Displaying publications 61 - 80 of 92 in total

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  1. 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: Spectrometry, Fluorescence
  2. Simple high-performance liquid chromatographic method for the determination of acyclovir in human plasma using fluorescence detection
    Peh KK, Yuen KH
    J Chromatogr B Biomed Sci Appl, 1997 May 23;693(1):241-4.
    PMID: 9200543
    A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of acyclovir in human plasma. The method entailed direct injection of the plasma sample after deproteination. It is both specific and sensitive with a detection limit of 30 ng/ml at a signal-to-noise ratio of 3:1, and is thus suitable for use in pharmacokinetic studies of acyclovir. The method had a mean absolute recovery of 96%, while the within-day and between-day coefficients of variation and percentages error were all less than 8%. The calibration curve was linear over a concentration range of 62.5-4000 ng/ml.
    Matched MeSH terms: Spectrometry, Fluorescence
  3. Simple high-performance liquid chromatographic method for determination of ketoconazole in human plasma
    Yuen KH, Peh KK
    J Chromatogr B Biomed Sci Appl, 1998 Sep 18;715(2):436-40.
    PMID: 9792531
    A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of ketoconazole in human plasma. The method entailed direct injection of the plasma sample after deproteinization using acetonitrile. The mobile phase comprised 0.05 M disodium hydrogen orthophosphate and acetonitrile (50:50, v/v) adjusted to pH 6. Analysis was run at a flow-rate of 1.5 ml/min with the detector operating at an excitation wavelength of 260 nm and an emission wavelength of 375 nm. The method is specific and sensitive with a quantification limit of approximately 60 ng/ml and a detection limit of 40 ng/ml at a signal-to-noise ratio of 3:1. Mean absolute recovery value was about 105%, while the within-day and between-day coefficient of variation and percent error values of the assay method were all less than 14%. The calibration curve was linear over a concentration range of 62.5-8000 ng/ml.
    Matched MeSH terms: Spectrometry, Fluorescence
  4. Exploring the interaction between the antiallergic drug, tranilast and human serum albumin: Insights from calorimetric, spectroscopic and modeling studies
    Tayyab S, Zaroog MS, Feroz SR, Mohamad SB, Malek SN
    Int J Pharm, 2015 Aug 1;491(1-2):352-8.
    PMID: 26142245 DOI: 10.1016/j.ijpharm.2015.06.042
    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.
    Matched MeSH terms: Spectrometry, Fluorescence
  5. Pharmacological evaluation of poly(3-methylthiophene) and its titanium(IV)phosphate nanocomposite: DNA interaction, molecular docking, and cytotoxic activity
    Baig U, Gondal MA, Alam MF, Wani WA, Younus H
    J. Photochem. Photobiol. B, Biol., 2016 Nov;164:244-255.
    PMID: 27710872 DOI: 10.1016/j.jphotobiol.2016.09.034
    Cancer and pathogenic microbial diseases have terribly affected human health over a longer period of time. In response to the increasing casualties due to cancer and microbial diseases, unique poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate composite were prepared via in-situ oxidative chemical polymerization in this work. The poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate composite were well characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. DNA binding studies by UV-Visible and fluorescence spectroscopic investigations indicated strong binding affinities of poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite; leading to structural damage of DNA. Poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite showed stronger interactions with DNA as compared to poly(3-methylthiophene) and from dye displacement assay it was confirmed that mode of binding of both the formulations was intercalative. The antimicrobial screening revealed that polymer and its composite displayed stronger antibacterial effects than ampicillin against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhimurium. Besides, the poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite showed dose dependent effects towards estrogen receptor positive breast cancer (MCF-7) and estrogen receptor negative breast cancer (MDA-MB-231) cell lines; with poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite showing better activities against both cell lines. In all in-vitro biological investigations, poly(3-methylthiophene)-titanium(IV)phosphate composite showed superior properties to that of the pure poly(3-methylthiophene), which encouraged us to suggest its potential as future therapeutic gear in drug delivery and other allied fields.
    Matched MeSH terms: Spectrometry, Fluorescence
  6. Binding of an anticancer drug, axitinib to human serum albumin: Fluorescence quenching and molecular docking study
    Tayyab S, Izzudin MM, Kabir MZ, Feroz SR, Tee WV, Mohamad SB, et al.
    J. Photochem. Photobiol. B, Biol., 2016 Sep;162:386-94.
    PMID: 27424099 DOI: 10.1016/j.jphotobiol.2016.06.049
    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.
    Matched MeSH terms: Spectrometry, Fluorescence
  7. Comprehensive insight into the binding of sunitinib, a multi-targeted anticancer drug to human serum albumin
    Kabir MZ, Tee WV, Mohamad SB, Alias Z, Tayyab S
    Spectrochim Acta A Mol Biomol Spectrosc, 2017 Jun 15;181:254-263.
    PMID: 28376387 DOI: 10.1016/j.saa.2017.03.059
    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 (3.04×104M-1), 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.
    Matched MeSH terms: Spectrometry, Fluorescence
  8. 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: Spectrometry, Fluorescence
  9. Selective magnetic nanographene oxide solid-phase extraction with high-performance liquid chromatography and fluorescence detection for the determination of zearalenone in corn samples
    Thongprapai P, Cheewasedtham W, Chong KF, Rujiralai T
    J Sep Sci, 2018 Dec;41(23):4348-4354.
    PMID: 30267469 DOI: 10.1002/jssc.201800441
    A magnetic nanographene oxide sorbent as a selective sorbent for the magnetic solid-phase extraction combined with high-performance liquid chromatography and fluorescence detection was developed and proved to be a robust method for zearalenone determination in corn samples. Optimum extraction of zearalenone (20 mg magnetic nanographene oxide sorbent, extraction for 15 min, desorption time of 15 min using 1 mL of 0.5% formic acid in methanol) resulted in low limits of detection (05 mg/L) and quantitation (0.13 mg/L) and good linearity range of 0.13-1.25 mg/L with the correlation coefficient of 0.9957. Acceptable recoveries (79.3-80.6%) with relative standard deviations below 4% and satisfactory intra- and interday precisions (2-7.4%) were achieved. Additionally, the proposed method has been proved to be good in several aspects: easily prepared sorbent with high affinity to zearalenone, convenient and fast procedure, and high extraction efficiency.
    Matched MeSH terms: Spectrometry, Fluorescence
  10. Synthesis, characterization and dna binding studies of [ruthenium(ii)(bpy)2 l]2+ where l are derivatives of imidazo[4,5-f]-1,10-phenanthrolines
    Ting T, Crouse K, Ahmad H
    Sains Malaysiana, 2015;44:619-628.
    Three novel ruthenium(II) complexes of the general formula [Ru(II)(bpy)2
    L]2+ were synthesized, where L =
    1,10-phenanthroline derivatives of position 2 imidazole having 3,4-didecyloxy-phenyl (ddip), 3,4-ditetradecyloxy-phenyl
    (dtip) and 3,4-dihexadecyloxy-phenyl (dhip). All complexes were characterized by elemental analysis, 1
    H-NMR and ESI-MS.
    Their photophysical properties have also been studied by UV-visible spectroscopy and fluorescence spectroscopy. The
    complexes exhibit Ru(II) metal centered emission at approximately 610 nm in acetonitrile solution at room temperature. DNA
    binding studies were carried out by UV-visible titration, luminescence titration and viscosity studies. The results indicated
    that [Ru(bpy)2
    (ddip)]2+ binds to CT-DNA by partial intercalation mode, while [Ru(bpy)2
    (dtip)]2+ and [Ru(bpy)2
    (dhip)]2+
    bind intercalatively via extended ligands.
    Matched MeSH terms: Spectrometry, Fluorescence
  11. Nanocrystalline cellulose decorated quantum dots based tyrosinase biosensor for phenol determination
    Manan FAA, Hong WW, Abdullah J, Yusof NA, Ahmad I
    Mater Sci Eng C Mater Biol Appl, 2019 Jun;99:37-46.
    PMID: 30889711 DOI: 10.1016/j.msec.2019.01.082
    Novel biosensor architecture based on nanocrystalline cellulose (NCC)/CdS quantum dots (QDs) nanocomposite was developed for phenol determination. This nanocomposite was prepared with slight modification of nanocrystalline cellulose (NCC) with cationic surfactant of cetyltriammonium bromide (CTAB) and further decorated with 3-mercaptopropionic acid (3-MPA) capped CdS QDs. The nanocomposite material was then employed as scaffold for immobilization of tyrosinase enzyme (Tyr). The electrocatalytic response of Tyr/CTAB-NCC/QDs nanocomposite towards phenol was evaluated using differential pulse voltammetry (DPV). The current response obtained is proportional to the concentration of phenol which attributed to the reduction of o-quinone produced at the surface of the modified electrode. Under the optimal conditions, the biosensor exhibits good linearity towards phenol in the concentration range of 5-40 μM (R2 = 0.9904) with sensitivity and limit of detection (LOD) of 0.078 μA/μM and 0.082 μM, respectively.
    Matched MeSH terms: Spectrometry, Fluorescence
  12. Supramolecular interaction of 6-shogaol, a therapeutic agent of Zingiber officinale with human serum albumin as elucidated by spectroscopic, calorimetric and molecular docking methods
    Feroz SR, Mohamad SB, Lee GS, Malek SN, Tayyab S
    Phytomedicine, 2015 Jun 01;22(6):621-30.
    PMID: 26055127 DOI: 10.1016/j.phymed.2015.03.016
    BACKGROUND: 6-Shogaol, one of the main bioactive constituents of Zingiber officinale has been shown to possess various therapeutic properties. Interaction of a therapeutic compound with plasma proteins greatly affects its pharmacokinetic and pharmacodynamic properties.

    PURPOSE: The present investigation was undertaken to characterize the interaction between 6-shogaol and the main in vivo transporter, human serum albumin (HSA).

    METHODS: Various binding characteristics of 6-shogaol-HSA interaction were studied using fluorescence spectroscopy. Thermal stability of 6-shogaol-HSA system was determined by circular dichroism (CD) and differential scanning calorimetric (DSC) techniques. Identification of the 6-shogaol binding site on HSA was made by competitive drug displacement and molecular docking experiments.

    RESULTS: Fluorescence quench titration results revealed the association constant, Ka of 6-shogaol-HSA interaction as 6.29 ± 0.33 × 10(4) M(-1) at 25 ºC. Values of the enthalpy change (-11.76 kJ mol(-1)) and the entropy change (52.52 J mol(-1) K(-1)), obtained for the binding reaction suggested involvement of hydrophobic and van der Waals forces along with hydrogen bonds in the complex formation. Higher thermal stability of HSA was noticed in the presence of 6-shogaol, as revealed by DSC and thermal denaturation profiles. Competitive ligand displacement experiments along with molecular docking results suggested the binding preference of 6-shogaol for Sudlow's site I of HSA.

    CONCLUSION: All these results suggest that 6-shogaol binds to Sudlow's site I of HSA through moderate binding affinity and involves hydrophobic and van der Waals forces along with hydrogen bonds.

    Matched MeSH terms: Spectrometry, Fluorescence
  13. Predicting the fluorescent enhancement rate by gold and silver nanospheres using finite-difference time-domain analysis
    Centeno A, Xie F, Alford N
    IET Nanobiotechnol, 2013 Jun;7(2):50-8.
    PMID: 24046905
    Metal-induced fluorescence enhancement (MIFE) is a promising strategy for increasing the sensitivity of fluorophores used in biological sensors. This study uses the finite-difference time-domain technique to predict the fluorescent enhancement rate of a fluorophore molecule in close proximity to a gold or silver spherical nanoparticle. By considering commercially available fluorescent dyes the computed results are compared with the published experimental data. The results show that MIFE is a complex coupling process between the fluorophore molecule and the metal nanoparticle. Nevertheless using computational electromagnetic techniques to perform calculations it is possible to calculate, with reasonable accuracy, the fluorescent enhancement. Using this methodology it will be possible to consider different shaped metal nanoparticles and any supporting substrate material in the future, an important step in building reliable biosensors capable of detecting low levels of proteins tagged with fluorescence molecules.
    Matched MeSH terms: Spectrometry, Fluorescence
  14. Optimization and validation of a HPLC method for simultaneous determination of aflatoxin B1, B2, G1, G2, ochratoxin A and zearalenone using an experimental design
    Rahmani A, Selamat J, Soleimany F
    Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2011;28(7):902-12.
    PMID: 21598138 DOI: 10.1080/19440049.2011.576436
    A reversed-phase HPLC optimization strategy is presented for investigating the separation and retention behavior of aflatoxin B1, B2, G1, G2, ochratoxin A and zearalenone, simultaneously. A fractional factorial design (FFD) was used to screen the significance effect of seven independent variables on chromatographic responses. The independent variables used were: (X1) column oven temperature (20-40°C), (X2) flow rate (0.8-1.2 ml/min), (X3) acid concentration in aqueous phase (0-2%), (X4) organic solvent percentage at the beginning (40-50%), and (X5) at the end (50-60%) of the gradient mobile phase, as well as (X6) ratio of methanol/acetonitrile at the beginning (1-4) and (X7) at the end (0-1) of gradient mobile phase. Responses of chromatographic analysis were resolution of mycotoxin peaks and HPLC run time. A central composite design (CCD) using response surface methodology (RSM) was then carried out for optimization of the most significant factors by multiple regression models for response variables. The proposed optimal method using 40°C oven temperature, 1 ml/min flow rate, 0.1% acetic acid concentration in aqueous phase, 41% organic phase (beginning), 60% organic phase (end), 1.92 ratio of methanol to acetonitrile (beginning) and 0.2 ratio (end) for X1-X7, respectively, showed good prediction ability between the experimental data and predictive values throughout the studied parameter space. Finally, the optimized method was validated by measuring the linearity, sensitivity, accuracy and precision parameters, and has been applied successfully to the analysis of spiked cereal samples.
    Matched MeSH terms: Spectrometry, Fluorescence
  15. Simultaneous detection of 12 mycotoxins in cereals using RP-HPLC-PDA-FLD with PHRED and a post-column derivatization system
    Soleimany F, Jinap S, Rahmani A, Khatib A
    Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2011 Apr;28(4):494-501.
    PMID: 21337232 DOI: 10.1080/19440049.2010.551547
    A new method for the simultaneous quantification of 12 mycotoxins was developed and optimized using reverse phase high performance liquid chromatography (RP-HPLC) with a photodiode array (PDA) and fluorescence detector (FLD), a photochemical reactor for enhanced detection (PHRED) and post-column derivatization. The mycotoxins included aflatoxins (AFB(1), AFB(2), AFG(1), and AFG(2)), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisins (FB(1), FB(2), and FB(3)), T-2 and HT-2 toxins. A double sample extraction with a phosphate-buffered saline solution (PBS) and methanol was used for co-extraction of mycotoxins, and a multifunctional immunoaffinity column was used for cleanup. Optimum conditions for separation of the mycotoxins were obtained to separate 12 mycotoxins in FLD and PDA chromatograms with a high resolution. The method gave recoveries in the range 72-111% when applied to spiked corn samples. The limits of detection (LOD) were 0.025 ng/g for AFB(1) and AFG(1), 0.012 ng/g for AFB(2) and AFG(2), 0.2 ng/g for OTA, 1.5 ng/g for ZEA, 6.2 ng/g for FB(1), FB(3) and HT-2 toxin, 9.4 ng/g for FB(2) and T-2 toxin, and 18.7 ng/g for DON. In addition, the limits of quantification (LOQ) ranged from 0.04 ng/g for AFB(2) and AFG(2) to 62 ng/g for DON. The method was successfully applied to the determination of these mycotoxins in 45 cereal samples obtained from the Malaysian market. The results indicated that the method can be applied for the multi-mycotoxin determination of cereals.
    Matched MeSH terms: Spectrometry, Fluorescence
  16. 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: Spectrometry, Fluorescence
  17. Molten globule-triggered inactivation of a thermostable and solvent stable lipase in hydrophilic solvents
    Hamid TH, Rahman RN, Salleh AB, Basri M
    Protein J, 2010 May;29(4):290-7.
    PMID: 20509044 DOI: 10.1007/s10930-010-9251-7
    The use of lipase in hydrophilic solvent is usually hampered by inactivation. The solvent stability of a recombinant solvent stable lipase isolated from thermostable Bacillus sp. strain 42 (Lip 42), in DMSO and methanol were studied at different solvent-water compositions. The enzymatic activities were retained in up to 45% v/v solvent compositions. The near-UV CD spectra indicated that tertiary structures were perturbed at 60% v/v and above. Far-UV CD in methanol indicated the secondary structure in Lip 42 was retained throughout all solvent compositions. Fluorescence studies indicated formations of molten globules in solvent compositions of 60% v/v and above. The enzyme was able to retain its secondary structures in the presence of methanol; however, there was a general reduction in beta-sheet and an increase in alpha-helix contents. The H-bonding arrangements triggered in methanol and DMSO, respectively, caused different forms of tertiary structure perturbations on Lip 42, despite both showing partial denaturation with molten globule formations.
    Matched MeSH terms: Spectrometry, Fluorescence
  18. Factors affecting nucleolytic efficiency of some ternary metal complexes with DNA binding and recognition domains. Crystal and molecular structure of Zn(phen)(edda)
    Seng HL, Ong HK, Rahman RN, Yamin BM, Tiekink ER, Tan KW, et al.
    J Inorg Biochem, 2008 Nov;102(11):1997-2011.
    PMID: 18778856 DOI: 10.1016/j.jinorgbio.2008.07.015
    The binding selectivity of the M(phen)(edda) (M=Cu, Co, Ni, Zn; phen=1,10-phenanthroline, edda=ethylenediaminediacetic acid) complexes towards ds(CG)(6), ds(AT)(6) and ds(CGCGAATTCGCG) B-form oligonucleotide duplexes were studied by CD spectroscopy and molecular modeling. The binding mode is intercalation and there is selectivity towards AT-sequence and stacking preference for A/A parallel or diagonal adjacent base steps in their intercalation. The nucleolytic properties of these complexes were investigated and the factors affecting the extent of cleavage were determined to be: concentration of complex, the nature of metal(II) ion, type of buffer, pH of buffer, incubation time, incubation temperature, and the presence of hydrogen peroxide or ascorbic acid as exogenous reagents. The fluorescence property of these complexes and its origin were also investigated. The crystal structure of the Zn(phen)(edda) complex is reported in which the zinc atom displays a distorted trans-N(4)O(2) octahedral geometry; the crystal packing features double layers of complex molecules held together by extensive hydrogen bonding that inter-digitate with adjacent double layers via pi...pi interactions between 1,10-phenanthroline residues. The structure is compared with that of the recently described copper(II) analogue and, with the latter, included in molecular modeling.
    Matched MeSH terms: Spectrometry, Fluorescence
  19. Comprehensive spectroscopic studies of synergism between Gadong starch based carbon dots and bovine serum albumin
    Sonthanasamy RSA, Sulaiman NMN, Tan LL, Lazim AM
    Spectrochim Acta A Mol Biomol Spectrosc, 2019 Jul 05;218:85-96.
    PMID: 30954801 DOI: 10.1016/j.saa.2019.03.108
    Carbon dots (C-dots) were used to study the binding mechanisms with serum protein, bovine serum albumin (BSA) by using two notable binding systems known as non-covalent and covalent interaction. Interaction between C-dots and BSA were estimated by Stern-Volmer equation and Double Log Regression Model (DLRM). According to the fluorescent intensity, quenching of model carrier protein by C-dots was due to dynamic quenching for non-covalent and static quenching for covalent binding. The binding site constant, KA and number of binding site, for covalent interaction is 1754.7L/mol and n≈1 (0.6922) were determined by DLRM on fluorescence quenching results. The blue shift of the fluorescence spectrum, from 450nm to 421nm (non-covalent) and 430nm (covalent) and suggested that both the microenvironment of C-dots and protein changed in relation to the protein concentration. The fluorescence intensity results show that protein structure has a significant role in Protein-C-dots interactions and type of binding influence physicochemical properties of C-dots differently. Understanding to this bio interface is important to utilize both quantum dots and biomolecules for biomedical field. It can be a useful guideline to design further applications in biomedical and bioimaging.
    Matched MeSH terms: Spectrometry, Fluorescence
  20. Dengue envelope domain III-peptide binding analysis via tryptophan fluorescence quenching assay
    Baharuddin A, Amir Hassan A, Othman R, Xu Y, Huang M, Ario Tejo B, et al.
    Chem Pharm Bull (Tokyo), 2014;62(10):947-55.
    PMID: 25273053
    In the efforts to find an anti-viral treatment for dengue, a simple tryptophan fluorescence-screening assay aimed at identifying dengue domain III envelope (EIII) protein inhibitors was developed. Residue Trp391 of EIII was used as an intrinsic probe to monitor the change in fluorescence of the tryptophan residue upon binding to a peptide. The analysis was based on the electron excitation at 280 nm and fluorescence emission at 300-400 nm of EIII, followed by quenching of fluorescence in the presence of potential peptidic inhibitors coded DS36wt, DS36opt, DN58wt and DN58opt. The present study found that the fluorescence of the recombinant EIII was quenched following the binding of DS36opt, DN58wt and DN58opt in a concentration-dependent manner. Since the λmax for emission remained unchanged, the effect was not due to a change in the environment of the tryptophan side chain. In contrast, a minimal fluorescence-quenching effect of DS36wt at 20 and 40 µM suggested that the DS36wt does not have any binding ability to EIII. This was supported by a simple native-page gel retardation assay that showed a band shift of EIII domain when incubated with DS36opt, DN58wt and DN58opt but not with DS36wt. We thus developed a low-cost and convenient spectrophotometric binding assay for the analysis of EIII-peptide interactions in a drug screening application.
    Matched MeSH terms: Spectrometry, Fluorescence
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