Absorbance change

The absorbance change (AM) at 340 nm can be used to determine the amount of pymvate remaining. The lactate dehydrogenase [9001-60-9] catalyzed reaction can also be used in the reverse direction to measure lactate. The reaction takes place in a buffer of pH 9—10 that neutralizes Hberated H". ... 

The release of dimethyl sulfoxide is accompanied by an increase in absorbance (D) at 325 nm. The absorbance D is defined as log(I(/I), where 1 and I are die intensities of die incident and transmitted light, respectively. Figure 3-15 illustrates die relationship between concentration and absorbance changes for die hydrolysis of die cobalt... 

Figure 3-15. Reiationship between concentration and absorbance changes for the hydroiysis of [Co(NH3)5L] ...

The neglect of higher-order terms in S2, etc. means that the changes in concentration or in instrument reading are small. In some cases, if a protonation equilibrium occurs, it has proved useful to add a pH indicator to provide a large absorbance change. 

From this it follows that the plot of the logarithm of the absorbance change against time gives k, not k2. The rationale is that the analytical method really monitors the entire conversion. The rate constant that characterizes the buildup of P2 reflects the loss of A by all the reactions that consume it. The time at which a given fraction of A has reacted is the same time at which the same fraction of the final P2 has formed. Of course, one can obtain the value of k2 by combining the data for the kinetics and the yield ... 

Figure 18. Absorbance change with time of the toluidine glucose reaction product at...

In the study of reactions of the types ether than exchange mentioned previously, the usual technique involves the spectrophotometric examination of reaction mixtures. The absorbance changes that occur, at a suitable wavelength where only one species (either reactant or product) absorbs, as the reaction proceeds are measured (manually or recorded). Treatment of the data via the Beer-Lambert law enables rate coefficients and laws to be found in the usual manner. Stopped flow and temperature jump techniques have been used for very rapid reactions. 

When a solution of Fe(III) and thiocyanate is mixed with a solution containing excess Cr in a flow apparatus " the absorbance change can be seen to involve three distinct stages, corresponding to (a) the very rapid reaction between FeNCS and Cr (Ar 2x 10 l.mole . sec ) (b) the reactions Fe +Cr, ... 

This technique provides an easy and convenient method to evaluate the association of small molecules to various polymorphic forms of nucleic acid structures from the measurement of absorbance changes in the absorption maximum of the hgand, where the nucleic acid has no absorbance. Information about overall DNA/RNA base preference and nature of binding can also... 

FIG. 6 Measurements of the interfacial adsorptivity and the extraction rate from the absorbance changes of the organic phase by means of the high-speed stirring method, (a) Heptane-water system... 

One way to see if a chemical will hurt people is to learn how the chemical is absorbed, changed, and released by the body for some chemicals, animal testing may be necessary. Animal testing may also be used to identify health effects such as cancer or birth defects. Without laboratory animals, scientists would lose a basic method to get information needed to make wise decisions to protect public health. Scientists have the responsibility to treat research animals with care and compassion. Laws today protect the welfare of research animals, and scientists must comply with strict animal care guidelines. 

Note that we define the fraction of dose absorbed as the upper limit of the percent of dose absorbed. Therefore, the percent of dose absorbed changes with time, but the fraction of dose absorbed does not. 

The catalyst can be regenerated by evacuation to remove cyclohexene oxide and addition of fresh BuOOH at the end of the first kinetic run. When a second dose of cyclohexene vapor was introduced to 3, very similar kinetic behavior was observed, Figure lb. However, the smaller absorbance change imphes that less cyclohexene was epoxidized, likely because of incomplete removal of the epoxide which blocks the active sites. 

Ruban, A.V., Young, A., and Horton, P. 1993b. Induction of nonphotochemical energy dissipation and absorbance changes in leaves evidence for changes in the state of the light harvesting system of photosystem II in vivo. Plant Physiol. 102 741-750. 

Absorbers are found at many synchrotron beamlines. Two different principles are realized. Tilt-absorbers are operated continuously, whereas filters on a revolving disc offer step-wise attenuation of flux. Absorbers change the spectral composition of the primary beam. Thus the utilization of an absorber during scattering experiments should be avoided. 

TFA is used for samples with weak absorbance changes or overlapping pKas. In TFA, absorbance (A) with respect to wavelength and pH is expressed as a matrix A. Two other matrices are set up. The C matrix shows the concentration (C) of each... 

Fig. 23. Comparison of physiological action spectra with action spectra for light-induced absorbance changes in the same organisms, (1) Bluelight-induced light growth response of Phycomyces45 (2) Action spectrum for the light-induced absorbance change in the C2-mutant of Phycomyces109) ...

Action spectrum for the light-induced absorbance change in Neurospora123... 

Fig. 8. Difference spectrum (green irradiated minus red irradiated) of phycochrome c (solid line), action spectrum for induction of filamentous growth of Nostoc muscorum (dotted line), and action spectrum for inhibition of C-phycoerythrin synthesis in Tolypothrix tenuis (dashed-dotted line). Abscissa wavelength in nm Ordinates relative absorbance change und relative action (after Bjorn and Bjorn 5))...

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