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Reactivities of Amino Acids and Proteins with Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
Iodine consumption by sulfhydry 1-reactive proteins proceeds at two rates: a fast initial rate, followed by the slow, continual disappearance of iodine at a constant rate.17 The equivalence point is taken at the transition from the fast to the slow rate. The liberation of hydrogen ions, expected from Equation 62, follows the same pattern. It is fast before the equivalence point, but levels off thereafter.18
Technetium-Labeled Compounds
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
Suresh C. Srivastava, Powell Richards
Amperometric titrations have been employed in the analytical determination of technetium, although results were not especially successful. Nitron pertechnetate is not insoluble enough to be useful for amperometric precipitation titrations but the use of tetraphenylarsonium chloride has shown promise. Even in the latter case, the reproducibility is only of the order of ±5%. Typical conditions employed are a supporting electrolyte containing 0.1 M HCl and 0.4 M KCl, and a fixed potential near —0.4 V vs SCE. It has been proposed47 that the use of tetraphenylstibonium chloride may provide better results due to the lower solubility of its pertechnetate reaction product. The amperometric titration method has been claimed to be generally useful for the identification of the oxidation state of technetium in radiopharmaceuticals prepared by the use of fast-acting reducing agents, including tin(II), by Russel and Cash.82 These authors have described their measurements on the reduction of pertechnetate by Sn(II) in media of various pH values, containing a number of commonly used phosphate ligands. The oxidation state of technetium was determined to be either (IV) or (V) depending upon the hgand and the pH of the medium. Mazzoccnin and co-woricers have employed Potentiometrie, biamperometric, and bipotentiometric detection of the equivalence point in the volumetric titrations of technetium(IV) solutions with Ce(IV). Coulometric titrations with electrogenerated tin(II), of pertechnetate, were also carried out.83
Topoisomerase II Inhibition by Antitumor Intercalators and Demethylepipodophyllotoxins
Published in Robert I. Glazer, Developments in Cancer Chemotherapy, 2019
Another finding of the nucleoid experiments is that m-AMSA changes the average Lk of the DNA in the cells. This can be shown by sedimenting nucleoids in sucrose gradients containing various concentrations of ethidium. Ethidium intercalates into the DNA and reduces its Tw. As the concentration of ethidium is raised, the progressive reduction in Tw first counters the negative supercoiling by bringing the value of Tw closer to the low value of Lk (Lk < Tw) in negatively supercoiled DNA. The reduction in supercoiling lowers the sedimentation rate of the nucleoids. When Tw = Lk, a minimum is reached in the supercoiling and in the sedimentation. As the ethidium concentration is raised further, Tw decreases further and becomes less than Lk; this results in the appearance of positive supercoils which cause the nucleoid sedimentation to increase. The sedimentation thus goes through a minimum which is the “equivalence point” in the ethidium titration. The ethidium concentration at the equivalence point (at which Lk = Tw) provides a measure of Lk; since Lk is topologically invariant, this value must have been the same in the cells at the time of lysis.
Efficacy and safety of oral Pentasa (prolonged-release mesalazine) in mild-to-moderate ulcerative colitis: a systematic review and meta-analysis
Published in Current Medical Research and Opinion, 2021
Kristine Paridaens, John R. Fullarton, Simon P. L. Travis
Meta-analyses to calculate the absolute effect size difference between Pentasa and comparator (placebo or active) were undertaken using random effects modelling for direct comparisons and Bayesian networking for indirect comparisons28. Random-effects models were created in Microsoft Excel 365 and results expressed as a weighted absolute risk difference (ARD) or weighted effect size (ES; for mean improvement in sigmoidoscopic index only), both with 95% confidence intervals (CIs). A p-value of <.05 was considered statistically significant. The Bayesian meta-analyses were carried out using WinBUGS 1.4.3 and used source-specific binomial dispersion and linear combinations before being converted to command line analytical code. The code for each data source combination was subjected to 10,000 sampling iterations and subsequently analyzed for mean, standard deviation (SD), median, and percentiles. A 95% credible interval (CrI) not spanning 0 (or other equivalence point) was considered to correspond to a statistical significance of p < .05. Heterogeneity between study-specific estimates was assessed using the chi-squared test (for categorical data) and I2 statistic (for continuous data).
Predicting HIV testing in low threshold community contexts among young African American women living in the Southern United States
Published in AIDS Care, 2020
Jalie A. Tucker, Susan D. Chandler, JeeWon Cheong
Delay discounting of future outcomes in favor of more immediate rewards was assessed using a computerized hypothetical money choice task (Richards, Zhang, Mitchell, & de Wit, 1999). Participants made repeated choices between a smaller money amount available immediately and a larger amount available at 5 delays (1, 2, 30, 180, and 365 days from now; e.g., $2 now or $10 in 30 days; $50 now or $100 in 180 days). An equivalence point was determined for each delay, estimating the amount of immediate money that was subjectively judged equivalent to the larger later amount. These equivalence points were used to derive a discount rate (log k) for analysis that modeled the nonlinear trajectory of changes in the devaluation of future rewards as a function of delay to receipt. Higher values indicate more immediate reward preferences. It was not necessary to incentivize choices because hypothetical and real money ranging from small to large amounts generate equivalent delay discounting rates in diverse populations, including among emerging adults (e.g., Dixon, Lik, Green, & Myerson, 2013; Johnson & Bickel, 2002; cf. Madden & Bickel, 2010).