The oxidation rates and efficiency of the photocatalytic system are highly dependent on a number of operational parameters that govern the photodegradation of the organic molecule. Several study have been reported the significance of operational parameter. The photodegradation depends on the some basic parameters which are concentration of substrate, amount of photocatalyst, pH of the solution, temperature of reaction medium, time of irradiation of light, the intensity of light, surface area of photocatalyst, dissolve oxygen in the reaction medium, nature of the photocatalyst, nature of the substrate, doping of metal ions and non metal and structure of photocatalyst and substrate. The photodegradation of organic compound have been studied by the several scientists and conclude the optimum conditions for the photodegradation of organic compound.The photodegradation of organic compounds was found maximum at low concentration of organic substrate with optimum amount of photocatalyst. The pH of the solution is also affect the photodegradation of organic substrate. The Titania show the maximum adsorption at low pH hence the photodegradation also found maximum at low pH. The surface area is the crucial factor for the photodegradation of organic substrate. If we are increasing the surface area of photocatalyst, the photodegradation of organic substrate increase. This is because that the number of active site increased with increasing the surface area. The amount of photocatalyst is the primary requirement of any photocatalysis process. The amount of photocatalyst should be optimum, if we take the high amount of photocatalyst the photodegradation is decreased, if we take the low amount of photocatalyst the photodegradation also decreased. The doping of metal ions and non-metal ions affect the photodegradation of organic substrate. Therefore, we have to use the metal ions which increased the positive charge on the surface of photocatalyst. The temperature and irradiation of light also affect the photodegradation of organic substrate. For the maximum photodegradation, the photocatalytic reaction should perform at room temperature not greater than 80 °C. The light of irradiation should be used which exit the electron easily from valence band to conduction band or equal to band gap energy. Keywords: A Review on the Factors Affecting the Photocatalytic Degradation of Hazardous Materials 2/10Copyright: ©2017 Kumar et al. for the removal of pollutants at high concentrations. The biological treatments are very slow, dispose large amount of sludge and required strict control of proper pH and temperature [21]. In this regard photo catalytic processes have advantages for the removal of pollutants even at low concentration for industrial waste water [22]. Moreover in photo oxidation, complete oxidation of organic pollutants take place within few hours, even at ppb level, without formation of secondary hazardous products using highly active and cheap catalysts which can be used in specially design reactor systems [23].Ti...

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Studies on the structure-function relationship of transporters require the availability of sufficient amounts of the protein in a functional state. In this paper, we report the functional expression, purification, and reconstitution of the human sodium/d-glucose cotransporter1 (hSGLT1) in Pichia pastoris and ligand-induced conformational changes of hSGLT1 in solution as studied by intrinsic tryptophan fluorescence. hSGLT1 gene containing FLAG tag at position 574 was cloned into pPICZB plasmid, and the resulting expression vector pPICZB-hSGLT1 was introduced into P. pastoris strain GS115 by electroporation. Purification of recombinant hSGLT1 by nickel-affinity chromatography yields about 3 mg of purified recombinant hSGLT1 per 1-liter of cultured Pichia cells. Purified hSGLT1 migrates on SDS-PAGE with an apparent mass of 55 kDa. Kinetic analysis of hSGLT1 in proteoliposomes revealed sodium-dependent, secondary active, phlorizin-sensitive, and stereospecific alpha-methyl-d-glucopyranoside transport, demonstrating its full catalytic activity. The position of the maximum intrinsic tryptophan fluorescence and titration with hydrophilic collisional quenchers KI, acrylamide, and trichloroethanol suggested that most of Trps in hSGLT1 in solution are in a hydrophobic environment. In the presence of sodium, sugars that have been identified earlier as substrate for the transporter increase intrinsic fluorescence in a saturable manner by a maximum of 15%. alpha-Methyl-d-glucopyranoside had the highest affinity (K(d) = 0.71 mM), followed by d-glucose, d-galactose, d-mannose, and d-allose which showed a much lower affinity. l-Glucose was without effect. d-Glucose also increased the accessibility of the Trps to hydrophilic collisional quenchers. On the contrary phlorizin, the well-established inhibitor of SGLT1, decreased intrinsic fluorescence by a maximum of 50%, and induced a blue shift of maximum (5 nm). Again, the effects were sodium-dependent and saturable and a high affinity K(d) of 5 muM was observed. In addition the surface of hSGLT1 was labeled with 1-anilinonaphthalene-8-sulfonic acid, a reporter molecule for the surface hydrophobicity. In the presence of sodium, addition of d-glucose decreased ANS fluorescence whereas phlorizin increased ANS fluorescence. Thus three conformational states of SGLT1 could be defined which differ in their packing density and hydrophobicity of their surface. They reflect properties of the empty carrier, the d-glucose loaded carrier facing the outside of membrane and the complex of the outside-orientated carrier with phlorizin.

In order to gain a better understanding of the structure-function relation in hSGLT1, single Trp residues were introduced into a functional hSGLT1 mutant devoid of Trps at positions that previously had been postulated to be involved in sugar recognition/translocation and/or phlorizin binding. The mutant proteins were expressed in Pichia pastoris, purified, and reconstituted into liposomes. In transport experiments the putative sugar binding site mutants W457hSGLT1 and W460hSGLT1 showed a drastic decrease in affinity toward alpha-methyl-d-glucopyranoside with Km values of 13.3 and 5.26 mM compared to 0.4 mM of the Trp-less hSGLT1. In addition, a strong decrease in the inhibitory effect of phlorizin was observed. In Trp fluorescence studies the position of the emission maxima of the mutants, their sensitivity to N-bromosuccinimide oxidation, and their interaction with water soluble quenchers demonstrate that Trp457 and Trp460 are in contact with the hydrophilic extravesicular environment. In both mutants Trp fluorescence was quenched significantly, but differently, by various glucose analogues. They also show significant protection by d-glucose and phlorizin against acrylamide, KI, or TCE quenching. W602hSGLT1 and W609hSGLT1, the putative aglucone binding site mutants, exhibit normal sugar and phlorizin affinity, and show fluorescence properties which indicate that these residues are located in a very hydrophilic environment. Phlorizin and phloretin, but not d-glucose, protect both mutants against collisional quenchers. Depth-calculations using the parallax method suggest a location of Trp457 and Trp460 at an average distance of 10.8 A and 7.4 A from the center of the bilayer, while Trp602 and Trp609 are located outside the membrane. These results suggest that in the native carrier residues Gln at position 457 and Thr at position 460 reside in a hydrophilic access pathway extending 5-7 A into the membrane to which sugars as well as the sugar moiety of inhibitory glucosides bind. Residues Phe602 and Phe609 contribute by their hydrophobic aromatic residues toward binding of the aglucone part of phlorizin. Thereby in the phlorizin-carrier complex a close vicinity between these two subdomains of the transporter is established creating a phlorizin binding pocket with the previously estimated dimensions of 10 x 17 x 7 A.