Displaying publications 1 - 20 of 59 in total

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  1. Contribution of process-induced molten-globule state formation in duck liver protein to the enhanced binding ability of (E,E)-2,4-heptadienal
    Han C, Zheng Y, Wang L, Zhou C, Wang J, He J, et al.
    J Sci Food Agric, 2023 May;103(7):3334-3345.
    PMID: 36786016 DOI: 10.1002/jsfa.12499
    BACKGROUND: Extracted proteins of alternative animal origin tend to present strong off-flavor perception due to physicochemical interactions of coextracted off-flavor compounds with proteins. To investigate the relationship between absorption behaviors of volatile aromas and the processes-induced variations in protein microstructures and molecular conformations, duck liver protein isolate (DLp) was subjected to heating (65/100 °C, 15 min) and ultra-high pressure (UHP, 100-500 MPa/10 min, 28 °C) treatments to obtain differential unfolded protein states.

    RESULTS: Heat and UHP treatments induced the unfolding of DLp to varied degrees, as revealed by fluorescence spectroscopy, ultraviolet-visible absorption, circular dichroism spectra and surface hydrophobicity measurements. Two types of heating-denatured states with varied unfolding degrees were obtained, while UHP at both levels of 100/500 MPa caused partial unfolding of DLp and the presence of a molten-globule state, which significantly enhanced the binding affinity between DLp and (E,E)-2,4-heptadienal. In particular, significantly modified secondary structures of DLp were observed in heating-denatured samples. Excessive denaturing and unfolding degrees resulted in no significant changes in the absorption behavior of the volatile ligand, as characterized by observations of fluorescence quenching and analysis of headspace concentrations.

    CONCLUSION: Defining process-induced conformational transition behavior of matrix proteins could be a promising strategy to regulate food flavor attributes and, particularly, to produce DLp coextracted with limited off-flavor components by modifying their interaction during extraction processes. © 2023 Society of Chemical Industry.

    Matched MeSH terms: Circular Dichroism
  2. Asperginols A and B, Diterpene Pyrones, from an Aspergillus sp. and the Structure Revision of Previously Reported Analogues
    Al-Khdhairawi AAQ, Low YY, Manshoor N, Arya A, Jelecki M, Alshawsh MA, et al.
    J Nat Prod, 2020 12 24;83(12):3564-3570.
    PMID: 33305943 DOI: 10.1021/acs.jnatprod.0c00618
    Two new diterpene pyrones, asperginols A (1) and B (2), and four known analogues (3-6) were isolated from the endophytic fungus Aspergillus sp. HAB10R12. The structures and absolute configurations of these compounds were elucidated based on the analysis of their NMR, MS, and X-ray diffraction data. The revision of the absolute configurations at C-10, C-11, and C-14 of the known diterpene pyrones (3-6) and the determination of the configuration at the polyene side chain for compounds (4-6) were made using chemical methods and vibrational circular dichroism analysis. This group of diterpene pyrone compounds showed unique structural features including a 7/6/6 tricyclic diterpene moiety with an unusual trans-syn-trans stereochemical arrangement. Compound 6 showed moderate activity against the HT-29 colon cancer cell line.
    Matched MeSH terms: Circular Dichroism
  3. Structures and Antimutagenic Effects of Onoceranoid-Type Triterpenoids from the Leaves of Lansium domesticum
    Matsumoto T, Kitagawa T, Teo S, Anai Y, Ikeda R, Imahori D, et al.
    J Nat Prod, 2018 10 26;81(10):2187-2194.
    PMID: 30335380 DOI: 10.1021/acs.jnatprod.8b00341
    A methanol extract of the dried leaves of Lansium domesticum showed antimutagenic effects against 3-amino-1,4-dimethyl-5 H-pyrido[4,3- b]indole (Trp-P-1) and 2-amino-1-methyl-6-phenylimidazo[4,5- bI]pyridine (PhIP) using the Ames assay. Nine new onoceranoid-type triterpenoids, lansium acids I-IX (1-9), and nine known compounds (10-16) were isolated from the extract. The structures of the new compounds were elucidated on the basis of chemical and spectroscopic evidence. The absolute stereostructures of the new compounds were determined via their electronic circular dichroism spectra. Several isolated onoceranoid-type triterpeneoids showed antimutagenic effects in an in vitro Ames assay. Moreover, oral intake of a major constituent, lansionic acid (10), showed antimutagenic effects against PhIP in an in vivo micronucleus test.
    Matched MeSH terms: Circular Dichroism
  4. Characterization of Climbazole-Bovine serum albumin interaction by experimental and in silico approaches
    Zahirul Kabir M, Tayyab H, Erkmen C, Kurbanoglu S, Mohamad SB, Uslu B
    Spectrochim Acta A Mol Biomol Spectrosc, 2023 Mar 05;288:122197.
    PMID: 36470090 DOI: 10.1016/j.saa.2022.122197
    Interactive association of an antifungal drug, climbazole (CBZ) with the carrier protein in bovine circulation, bovine serum albumin (BSA) was explored by fluorescence and absorption spectroscopy along with in silico techniques. The fluorescence and absorption spectral alterations of the protein upon addition of CBZ affirmed the complex foration between CBZ and BSA. The inverse temperature dependence behaviour of the KSV values as well as the hyperchromic result of the protein's absorption signals characterized CBZ-triggered quenching of BSA fluorescence as the static quenching. A weak binding affinity (Ka = 3.12-1.90-× 103 M-1) was reported towards the CBZ-BSA association process. Interpretation of thermodynamic data (entropy change = +14.68 J mol-1 K-1 and enthalpy change = -15.07 kJ mol-1) and in silico analyses anticipated that hydrophobic forces, van der Waals forces and hydrogen bonds were the key intermolecular forces in the complex stabilization. Inclusion of CBZ to BSA produced microenvironmental perturbations around Tyr and Trp residues, and also significantly defended temperature-induced destabilization of BSA. The binding locus of CBZ was detected in the proximity of Sudlow's sites I (subdomain IIA) and II (subdomain IIIA) of BSA, exhibiting greater preference towards site II, as revealed by competitive site-marker displacement investigations and in silico analysis. The stability of the CBZ-BSA complex was further validated by the molecular dynamics simulation assessments.
    Matched MeSH terms: Circular Dichroism
  5. In vitro interactions of two pesticides, propazine and quinoxyfen with bovine serum albumin: Spectrofluorometric and molecular docking investigations
    Duman B, Erkmen C, Zahirul Kabir M, Ching Yi L, Mohamad SB, Uslu B
    Spectrochim Acta A Mol Biomol Spectrosc, 2023 Nov 05;300:122907.
    PMID: 37257323 DOI: 10.1016/j.saa.2023.122907
    Binding mechanisms of two selected pesticides, propazine (PRO) and quinoxyfen (QUI) with bovine serum albumin (BSA) was examined using fluorescence, absorption and molecular docking methods. Intrinsic fluorescence of BSA was quenched in the presence of both PRO and QUI. The quenching was ascertained to be conversely linked to temperature, which suggested the contribution of static quenching process in the PRO-BSA and QUI-BSA complex formations. This results were validated by the enhancement in absorption spectrum of BSA upon binding with PRO and QUI. Binding constant values (Kf = 9.55-0.60 × 10-3 M-1 for PRO-BSA system; Kf = 7.08-5.01 × 102 M-1 for QUI-BSA system) and number of binding site (n) values for the PRO-BSA and QUI-BSA systems at different temperatures affirmed a weak binding strength with a set of equivalent binding sites on BSA. Thermodynamic data obtained for both the PRO-BSA and QUI-BSA interactions predicted that the association process was spontaneous and non-covalent contacts such as hydrophobic interactions, van der Waals forces and hydrogen bonds participated in the binding reactions. This result was further supported by the molecular docking assessments. Three-dimensional spectral results revealed the microenvironmental alterations near tryptophan (Trp) and tyrosine (Tyr) residues in BSA by the addition of PRO and QUI. The docking analysis demonstrated the binding pattern for the PRO-BSA and QUI-BSA systems and disclosed the preferred binding site of both PRO and QUI as site I (subdomain IIA) of BSA.
    Matched MeSH terms: Circular Dichroism
  6. Self-adjuvanting vaccine against group A streptococcus: application of fibrillized peptide and immunostimulatory lipid as adjuvant
    Azmi F, Ahmad Fuaad AA, Giddam AK, Batzloff MR, Good MF, Skwarczynski M, et al.
    Bioorg Med Chem, 2014 Nov 15;22(22):6401-8.
    PMID: 25438764 DOI: 10.1016/j.bmc.2014.09.042
    Peptides are of great interest to be used as vaccine antigens due to their safety, ease of manufacturing and specificity in generating immune response. There have been massive discoveries of peptide antigens over the past decade. However, peptides alone are poorly immunogenic, which demand co-administration with strong adjuvant to enhance their immunogenicity. Recently, fibril-forming peptides such as Q11 and lipoamino acid-based carrier have been identified to induce substantial immune responses when covalently linked to peptide epitope. In this study, we have incorporated either Q11 or lipoamino acids to a peptide epitope (J14) derived from M protein of group A streptococcus to develop self-adjuvanting vaccines. J14, Q11 and lipoamino acids were also conjugated together in a single vaccine construct in an attempt to evaluate the synergy effect of combining multiple adjuvants. Physicochemical characterization demonstrated that the vaccine constructs folded differently and self-assembled into nanoparticles. Significantly, only vaccine constructs containing double copies of lipoamino acids (regardless in conjugation with Q11 or not) were capable to induce significant dendritic cells uptake and subsequent J14-specific antibody responses in non-sizes dependent manners. Q11 had minimal impact in enhancing the immunogenicity of J14 even when it was used in combination with lipoamino acids. These findings highlight the impact of lipoamino acids moiety as a promising immunostimulant carrier and its number of attachment to peptide epitope was found to have a profound effect on the vaccine immunogenicity.
    Matched MeSH terms: Circular Dichroism
  7. Targeting chemical and thermal stability of ovalbumin by simulated honey sugar cocktail
    Wong YH, Kadir HA, Tayyab S
    Int J Biol Macromol, 2015 Feb;73:207-14.
    PMID: 25434804 DOI: 10.1016/j.ijbiomac.2014.11.015
    Effect of simulated honey sugar cocktail (SHSC) on chemical and thermal stability of ovalbumin (OVA) was investigated using multiple-spectroscopic techniques. Urea-induced denaturation of OVA produced a transition, characterized by the start-, the mid- and the end-points at 3.2 M, 5.9/5.6 M and 8.5/8.0 M urea, respectively, when studied by MRE222nm and tryptophan fluorescence measurements. Presence of 10% or 20% (w/v) SHSC in the incubation mixture shifted the transition curve towards higher urea concentration in a concentration dependent manner. A comparison of far- and near-UV CD, UV-difference, ANS fluorescence and 3-D fluorescence spectral results of native OVA and 5.9 M urea-denatured OVA (U-OVA), obtained in the absence and the presence of 20% (w/v) SHSC suggested SHSC-induced stabilization of U-OVA. Furthermore, a significant shift towards higher denaturant concentration was also noticed in the GdnHCl and thermal transition curves of OVA in the presence of 20% (w/v) SHSC. Taken together, all these results suggested stabilization of OVA against chemical and thermal denaturations by SHSC.
    Matched MeSH terms: Circular Dichroism
  8. Fulltext Stabilizing effect of various polyols on the native and the denatured states of glucoamylase
    Zaroog MS, Abdul Kadir H, Tayyab S
    ScientificWorldJournal, 2013;2013:570859.
    PMID: 24163624 DOI: 10.1155/2013/570859
    Different spectral probes were employed to study the stabilizing effect of various polyols, such as, ethylene glycol (EG), glycerol (GLY), glucose (GLC) and trehalose (TRE) on the native (N), the acid-denatured (AD) and the thermal-denatured (TD) states of Aspergillus niger glucoamylase (GA). Polyols induced both secondary and tertiary structural changes in the AD state of enzyme as reflected from altered circular dichroism (CD), tryptophan (Trp), and 1-anilinonaphthalene-8-sulfonic acid (ANS) fluorescence characteristics. Thermodynamic analysis of the thermal denaturation curve of native GA suggested significant increase in enzyme stability in the presence of GLC, TRE, and GLY (in decreasing order) while EG destabilized it. Furthermore, CD and fluorescence characteristics of the TD state at 71°C in the presence of polyols showed greater effectiveness of both GLC and TRE in inducing native-like secondary and tertiary structures compared to GLY and EG.
    Matched MeSH terms: Circular Dichroism
  9. Multispectroscopic and molecular modeling approach to investigate the interaction of flavokawain B with human serum albumin
    Feroz SR, Mohamad SB, Bujang N, Malek SN, Tayyab S
    J Agric Food Chem, 2012 Jun 13;60(23):5899-908.
    PMID: 22624666 DOI: 10.1021/jf301139h
    Interaction of flavokawain B (FB), a multitherapeutic flavonoid from Alpinia mutica with the major transport protein, human serum albumin (HSA), was investigated using different spectroscopic probes, i.e., intrinsic, synchronous, and three-dimensional (3-D) fluorescence, circular dichroism (CD), and molecular modeling studies. Values of binding parameters for FB-HSA interaction in terms of binding constant and stoichiometry of binding were determined from the fluorescence quench titration and were found to be 6.88 × 10(4) M(-1) and 1.0 mol of FB bound per mole of protein, respectively, at 25 °C. Thermodynamic analysis of the binding data obtained at different temperatures showed that the binding process was primarily mediated by hydrophobic interactions and hydrogen bonding, as the values of the enthalpy change (ΔH) and the entropy change (ΔS) were found to be -6.87 kJ mol(-1) and 69.50 J mol(-1) K(-1), respectively. FB binding to HSA led to both secondary and tertiary structural alterations in the protein as revealed by intrinsic, synchronous, and 3-D fluorescence results. Increased thermal stability of HSA in the presence of FB was also evident from the far-UV CD spectral results. The distance between the bound ligand and Trp-214 of HSA was determined as 3.03 nm based on the Förster resonance energy transfer mechanism. Displacement experiments using bilirubin and warfarin coupled with molecular modeling studies assigned the binding site of FB on HSA at domain IIA, i.e., Sudlow's site I.
    Matched MeSH terms: Circular Dichroism
  10. Interaction of a tyrosine kinase inhibitor, vandetanib with human serum albumin as studied by fluorescence quenching and molecular docking
    Kabir MZ, Feroz SR, Mukarram AK, Alias Z, Mohamad SB, Tayyab S
    J Biomol Struct Dyn, 2016 Aug;34(8):1693-704.
    PMID: 26331959 DOI: 10.1080/07391102.2015.1089187
    Interaction of a tyrosine kinase inhibitor, vandetanib (VDB), with the major transport protein in the human blood circulation, human serum albumin (HSA), was investigated using fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and molecular docking analysis. The binding constant of the VDB-HSA system, as determined by fluorescence quenching titration method was found in the range, 8.92-6.89 × 10(3 )M(-1) at three different temperatures, suggesting moderate binding affinity. Furthermore, decrease in the binding constant with increasing temperature revealed involvement of static quenching mechanism, thus affirming the formation of the VDB-HSA complex. Thermodynamic analysis of the binding reaction between VDB and HSA yielded positive ΔS (52.76 J mol(-1) K(-1)) and negative ΔH (-6.57 kJ mol(-1)) values, which suggested involvement of hydrophobic interactions and hydrogen bonding in stabilizing the VDB-HSA complex. Far-UV and near-UV CD spectral results suggested alterations in both secondary and tertiary structures of HSA upon VDB-binding. Three-dimensional fluorescence spectral results also showed significant microenvironmental changes around the Trp residue of HSA consequent to the complex formation. Use of site-specific marker ligands, such as phenylbutazone (site I marker) and diazepam (site II marker) in competitive ligand displacement experiments indicated location of the VDB binding site on HSA as Sudlow's site I (subdomain IIA), which was further established by molecular docking results. Presence of some common metal ions, such as Ca(2+), Zn(2+), Cu(2+), Ba(2+), Mg(2+), and Mn(2+) in the reaction mixture produced smaller but significant alterations in the binding affinity of VDB to HSA.
    Matched MeSH terms: Circular Dichroism
  11. Influence of Buffer Composition and Calcium Chloride on GdnHCl Denaturation of Bacillus licheniformis α-Amylase
    Kandandapani S, Tan CY, Shuib AS, Tayyab S
    Protein Pept Lett, 2016;23(6):537-43.
    PMID: 26936029
    The influence of buffer composition on the conformational stability of native and calciumdepleted Bacillus licheniformis α-amylase (BLA) was investigated against guanidine hydrochloride (GdnHCl) denaturation using circular dichroism, fluorescence and UV-difference spectroscopy. Differential effect of buffer composition on GdnHCl denaturation of BLA was evident from the magnitude of these spectral signals, which followed the order: sodium phosphate > Tris-HCl > HEPES > MOPS. These effects became more pronounced with calcium-depleted BLA. Sephacryl S-200 gel chromatographic results showed significant BLA aggregation in the presence of 6 M GdnHCl.
    Matched MeSH terms: Circular Dichroism
  12. Characterization of the binding of an anticancer drug, lapatinib to human serum albumin
    Kabir MZ, Mukarram AK, Mohamad SB, Alias Z, Tayyab S
    J. Photochem. Photobiol. B, Biol., 2016 Jul;160:229-39.
    PMID: 27128364 DOI: 10.1016/j.jphotobiol.2016.04.005
    Interaction of a promising anticancer drug, lapatinib (LAP) with the major transport protein in human blood circulation, human serum albumin (HSA) was investigated using fluorescence and circular dichroism (CD) spectroscopy as well as molecular docking analysis. LAP-HSA complex formation was evident from the involvement of static quenching mechanism, as revealed by the fluorescence quenching data analysis. The binding constant, Ka value in the range of 1.49-1.01×10(5)M(-1), obtained at three different temperatures was suggestive of the intermediate binding affinity between LAP and HSA. Thermodynamic analysis of the binding data (∆H=-9.75kJmol(-1) and ∆S=+65.21Jmol(-1)K(-1)) suggested involvement of both hydrophobic interactions and hydrogen bonding in LAP-HSA interaction, which were in line with the molecular docking results. LAP binding to HSA led to the secondary and the tertiary structural alterations in the protein as evident from the far-UV and the near-UV CD spectral analysis, respectively. Microenvironmental perturbation around Trp and Tyr residues in HSA upon LAP binding was confirmed from the three-dimensional fluorescence spectral results. LAP binding to HSA improved the thermal stability of the protein. LAP was found to bind preferentially to the site III in subdomain IB on HSA, as probed by the competitive drug displacement results and supported by the molecular docking results. The effect of metal ions on the binding constant between LAP and HSA was also investigated and the results showed a decrease in the binding constant in the presence of these metal ions.
    Matched MeSH terms: Circular Dichroism
  13. Exploring the combination characteristics of lumefantrine, an antimalarial drug and human serum albumin through spectroscopic and molecular docking studies
    Musa KA, Ridzwan NFW, Mohamad SB, Tayyab S
    J Biomol Struct Dyn, 2021 Feb;39(2):691-702.
    PMID: 31913089 DOI: 10.1080/07391102.2020.1713215
    Binding of lumefantrine (LUM), an antimalarial drug to human serum albumin (HSA), the main carrier protein in human blood circulation was investigated using fluorescence quenching titration, UV-vis absorption and circular dichroism (CD) spectroscopy as well as molecular docking. LUM-induced quenching of the protein (HSA) fluorescence was characterized as static quenching, as revealed by the decrease in the value of the Stern-Volmer quenching constant, K
    sv
    with increasing temperature, thus suggesting LUM-HSA complex formation. This was also confirmed from the UV-vis absorption spectral results. Values of the association constant, Ka for LUM-HSA interaction were found to be within the range, 7.27-5.01 × 104 M-1 at three different temperatures, i.e. 288 K, 298 K and 308 K, which indicated moderate binding affinity between LUM and HSA. The LUM-HSA complex was stabilized by hydrophobic interactions, H-bonds, as well as van der Waals forces, as predicted from the thermodynamic data (ΔS = +50.34 J mol-1 K-1 and ΔH = -12.3 kJ mol-1) of the binding reaction. Far-UV and near-UV CD spectral results demonstrated smaller changes in both secondary and tertiary structures of HSA upon LUM binding, while three-dimensional fluorescence spectra suggested alterations in the microenvironment around protein fluorophores (Trp and Tyr). LUM binding to HSA offered stability to the protein against thermal stress. Competitive drug displacement results designated Sudlow's Site I, located in subdomain IIA of HSA as the preferred binding site of LUM on HSA, which was well supported by molecular docking analysis.Communicated by Ramaswamy H. Sarma.
    Matched MeSH terms: Circular Dichroism
  14. Does recovery in the spectral characteristics of GdnHCl-denatured Bacillus licheniformis α-amylase due to added calcium point towards protein stabilization?
    Halim AA, Feroz SR, Tayyab S
    Biosci Biotechnol Biochem, 2013;77(1):87-96.
    PMID: 23291750
    Treatment of Bacillus licheniformis α-amylase (BLA) with guanidine hydrochloride (GdnHCl) produced both denatured and aggregated forms of the enzyme as studied by circular dichroism, fluorescence, UV difference spectroscopy, size exclusion chromatography (SEC), and enzymatic activity. The presence of CaCl(2) in the incubation mixture produced significant recovery in spectral signals, being complete in presence of 10 mM CaCl(2), as well as in enzymatic activity, which is indicative of protein stabilization. However, the SEC results obtained with GdnHCl-denatured BLA both in the absence and the presence of 10 mM CaCl(2) suggested significant aggregation of the protein in the absence of CaCl(2) and disaggregation in its presence. Although partial structural stabilization with significant retention of enzymatic activity was observed in the presence of calcium, it was far from the native state, as reflected by spectral probes. Hence, spectral results as to BLA stabilization should be treated with caution in the presence of aggregation.
    Matched MeSH terms: Circular Dichroism
  15. Conformational analysis of champedak galactose-binding lectin under different urea concentrations
    Kameel NI, Wong YH, Shuib AS, Tayyab S
    Plant Physiol Biochem, 2016 Jan;98:57-63.
    PMID: 26642433 DOI: 10.1016/j.plaphy.2015.11.007
    Conformational analysis of champedak galactose-binding (CGB) lectin under different urea concentrations was studied in phosphate-buffered saline (pH 7.2) using far-ultraviolet circular dichroism (far-UV CD), tryptophan (Trp) fluorescence and ANS fluorescence. In all cases, CGB lectin displayed a two-step, three-state transition. The first transition (from the native state to the intermediate state) started at ∼2.0 M urea and ended at ∼4.5 M urea, while the second transition (from the intermediate state to the completely denatured state) was characterized by the start- and end-points at ∼5.75 M and ∼7.5 M urea, respectively, when analyzed by the emission maximum of Trp fluorescence. A marked increase in the Trp fluorescence, ANS fluorescence and -CD values at 218 nm (-CD218 nm) represented the first transition, whereas a decrease in these parameters defined the second transition. On the other hand, emission maximum of the Trp fluorescence showed a continuous increase throughout the urea concentration range. Transformation of tetramer into monomer represented the first transition, whereas the second transition reflected the unfolding of monomer. Far-UV CD, Trp fluorescence and ANS fluorescence spectra were used to characterize the native, the intermediate and the completely denatured states of CGB lectin, obtained at 0.0 M, 5.0 M and 9.0 M urea, respectively. The intermediate state was characterized by the presence of higher secondary structures, increased ANS binding as well as increased Trp fluorescence intensity. A gradual decrease in the hemagglutination activity of CGB lectin was observed with increasing urea concentrations, showing complete loss at 4.0 M urea.
    Matched MeSH terms: Circular Dichroism
  16. A Comparative Analysis of Protein Stabilizing Potential of Honey and Simulated Honey Sugar Cocktail
    Wong YH, Kadir HA, Tayyab S
    Protein Pept Lett, 2016;23(10):898-904.
    PMID: 27586182
    Urea and thermal denaturations of bovine serum albumin (BSA) were studied in the absence and the presence of honey or simulated honey sugar cocktail (SHSC) using far-UV CD and ANS fluorescence spectroscopy. Presence of 20% (w/v) honey or SHSC in the incubation mixture shifted the urea transition curve towards higher urea concentrations, being higher in the presence of honey and transformed the two-step, three-state transition into a single-step, two-state transition. A comparison of the far-UV CD and the ANS fluorescence spectra of 4.6 M urea-denatured BSA (U-BSA) in the absence and the presence of 20% (w/v) honey or SHSC suggested greater stabilizing potential of honey than SHSC, as U-BSA maintained native like conformation in the presence of 20% (w/v) honey. Furthermore, thermal transition curves of BSA were also shifted towards higher temperature range in the presence of 20% (w/v) SHSC and honey, showing greater shift in the presence of honey. The far-UV CD spectra of the heat-denatured BSA also showed greater stabilization in the presence of honey. Taken together all these results suggested greater protein stabilizing potential of honey than SHSC against chemical and thermal denaturations of BSA.
    Matched MeSH terms: Circular Dichroism
  17. Evaluation of pendimethalin binding to human serum albumin: Insights from spectroscopic and molecular modeling approach
    Lee WQ, Affandi IS, Feroz SR, Mohamad SB, Tayyab S
    J Biochem Mol Toxicol, 2017 Feb;31(2).
    PMID: 27636401 DOI: 10.1002/jbt.21839
    Interaction of pendimethalin (PM) herbicide with the major transporter in human circulation, human serum albumin (HSA), was studied using fluorescence, circular dichroism (CD), and molecular modeling methods. The attenuation of the fluorescence intensity of HSA in the presence of PM revealed formation of the PM-HSA complex. Analysis of the fluorescence quenching data showed moderately strong binding affinity between PM and HSA. Both hydrophobic interactions and hydrogen bonding were suggested to stabilize the PM-HSA complex, based on thermodynamic data. Binding of PM to HSA induced perturbation in the microenvironment around the aromatic fluorophores as well as secondary and tertiary structural changes in the protein. Complexation of PM with HSA led to an increase in its thermal stability. Both site marker displacement and molecular modeling results suggested site I, located in subdomain IIA as the preferred binding site of PM on HSA.
    Matched MeSH terms: Circular Dichroism
  18. Interactive association between RhoA transcriptional signaling inhibitor, CCG1423 and human serum albumin: Biophysical and in silico studies
    Kabir MZ, Ghani H, Mohamad SB, Alias Z, Tayyab S
    J Biomol Struct Dyn, 2018 Aug;36(10):2495-2507.
    PMID: 28749242 DOI: 10.1080/07391102.2017.1360207
    Multiple spectroscopic techniques, such as fluorescence, absorption, and circular dichroism along with in silico studies were used to characterize the binding of a potent inhibitor molecule, CCG1423 to the major transport protein, human serum albumin (HSA). Fluorescence and absorption spectroscopic results confirmed CCG1423-HSA complex formation. A strong binding affinity stabilized the CCG1423-HSA complex, as evident from the values of the binding constant (Ka = 1.35 × 106-5.43 × 105 M-1). The KSV values for CCG1423-HSA system were inversely correlated with temperature, suggesting the involvement of static quenching mechanism. Thermodynamic data anticipated that CCG1423-HSA complexation was mainly driven by hydrophobic and van der Waals forces as well as hydrogen bonds. In silico analysis also supported these results. Three-dimensional fluorescence and circular dichroism spectral analysis suggested microenvironmental perturbations around protein fluorophores and structural (secondary and tertiary) changes in the protein upon CCG1423 binding. CCG1423 binding to HSA also showed some protection against thermal denaturation. Site-specific marker-induced displacement results revealed CCG1423 binding to Sudlow's site I of HSA, which was also confirmed by the computational results. A few common ions were also found to interfere with the CCG1423-HSA interaction.
    Matched MeSH terms: Circular Dichroism
  19. Acid-Induced Unfolding of Champedak Galactose-Binding Lectin
    Kameel NI, Shuib AS, Tayyab S
    Protein Pept Lett, 2016;23(12):1111-1117.
    PMID: 27774894
    Acid denaturation of champedak galactose-binding (CGB) lectin was studied in the pH range, 7.0-1.0 using intrinsic fluorescence and ANS fluorescence measurements. The lectin remained stable up to pH 5.0 and showed local disordering in the vicinity of the protein fluorophores within the pH range, 5.0-3.5. Decrease in the pH from pH 3.5 to pH 2.5 led to structural transition, marked by the decrease in the intrinsic fluorescence and increase in the ANS fluorescence signals. This can be ascribed to the dissociation of the tetrameric lectin into monomeric forms. Further decrease in the pH up to pH 1.5 produced another transition, which specified the unfolding of monomers as reflected from the decrease in both intrinsic fluorescence and ANS fluorescence signals. Characterization of the conformational states obtained at pH 7.0, pH 2.5 and pH 1.5 based on intrinsic and ANS fluorescence spectra, gel chromatographic behavior and thermal denaturation confirmed the existence of folded monomeric forms at pH 2.5 and unfolded states at pH 1.5. However, the aciddenatured state of CGB lectin at pH 1.5 retained significant residual structure, as evident from the greater loss of both secondary and tertiary structures in the presence of 6 M guanidine hydrochloride at low pH values. Anion-induced refolding below pH 1.5 was also seen using ANS fluorescence measurements.
    Matched MeSH terms: Circular Dichroism
  20. Combination mode of antimalarial drug mefloquine and human serum albumin: Insights from spectroscopic and docking approaches
    Musa KA, Ridzwan NFW, Mohamad SB, Tayyab S
    Biopolymers, 2020 Feb;111(2):e23337.
    PMID: 31691964 DOI: 10.1002/bip.23337
    The interaction between mefloquine (MEF), the antimalarial drug, and human serum albumin (HSA), the main carrier protein in blood circulation, was explored using fluorescence, absorption, and circular dichroism spectroscopic techniques. Quenching of HSA fluorescence with MEF was characterized as static quenching and thus confirmed the complex formation between MEF and HSA. Association constant values for MEF-HSA interaction were found to fall within the range of 3.79-5.73 × 104  M-1 at various temperatures (288, 298, and 308 K), which revealed moderate binding affinity. Hydrogen bonds and hydrophobic interactions were predicted to connect MEF and HSA together in the MEF-HSA complex, as deduced from the thermodynamic data (ΔS = +133.52 J mol-1 K-1 and ΔH = +13.09 kJ mol-1 ) of the binding reaction and molecular docking analysis. Three-dimensional fluorescence spectral analysis pointed out alterations in the microenvironment around aromatic amino acid (tryptophan and tyrosine) residues of HSA consequent to the addition of MEF. Circular dichroic spectra of HSA in the wavelength ranges of 200-250 and 250-300 nm hinted smaller changes in the protein's secondary and tertiary structures, respectively, induced by MEF binding. Noncovalent conjugation of MEF to HSA bettered protein thermostability. Site marker competitive drug displacement results suggested HSA Sudlow's site I as the MEF binding site, which was also supported by molecular docking analysis.
    Matched MeSH terms: Circular Dichroism
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