B Quantitative Measurements

Note It is convenient to work in pairs for this experiment. In preparing for and executing the kinetic runs, you must be well organized so that you can work quickly. You may need to perform several kinetic runs before you are able to work rapidly enough to get acceptable results. 

Preparation Sign in at www.cengage.com/login to answer Pre-Lab Exercises, access videos, and read the MSDSs for the chemicals used or produced in this procedure. Review Section 2.5. 

Apparatus UV-Vis spectrophotometer or colorimeter, three capped cuvettes, three calibrated Pasteur pipets, glass stirring rod, timer, and thermometer. 

Setting Up Have at your disposal 0.5 M stock solutions of anisole, diphenyl ether, and acetanilide in 15 M(90%) aqueous acetic acid and a 0.02 Msolution of bromine in 15 M acetic acid. Calibrate the spectrophotometer to zero absorbance at 400 nm using a solution of the arene substrate in acetic acid. Prepare this solution by using a 2-mL pipet to combine 2 mL of 15 M acetic acid and 2 mL of the stock solution of the substrate arene in a clean and dry cuvette. Stir the solution to ensure homogeneity and place the cuvette in the spectrophotometer. Adjust the absorbance reading of the spectrometer to zero. Record the laboratory temperature. 

Reaction Once you have zeroed the spectrophotometer for a particular substrate, clean and dry the cuvette used for the calibration, and continue with the following operations. (1) Add 2 mL of 0.02 M bromine solution to the cuvette (2) add 2 mL of the 0.5 M solution of substrate (3) quickly stir the solution one time only, and have your partner record the exact time of mixing (4) place the cuvette in the spectrophotometer and (5) record the absorbance of the solution at 400 nm as a function of time. Obtain as many readings as possible before the absorbance drops below about 0.5, although readings may be taken below 0.5. Record the time at which the needle on the meter crosses a line on the absorbance scale rather than attempting interpolation between those lines. 

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Figure 2 DNA damage induced by ionizing radiation. A) DNA damage and repair. All the constitutive elements of DNA (sugar-phosphate backbone and bases) are possibly modified by ionizing radiation. Single strand breaks (SSB), oxidized bases and abasic site are processed by base excision repair (BER), double strand breaks (DSB) by homologous recombination and non homologous end joining (HR and NHEJ) and DNA-protein crosslinks by nucleotide excision repair (NER). B) Quantitative measurement of radiation-induced and spontaneous DNA damage.

Tengerdy, R. P., Nagy, J. G. and Martin, B. Quantitative measurement of bacterial growth by the reduction of tetrazollum salts. Appl. Microbiol. 15 954 (1967). 

The goal of chromatography is to separate a sample into a series of chromatographic peaks, each representing a single component of the sample. Resolution is a quantitative measure of the degree of separation between two chromatographic peaks, A and B, and is defined as... 

The values of the ratio lo/b are thus seen to be quantitative measures of the hindrance to rotation in these polymers. The following observations are pertinent to the trends in this behavior ... 

An alternative, single mechanism for both bases may be formulated, however, by taking into account the differences in basicity (piCa = 5.25 and 11.01, for Py and EtsN, respectively [148]), and hydrophobicity between the two bases. A quantitative measure of the latter property is given by logP, the partition coefficient of the solute between n-octanol and water (logP = log([solute] octanol/[solute]water)> 0.65 and 1.45 for Py and EtsN, respectively [149]. This unified mechanism is shown in Fig. 4, where B refers to the base employed. 

The LOQ is regarded as the lower limit for precise quantitative measurements. Several authors, such as Miller and Miller, Skoog and Leary, and Smith, have suggested that the LOQ be defined as a concentration which would produce a signal 10-12 times b- At this point, the standard deviation is small enough (approximately 10-15%) so that the quantitated value can be deemed reliable. 

Hwang, S.-J., et al. (1996). Comparison of three different hybridization assays in the quantitative measurement of serum hepatitis B vims DNA. J. Virol. Methods 62,123-129. 

Figure 8.2 Design of protein-embedding barcode is depicted in (a) five thin layers of matrix (the thicker lines) coated with variable concentration of tested protein (thinner lines located above the matrix), (b) A FFPE tissue section of bladder cancer IHC-stained by monoclonal antibody to E-cadherine showing variable intensity of positive staining results which is compared with a protein-embedding bar code as designed in this chapter. Using computer-assisted image analysis with a special software, an automatic quantitative measurement of protein is performed. See color insert.

Fig. 13.5. Quantitative measurements of contact stiffness by UFM (a) theoretical calculation of the UFM response on Si (1) and Ge (2) surface, using the engineering parameters ESi = 164 GPa, EGe = 121 GPa, surface energy in an ambient environment y = 1 N m-1, and the manufacturer s data for cantilever stiffness kc = 2.8 nN nm-1 and tip radius Rt = 10 nm (b) experimentally measured UFM response of a silicon surface (c) schematic illustration of the differential UFM approach to the measurement of contact stiffness (Kolosov and Yamanaka 1993), from the threshold amplitude values (ai and a2) for two different normal force values (Fi and P2), the contact stiffness Seff is given by Seff = (F2 — -Fi)/(a2 — ) (d) experimental stiffness measurements... 

Two main types of analysis are required (a) qualitative determination of the presence of elements and (b) quantitative determination of the amount of elements or species of interest contained in pharmaceutical products. Most analyses for pharmaceutical applications involve separation steps combined with ICP-MS, such as HPLC-ICP-MS or gel electrophoresis and the analysis of gel blots by LA-ICP-MS. Phosphorylated proteins (e.g., (3-casein) have been measured by LA-ICP-MS with a detection limit of 16pmol. HPLC-ICP-MS has been employed for the identification and quantification of metabolites of bradykinin in human and rat plasma.1... 

In Section 3.4a we examine a model for the second virial coefficient that is based on the concept of the excluded volume of the solute particles. A solute-solute interaction arising from the spatial extension of particles is the premise of this model. Therefore the potential exists for learning something about this extension (i.e., particle dimension) for systems for which the model is applicable. In Section 3.4b we consider a model that considers the second virial coefficient in terms of solute-solvent interaction. This approach offers a quantitative measure of such interactions through B. In both instances we only outline the pertinent statistical thermodynamics a somewhat fuller development of these ideas is given in Flory (1953). Finally, we should note that some of the ideas of this section are going to reappear in Chapter 13 in our discussions of polymer-induced forces in colloidal dispersions and of coagulation or steric stabilization (Sections 13.6 and 13.7). 

The actual concentration of electrolyte at the CCC depends on the following (a) the time allowed to elapse before the evaluation is made, (b) the uniformity or, more likely, the polydispersity of the sample, (c) the potential at the surface, (d) the value of A, and (e) the valence of the ions. In a series of tests on any particular system, items (a)-(d) remain constant, so the CCC is a quantitative measure of the effect of the valence of the added ions. Table 13.1 summarizes some experimental results of this sort. 

Hopkinson s Pressure Bar Test. The quantitative measurement of the press developed by expls over small intervals of time, which is a measure of expl violence, was made possible by application of the method conceived by Prof B. Hopkinson. The application of Hopkinson s principle to a wide field of research such as iaitiation of deton, properties of the deton wave, and the design of detonators fuses and the design of a variety of instruments were carried out by physicists of the Res Dept, Woolwich, England... 

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