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Links between peptides and Mn oxide: nano-sized manganese oxide embedded in a peptide matrix
Najafpour, Mohammad Mahdi,Madadkhani, Sepideh,Akbarian, Somayyeh,Zand, Zahra,Hołyń,ska, Małgorzata,Kompany-Zareh, Mohsen,Tatsuya, Tomo,Singh, Jitendra Pal,Chae, Keun Hwa,Allakhverdiev, Suleyman I The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.12
<P>Herein we report on a poly-peptide/Mn oxide nanocomposite as a model for the water-oxidizing catalyst in Photosystem II. The material is obtained by the reaction of poly-l-tyrosine, Mn(OAc)2·4H2O and KMnO4. HRTEM images of the nanocomposite indicate the presence of nanoparticles dispersed in a poly-l-tyrosine matrix with no crystalline phases. A broad peak at ∼400-550 nm in the UV-visible spectrum is related to Mn oxide formation. X-ray absorption studies suggest that the Mn atoms are in the oxidation state of +IV and a coordination number of around three was obtained for Mn in the structure. The water-oxidizing activity of the material under electrochemical conditions was also investigated. Electrochemical experiments proved the presence of Mn(iv) oxide. Determination of oxygen coupled to electrochemistry revealed the role of poly-l-tyrosine in decreasing the overpotential for water oxidation. In the next step, the interaction of the nanocomposite and imidazole as a model for the tyrosine 161 and histidine 190 residues in Photosystem II was studied with fluorescence spectroscopy using the multivariate curve resolution-alternating least squares method.</P>
Najafpour, Mohammad Mahdi,Ghobadi, Mohadeseh Zarei,Hosseini, Seyedeh Maedeh,Chae, Keun Hwa,Mehrabani, Somayeh,Rafighi, Parvin,Bagheri, Robabeh,Song, Zhenlun Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.22
<P><B>Abstract</B></P> <P>Water oxidation is a bottleneck of the hydrogen production through the water-splitting reaction. Herein, the promising role of fluoride on the water-oxidizing activity of a nanolayered Mn oxide under the electrochemical condition is reported. The experiments show the increase of the water-oxidizing activity of the nanolayered Mn oxide under an electro-water oxidation circumstance in the presence of potassium fluoride as a promising additive to an electrolyte. As a result, the required overpotential is decreased and the yield of oxygen evolution raised in the water-oxidation reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen production by water splitting is a promising way to store sustainable energies. </LI> <LI> Mn oxide is promising to be used in water splitting systems. </LI> <LI> The effect of fluoride on water-oxidizing activity of nanolayered Mn oxide was reported. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Herein, the promising role of fluoride on the water-oxidizing activity of a nanolayered Mn oxide under the electrochemical condition is reported.</P> <P>[DISPLAY OMISSION]</P>
Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.
Najafpour, Mohammad Mahdi,Moghaddam, Atefeh Nemati,Yang, Young Nam,Aro, Eva-Mari,Carpentier, Robert,Eaton-Rye, Julian J,Lee, Choon-Hwan,Allakhverdiev, Suleyman I W. Junk ; Kluwer Academic Publishers 2012 Photosynthesis research Vol.114 No.1
<P>The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster.</P>
A new strategy to make an artificial enzyme: photosystem II around nanosized manganese oxide
Najafpour, Mohammad Mahdi,Madadkhani, Sepideh,Akbarian, Somayyeh,Hołyń,ska, Małgorzata,Kompany-Zareh, Mohsen,Tomo, Tatsuya,Singh, Jitendra Pal,Chae, Keun Hwa,Allakhverdiev, Suleyman I. The Royal Society of Chemistry 2017 Catalysis Science & Technology Vol.7 No.19
<▼1><P>A new strategy to make an artificial enzyme was reported.</P></▼1><▼2><P>Herein we report a new strategy to disperse Mn oxide into the apoenzyme of photosystem II. The compound was characterized by scanning electron microscopy, transmission electron microscopy, UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray diffraction and some electrochemical methods. Under electrochemical conditions, the peaks attributed to Mn(ii)/(iii), Mn(iii)/(iv) and Mn(ii)/(iv) were assigned and compared with other manganese oxides. Linear sweep voltammetry shows that water electro-oxidation occurs at 80 mV less than that for the apoenzyme of photosystem II. Thus, Mn oxide maintains its water-oxidizing activity under these conditions. The compound is a new type of structural and functional model for the water-oxidizing complex in photosystem II.</P></▼2>
Ghasem Najafpour Darzi,Pouya Sirous Rezaei,Hoda Shafaghat 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.3
A high performance thermostable α-amylase at low pH values has been synthesized. Sugarcane bagasse was hydrolyzed in a dilute acid solution and utilized as carbon source for the growth of Aspergillus niger strain NCIM 548. Glucose, xylose and arabinose with the ratio of 1.0 : 0.9 : 0.3 (w/w/w) were detected in the hydrolyzate by HPLC analysis. Optimization of the fermentation conditions for α-amylase production was performed by varying four influential parameters such as Sugarcane bagasse hydrolyzate (SBH), NH4Cl, pH and incubation time using a central composite design (CCD) under response surface methodology (RSM). The optimum values of SBH, NH4Cl, pH and incubation time were 20.49, 2.34 g/l, 5.65 and 76.67 h, respectively. The acido-thermophilic enzyme showed maximum stability at 70 oC and pH value of 4. The rate constant, Km and maximum reaction rate, Vmax were 18.79 g/l and 15.85 g/l·min,respectively.
Heidari, Sima,Najafpour, Mohammad Mahdi,Hołyń,ska, Małgorzata,Singh, Jitendra Pal,Chae, Keun Hwa,Khatamian, Masoumeh The Royal Society of Chemistry 2018 Dalton transactions Vol.47 No.5
<P>For the first time, using scanning electron microscopy, transmission electron microscopy, X-ray absorption near edge structure and extended X-ray absorption fine structure X-ray diffraction, it is showed that MnCO3, MnWO4, Mn3(PO4)2·3H2O, MnS and Mn(VO3)2·<I>x</I>H2O under the water-oxidation conditions and in the presence of cerium(iv) ammonium nitrate, are converted to Mn oxide without a high-range order. A mechanism is proposed for such conversion and as Mn oxide is an efficient water-oxidizing catalyst, it is thus a candidate as a contributor to the observed catalytic activity.</P>
Removal of melanoidin from molasses spent wash using fly ash-clay adsorbents
Ali Ramezani,Ghasem Najafpour Darzi,Maedeh Mohammadi 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.4
Removal of melanoidin pigment from molasses spent wash was investigated using a new adsorbent. Solid adsorbents were fabricated from charcoal fly ash and clay. The effect of various molasses concentration (6 to 12 g/l)on removal efficiency was studied. The obtained results revealed that maximum removal efficiency of 82% was achieved at the molasses concentration of 6 g/l and contact time of 7 h. The saturated porous adsorbents were regenerated and reused to conduct similar experiments. The achieved data showed that more than 90% of the capacity of the fresh adsorbent was recovered after regeneration. Various adsorption isotherms of Langmuir, Freundlich, Temkin and Harkins-Jura were applied to interpret the obtained experimental data. The obtained results revealed that the sorption data were well described by the Harkins-Jura model. Also, various kinetic models of pseudo-first order, pseudo-second order,Elovich and intra-particle diffusion were used to predict the characteristic parameters which are useful in process design. It was concluded that the best fit was obtained with pseudo-second order kinetic model at low molasses concentrations.
Manganese ferrite (MnFe2O4) Nanoparticles: From synthesis to application -A review
Neda Akhlaghi,Ghasem Najafpour Darzi 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.103 No.-
Manganese ferrite (MnFe2O4) nanoparticle, a spinel ferrite nanomaterial, is one of the important magneticmetal oxide nanoparticles with distinctive physical and chemical properties. This nanoparticlecan be easily synthesized through various methods with controllable size and desired morphology. MnFe2O4 is an efficient candidate for various applications like biomedical, analytical, and storage devices. In this review, several synthesis methods and physicochemical properties of MnFe2O4 nanoparticles arediscussed. Then, a comprehensive overview of the latest and most promising researches on massiveapplications of MnFe2O4-based nanostructures, including hyperthermia cancer therapy, magnetic resonanceimaging (MRI), energy conversion and storage devices like Lithium-ion batteries and supercapacitors,as well as catalytic activities, sensors, hydrogen production, heavy metal removal, and drug deliveryare presented. Overall, herein, a deep understanding of the unlimited ability of MnFe2O4 nanoparticles indiverse applications is provided.