Ejaz Ahmad

Publications (25) View all

• Article: At very low concentrations known chaotropes act as kosmotropes for the N and B isoforms of human serum albumin.

  Priyankar Sen, Mohd Moin Khan, Asif Equbal, Ejaz Ahmad, Rizwan Hasan Khan
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  ABSTRACT: Very few studies have been done to understand the effect of millimolar concentrations of chaotropes on protein structure. In our previous study we observed that the secondary and tertiary structure of human serum albumin (HSA) increases in the presence of 5 mmol/L urea. Micelle formation in amphoteric detergents increases in the presence of equivalent concentrations of urea. Here, we observed a significant increase in the secondary and tertiary structure of HSA. Interestingly, guanidine hydrochloride, another chaotropic agent, also shows a similar effect. Our results show electrostatic interaction may play a role in neutral to basic transition in HSA. This study further supports the claim that at millimolar concentrations the chaotropes may act as kosmotropes for proteins.
  Biochemistry and Cell Biology 04/2013; 91(2):72-8. · 2.67 Impact Factor
• Source

  Available from: Nida Zaidi

  Article: Biophysical insight into furosemide binding to human serum albumin: a study to unveil its impaired albumin binding in uremia.

  Nida Zaidi, Ejaz Ahmad, Mohd Rehan, Gulam Rabbani, Mohammad R Ajmal, Yusra Zaidi, Naidu Subbarao, Rizwan H Khan
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  ABSTRACT: Exogenous substances like drugs, when absorbed, enter into the circulatory system and bind reversibly and extensively to human serum albumin (HSA). But transport of various drugs like a diuretic, furosemide (FUR), via albumin in uremia is seriously compromised due to accumulation of uremic toxins. The reason behind it is explored by investigating the binding mechanism of FUR to HSA. Isothermal titration calorimetry results show that FUR binds with HSA at high (K ∼ 10) and low affinity (K ∼ 10) sites whereas spectroscopic results predict binding at a single site (K ∼ 10). Thermodynamic analysis shows that the HSA-FUR complex formation occurs via hydrogen bonds and hydrophobic interactions and undergoes slight structural changes, as evident by FTIR and far-UV CD. Further, the lifetime of HSA decreases only marginally and thus the magnitude of energy transfer efficiency is small, as obtained by time-resolved measurements. A displacement experiment predicts that the FUR binds mainly to site I but a new site having lower affinity is also observed, which shares some residues with site II as supported by molecular docking results. Results revealed that in uremia, FUR indirectly competes for Arg410, Lys414, and Ser489 with site II bound uremic toxins and directly competes for site I with site I bound uremic toxins.
  The Journal of Physical Chemistry B 03/2013; 117(9):2595-604. · 3.70 Impact Factor
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  Available from: Arham Shareef Ahmed

  Article: Antibacterial and Cytotoxic Efficacy of Extracellular Silver Nanoparticles Biofabricated from Chromium Reducing Novel OS4 Strain of Stenotrophomonas maltophilia.

  Mohammad Oves, Mohammad Saghir Khan, Almas Zaidi, Arham S Ahmed, Faheem Ahmed, Ejaz Ahmad, Asif Sherwani, Mohammad Owais, Ameer Azam
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  ABSTRACT: Biofabricated metal nanoparticles are generally biocompatible, inexpensive, and ecofriendly, therefore, are used preferably in industries, medical and material science research. Considering the importance of biofabricated materials, we isolated, characterized and identified a novel bacterial strain OS4 of Stenotrophomonas maltophilia (GenBank: JN247637.1). At neutral pH, this Gram negative bacterial strain significantly reduced hexavalent chromium, an important heavy metal contaminant found in the tannery effluents and minings. Subsequently, even at room temperature the supernatant of log phase grown culture of strain OS4 also reduced silver nitrate (AgNO3) to generate nanoparticles (AgNPs). These AgNPs were further characterized by UV-visible, Nanophox particle size analyzer, XRD, SEM and FTIR. As evident from the FTIR data, plausibly the protein components of supernatant caused the reduction of AgNO3. The cuboid and homogenous AgNPs showed a characteristic UV-visible peak at 428 nm with average size of ∼93 nm. The XRD spectra exhibited the characteristic Bragg peaks of 111, 200, 220 and 311 facets of the face centred cubic symmetry of nanoparticles suggesting that these nanoparticles were crystalline in nature. From the nanoparticle release kinetics data, the rapid release of AgNPs was correlated with the particle size and increasing surface area of the nanoparticles. A highly significant antimicrobial activity against medically important bacteria by the biofabricated AgNPs was also revealed as decline in growth of Staphylococcus aureus (91%), Escherichia coli (69%) and Serratia marcescens (66%) substantially. Additionally, different cytotoxic assays showed no toxicity of AgNPs to liver function, RBCs, splenocytes and HeLa cells, hence these particles were safe to use. Therefore, this novel bacterial strain OS4 is likely to provide broad spectrum benefits for curing chromium polluted sites, for biofabrication of AgNPs and ultimately in the nanoparticle based drug formulation for the treatment of infectious diseases.
  PLoS ONE 01/2013; 8(3):e59140. · 4.09 Impact Factor
• Article: Monomeric Banana Lectin at Acidic pH Overrules Conformational Stability of Its Native Dimeric Form.

  Javed M Khan, Atiyatul Qadeer, Ejaz Ahmad, Raghib Ashraf, Bharat Bhushan, Sumit K Chaturvedi, Gulam Rabbani, Rizwan H Khan
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  ABSTRACT: Banana lectin (BL) is a homodimeric protein categorized among jacalin-related family of lectins. The effect of acidic pH was examined on conformational stability of BL by using circular dichroism, intrinsic fluorescence, 1-anilino-8-napthalene sulfonate (ANS) binding, size exclusion chromatography (SEC) and dynamic light scattering (DLS). During acid denaturation of BL, the monomerization of native dimeric protein was found at pH 2.0. The elution profile from SEC showed two different peaks (59.65 ml & 87.98 ml) at pH 2.0 while single peak (61.45 ml) at pH 7.4. The hydrodynamic radii (R h) of native BL was 2.9 nm while at pH 2.0 two species were found with R h of 1.7 and 3.7 nm. Furthermore at, pH 2.0 the secondary structures of BL remained unaltered while tertiary structure was significantly disrupted with the exposure of hydrophobic clusters confirming the existence of molten globule like state. The unfolding of BL with different subunit status was further evaluated by urea and temperature mediated denaturation to check their stability. As inferred from high Cm and ΔG values, the monomeric form of BL offers more resistance towards chemical denaturation than the native dimeric form. Besides, dimeric BL exhibited a Tm of 77°C while no loss in secondary structures was observed in monomers even up to 95°C. To the best of our knowledge, this is the first report on monomeric subunit of lectins showing more stability against denaturants than its native dimeric state.
  PLoS ONE 01/2013; 8(4):e62428. · 4.09 Impact Factor
• Source

  Available from: Ejaz Ahmad

  Dataset: Revisiting ligand-induced conformational changes in proteins: essence, advancements, implications and future challenges.

  Ejaz Ahmad, Gulam Rabbani, Nida Zaidi, Mohammad Azam Khan, Atiyatul Qadeer, Mohd Ishtikhar, Saurabh Singh, Rizwan Hasan Khan