Basis Of Absorbance Research Articles

BF3 detection by pyrazolo-pyridine based fluorescent probe and applications in bioimaging and paper strip analysis

A new pyrazolo[4,3-e] pyridine probe (MPDPP) was designed, synthesized and characterized for detecting BF3 species in semi-aqueous CH3CN-H2O (8:2, v/v) solution. Probe MPDPP showed a 33 nm longer wavelength in fluorescence emission after adding BF3 (from 440 to 473 nm). It was estimated that probe had an analytical limit of detection of 1.6 nM of BF3. The probe detects BF3 with good repeatability when alternating between BF3 and Et3N. On the basis of absorbance and fluorescence experiments, NMR titrations, and ESI-MS, a plausible binding mechanism has been proposed. Additionally, the probe has been successfully applied to the bio-imaging of BF3 in E.Coli and Hela cells and measurement of BF3 in real water samples.

Characterization of silver nano-particles synthesized using fenugreek leave extract and its antibacterial activity

In the present study silver nano-particles were synthesised by green synthesis method using fenugreek leaves extract, provides necessary bioactive for reduction of silver ions to silver nanoparticles. The sharp bands of silver nanoparticles were observed around 432 nm. Synthesis process was further optimized for pH, extraction temperature, Ag ion concentration, extract volume and extraction time on the basis of absorbance and average particles size respectively. FTIR analysis showed presence of corresponding peaks of O–H stretching and N–H amide groups. FESEM images revealed the structure and morphology of spherical AgNPs of average size 30 nm. The antibacterial activity of thus synthesized AgNPs was then tested against S. aureus, E. coli, P. aeruginosa and V. cholera and found synthesized AgNPs have higher inhibitory action against P. aeruginosa compared to other bacteria. The larger size of nano-particles is less active than smaller size of nano-particles due to small surface area.

Manufacturing process and optical properties of zinc oxide thin films as photoanode in DSSC

Purpose: It has been recently observed, that zinc oxide thin films are gaining much popularity, particularly in applications such as toxic gas sensors, photocatalytic materials and photovoltaic cells. Due to much better physical properties of ZnO compared to the ones of titanium dioxide (TiO2), which is currently the most used material in dye sensitized solar cells, efforts are being made to fabricate DSSCs with thin films and/or nanostructures, including nanowires, nanofibres and nanoparticles of zinc oxide. Design/methodology/approach: In this paper, zinc oxide thin films were prepared using sol-gel and spin coating methods from Zn(COO)2 x 2H2O dissolved in ethanol and acetic acid with ZnO monocrystalline nanoparticles of 0 and 10% (wt.) relative to the final concentration of produced solutions. The effect of calcination process on ZnO thin films at 600°C were examined using atomic force microscope to investigate the morphology of semiconductor coatings, infrared spectroscopy to prove the chemical structure of material. Besides, optical properties were analysed on the basis of absorbance in the function of wavelength spectra and the values of energy band gaps were studied. Findings: The topography analysis of ZnO thin films showed an increase in roughness with the increase of zinc oxide nanoparticles in the thin films material. In addition, the analysis of the optical properties of ZnO thin films showed a decrease in absorption level in the range of near-ultraviolet wavelength for the obtained layers after annealing. Research limitations/implications: It was found that ZnO thin films produced by spin coating and calcination method are a proper material for photoanode in dye-sensitized solar cells, as zinc oxide layers provide better conductivity across the photovoltaic cell. Practical implications: The results provide the possibility of production DSSCs with zinc oxide thin films as photoanode. Originality/value: The dye-sensitized solar cells based on zinc oxide photoanodes could be alternative semiconductor material to titanium dioxide, which is used in nowadays solar cells. It was estimated that ZnO, especially zinc oxide nanostructures have much better physical properties, than TiO2 structures. What is more, zinc oxide thin layers are characterized by the lower energy losses resulting from the physical properties of such nanostructures, which results in more efficient solar energy into electricity conversion.

Isolation and structural identification of glycopolymers of Bifidobacterium bifidum BIM B-733D as putative players in pathogenesis of autoimmune thyroid diseases.

Bifidobacterium bifidum 791 (commercially available as B. bifidum BIM B-733D) cell-surface biopolymers (BPs) interact selectively with human serum thyroid peroxidase (TPO) and thyroglobulin (Tg) autoantibodies (anti TPO and anti Tg, respectively). BPanti-TPO and BPanti-Tg were isolated from the soluble fraction of B. bifidum BIM B-733D by affinity chromatography with anti-TPO or anti-Tg, respectively. Homogeneity of affinity eluates (AEanti-TPO and AEanti-Tg) was tested by size exclusion chromatography. For each AE, the elution profiles generated on the basis of absorbance at 280 nm do not conform to ELISA data for functional activity characteristic of BPs. Moreover, high functional activity was detected in chromatographic fractions that had significantly different molecular weights and no absorbance at 280 nm, which suggests a non-protein (carbohydrate) nature of BPanti-TPO and BPanti-Tg. The semi-preparative size exclusion chromatography of AEanti-TPO and AEanti-Tg with detection by refractometer gave 5,000-7,000 Da fractions containing substances that interact selectively with either anti TPO (BPanti-TPO) or anti-Tg (BPanti-Tg) according to ELISA data. Analysis by two-dimensional NMR spectroscopy including a 1H, 13C-heteronuclear single-quantum coherence experiment indicated that both substances are linear α-1,6-glucans. For the first time, an immunological similarity (molecular mimicry) of glycopolymers of B. bifidum BIM B-733D and human thyroid proteins, TPO and Tg, was shown. On the whole, our data point to a possible role of bifidobacteria in the pathogenesis of autoimmune thyroid diseases (ATD). The main requirements for triggering/acceleration or prevention/abrogation of ATD by bifidobacteria through molecular mimicry mechanism are hypothesised to be (1) genetic predisposition to ATD and (2) intestinal epithelium penetration by α-1,6-glucan.

Identification and Quantitation of Newly Synthesized Proteins in Escherichia coli by Enrichment of Azidohomoalanine-labeled Peptides with Diagonal Chromatography

A method is presented to identify and quantify several hundreds of newly synthesized proteins in Escherichia coli upon pulse labeling cells with the methionine analogue azidohomoalanine (azhal). For the first 30 min after inoculation, a methionine-auxotrophic strain grows equally well on azhal as on methionine. Upon a pulse of 15 min and digestion of total protein, azhal-labeled peptides are isolated by a retention time shift between two reversed phase chromatographic runs. The retention time shift is induced by a reaction selective for the azido group in labeled peptides using tris(2-carboxyethyl)phosphine. Selectively modified peptides are identified by reversed phase liquid chromatography and on-line tandem mass spectrometry. We identified 527 proteins representative of all major Gene Ontology categories. Comparing the relative amounts of 344 proteins synthesized in 15 min upon a switch of growth temperature from 37 to 44 degrees C showed that nearly 20% increased or decreased more than 2-fold. Among the most up-regulated proteins many were chaperones and proteases in accordance with the cells response to unfolded proteins due to heat stress. Comparison of our data with results from previous microarray experiments revealed the importance of regulation of gene expression at the level of transcription of the most elevated proteins under heat shock conditions and enabled identification of several candidate genes whose expression may predominantly be regulated at the level of translation. This work demonstrates for the first time the use of a bioorthogonal amino acid for proteome-wide detection of changes in the amounts of proteins synthesized during a brief period upon variations in cellular growth conditions. Comparison of such data with relative mRNA levels enables assessment of the separate contributions of transcription and translation to the regulation of gene expression.

Spectroscopic Photovoltage Chracterization of PPV Thin Films Suitable for Pled Applications

AbstractWe have studied photovoltage spectra of PPV thin films using both conventional single layer LED structure (ITO/PPV/Al), and capacitive structure consisting of ITO/Mica/PPV/ITO films. The photovoltage spectra for both types of devices have sharp features and are identical indicating that the features observed are primarily due to PPV material itself. We observed two sharp peaks in the energy range of 2.5 -2.7 eV (i.e. above HOMO-LUMO gap) in photovoltage spectrum. The lineshape of the peaks strongly suggests that the peaks are most probably associated with photoionization of excitons. Temperature dependence of spectral lineshape of photocurrent peaks has been studied in the range of 80K-300K. The magnitudes of photocurrent peaks are weakly dependent on temperature, while other spectral features such as peak position and peak width are nearly independent of temperature. On the basis of absorbance, photovoltage and PL spectra, we conclude that both polarons and photoionization of excitons contribute to steady state photovoltage spectra.

Alternative procedure for the purification of the heat-stable enterotoxin of enterotoxigenic escherichia coli pathogenic for calves

A method for purification of the heat-stable enterotoxin (ST) of enterotoxigenic Escherichia coli (ETEC) strains (C1444 and B41) pathogenic for calves and some physiochemical properties of the ST are described. The method involved ultrafiltration on PM-10 and UM-2 Diaflo membranes, acetone fractionation, ion-exchange chromatography on AG 1-X2, chromatofocusing and a combination of hydrophobic interaction chromatography on octyl-Sepharose CL-4B and gel-permeation on Bio-Gel P-2. Polyacrylamide gel electrophoresis in sodium dodecyl sulphate of fluorescamine-labeled purified, reduced and alkylated ST preparations revealed a single band with approximate molecular masses of 2500 and 2200 for the C1444 and B41 STs, respectively. For the C1444 ST, the final purification achieved was approximately 27 000-fold on the basis of absorbance at 280 nm per mouse effective dose. However, it was 2000-fold when calculated on the basis of mg protein per effective dose (5 ng). Amino acid composition of the C1444 ST was found to be different from that of the B41 ST suggesting that the ST produced by bovine isolates may be heterogeneous in their structure.

Isoelectric focusing of long-acting thyroid stimulator immunoglobulin G.

Isoelectric focusing of long-acting thyroid stimulator immunoglobulin G [LATS-IgG] was used to determine the distribution of LATS activity among IgGs of various isoelectric points and to determine if isoelectric focusing techniques might yield LATS-IgG of increased biologic activity. LATS-IgG prepared from 16 LATS-positive sera was fractionated by isoelectric focusing [72 hr, 1200 V] using a 1% Ampholine solution, pH range 7.0 to 10.0. On the basis of absorbance at 280 nm, the effluent was gathered into 8 fractions. The 8 LATS-IgG subfractions and the parent IgG were tested in the same mouse bioassay. Following each of the 16 isoelectric focusing runs, maximal LATS activity was confined to one [6 instances] or two [10 instances] IgG subfractions [peak pi 8.99 ± 0.08 and 8.78 ± 0.09, respectively], with a 4- to 7-fold increase in LATS activity per mg protein compared to the parent IgG. However, of 12 LATS-negative Graves' disease IgGs submitted to isoelectric focusing, none of the IgG subfractions so deriv...