Publications by authors named "Saharuddin B Mohamad"

23 Publications

  • Page 1 of 1

Biomolecular interaction mechanism of an anticancer drug, pazopanib with human serum albumin: a multi-spectroscopic and computational approach.

J Biomol Struct Dyn 2021 Apr 19:1-12. Epub 2021 Apr 19.

Biomolecular Research Group, Biochemistry Program, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.

Pazopanib (PZP) is a multi-targeting tyrosine kinase inhibitor and is currently approved by FDA for the treatment of soft tissue sarcoma and renal cancer. Molecular interaction mechanism of PZP with human serum albumin (HSA) was explored under simulated physiological conditions (pH = 7.4), using fluorescence and UV absorption spectroscopy along with computational methods. Based on the inverse correlation between the Stern-Volmer constant () and temperature, it was concluded that PZP quenched the protein fluorescence through static quenching mechanism. This was also confirmed from the UV-vis absorption spectral results. Moderate binding affinity between PZP and HSA was evident from the values (5.51 - 1.05 × 10 M) while PZP-HSA complex formation was driven by hydrophobic and van der Waals interactions as well as hydrogen bonds, as revealed by positive entropy change (ΔS = +98.37 J mol K) and negative enthalpy change (ΔH = -60.31 kJ mol). Three-dimensional fluorescence spectral results disclosed microenvironmental perturbations around Trp and Tyr residues of the protein upon PZP binding. Interestingly, the addition of PZP to HSA significantly protected the protein against thermal stress. Competitive drug displacement results obtained with warfarin, phenylbutazone and diazepam elucidated Sudlow's Site I, positioned in subdomain IIA of HSA, as the preferred binding site of PZP which was well supported by molecular docking analysis, while molecular dynamics simulation results suggested the stability of the PZP-HSA complex.Communicated by Vsevolod Makeev.
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http://dx.doi.org/10.1080/07391102.2021.1911850DOI Listing
April 2021

Biophysical and computational view on the combination between an anticancer drug, saracatinib and human serum albumin.

J Biomol Struct Dyn 2021 Jul 22;39(10):3565-3575. Epub 2020 May 22.

Centre of Research for Computational Sciences and Informatics for Biology, Bioindustry, Environment, Agriculture and Healthcare, University of Malaya, Kuala Lumpur, Malaysia.

Interaction behaviour of an anticancer drug, saracatinib (SCB) with human serum albumin (HSA), the major carrier protein in human blood circulation was investigated using fluorescence and absorption spectroscopy as well as computational methods. Analysis of the fluorescence quenching data along with absorption results confirmed the complex formation between SCB and HSA, based on the inverse correlation of the Stern-Volmer constant () with temperature and hyperchromic effect in the absorption spectra. Moderate binding affinity between SCB and HSA was evident from the binding constant, value (1.08-0.74 × 10 M), while the SCB-HSA complexation was anticipated to be stabilized by hydrophobic and van der Waals interactions along with hydrogen bonds, as revealed from the thermodynamic data (Δ = + 29.40 J mol K and Δ = - 13.90 kJ mol). Addition of SCB to HSA significantly defended the thermal denaturation of the protein, though it perturbed the surrounding medium around Tyr and Trp residues. Site marker displacement results elucidated Sudlow's site I, positioned in subdomain IIA of HSA as the preferred binding site of SCB, which was well supported by molecular docking. Molecular dynamics simulation results suggested the stability of the SCB-HSA complex.Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2020.1766571DOI Listing
July 2021

Exploring the combination characteristics of lumefantrine, an antimalarial drug and human serum albumin through spectroscopic and molecular docking studies.

J Biomol Struct Dyn 2021 Feb 22;39(2):691-702. Epub 2020 Jan 22.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.

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, 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, for LUM-HSA interaction were found to be within the range, 7.27-5.01 × 10 M 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 (Δ = +50.34 J mol K and Δ = -12.3 kJ mol) 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.
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http://dx.doi.org/10.1080/07391102.2020.1713215DOI Listing
February 2021

Combination mode of antimalarial drug mefloquine and human serum albumin: Insights from spectroscopic and docking approaches.

Biopolymers 2020 Feb 6;111(2):e23337. Epub 2019 Nov 6.

Faculty of Science, Biochemistry Programme, Biomolecular Research Group, Institute of Biological Sciences, University of Malaya, Kuala Lumpur, Malaysia.

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 × 10  M 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 K and ΔH = +13.09 kJ mol ) 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.
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http://dx.doi.org/10.1002/bip.23337DOI Listing
February 2020

Exploring the interaction between tyrphostin 9 and human serum albumin using biophysical and computational methods.

J Biomol Struct Dyn 2020 Sep 11;38(14):4134-4142. Epub 2019 Oct 11.

Biochemistry Programme, Biomolecular Research Group, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.

Tyrphostin 9 (Tyr 9) is a potent platelet-derived growth factor receptor (PDGFR) inhibitor, which induces apoptosis in various cancer cell types. The binding of Tyr 9 to the major transport protein, human serum albumin (HSA) was investigated using several spectroscopic techniques and molecular docking method. Fluorescence quenching titration results showed progressive decrease in the protein fluorescence with increasing drug concentrations. A decreasing trend of the Stern-Volmer constant, with increasing temperature characterized the drug-induced quenching as static quenching, thus pointed towards the formation of Tyr 9-HSA complex. The binding constant of Tyr 9-HSA interaction was found to lie within the range 3.48-1.69 × 10 M at three different temperatures, 15 °C, 25 °C and 35 °C, respectively and suggested intermediate binding affinity between Tyr 9 and HSA. The drug-HSA complex seems to be stabilized by hydrophobic forces, van der Waals forces and hydrogen bonds, as suggested from the thermodynamic data as well as molecular docking results. The far-UV and the near-UV CD spectral results showed slight alteration in the secondary and tertiary structures, respectively, of the protein upon Tyr 9 binding. Interaction of Tyr 9 with HSA also produced microenvironmental perturbations around protein fluorophores, as evident from the three-dimensional fluorescence spectral results but increased protein's thermal stability. Both competitive drug binding results and molecular docking analysis suggested Sudlow's Site I of HSA as the preferred Tyr 9 binding site. Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2019.1673210DOI Listing
September 2020

Biomolecular interaction of a platelet aggregation inhibitor, 3,4-methylenedioxy-β-nitrostyrene with human serum albumin: multi-spectral and computational characterization.

J Biomol Struct Dyn 2020 Jun 15;38(9):2693-2703. Epub 2019 Jul 15.

Faculty of Science, Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, University of Malaya, Kuala Lumpur, Malaysia.

Molecular interaction of the 3,4-methylenedioxy-β-nitrostyrene (MNS), an inhibitor of platelet aggregation with the main transport protein, albumin from human serum (HSA) was explored using absorption, fluorescence and circular dichroism (CD) spectroscopy in combination with analyses. The MNS-HSA complexation was corroborated from the fluorescence and absorption spectral results. Implication of static quenching mechanism for MNS-HSA system was predicted from the Stern-Volmer constant, temperature relationship as well as the bimolecular quenching rate constant, values. Stabilization of the complex was affirmed by the value of the binding constant ( = 0.56-1.48 × 10 M). Thermodynamic data revealed that the MNS-HSA association was spontaneously driven mainly through hydrophobic interactions along with van der Waal's interaction and H-bonds. These results were well supported by interpretations. Far-UV and near-UV CD spectral results manifested small variations in the protein's secondary and tertiary structures, respectively, while three-dimensional fluorescence spectra displayed microenvironmental fluctuations around protein's fluorophores, upon MNS binding. Significant improvement in the protein's thermostability was evident from the temperature-stability results of MNS-bound HSA. Binding locus of MNS, as identified by competitive drug displacement findings as well as analysis, was found to be located in subdomain IIA (Sudlow's site I) of the protein.Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2019.1640133DOI Listing
June 2020

Molecular interaction study of an anticancer drug, ponatinib with human serum albumin using spectroscopic and molecular docking methods.

Spectrochim Acta A Mol Biomol Spectrosc 2019 May 12;214:199-206. Epub 2019 Feb 12.

Bioinformatics Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia; Centre of Research for Computational Sciences and Informatics for Biology, Bioindustry, Environment, Agriculture and Healthcare, University of Malaya, Kuala Lumpur, Malaysia.

Binding of a potent anticancer agent, ponatinib (PTB) to human serum albumin (HSA), main ligand transporter in blood plasma was analyzed with several spectral techniques such as fluorescence, absorption and circular dichroism along with molecular docking studies. Decrease in the K value with increasing temperature pointed towards PTB-induced quenching as the static quenching, thus affirming complexation between PTB and HSA. An intermediate binding affinity was found to stabilize the PTB-HSA complex, as suggested by the K value. Thermodynamic analysis of the binding phenomenon revealed participation of hydrophobic and van der Waals interactions along with hydrogen bonds, which was also supported by molecular docking analysis. Changes in both secondary and tertiary structures as well as in the microenvironment around Trp and Tyr residues of HSA were anticipated upon PTB binding to the protein, as manifested from circular dichroism and three-dimensional fluorescence spectra, respectively. Binding of PTB to HSA led to protein's thermal stabilization. Competitive ligand displacement experiments using different site markers such as warfarin, indomethacin and ketoprofen disclosed the binding site of PTB as Sudlow's site I in HSA, which was further confirmed by molecular docking analysis.
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http://dx.doi.org/10.1016/j.saa.2019.02.028DOI Listing
May 2019

Probing the interaction of 2,4-dichlorophenoxyacetic acid with human serum albumin as studied by experimental and computational approaches.

Spectrochim Acta A Mol Biomol Spectrosc 2019 Jan 19;207:284-293. Epub 2018 Sep 19.

Bioinformatics Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia; Centre of Research for Computational Sciences and Informatics for Biology, Bioindustry, Environment, Agriculture and Healthcare, University of Malaya, Kuala Lumpur, Malaysia.

To characterize the binding of a widely used herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D) to the major transporter in human circulation, human serum albumin (HSA), multi-spectroscopic approaches such as fluorescence, absorption and circular dichroism along with computational methods were employed. Analysis of the fluorescence and absorption spectroscopic data confirmed the 2,4-D-HSA complex formation. A static quenching mechanism was evident from the inverse temperature dependence of the K values. The complex was stabilized by a weak binding affinity (K = 5.08 × 10 M at 298 K). Quantitative analysis of thermodynamic data revealed participation of hydrophobic and van der Waals interactions as well as hydrogen bonds in the binding process. Circular dichroism and three-dimensional fluorescence spectral results showed structural (secondary and tertiary) changes in HSA as well as microenvironmental perturbation around protein fluorophores (Trp and Tyr residues) upon 2,4-D binding. Addition of 2,4-D to HSA was found to improve protein's thermal stability. Competitive displacement results as well as computational analyses suggested preferred location of the 2,4-D binding site as Sudlow's site I (subdomain IIA) in HSA.
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http://dx.doi.org/10.1016/j.saa.2018.09.033DOI Listing
January 2019

Biophysical and computational characterization of vandetanib-lysozyme interaction.

Spectrochim Acta A Mol Biomol Spectrosc 2018 Jan 18;189:485-494. Epub 2017 Aug 18.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia; Centre of Research for Computational Sciences and Informatics for Biology, Bioindustry, Environment, Agriculture and Healthcare, University of Malaya, Kuala Lumpur, Malaysia. Electronic address:

Interaction of an anticancer drug, vandetanib (VDB) with a ligand transporter, lysozyme (LYZ) was explored using multispectroscopic techniques, such as fluorescence, absorption and circular dichroism along with computational analysis. Fluorescence data and absorption results confirmed VDB-LYZ complexation. VDB-induced quenching was characterized as static quenching based on inverse correlation of K with temperature as well as k values. The complex was characterized by the weak binding constant (K=4.96-3.14×10M). Thermodynamic data (ΔS=+12.82JmolK; ΔH=-16.73kJmol) of VDB-LYZ interaction revealed participation of hydrophobic and van der Waals forces along with hydrogen bonds in VDB-LYZ complexation. Microenvironmental perturbations around tryptophan and tyrosine residues as well as secondary and tertiary structural alterations in LYZ upon addition of VDB were evident from the 3-D fluorescence, far- and near-UV CD spectral analyses, respectively. Interestingly, addition of VDB to LYZ significantly increased protein's thermostability. Molecular docking results suggested the location of VDB binding site near the LYZ active site while molecular dynamics simulation results suggested stability of VDB-LYZ complex. Presence of Mg, Ba and Zn was found to interfere with VDB-LYZ interaction.
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http://dx.doi.org/10.1016/j.saa.2017.08.051DOI Listing
January 2018

Interactive association between RhoA transcriptional signaling inhibitor, CCG1423 and human serum albumin: Biophysical and in silico studies.

J Biomol Struct Dyn 2018 Aug 18;36(10):2495-2507. Epub 2017 Aug 18.

a Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science , University of Malaya , Kuala Lumpur , Malaysia.

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 (K = 1.35 × 10-5.43 × 10 M). The K 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.
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http://dx.doi.org/10.1080/07391102.2017.1360207DOI Listing
August 2018

Comprehensive insight into the binding of sunitinib, a multi-targeted anticancer drug to human serum albumin.

Spectrochim Acta A Mol Biomol Spectrosc 2017 Jun 28;181:254-263. Epub 2017 Mar 28.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia; Centre of Research for Computational Sciences and Informatics for Biology, Bioindustry, Environment, Agriculture and Healthcare, University of Malaya, Kuala Lumpur, Malaysia. Electronic address:

Binding studies between a multi-targeted anticancer drug, sunitinib (SU) and human serum albumin (HSA) were made using fluorescence, UV-vis absorption, circular dichroism (CD) and molecular docking analysis. Both fluorescence quenching data and UV-vis absorption results suggested formation of SU-HSA complex. Moderate binding affinity between SU and HSA was evident from the value of the binding constant (3.04×10M), obtained at 298K. Involvement of hydrophobic interactions and hydrogen bonds as the leading intermolecular forces in the formation of SU-HSA complex was predicted from the thermodynamic data of the binding reaction. These results were in good agreement with the molecular docking analysis. Microenvironmental perturbations around Tyr and Trp residues as well as secondary and tertiary structural changes in HSA upon SU binding were evident from the three-dimensional fluorescence and circular dichroism results. SU binding to HSA also improved the thermal stability of the protein. Competitive displacement results and molecular docking analysis revealed the binding locus of SU to HSA in subdomain IIA (Sudlow's site I). The influence of a few common ions on the binding constant of SU-HSA complex was also noticed.
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http://dx.doi.org/10.1016/j.saa.2017.03.059DOI Listing
June 2017

Interaction of stattic, a STAT3 inhibitor with human serum albumin: spectroscopic and computational study.

J Biomol Struct Dyn 2017 12 26;35(16):3581-3590. Epub 2016 Dec 26.

a Faculty of Science, Biomolecular Research Group , Biochemistry Programme, Institute of Biological Sciences, University of Malaya , Kuala Lumpur , Malaysia.

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http://dx.doi.org/10.1080/07391102.2016.1264887DOI Listing
December 2017

Evaluation of pendimethalin binding to human serum albumin: Insights from spectroscopic and molecular modeling approach.

J Biochem Mol Toxicol 2017 Feb 16;31(2). Epub 2016 Sep 16.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.

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.
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http://dx.doi.org/10.1002/jbt.21839DOI Listing
February 2017

Binding of an anticancer drug, axitinib to human serum albumin: Fluorescence quenching and molecular docking study.

J Photochem Photobiol B 2016 Sep 1;162:386-394. Epub 2016 Jul 1.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.

Binding characteristics of a promising anticancer drug, axitinib (AXT) to human serum albumin (HSA), the major transport protein in human blood circulation, were studied using fluorescence, UV-vis absorption and circular dichroism (CD) spectroscopy as well as molecular docking analysis. A gradual decrease in the Stern-Volmer quenching constant with increasing temperature revealed the static mode of the protein fluorescence quenching upon AXT addition, thus confirmed AXT-HSA complex formation. This was also confirmed from alteration in the UV-vis spectrum of HSA upon AXT addition. Fluorescence quenching titration results demonstrated moderately strong binding affinity between AXT and HSA based on the binding constant value (1.08±0.06×10(5)M(-1)), obtained in 10mM sodium phosphate buffer, pH7.4 at 25°C. The sign and magnitude of the enthalpy change (∆H=-8.38kJmol(-1)) as well as the entropy change (∆S=+68.21Jmol(-1)K(-1)) clearly suggested involvement of both hydrophobic interactions and hydrogen bonding in AXT-HSA complex formation. These results were well supported by molecular docking results. Three-dimensional fluorescence spectral results indicated significant microenvironmental changes around Trp and Tyr residues of HSA upon complexation with AXT. AXT binding to the protein produced significant alterations in both secondary and tertiary structures of HSA, as revealed from the far-UV and the near-UV CD spectral results. Competitive drug displacement results obtained with phenylbutazone (site I marker), ketoprofen (site II marker) and hemin (site III marker) along with molecular docking results suggested Sudlow's site I, located in subdomain IIA of HSA, as the preferred binding site of AXT.
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http://dx.doi.org/10.1016/j.jphotobiol.2016.06.049DOI Listing
September 2016

Characterization of the binding of an anticancer drug, lapatinib to human serum albumin.

J Photochem Photobiol B 2016 Jul 13;160:229-39. Epub 2016 Apr 13.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia; Centre of Research for Computational Sciences and Informatics for Biology, Bioindustry, Environment, Agriculture and Healthcare, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia. Electronic address:

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.
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http://dx.doi.org/10.1016/j.jphotobiol.2016.04.005DOI Listing
July 2016

Interaction of a tyrosine kinase inhibitor, vandetanib with human serum albumin as studied by fluorescence quenching and molecular docking.

J Biomol Struct Dyn 2016 Aug 27;34(8):1693-704. Epub 2016 Jan 27.

a Faculty of Science, Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences , University of Malaya , Kuala Lumpur , Malaysia.

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.
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http://dx.doi.org/10.1080/07391102.2015.1089187DOI Listing
August 2016

Exploring the interaction between the antiallergic drug, tranilast and human serum albumin: Insights from calorimetric, spectroscopic and modeling studies.

Int J Pharm 2015 Aug 30;491(1-2):352-8. Epub 2015 Jun 30.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.

The interaction of tranilast (TRN), an antiallergic drug with the main drug transporter in human circulation, human serum albumin (HSA) was studied using isothermal titration calorimetry (ITC), fluorescence spectroscopy and in silico docking methods. ITC data revealed the binding constant and stoichiometry of binding as (3.21 ± 0.23) × 10(6)M(-1) and 0.80 ± 0.08, respectively, at 25°C. The values of the standard enthalpy change (ΔH°) and the standard entropy change (ΔS°) for the interaction were found as -25.2 ± 5.1 kJ mol(-1) and 46.9 ± 5.4 J mol(-1)K(-1), respectively. Both thermodynamic data and modeling results suggested the involvement of hydrogen bonding, hydrophobic and van der Waals forces in the complex formation. Three-dimensional fluorescence data of TRN-HSA complex demonstrated significant changes in the microenvironment around the protein fluorophores upon drug binding. Competitive drug displacement results as well as modeling data concluded the preferred binding site of TRN as Sudlow's site I on HSA.
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http://dx.doi.org/10.1016/j.ijpharm.2015.06.042DOI Listing
August 2015

Spectrofluorometric and molecular docking studies on the binding of curcumenol and curcumenone to human serum albumin.

Int J Mol Sci 2015 Mar 6;16(3):5180-93. Epub 2015 Mar 6.

Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.

Curcumenol and curcumenone are two major constituents of the plants of medicinally important genus of Curcuma, and often govern the pharmacological effect of these plant extracts. These two compounds, isolated from C. zedoaria rhizomes were studied for their binding to human serum albumin (HSA) using the fluorescence quench titration method. Molecular docking was also performed to get a more detailed insight into their interaction with HSA at the binding site. Additions of these sesquiterpenes to HSA produced significant fluorescence quenching and blue shifts in the emission spectra of HSA. Analysis of the fluorescence data pointed toward moderate binding affinity between the ligands and HSA, with curcumenone showing a relatively higher binding constant (2.46 × 105 M-1) in comparison to curcumenol (1.97 × 104 M-1). Cluster analyses revealed that site I is the preferred binding site for both molecules with a minimum binding energy of -6.77 kcal·mol-1. However, binding of these two molecules to site II cannot be ruled out as the binding energies were found to be -5.72 and -5.74 kcal·mol-1 for curcumenol and curcumenone, respectively. The interactions of both ligands with HSA involved hydrophobic interactions as well as hydrogen bonding.
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http://dx.doi.org/10.3390/ijms16035180DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4394470PMC
March 2015

Probing the interaction of a therapeutic flavonoid, pinostrobin with human serum albumin: multiple spectroscopic and molecular modeling investigations.

PLoS One 2013 8;8(10):e76067. Epub 2013 Oct 8.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.

Interaction of a pharmacologically important flavonoid, pinostrobin (PS) with the major transport protein of human blood circulation, human serum albumin (HSA) has been examined using a multitude of spectroscopic techniques and molecular docking studies. Analysis of the fluorescence quenching data showed a moderate binding affinity (1.03 × 10(5) M(-1) at 25°C) between PS and HSA with a 1∶1 stoichiometry. Thermodynamic analysis of the binding data (ΔS = +44.06 J mol(-1) K(-1) and ΔH = -15.48 kJ mol(-1)) and molecular simulation results suggested the involvement of hydrophobic and van der Waals forces, as well as hydrogen bonding in the complex formation. Both secondary and tertiary structural perturbations in HSA were observed upon PS binding, as revealed by intrinsic, synchronous, and three-dimensional fluorescence results. Far-UV circular dichroism data revealed increased thermal stability of the protein upon complexation with PS. Competitive drug displacement results suggested the binding site of PS on HSA as Sudlow's site I, located at subdomain IIA, and was well supported by the molecular modelling data.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0076067PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3792979PMC
June 2014

X-linked chronic granulomatous disease in a male child with an X-CGD carrier, Klinefelter brother.

Asian Pac J Allergy Immunol 2013 Jun;31(2):167-72

Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia.

Background: Chronic granulomatous disease (CGD) is a rare primary immunodeficiency (PID) caused by a dysfunctional respiratory burst enzyme NADPH-oxidase. The concurrence of Klinefelter's Syndrome (KS) and CGD would be extremely rare.

Objective: We describe the study of a family where the youngest male child had X-linked CGD (X-CGD) while his older brother was both an X-CGD carrier and a Klinefelter.

Methods: Flow cytometry was used to study respiratory burst and gp91-phox expression, while genetic investigation was done by RT-PCR, PCR and X-chromosome short tandem repeat (X-STR) analysis.

Results: The Dihydrorhodamine (DHR) assay showed the patient's neutrophils failed to produce a respiratory burst, while both the mother and an older brother showed a bimodal response. gp91-phox expression was absent in the patient's neutrophils, and bimodal in the mother's and brother's neutrophils. The patient's cDNA showed a C>T change at nucleotide 676 of the CYBB gene. The same change was seen in the patient's gDNA, while the brother and mother were heterozygous, with C and T, in this position. The c.676C>T is a nonsense mutation that leads to premature termination of the gp91-phox protein. The brother karyotyped as 47, XXY and X chromosome analysis showed that he had inherited both his mother's X chromosomes.

Conclusions: This study showed that the patient had gp91-phox deficient CGD while his older brother was a CGD carrier and a Klinefelter, who had inherited both his mother's X chromosomes. This is the first report of such a concurrence in an individual, and argues for family members to be included in PID studies.
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http://dx.doi.org/10.12932/AP0274.31.2.2013DOI Listing
June 2013

Multispectroscopic and molecular modeling approach to investigate the interaction of flavokawain B with human serum albumin.

J Agric Food Chem 2012 Jun 4;60(23):5899-908. Epub 2012 Jun 4.

Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia.

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.
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http://dx.doi.org/10.1021/jf301139hDOI Listing
June 2012

Characterization of human Gc protein-derived macrophage activation factor (GcMAF) and its functional role in macrophage tumoricidal activity.

Adv Exp Med Biol 2003 ;510:77-82

Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, Tokushima, 770-8506, Japan.

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http://dx.doi.org/10.1007/978-1-4615-0205-0_13DOI Listing
August 2003

Tumor cell alpha-N-acetylgalactosaminidase activity and its involvement in GcMAF-related macrophage activation.

Comp Biochem Physiol A Mol Integr Physiol 2002 May;132(1):1-8

Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, Tokushima 770-8506, Japan.

Alpha-N-acetyl galactosaminidase (alpha-NaGalase) has been reported to accumulate in serum of cancer patients and be responsible for deglycosylation of Gc protein, which is a precursor of GcMAF-mediated macrophage activation cascade, finally leading to immunosuppression in advanced cancer patients. We studied the biochemical characterization of alpha-NaGalase from several human tumor cell lines. We also examined its effect on the potency of GcMAF to activate mouse peritoneal macrophage to produce superoxide in GcMAF-mediated macrophage activation cascade. The specific activity of alpha-NaGalases from human colon tumor cell line HCT116, human hepatoma cell line HepG2, and normal human liver cells (Chang liver cell line) were evaluated using two types of substrates; GalNAc-alpha-PNP (exo-type substrate) and Gal-beta-GalNAc-alpha-PNP (endo-type substrate). Tumor-derived alpha-NaGalase having higher activity than normal alpha-NaGalase, had higher substrate specificity to the exo-type substrate than to the endo-type substrate, and still maintained its activity at pH 7. GcMAF enhance superoxide production in mouse macrophage, and pre-treatment of GcMAF with tumor cell lysate reduce the activity. We conclude that tumor-derived alpha-NaGalase is different in biochemical characterization compared to normal alpha-NaGalase from normal Chang liver cells. In addition, tumor cell-derived alpha-NaGalase decreases the potency of GcMAF on macrophage activation.
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http://dx.doi.org/10.1016/s1095-6433(01)00522-0DOI Listing
May 2002
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