Biomedical subjects
S M Gullo
Publications and source records attributed to S M Gullo.
Safe handling of antineoplastic drugs: translating the recommendations into practice. 1988.
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Kinetic and structural model for the binding of formate to the rapid form of cytochrome c oxidase.
The binding of formate to the rapid form of cytochrome c oxidase from bovine heart has been examined at pH 8.8 and high ionic strength. The optical changes included (1) a transient decrease at 414 nm, followed by a biphasic increase, and (2) an isosbestic wavelength. The apparent blue shift in the Soret envelope, following the transient, was consistent with a 430-->414 transition in cytochrome a3, described previously for acid jump conditions in the absence of formate [Papadopoulos, P. G., Walter, S. A., Li, J., & Baker, G. M. (1991) Biochemistry 30, 840-850]. A two-step binding mechanism was implied by the biphasic increase, but the k(obs) values for each phase, when plotted against formate concentration, were unable to statistically discriminate two rival kinetic models. Both models postulated a rapid 430 + L<-->414.L step (where L = HCOOH + HCOO-), but they differed in whether the slower step depended on L. The equilibrium dissociation constant, KDapp, for the overall binding reaction was 0.3 mM. An analysis of the rival mechanisms indicated this value to be consistent with a step that was independent of L. A slow 414.L<-->414'.L conversion was therefore postulated, and the Keq for this step was found to be approximately 9. The analysis to this point assumed that cytochrome alpha 3 was entirely in the 430 state at the time of formate addition. Modeling of the transient could not be achieved, however, unless cytochrome a3 was present as a rapid equilibrium mixture of 414 and 430 states. The 414, 414.L, and 414'.L states were assumed to be electronically identical to account for the isosbestic wavelength.(ABSTRACT TRUNCATED AT 250 WORDS)
Evaluation of ligand exchange as a model of heterogeneity within the binuclear core of cytochrome c oxidase.
Dilution of detergent-solubilized cytochrome c oxidase has been found to increase the pH sensitivity of the a3-CuB site. Comparison of a large number of preparations, each purified at pH 8.8, showed either one or two exponential reactivity with cyanide, indicating that pH was not the only factor regulating kinetic heterogeneity within the binuclear core. Differences in heme a concentration during the soluble stages of purification were shown to have a substantial effect on the distribution of both optical and kinetic states within the isolated enzyme. Similar dilution effects were also inducible after purification. In particular, the apparent pKa of the Soret band maximum was shifted to higher pH following dilution of the enzyme. The resulting increase in the 414-nm conformer was also associated with enhanced conversion to the slow cyanide-binding form, suggesting that a single protonation event may give rise to both optical and kinetic changes. Two lines of evidence were contrary to this: First, by appropriate choice of experimental conditions it was possible to observe 30-50% of the cytochrome a3 centers in the 414-nm state with no associated evidence of the slow conformer. Second, the addition of formate at pH 8.8 induced conversion to both slow and 414-nm conformers, but the rates and extents of conversion were not correlated. Separate structural events are therefore proposed to modulate the optical and kinetic properties of the binuclear core. Since acidic pH has the well-established ability to induce both rapid-->slow and 430-->414-nm conversions, we suggest that the effects of dilution and formate are to mimic an acid jump by facilitating proton uptake into the binuclear core.
Props and jokes provide patients with "healing hugs".
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Implanted ports. Technologic advances and nursing care issues.
The IVAD has an established role in the care of patients requiring frequency or long-term vascular access. IVADs are used in all types of settings including hospitals, ambulatory clinics, and the home. Nurses are responsible for identifying patients who would benefit from an IVAD, conducting preoperative teaching and postoperative assessment, accessing the port, administering medications, performing site care, maintaining patency, teaching self-care, and troubleshooting. An abundance of controversial issues in the management of IVADs offers a wide range for potential research studies. In addition, the impact of evolving technology will continue to influence the care issues surrounding IVADs. Continual appraisal of new information is essential for nurses to remain current and competent in meeting the needs of patients with IVADs.
IV vesicants: how to avoid extravasation.
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Safe handling of antineoplastic drugs: translating the recommendations into practice.
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