Spectrophotometric Parameters Research Articles

Absorption spectra of nitroanilines in micellar solution-II

The absorption spectra of nitroanilines ( o-, m- and p-) in aqueous and nonaqueous solution of neutral surfactant-Triton X-100 (TX-100) reveal many interesting phenomena. Nitroanilines and TX-100 behave as electron acceptor and donor, respectively, in both media during charge-transfer (CT) complex formation though water plays an important role in aqueous media. The thermodynamic and spectrophotometric parameters of nitroanilines-TX-100 interactions in two media have been determined and the electron accepting capability among the nitroanilines have been also established. In addition to this, role of surface in CT interaction, the site of CT interaction, intensity and stability of CT interaction between nitroanilines and TX-100 have been pointed out.

Spectrophotometric parameters of conformational states of hemoglobin and its complexes with ligands in the sturgeons

Spectrophotometric parameters of conformational states of hemoglobin and its complexes with ligands in the sturgeons

Spectrophotometric parameters of conformational states of hemoglobin and its complexes with ligands in the sturgeons

Parameters of carbo-, carboxy-, oxy-, deoxy-, and methemoglobin of the human and four species of sturgeons (sterlet, Russian sturgeon, starred sturgeon, great sturgeon) were analyzed spectrophotometrically. It has been shown that in the absorption spectra of all forms of hemoglobins there is only one Soret γ1 band due to the prosthetic group of the pigment; the wavelength of this band is undoubtedly associated with the hemoglobin conformation. This permits the use of the band as an indicator parameter to control an initial state of the fish hemoglobin solutions, the analysis of conformational states of the pigment macromolecules, and the study of hemoglobin derivatives (its complexes with ligands).

Determination of biotreatability of a kraft pulp bleaching wastewater based on conventional and spectrophotometric parameters

The biological treatability of a pulp bleaching wastewater from a conventional Kraft pulp mill was investigated in batch activated sludge reactors. Substrate removal was followed in terms of the parameters COD and BOD5 and by the measurement of spectrophotometric changes. These measurements provided information on the specific pollutant groups that were removed during biodegradation. The nonbiodegradable fraction of these wastes was assessed as 30–40% of the initial wastewater COD. Sludge growth was negligibly small under the present substrate to bio‐mass ratios. Negligible changes in chloride levels during aeration were indicative that no deha‐logenation of chlorinated compounds occurred.

NMR Hydrogen Exchange of the OB-fold Protein LysN as a Function of Denaturant: The Most Conserved Elements of Structure are the Most Stable to Unfolding

The structure of LysN contains an OB-fold motif composed of a structurally conserved five-stranded β-barrel capped by a poorly conserved α-helix between strands β3 and β4. Two additional α-helices, unique to the LysN structure, flank the N terminus of the OB-fold. The stability of LysN to unfolding has been investigated with NMR native state hydrogen exchange measurements as a function of guanidinium hydrochloride concentration, and equilibrium unfolding transitions monitored by ellipticity at 222nm and fluorescence at 350nm. The spectrophotometric measurements suggest an apparent two-state unfolding transition with ΔGu(0)∼6kcal/mol andm ∼3kcal/(molM). By contrast, NMR hydrogen exchange measurements manifest a distribution of ΔGu(0) and m values which indicate that the protein can undergo subglobal unfolding. The largest ΔGu(0) values from hydrogen exchange are for residues in the β-sheet of the protein. These values, which reflect complete unfolding of the protein, are between 3 and 4kcal/mol higher than those obtained from circular dichroism or fluorescence. This discrepancy may be due to the comparison of NMR hydrogen exchange parameters measured at residue-level resolution, with spectrophotometric parameters that reflect an unresolved super position of unfolding transitions of the α-helices and β-strands. The largest ΔGu(0) values obtained from hydrogen exchange for the subset of residues in the α-helices of the protein, agree with the ΔGu(0) values obtained from circular dichroism or fluorescence. Based on the hydrogen exchange data, however, the three α-helices of LysN are on average 3kcal/mol less stable than the β-sheet. Consistent with the subglobal unfolding of LysN evinced by hydrogen exchange, a deletion mutant that lacks the first α-helix of the protein retains a cooperatively folded structure. Taken together with previous results on the OB-fold proteins SN and CspA, the present results for LysN suggest that the most conserved elements of structure in the OB-fold motif are the most resistant to denaturation. In all three proteins, stability to denaturation correlates with sequence hydrophobicity.

The ABCD system of melanoma detection

The ABCD (Asymmetry, Border, Color, and Dimension) criteria represent a commonly used clinical guide for the diagnosis of early melanoma. The authors revised these criteria in the light of objective measurements of the features of pigmented skin lesions obtained by telespectrophotometric analysis (TS) in the visible and near-infrared wavelengths. This study involves a consecutive series of 186 patients with 195 cutaneous pigmented lesions (53 melanomas and 142 nonmelanoma lesions). Each lesion was subjected to TS in vivo, before surgery. For this purpose, the authors used four spectrophotometric parameters that could be closely related to the four criteria of the ABCD guide, namely, roundness (an estimate of how a lesion contour resembles a circle), smoothness (an indicator of the regularity of a lesion border), mean reflectance (the ability of a lesion to diffuse or reflect the incident light), and size (the greatest dimension of a lesion). When melanomas and nonmelanoma lesions were compared by univariate analysis, all four spectrophotometric parameters considered proved to be significantly different (P=0.05). Multivariate logistic analysis showed that mean reflectance in the infrared (P < 0.01) and size (P=0.03) were parameters independently associated with melanoma. Melanoma showed lower reflectance and greater size than benign lesions. Information provided by TS substantially validates the importance of the ABCD clinical guide and suggests that color is the most important parameter in discriminating melanoma from nevi. In particular, melanoma appears darker than other pigmented lesions.

Evolution of the CIELAB and other spectrophotometric parameters during wine fermentation. Influence of some pre and postfermentative factors

The evolution of CIELAB and other color parameters has been studied during wine fermentation, as well as the influence of grape temperature on color extraction. In the postfermentative phase, two different fining treatments have been tested to check their influence on color parameters. Grape temperature affected color during the first days but at the end of alcoholic fermentation color characteristics of both wines were almost the same and they evolved similarly. Fining treatments influenced color slightly, while cold stabilization had more of an effect due to the precipitation of color pigments. Some correlations were found within the CIELAB parameters and between them and other color parameters.

Circumstellar material in the symbiotic binary V443 herculis

A quantitative model explaining a periodic wave-like variation in both the optical continuum and the emission line fluxes of the symbiotic binary V443 Her is presented. The model suggests that behaviour of spectrophotometric parameters is caused by a different projection of the circumstellar matter located mostly between the components of the binary, viewing the system at different orbital phases. Our model suggests that the inclination of the orbit is 18° (+12°, −3°) and the mass ratio of the cool to the hot component is 2(+1). It is shown that the previous interpretation in terms of a reflection effect is incorrect.

Potentiometric and spectrophotometric study of the acid-base equilibria of Cr(VI) at 25�C and different ionic strengths of aqueous KNO3

The hydrolysis of the chromate ion has been studied using a potentiometric-spectrophotometric automated titration system, titrating basic K2CrO4−KNO3 solutions with previously standarized HNO3−KNO3 solutions. The temperature was kept constant at 25°C and the ionic strengths were 0.5, 1.0 and 2.0 mol-dm−3. The resulting titration curves can be interpreted in terms of two equilibria involving the formation of HCrO 4 − (aq) and Cr2O 7 2− (aq). A spectrophotometric batch study was also carried out in order to obtain the thermodynamic constant for the HCrO 4 − (aq) formation as well as the spectrophotometric parameters at low ionic strengths. The proposed stoichiometric constants for the two reactions and the molar absorptivities for the three species at different wavelengths and ionic strengths are also given.

THE HII REGIONS OF THE SPIRAL GALAXY M101

ABSTRACT images of extragalactic H II regions has yielded new results for radial changes in spectrophotometric parameters. We identify a change in the radial oxygen abundance, with an apparent discontinuity at a radius of 5.5' as well as presenting evidence for an increase in the reddening of each region toward the center of the galaxy. A high-resolution overlay of the best radio data onto our optical imagery is included.

Measurements of some spectrophotometric parameters of curcumin in 12 polar and nonpolar organic solvents

Curcumin (Turmeric Yellow) dissolves in various polar and nonpolar organic solvents (Table 1) and gives sensitive and stable yellow to greenish-yellow (depending on the solvent) colors. λ max, molar absorptivity, durability, sensitivity, limit of detection, linearity, precision, and accuracy have been evaluated for each of the 12 curcumin-solvent nonaqueous systems.

Spectrophotometric Determination of Bromhexine Hydrochloride in Pharmaceutical Preparations

The presence of an aromatic primary amino group in bromhexine HCl enables the use of diazotization-coupling, according to the classic Bratton-Marshall method, for its analysis in pharmaceutical preparations. Spectrophotometric parameters were established for standardization of the method, including statistical analysis of data. Substances such as potassium guaiacolsulfonate, ampicillin, cephalexin, oxytetracycline HCl, amoxycillin, and erythromycin ethylsuccinate do not interfere with the determination. The precision of the method is about 2.0%.

Influence des ions chlorure sur la determination quantitative de la tribromamine en milieu aqueux par spectrophotometrie d'absorption electronique

Use of seawater in the condenser cooling systems of plants such as those of electric power stations poses serious problems because of marine biofouling in the cooling circuits. Chlorination at the condenser inlet has proved to be the most reliable and effective method to prevent the growth of common biofoulers as molluscs; in counterpart this process leads to the discharge of toxic chlorinated and/or brominated effluents around the outlet. When chlorine or hypochlorite is added to seawater a great number of reactions occur; in addition to organic matter, bromide and ammonium ions must be taken into account not only because of their reactivity towards chlorine but also because of their usual relatively high concentration levels: NH + 4+Br −+ ClO HClO − →(NHBr 2, NBr 3, NHBrCl, NBr 2Cl−HBrO, BrO− etc. . In this study we have taken an interest in the stability of the tribrominated species (NBr 3) which occurs, mixed with dibromochloramine (NBr 2Cl), when the chlorine to ammonium ratio is high (Cl 2/NH + 4 > 3) as it is ussually the case. Our work is about the effect of salinity, a specific seawater parameter, upon the formation and decomposition steps. To prevent other side-reactions, especially with organic compounds, all experiments have been carried out in artificial seawater, the biocide reagent used being bromine. The main analytical technique has been the electronic absorption spectrophotometry. From the results which are detailed in the study and illustrated in Figs 1–5, two important features appear: 1. (i) The quantitative determination of tribromamine in chlorinated seawater by using uncorrected values of the spectrophotometric parameters measured in fresh water leads to wrong results: the higher the chloride concentration is the higher the absorption spectra are modified. Chloride interferences can only be neglected when the halide concentration is lower than 0.1 M which is not the case of most seawaters. 2. (ii) Chloride ions promote hydrolysis of tribromamine as bromide ions do. To investigate quantitatively this reaction we have chosen the kinetic model described in the literature: − d(NBr 3) d t =k 1 (NBr 3) 2(HO −) (HOBr) +k 2 (NBr 3) 2 As shown by the comparison of the apparent rate constants k i ́ measured in the case of SO 2− 4 and Cl − ions k′ 1 μ SO 2− 4 0.1 ≃k′ 1 μ SO 2− 4 0.5 <k′ 1 μ Cl− 0.1 ≪k′ 1 μ Cl− 0.5 the nature of the ionic species seems to have a more important effect on the tribromamine decomposition than the ionic strength.

The disodium salt of 1,10-phenanthroline-4,7-diphenyl- p-disulfonic acid as an analytical reagent. A spectrophotometric study of the complexes formed

A spectrophotometric study is presented on the formation of colored complexes: disodium salt of 1,10-phenanthroline-4,7-diphenyl- p-disulfonic acid/metallic ions. In this paper, the relationship existing between the ionic radius of the cation and stoichiometries of the complex or complexes formed is found, giving the values of the apparent constants obtained for each of them. The optimum pH of the reaction is also established, as well as its spectrophotometric parameters.

Doseamento do fósforo em medicamentos reidratantes

The phosphor content in rehydrating solutions it was determined through of the molybdenium blue method, using hydrazine sulfate as a reducing agent. Besides the spectrophotometric parameters it was studied the ions interference that generally are present in this kind of pharmaceutical formulation.

Calibration En Magnitudes Absolues De La Classification BCD. Application à La Détermination Du Module De Distance Du Grand Nuage De Magellan

The calibration of the BCD stellar classification in absolute magnitudes (classification in three parameters λ1, D, Φb) was used to determine the distance modulus of the Large Magellanic Cloud. The described method makes use of the spectrophotometric parameters of B and A supergiants of the Large Cloud and gives a value of the distance modulus which is independent from other determinations, in particular from those which are based on the RR Lyrae and the Cepheid variables. The value found for the distance is slightly smaller than those generally admitted. The results are still based only on a limited number of measurements and new observations are in process; however, it seems doubtful that one will obtain much larger values. In other respects, the observations have shown that the parameter λ1 was still sensitive to luminosity for the B and A stars brighter than M = −8 and that the calibration of the λ1D diagram in absolute magnitudes can be extended up to M = −9.

Quantitative Spectral Classification in the BCD System for LMC Supergiants

In December 1970 and January 1971, spectra of 13 LMC supergiants have been obtained with the Chalonge spectrograph attached to the Cassegrain focus of the 152 cm ESO reflector at La Silla. The spectrophotometric parameters λ1, D, φb and φuv were measured and the first results deal with (a) spectral classification and (b) the distance modulus of the LMC.