Extinction coefficient, determination for

As soon as the protein is activated with the heterobifunctional crosslinker, the extinction coefficient determined for pure Amb a 1 no longer applies because the heterobifunctional crosslinker absorbs at 280 nm. At this step in the production of AIC, the manufacturing overhead cost requires the use of a fast protein assay, whereas the exact stoichiometry of the subsequent reaction dictates the use of an accurate and precise method. Hence we developed a new extinction coefficient for the activated protein based on experimental data and demonstrated that within the normal activation range of 9 to 12 crosslinkers per Amb a 1, the new extinction coefficient remained constant. The concentration of the purified activated Amb a 1 determined by this direct absorbance A280 method is more precise and accurate than could be assigned by a colorimetric assay. Consequently, the activated Amb a 1 concentration allows for the accurate addition of 1018 ISS required to consistently produce AIC with optimal activity. 

Polymeric fractions were obtained from wines, seed and skin extracts by fractionation on a Toyopearl HW-40 column as described by Souquet et al (4). Two aliquots of the fractions containing polymeric material were t en to dryness under vacuum. The first one was used to determine proanthocyanidin composition by thiolysis followed with HPLC analysis (17). The other one was dissolved in MeOH acidified with 2% HCl and used to estimate the concentration of total polymeric polyphenols and polymeric pigments by measuring the absorbance, respectively at 280 nm and 530 nm. Absorbance data were converted to equivalent epicatechin and equivalent malvidin-3-glucoside, respectively, using the extinction coefficients determined for each compounds under similar conditions. 

PNP production was monitored at 402 nm and quantitated using extinction coefficients determined experimentally for each reaction medium. The fraction of reactant conversion to product was given by the ratio (Aj. - Aq)/(A - A ) where the subscripts t, o, and <<> refer, respectively, to absorbance values taken at time t, initially, and at long reaction times when PNP liberation clearly stopped. 

For organic materials, ultraviolet absorption spectra are substantially determined by the presence of functional groups. Identical functional groups in different molecules may not absorb at precisely the same wavelength due to different structural environments which modify the local electric field. The magnitude of the molar extinction coefficient ( e ) for a particular absorption is directly proportional to the probability of occurrence of the particular electronic transition. Spectral features of some isolated chromophoric groups are presented in Table 2... 

The color of pyranoanthocyanins is more orange than that of anthocyanins, which leads one to suppose that they can contribute to the red tile and orange hues characteristics of aged wines. Similar molar extinction coefficients values for malvidin 3-glucoside (1.6 x 10" L/mol/cm) and its corresponding carboxypyra-noanthocyanin (i.e., vitisin A 1.3 x lO L/mol/cm) were determined by Mateus and... 

Extinction coefficients used for ricin A-chain and blocked ricin B-chain at 280 nm for 0.1% solutions were 0.765 and 1.48, respectively (Olsnes and Pihl, 1973). The extinction coefficient for MIANS is 20,000 M cm" at 322 nm (Gupte and Lane, 1979). The empirically determined contribution of MIANS to the absorbance of the labeled protein at 280 nm was 0.9 x A320. 

As can be seen in Fig. 5, N conversion using H-ZSM-11 zeolite seems to be correlated with the number of Bronsted sites on the external surface (deduced from measurements of methylene blue adsorption capacity) and not with the total niunber of Bronsted sites (determined by the total pyridine adsorbed on Bronsted sites and desorbed at 150°C by FT-IR spectroscopy), using the literature data on the integrated molar extinction coefficients [17], (for infrared absorption bands of pyridine adsorbed on solids acid catalyst [17], providing no dependence of the integrated coefficients on the catalyst or strength of the sites). 

FIGURE 7. Extinction coefficient, k, for CO by photoelectric detection with an effective instrumental resolution of about 0.4 nm. Extinction coefficient determined through the relation Iq/1 = exp (k ns.). Curve (1) estimated extinction coefficient, curve (2) measured values, see reference 42 (from Shemansky permission). 

The average Ni/V ratio for the three oil components was 15.2, and this value was used to calculate a weighted extinction coefficient used for all metalloporphyrin determinations. 

An additional complication is that many metabolities/cofactors have temperature-dependent extinction coefficients those for NADH and for potassium ferri-cyanide, for example, are about 10% lower at 80° than at 20°. Fourage et al. point out that the effect of temperature on the absorbance and Xmax of p-nitrophenol can lead to substantial errors in fccat values measured by continuous release of p-nitrophenol, if the calibration curve is not determined at the same temperature as the assay. 

Note that the slope of the absorbancetime plot allows the determination of the (usually) unknown extinction coefficient r for the electrogenerated species, providing that c and Dq are known. No knowledge of the electrogenerated species diffusion coefficient Dr is necessary. Usually the concentration is known and it is a simple matter to determine Dq from a chronoamperometry, chronocoulometry, or ultramicroelectrode experiment. If both c and Do are unknown, then they can be obtained from a potential step experiment at an ultramicroelectrode [47, 48]. 

To answer the following questions assume you have access to hydrogen, iodine, hydrogen iodide, a transparent reaction vessel, a visible-light spectrometer, and a means for changing the temperature, (a) Which gas or gases concentration could you readily monitor with the spectrometer (b) To use Beer s law (Equation 14.5) you need to determine the extinction coefficient, e, for the substance in question. How would you determine e ... 

Each substance has a different molar extinction coefficient 8 for each wavelength of its absorption spectrum. Generally, the 8 value quoted is that determined for the absorption maximum - max.> namely 8 max. ... 

The ultraviolet absorption spectrum of thiazole was first determined in 1955 in ethanolic solution by Leandri et al. (172), then in 1957 by Sheinker et al. (173), and in 1967 by Coltbourne et al. (174). Albert in 1957 gave the spectrum in aqueous solution at pH 5 and in acidic solution (NHCl) (175). Nonhydroxylic solvents were employed (176, 177), and the vapor-phase spectrum was also determined (123). The results summarized in Table 1-15 are homogeneous except for the first data of Leandri (172). Both bands A and B have a red shift of about 3 nm when thiazole is dissolved in hydrocarbon solvents. This red shift of band A increases when the solvent is hydroxylic and, in the case of water, especially when the solution becomes acidic and the extinction coefficient increases simultaneously. 

The solvent used was 5 %v/v ethyl acetate in n-hexane at a flow rate of 0.5 ml/min. Each solute was dissolved in the mobile phase at a concentration appropriate to its extinction coefficient. Each determination was carried out in triplicate and, if any individual measurement differed by more than 3% from either or both replicates, then further replicate samples were injected. All peaks were symmetrical (i.e., the asymmetry ratio was less than 1.1). The efficiency of each solute peak was taken as four times the square of the ratio of the retention time in seconds to the peak width in seconds measured at 0.6065 of the peak height. The diffusivities obtained for 69 different solutes are included with other physical and chromatographic properties in table 1. The diffusivity values are included here as they can be useful in many theoretical studies and there is a dearth of such data available in the literature (particularly for the type of solutes and solvents commonly used in LC separations). 

For methane-air fireballs, Hardee et al. (1978) found an of 469 kW/m. If an extinction coefficient of k = 0.18 m (as measured in LNG fires) is used, the curve shown in Figure 6.8 can be obtained from the equations given by Hardee et al. (1978). Equation (6.2.3) overstates emissivity as determined through experiments. Possible explanations are... 

To obtain reliable, accurate, and reproducible methods for quantitative estimation of deoxy sugars, certain conditions must be fulfilled. Thus, it is necessary that the chromogen be formed quantitatively from the sugar. The chromogen must then react quantitatively with the compound used for color formation, and lastly, the dye, once formed, should be stable and have a well defined molar extinction coefficient. In methods in which all of these conditions are not or cannot be fulfilled, recourse must be had to simultaneous determinations with suitable standard substances, a requirement not always easy to fulfil. 

Despite the above-mentioned short-comings, this approach to the estimation of those deoxy sugars which yield malonaldehyde when oxidized with periodate, seemed promising, since, as has been seen (58,59), the dye is formed quantitatively in the reaction of malonaldehyde with 2-thiobarbituric acid also, more recently, its constitution (49,57) and molar extinction coefficient (36) have been established. Thus, if conditions could be found in which malonaldehyde, while being formed quantitatively from the deoxy sugars, would be stable, an ideal method, independent of standard compounds, would be available for the quantitative determination of all of these sugars. 

The development and adaptation of procedures for the separation, isolation, purification, identification, and analysis of the components of the pyrethrum mixture have been studied and evaluated. Results of studies to determine the molar extinction coefficient of pyrethrin I as well as a gas chromatographic procedure for the determination of pyrethrins are reported. The use of chromatographic separation procedures (including partition, adsorption, gas, and thin-layer chromatography), colorimetry, and infrared spectrophotometry are discussed. 

Cryophotochemical techniques have been developed that (i) allow a controlled synthetic approach to mini-metal clusters 112), Hi) have the potential for "tailor-making small, bimetallic clusters (mini-alloy surfaces) 114,116), Hi) permit the determination of relative extinction-coefficients for naked-metal clusters 149), and iv) allow naked-cluster, cryophotochemical experiments to be conducted in the range of just a few atoms or so 112,150,151). 

The relative extinction-coefficients for Agi,2,s determined by pho-toaggregation procedures were found not to be strongly matrix-dependent (see Table VIII). Moreover, the results for Agj were in good agreement with those obtained by quantitative, metal-atom deposition-techniques. 

---