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Nickel-Impregnated Silica Nanoparticle Synthesis and Their Evaluation for Biocatalyst Immobilization
Reddy Shetty Prakasham G. Sarala Devi Chaganti Subba Rao V. S. S. Sivakumar T. Sathish P. N. Sarma 《Applied biochemistry and biotechnology》2010,160(7):1888-1895
In the present investigation, impact of nickel-impregnated silica paramagnetic particles (NSP) as biocatalyst immobilization
matrices was investigated. These nanoparticles were synthesized by sol–gel route using a nonionic surfactant block co polymer
[poly (ethylene glycol)-block-poly-(propylene glycol)-block-poly (ethylene glycol)]. Diastase enzyme was immobilized on these particles (enzyme-impregnated NSP) as model enzyme and
characterized using Fourier-transform infrared spectroscopy and X-ray crystallography. Analysis of enzyme-binding nature with
these nanoparticles at different physiological conditions revealed that binding pattern and activity profile varied with the
pH of the reaction mixture. The immobilized enzyme was further characterized for its biocatalytic activity with respect to
kinetic properties such as Km and Vmax and compared with free enzyme. Paramagnetic nanoparticle-immobilized enzyme showed
more affinity for substrate compared to free one. The nature of silica and nickel varied from amorphous to crystalline nature
and vice versa upon immobilization of enzyme. To the best of our knowledge, this is the first report of its kind for change
of nature from one form to other under normal temperatures upon diastase interaction with NSP. 相似文献
146.
P. Poornesh Pramod K. Hegde M.G. Manjunatha A.V. Adhikari 《Optics & Laser Technology》2010,42(1):230-989
An experimental investigation of the third-order nonlinear optical properties of new poly{2-{5-[3,4-ditetradecyloxy-5-(1,3,4-oxadiazol-2-yl)thiophen-2-yl]-1,3,4-oxadiazol-2-yl}pyridine} (P) in tetrahydrofuran (THF) solution and in solid poly(methylmethacrylate) (PMMA) matrix, by Z-scan technique is reported. The Z-scan traces reveal that the composite films exhibit large negative nonlinear refractive index of the order 10−10 esu. The excited-state absorption cross-section was found to be larger than the ground-state absorption indicating that the operating nonlinear process is reverse saturable absorption (RSA). The new polymer P exhibits good optical power limiting properties in the nanosecond regime in solution and as well in solid PMMA matrix. 相似文献
147.
Vivekananda Shetty Thomas A. Neubert 《Journal of the American Society for Mass Spectrometry》2009,20(8):1540-1548
We investigated the formation of hydroxyl radical (OH·) and H2O2 mediated oxidation products of a synthetic peptide, HCSAGIGRS, which is an active site sequence motif of protein tyrosine
phosphatase 1B (PTP1B). We determined that a novel cysteine sulfinamide HC[S(O)N]SAGIGRS is produced in the oxidation reaction
by Fenton reagents (Fe+2/H2O2) as well as by H2O2. These products were characterized by tandem mass spectrometry experiments on both singly and doubly charged precursor ions.
MS3 experiments using an ion trap instrument as well as LC-MS/MS experiments using a quadrupole time-of-flight (Q-TOF) instrument
demonstrated that HC[S(O)N]SAGIGRS is not a water loss product of cysteine sulfinic acid [HC(SO2H)SAGIGRS]. We also obtained data from tandem mass spectrometry experiments that provided evidence for the existence of stable
cysteine sulfenic acid [HC(SOH)SAGIGRS] in solution. A mechanism for the formation of the cysteine sulfinamide product is
proposed based on the above experimental results. The preparation and identification of cysteine sulfinamide in this study
may provide insight into the mechanism of both OH· and H2O2 induced oxidation reactions of protein tyrosine phosphatases. 相似文献
148.
Pramod G Prasanthkumar KP Mohan H Manoj VM Manoj P Suresh CH Aravindakumar CT 《The journal of physical chemistry. A》2006,110(40):11517-11526
Pulse radiolysis and density functional theory (DFT) calculations at B3LYP/6-31+G(d,p) level have been carried out to probe the reaction of the water-derived hydroxyl radicals (*OH) with 5-azacytosine (5Ac) and 5-azacytidine (5Acyd) at near neutral and basic pH. A low percentage of nitrogen-centered oxidizing radicals, and a high percentage of non-oxidizing carbon-centered radicals were identified based on the reaction of transient intermediates with 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate), ABTS2-. Theoretical calculations suggests that the N3 atom in 5Ac is the most reactive center as it is the main contributor of HOMO, whereas C5 atom is the prime donor for the HOMO of cytosine (Cyt) where the major addition site is C5. The order of stability of the adduct species were found to be C6-OH_5Ac*>C4-OH_5Ac*>N3-OH_5Ac*>N5-OH_5Ac* both in the gaseous and solution phase (using the PCM model) respectively due to the additions of *OH at C6, C4, N3, and N5 atoms. These additions occur in direct manner, without the intervention of any precursor complex formation. The possibility of a 1,2-hydrogen shift from the C6 to N5 in the nitrogen-centered C6-OH_5Ac* radical is considered in order to account for the experimental observation of the high yield of non-oxidizing radicals, and found that such a conversion requires activation energy of about 32 kcal/mol, and hence this possibility is ruled out. The hydrogen abstraction reactions were assumed to occur from precursor complexes (hydrogen bonded complexes represented as S1, S2, S3, and S4) resulted from the electrostatic interactions of the lone pairs on the N3, N5, and O8 atoms with the incoming *OH radical. It was found that the conversion of these precursor complexes to their respective transition states has ample barrier heights, and it persists even when the effect of solvent is considered. It was also found that the formation of precursor complexes itself is highly endergonic in solution phase. Hence, the abstraction reactions will not occur in the present case. Finally, the time dependent density functional theory (TDDFT) calculations predicted an absorption maximum of 292 nm for the N3-OH_5Ac* adduct, which is close to the experimentally observed spectral maxima at 290 nm. Hence, it is assumed that the addition to the most reactive center N3, which results the N3-OH_5Ac* radical, occurs via a kinetically driven process. 相似文献
149.
150.
A phase-shifting piezo device commonly employed in phase-shifting interferometry exhibits a nonlinear response to applied voltage. Hence, a method for estimation of phase distribution in the presence of nonlinear phase steps is presented. The proposed method compensates for the harmonics present in the intensity fringe, allows the use of arbitrary phase-step values between 0 and tau rad, and does not impose constraints on the selection of particular phase-step values for minimizing nonlinearity and compensating for the harmonics. The comparison of the proposed method with other well-known benchmarking algorithms shows that our method is highly efficient and also works well in the presence of noise. 相似文献