential interest.


Assuntos
Amiloide/metabolismo , Cistatinas/metabolismo , Miocárdio/metabolismo , Dobramento de Proteína , Animais , Búfalos/metabolismo , Dicroísmo Circular , Microscopia Eletrônica , Complexos Multiproteicos , Miocárdio/patologia , Polietilenoglicóis/metabolismo , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência
4.
Soft Matter ; 10(15): 2591-9, 2014 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-24647567

RESUMO

Different proteins have different amino acid sequences as well as conformations, and therefore different propensities to aggregate. Electrostatic interactions have an important role in the aggregation of proteins as revealed by our previous report (J. M. Khan et al., PLoS One, 2012, 7, e29694). In this study, we designed and executed experiments to gain knowledge of the role of charge variations on proteins during the events of protein aggregation with lysozyme as a model protein. To impart positive and negative charges to proteins, we incubated lysozyme at different pH values of below and above the pI (∼11). Negatively charged SDS was used to 'antagonize' positive charges on lysozyme. We examined the effects of pH variations on SDS-induced amyloid fibril formation by lysozyme using methods such as far-UV circular dichroism, Rayleigh scattering, turbidity measurements, dye binding assays and dynamic light scattering. We found that sub-micellar concentrations of SDS (0.1 to 0.6 mM) induced amyloid fibril formation by lysozyme in the pH range of 10.0-1.0 and maximum aggregation was observed at pH 1.0. The morphology of aggregates was fibrillar in structure, as visualized by transmission electron microscopy. Isothermal titration calorimetry studies demonstrated that fibril formation is exothermic. To the best of our current understanding of the mechanism of aggregation, this study demonstrates the crucial role of electrostatic interactions during amyloid fibril formation. The model proposed here will help in designing molecules that can prevent or reverse the amyloid fibril formation or the aggregation.


Assuntos
Muramidase/química , Dodecilsulfato de Sódio/química , Animais , Benzotiazóis , Galinhas , Vermelho Congo/química , Vermelho Congo/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Muramidase/metabolismo , Ligação Proteica , Estrutura Secundária de Proteína , Prótons , Dodecilsulfato de Sódio/metabolismo , Eletricidade Estática , Tiazóis/química , Tiazóis/metabolismo
5.
Phys Chem Chem Phys ; 16(11): 5150-61, 2014 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-24481490

RESUMO

Amyloid fibrils are associated with neurodegenerative disorders and are formed by a number of proteins. In this study, the amyloid-forming behavior of several different serum albumins was examined at pH 3.5 i.e., about two pH units below their isoelectric points (pI ∼ 5.5) to examine the roles played by negative charge and hydrophobicity of exogenously added surfactants such as SDS, SDBS and AOT. The propensities of SDS, SDBS and AOT to promote the formation of amyloid fibrils were investigated by using measurements of turbidity, Rayleigh scattering, ThT and CR dye binding, DLS as well as far-UV CD. At submicellar concentrations of SDS and SDBS (0.5-2.5 mM) amyloid fibrils were formed by all albumins studied whereas at higher concentrations amyloid fibril formation was completely inhibited. Interestingly AOT promoted amyloid fibril formation up to 11 mM without any inhibition. The interaction between the albumins and the surfactants was exothermic, as confirmed by isothermal titration calorimetry (ITC). From the turbidity, Rayleigh scattering and dynamic light scattering data, it was concluded that amyloid induction was promoted most by AOT followed by SDBS and SDS. Similar studies were performed at pH 7.4 i.e., about two units of pH above the albumins pI, and no amyloid fibrils were formed. From these studies we conclude that negatively charged surfactants induce amyloid fibril formation in serum albumins with the help of electrostatic and hydrophobic interactions. Besides the study performed at pH 7.4 indicates that hydrophobic interactions alone can not induce aggregation in serum albumins.


Assuntos
Albumina Sérica/química , Animais , Calorimetria , Dicroísmo Circular , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Cinética , Mamíferos , Microscopia Eletrônica de Transmissão , Nefelometria e Turbidimetria , Espalhamento de Radiação , Espectrofotometria Ultravioleta
6.
Int J Biol Macromol ; 233: 123623, 2023 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-36773857

RESUMO

Numerous pathophysiological conditions known as amyloidosis, have been connected to protein misfolding leading to aggregation of proteins. Inhibition of cytotoxic aggregates or disaggregation of the preformed fibrils is thus one of the important strategies in the prevention of such diseases. Growing interest and exploration of identification of small molecules mainly natural compounds can prevent or delay amyloid fibril formation. We examined the mechanism of interaction and inhibition of human lysozyme (HL) aggregates with luteolin (LT). Biophysical and computational approaches have been employed to study the effect of LT on HL amyloid aggregation. Transmission Electronic Microscopy, Thioflavin T fluorescence, UV-vis spectroscopy, and RLS demonstrates that LT inhibit HL fibril formation. ANS fluorescence and hemolytic assay was also employed to examine the effect of the LT on toxicity of HL aggregation. Docking and molecular dynamics results showed that LT interacted with HL via hydrophobic and hydrogen interactions, thus reducing fibrillation levels. These findings highlight the benefit of polyphenols as safe therapy for preventing amyloid related diseases.


Assuntos
Amiloidose , Luteolina , Humanos , Luteolina/farmacologia , Muramidase/química , Amiloide/química , Proteínas Amiloidogênicas
7.
Int J Biol Macromol ; 237: 124219, 2023 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-36990415

RESUMO

Protein misfolding and related formation of amyloid fibrils are associated with several conformational diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), prion diseases, and Diabetes mellitus, Type 2 (DM-II). Several molecules including antibiotics, polyphenols, flavonoids, anthraquinones, and other small molecules are implicated to modulate amyloid assembly. The stabilization of the native forms of the polypeptides and prevention of their misfolding and aggregation are of clinical and biotechnological importance. Among the natural flavonoids, luteolin is of great importance because of its therapeutic role against neuroinflammation. Herein, we have explored the inhibitory effect of luteolin (LUT) on aggregation of a model protein, human insulin (HI). To understand the molecular mechanism of the inhibition of aggregation of HI by LUT, we employed molecular simulation, UV-Vis, fluorescence, and circular dichroism (CD) spectroscopies along with the dynamic light scattering (DLS). The analysis of the tuning of the HI aggregation process by luteolin revealed that interaction of HI with LUT resulted in the decrease in binding of the various fluorescent dyes, such as thioflavin T (ThT) and 8-anilinonaphthalene-1-sulfonic acid (ANS) to this protein. Retention of the native-like CD spectra and resistance to the aggregation in the presence of LUT has confirmed the aggregation inhibitory potential of LUT. The maximum inhibitory effect was found at the protein-to-drug ratio of 1:12, and no significant change was observed beyond this concentration.


Assuntos
Proteínas Amiloidogênicas , Luteolina , Humanos , Amiloide/química , Insulina/química , Peptídeos
8.
Int J Biol Macromol ; 253(Pt 3): 126823, 2023 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-37703975

RESUMO

The increasing frequency of Dengue is a cause of severe epidemics and therefore demands strategies for effective prevention, diagnosis, and treatment. DENV-protease is being investigated as a potential therapeutic target. However, due to the flat and highly charged active site of the DENV-protease, designing orthosteric medicines is very difficult. In this study, we have done a thorough analysis of pH-dependent conformational changes in recombinantly expressed DENV protease using various spectroscopic techniques. Our spectroscopic study of DENV protease (NS2B-NS3pro) at different pH conditions gives important insights into the dynamicity of structural conformation. At physiological pH, the DENV-protease exists in a random-coiled state. Lowering the pH promotes the formation of alpha-helical and beta-sheet structures i.e. gain of secondary structure as shown by Far-UV CD. The light scattering and Thioflavin T (ThT)-binding assay proved the aggregation-prone tendency of DENV-protease at pH 4.0. Further, the confocal microscopy image intensity showed the amorphous aggregate formation of DENV protease at pH 4.0. Thus, the DENV protease acquires different conformations with changes in pH conditions. Together, these results have the potential to facilitate the design of a conformation destabilizer-based therapeutic strategy for dengue fever.


Assuntos
Vírus da Dengue , Serina Endopeptidases , Serina Endopeptidases/química , Proteínas não Estruturais Virais/química , Domínio Catalítico , Concentração de Íons de Hidrogênio , Inibidores de Proteases/farmacologia
9.
Colloids Surf B Biointerfaces ; 216: 112563, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35588684

RESUMO

Protein aggregation leads to several human pathologies such as Alzheimer's disease (AD), type 2 diabetes (T2D), Parkinson's disease (PD), etc. Due to the overlap in the mechanisms of type 2 diabetes and brain disorders, common effective pharmacological interventions to treat both T2D and AD is under extensive research. Therefore, major aim of research is to repurpose already established treatment of diabetes to cure AD as well. This study evaluates mechanistic insight into anti-amyloidogenic potential of anti-diabetic drug Vildagliptin (VLD) on human serum albumin fibrillation (HSA) by using biophysical, calorimetric, imaging techniques along with hemolytic assay. Dynamic light scattering (DLS) and Rayleigh light scattering (RLS) results showed presence of few small-sized aggregates in the presence of VLD which are formed by deaccelerating the amyloidogenesis as shown by thioflavin T (ThT) fluorescence and Congo red (CR) binding assay. Further, Isothermal titration calorimetry (ITC), steady state fluorescence quenching, molecular docking results revealed that VLD form complex with amyloid facilitating state of HSA and consequently mask the hydrophobic residues involved in amyloidogenesis as evident from decrease in ANS fluorescence. Differential scanning calorimetry (DSC) results confirm that VLD stabilizes the amyloid facilitating state of HSA. In addition, SEM images demonstrated that VLD alleviates the hemolytic effect induced by fibrils of HSA. This study reports VLD as a potential inhibitor of amyloid fibrillation and provides promising results to repurpose VLD as a drug candidate for the cure of Alzheimer's diseases along with diabetes.


Assuntos
Amiloidose , Diabetes Mellitus Tipo 2 , Amiloide/química , Proteínas Amiloidogênicas , Diabetes Mellitus Tipo 2/tratamento farmacológico , Humanos , Simulação de Acoplamento Molecular , Albumina Sérica Humana , Vildagliptina/farmacologia
10.
Int J Biol Macromol ; 150: 1258-1271, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31743708

RESUMO

Protein misfolding and deposition of aggregated proteins inside as well as outside of the cells have been associated with several neurotoxic and neurodegenerative disorders like Alzheimer's, Parkinson's and familial amyloid polyneuropathy etc. that could be controlled by anti-aggregation methodologies employing either inhibition or disaggregation of toxic aggregates. Also, the Alzheimer's disease develops in later life is somehow related to the high mid-life blood pressure. Therefore the present work targets the amyloid inhibiting potential of diuretics (a class of antihypertensive drugs) - Indapamide (INDP) and Hydrochlorothiazide (HCTZ) against human serum albumin (HSA) and human lysozyme (HL) fibrillogenesis. The effect of both INDP and HCTZ on the kinetics of amyloid formation of HSA and HL was illustrated and various biophysical techniques like Thioflavin T (ThT) and 8-Anilinonaphthalene-1-sulfonic acid (ANS) fluorescence measurement, Congo red measurements and circular dichroism (CD) measurements depicted the inhibitory action of both INDP and HCTZ in a dose dependent manner. Transmission Electronic Microscopy (TEM) confirmed the absence of fibrillar structures when HSA and HL were co-incubated with INDP and HCTZ. In addition, molecular docking results revealed that both the drugs interacts with HSA and HL through hydrophobic interactions as well as hydrogen bonding, and also showed non-hemolytic activity on human RBCs demonstrated by the Hemolytic assay. Thus, both INDP and HCTZ could be propitious as a therapeutic agent and aid in the cure of amyloid related diseases.


Assuntos
Amiloide , Citoproteção , Diuréticos , Simulação de Acoplamento Molecular , Agregação Patológica de Proteínas/metabolismo , Amiloide/química , Amiloide/metabolismo , Diuréticos/química , Diuréticos/farmacologia , Humanos , Muramidase/química , Muramidase/metabolismo , Albumina Sérica Humana/química , Albumina Sérica Humana/metabolismo
11.
Front Chem ; 6: 311, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30123793

RESUMO

Inhibition of fibrillation process and disaggregation of mature fibrils using small peptide are the promising remedial strategies to combat neurodegenerative diseases. However, designing peptide-based drugs to target ß-sheet-rich amyloid has been a major challenge. The current work describes, for the first time, the amyloid inhibitory potential of the two short peptides (selected on the basis of predisposition of their amino acid residues toward ß-sheet formation) using combination of biophysical, imaging methods, and docking approaches. Results showed that peptides employed different mechanisms to inhibit the amyloid fibrillation. Furthermore, they were also effective in blocking the amyloid fibrillation pathway. In contrary to the insulin fibrillar mesh, significantly less fibrillar species appeared in the presence of peptides, as confirmed by transmission electron microscopy. Circular dichroism analysis indicated that although peptides did not stabilize the native state of insulin, they inhibited amyloid aggregation by reducing the formation of ß-sheet rich structures. Hemolytic assay revealed the non-hemolytic nature of the species formed when insulin was co-incubated with the peptides. Therefore, despite the inherent potential to form ß-sheet structure, these peptides inhibited the amyloid formation and potentially can be used as therapeutics for the treatment of amyloid-related diseases.

12.
Int J Biol Macromol ; 104(Pt A): 1267-1279, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28684356

RESUMO

Non-immune carbohydrate binding proteins are broadly defined as lectins. Having been reported from all kingdoms of life, phytolectins are the most widely studied group of lectins. Sauromatum guttatum agglutinin (SGA) was isolated from the plant tubers and characterized for structural variations due to solvent perturbation using polarimetry, fluorescence and light scattering. For the ß-sheet rich SGA, a pH and temperature induced molten globule like intermediate was identified. In isothermal titration microcalorimetry, SGA demonstrated cooperative binding to a complex glycoprotein in enthalpically driven mechanism. Fine sugar specificity exploration identified core pentasaccharide as the most common and highest binding motif with complex N-glycans and fucosylated core N-glycans as additional motifs. Molecular cloning of SGA which has previously been demonstrated to have anti-cancer and anti-insect activities is being reported for the first time. Full length cDNA sequence was obtained with RACE-PCR based upon the conserved carbohydrate recognition site [QXDXNXVXY] present in all GNA-related lectins. Quaternary structure was proposed by homology modeling and an attempt was made to explain the structure-function relationship by in silico analysis.


Assuntos
Araceae/química , Metabolismo dos Carboidratos , Simulação por Computador , Lectinas de Plantas/química , Lectinas de Plantas/metabolismo , Sequência de Carboidratos , Clonagem Molecular , Concentração de Íons de Hidrogênio , Filogenia , Lectinas de Plantas/genética , Polissacarídeos/química , Polissacarídeos/metabolismo , Análise Espectral , Temperatura
13.
Curr Protein Pept Sci ; 7(2): 165-70, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16611141

RESUMO

The application of recombinant immunotoxin and radioimmunoconjugate in Cancer therapy has revived the "magic bullet" concept predicted a century ago. Many of the recombinant antibodies have received FDA approval for various indication of cancer in recent years and numerous others are in clinical trials.


Assuntos
Anticorpos Monoclonais , Neoplasias , Proteínas Recombinantes , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/uso terapêutico , Ensaios Clínicos como Assunto , Humanos , Imunotoxinas/uso terapêutico , Neoplasias/imunologia , Neoplasias/terapia , Radioimunoterapia , Proteínas Recombinantes/imunologia , Proteínas Recombinantes/uso terapêutico
14.
Indian J Clin Biochem ; 21(2): 149-52, 2006 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23105633

RESUMO

Mercury pollution and acute neurotoxicity of mercury is well known. The recent reports suggest the adverse effect of low dose mercury, though the available literature is still silent on its mechanism. This study was therefore undertaken to probe the effect of low dose methyl mercury induced heavy metal toxicity on free radical stress and its impact on behaviour of male albino rats. Male albino rats were exposed to 1 mg/kg body wt of methylmercury chloride for seven days, on day 8 they were tested for motor and memory functions. They were sacrificed later for biochemical estimations for rate of lipid peroxidation, nucleic acids, proteins in cerebrum, cerebellum and brain stem. There was an increase in the rate of lipid peroxidation showing methyl mercury induced free radical stress. The motor and memory functions demonstrated a clear decline, besides there was a lowering in the levels of nucleic acids and proteins as compared to controls. The results are important in view of recent reports that methyl mercury induced free radical stress results in early ageing and may serve as an initiating factor more specifically for neurodegenerative disorders like Alzeihemer's disease and dementias. The current findings support the notion that incorporating dietary antioxidants like curcumin, ascorbic acid and α-tocopherol in routine diet from early age may help combat the risk of developing such disorders in ensuing years.

15.
Protein Pept Lett ; 23(2): 107-19, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26556631

RESUMO

Solvent perturbation was used to study variations in structure of Arisaema helliborifolium lectin (AHL) with the help of circular dichroism (CD), intrinsic fluorescence (IF), extrinsic fluorescence, quenching and dynamic light scattering (DLS). AHL was studied under acidic, alkaline and 6 M guanidine hydrochloride (GuHCl) equilibrium states. Three structural states were identified for AHL at different conditions, that are native (N; pH 7.0), molten globule (MG; pH 2.0) and unfolded (U; pH 12.0). CD analysis revealed that 50% of secondary structure of AHL was ß-sheet component. A complete loss of secondary structure was observed at GuHCl treatment. The tertiary structural changes as studied by changes in microenvironment of trp residues also suggested a pH induced MG state as in case of CD. Parameter-A analysis pointed at the multi-step unfolding process of lectin under varying pH (pH 1-13). A comparision of CD and IF data further indicated that different pathways were followed for secondary and tertiary structure unfolding. Tryptophans of native AHL were only partially exposed to solvent belonging to Class II. Hydrodynamic diameter (Dh ) measurements of AHL via DLS also confirmed of a pH induced molten globule. A thermally induced molten globule was identified for AHL between 54-60 °C as monitored by DLS. An irreversible thermal denaturation was observed with the formation of a large aggregate. The Dh of AHL at neutral pH was confirmed by transmission electron microscopy (TEM).


Assuntos
Arisaema/química , Lectinas/química , Estrutura Secundária de Proteína , Termodinâmica , Dicroísmo Circular , Difusão Dinâmica da Luz , Fluorescência , Concentração de Íons de Hidrogênio , Desnaturação Proteica , Dobramento de Proteína , Triptofano/química
16.
Int J Biol Macromol ; 83: 315-25, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26616452

RESUMO

Electrostatic and hydrophobic interactions have an important role in the protein aggregation. In this study, we have investigated the effect of charge and hydrophobicity of oppositely charged surfactants i.e., anionic (AOT and SDS) and cationic (CTAB and DTAB) on hen egg white lysozyme at pH 9.0 and 13.0, respectively. We have employed various methods such as turbidity measurements, Rayleigh light scattering, ThT, Congo red and ANS dye binding assays, far-UV CD, atomic force microscopy, transmission electron and fluorescence microscopy. At lower molar ratio, both anionic and cationic surfactants promote amyloid fibril formation in lysozyme at pH 9.0 and 13.0, respectively. The aggregation was proportionally increased with respect to protein concentration and hydrophobicity of surfactant. The morphology of aggregates at both the pH was fibrillar in structure, as visualized by dye binding and microscopic imaging techniques. Initially, the interaction between surfactants and lysozyme was electrostatic and then hydrophobic as investigated by ITC. This study demonstrates the crucial role of charge and hydrophobicity during amyloid fibril formation.


Assuntos
Amiloide/química , Muramidase/química , Agregados Proteicos/efeitos dos fármacos , Tensoativos/farmacologia , Animais , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Tensoativos/química
17.
Protein Pept Lett ; 23(10): 884-891, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27586184

RESUMO

Acetonitrile is a mild solvent, which induces ß-sheet conformation in proteins. The global conformational changes in Hb in the presence of ACN were studied using intrinsic fluorescence experiments, acrylamide quenching, ANS fluorescence measurements, soret absorbance spectroscopy, fourier transform infrared spectroscopy, circular dichroism, thioflavin T and congo red assay. Molecular docking showed the binding of hydrophobic residues of Hb to ACN. Hb exists as a partially unfolded intermediate state at 30% v/v ACN. Hb aggregates were obtained at 60% v/v ACN concentration, which were further confirmed by transmission electron microscopy.


Assuntos
Hemoglobinas/química , Animais , Bovinos , Dicroísmo Circular , Técnicas In Vitro , Microscopia Eletrônica de Transmissão , Simulação de Acoplamento Molecular , Dobramento de Proteína , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier
18.
Spectrochim Acta A Mol Biomol Spectrosc ; 168: 123-131, 2016 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-27288964

RESUMO

The synthesis of inner transition metal nanoparticles via an ecofriendly route is quite difficult. This study, for the first time, reports synthesis of terbium oxide nanoparticles using fungus, Fusarium oxysporum. The biocompatible terbium oxide nanoparticles (Tb2O3 NPs) were synthesized by incubating Tb4O7 with the biomass of fungus F. oxysporum. Multiple physical characterization techniques, such as UV-visible and photoluminescence spectroscopy, TEM, SAED, and zeta-potential were used to confirm the synthesis, purity, optical and surface characteristics, crystallinity, size, shape, distribution, and stability of the nanoemulsion of Tb2O3 NPs. The Tb2O3 NPs were found to inhibit the propagation of MG-63 and Saos-2 cell-lines (IC50 value of 0.102µg/mL) and remained non-toxic up to a concentration of 0.373µg/mL toward primary osteoblasts. Cell viability decreased in a concentration-dependent manner upon exposure to 10nm Tb2O3 NPs in the concentration range 0.023-0.373µg/mL. Cell toxicity was evaluated by observing changes in cell morphology, cell viability, oxidative stress parameters, and FACS analysis. Morphological examinations of cells revealed cell shrinkage, nuclear condensation, and formation of apoptotic bodies. The level of ROS within the cells-an indicator of oxidative stress was significantly increased. The induction of apoptosis at concentrations ≤IC50 was corroborated by 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) staining (DNA damage and nuclear fragmentation). Flow-cytometric studies indicated that the response was dose dependent with a threshold effect.


Assuntos
Neoplasias Ósseas/tratamento farmacológico , Nanopartículas , Osteossarcoma/tratamento farmacológico , Óxidos/farmacologia , Térbio/farmacologia , Neoplasias Ósseas/metabolismo , Neoplasias Ósseas/patologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Fusarium/química , Humanos , Nanopartículas/química , Nanopartículas/ultraestrutura , Nanotecnologia , Osteossarcoma/metabolismo , Osteossarcoma/patologia , Estresse Oxidativo/efeitos dos fármacos , Óxidos/química , Espécies Reativas de Oxigênio/metabolismo , Térbio/química
19.
Biochim Biophys Acta ; 1646(1-2): 131-5, 2003 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-12637019

RESUMO

Antienzyme polyclonal antibodies against stem bromelain were raised in male albino rabbits and the Fab' monomers isolated from the IgG of the immune sera. Incubation of bromelain with the Fab' resulted in binding and gel filtration of the resulting complex suggested a 1:1 stoichiometry. Complexing with the Fab' resulted in significant stabilization of bromelain against thermal inactivation and alkaline pH.


Assuntos
Bromelaínas/imunologia , Fragmentos Fab das Imunoglobulinas/imunologia , Animais , Complexo Antígeno-Anticorpo/química , Bromelaínas/administração & dosagem , Estabilidade Enzimática/imunologia , Temperatura Alta , Concentração de Íons de Hidrogênio , Fragmentos Fab das Imunoglobulinas/isolamento & purificação , Masculino , Coelhos
20.
Environ Toxicol Pharmacol ; 20(2): 351-60, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21783611

RESUMO

Post Minamata incident there has been awareness about mercury toxicity even among the general public. Previous researches contributed a vast amount of data regarding acute mercury exposure, but gradually information about the low dose [Ninomiya, T., Ohmori, H., Hashimoto, K., Tsuruta, K., Ekino, S., 1995. Expansion of methylmercury poisoning outside minamata: an epidemiological study on chronic methylmercury poisoninig outside of Minamata. Environ. Res. 70 (1) 47-50; Lebel, J., Mergler, D., Lucotte, M., Amorim, M., Dolbec, J., Miranda, D., Arantes, G., Rheault, I., Pichet, P., 1996. Evidence of early nervous system dysfunction in Amazonian populations exposed to low-levels of methylmercury. Neurotoxicology 17 (1) 157-167] of mercury toxicity has been trickling in. With mercury contaminating rain-, ground- and sea-water no one is safe. Polluted water leads to mercury laced fish, meat and vegetable. In aquatic environments, inorganic mercury is microbiologically transformed into lipophilic organic compound 'methylmercury'. This transformation makes mercury more prone to biomagnification in food chains. Consequently, populations with traditionally high dietary intake of food originating from fresh or marine environment have highest dietary exposure to mercury. Extensive research done on locals across the globe have already established this, persons who routinely consume fish or a particular species of fish are at an increased risk of methylmercury poisoning. The easy access of the toxicant to man through multiple pathways air, water, food, cosmetic products and even vaccines increase the exposure. Foetus and children are more susceptible towards mercury toxicity. Mothers consuming diet containing mercury pass the toxicant to foetus and to infants through breast milk. Decreased performance in areas of motor function and memory has been reported among children exposed to presumably safe mercury levels. Similarly, disruption of attention, fine motor function and verbal memory was also found in adults on exposure to low mercury levels. It is an occupational hazard for dental staff, chloralkali factory workers and goldminers, etc. Mercury has been found to be a causative agent of various sorts of disorders, including neurological, nephrological, immunological, cardiac, motor, reproductive and even genetic. Recently heavy metal mediated toxicity has been linked to diseases like Alzeihemer's, Parkinson's, Autism, Lupus, Amyotrophic lateral sclerosis, etc. Besides this, it poses danger to wildlife. Therefore, it becomes imperative to spread the information regarding the threat of mercury exposure amongst the scientists and masses.

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