A model for the photodissociation of ICN in its lowest continuum is developed and is used to predict the partitioning of available energy between translational, rotational, and vibrational energies of the recoiling fragments. The model is based on three major assumptions: (i) that only one upper electronic state is involved, (ii) that light absorption affects only the breaking C–I bond, thus allowing the upper-state potential surface to be calculated quasidiatomically from spectral and thermodynamic data, and (iii) that the mechanics of the “half-collision” of the recoiling fragments on this potential surface may be treated as classical to predict the average partitioning between translational, rotational, and vibrational energies, and by a classical-energy forced quantum oscillator approximation to predict the partitioning between vibrational states. The model predicts that most of the available energy will go into translation, which is consistent with flash photolysis studies and with crude measurements of the photofragment spectrum.
Indirect calorimetry is the best measure to guide calorie administration during nutrition support. This article presents an update of the types of currently available indirect calorimeters and reviews the recent advances that guide the clinical application of indirect calorimetry. The emphasis of this report is placed on issues that the practicing clinician can use to evaluate, interpret, and apply measurements of energy expenditure.
Guanosine 3':5'-cyclic monophosphate (cGMP)dependent protein kinase has been purified to homogeneity from bovine lung by affinity chromatography and characterized. Partially purified protein kinase, specifically activated by low concentrations of cGMP (22 nM), was adsorbed onto 8(2-aminoethyl)amino-adenosine 3':5'-cyclic monophosphate-Sepharose. After washing to remove nonspeic proteins, cGMP-dependent protein kinase was specifically eluted by 0.1 mM cGMP. The purified protein contained cGMP-dependent protein kinase and specific cGMP binding activities. Purification of the holoenzyme was possible because subunit dissociation does not occur upon cyclic nucleotide binding. cGMPdependent protein kinase holoenzyme -has an apparent molecular weight of 150,000 as determined by glycerol density gradient sedimentation. On sodium dodecyl sulfate/polyacrylamide gel electrophoresis, a single protein band of 74,000 molecular weight was observed that suggested the holoenzyme is a dimer composed of subunits of identical molecular weight. cGMP-dependent protein kinase required high concentrations of Mg+2 for optimal activity; a heat-stable protein kinase modulator which inhibited adenosine 3':5'-yclic monophosphatedependent protein kinase activity had no effect on the activity of purified cGMP-dependent protein kinase. Elevations in guanosine 3':5'-cyclic monophosphate (cGMP) are associated with cellular responses which differ from those associated with elevations in adenosine 3':5'-cyclic monophosphate (cAMP) (1). In analogy with the observations that cAMP effects are mediated through cAMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) (2-4), Kuo and Greengard have proposed that specific cGMP-dependent protein kinase(s) mediate the biological effects of cGMP (5). Protein phosphokinase activities specifically stimulated by low concentrations of cGMP have been described in lobster muscle (5), various species of arthropoda (6) and in several mammalian tissues (7-11). The substrate specificity of cGMP-dependent protein kinase appears to differ from that of cAMP-dependent protein kinase (9, 12, 13) which suggests that the cGMP-dependent enzyme differs in both nucleotide binding and catalytic phosphotransferase specificities.Apparent low cellular concentrations and instability of cGMP-dependent protein kinase in mammalian tissues have retarded purification and characterization of the enzyme. The present report describes successful purification of cGMPdependent protein kinase from bovine lung through the use of affinity chromatography. Because we observed that, unlike cAMP-dependent protein kinase, the binding of cGMP and consequent activation of cGMP-dependent protein kinase does not involve subunit dissociation, the holoenzyme can be purified by specific binding through the cGMP receptor site to an immobilized cyclic nucleotide derivative, followed by ligand elution with cGMP. Properties of the purified enzyme are described.
METHODSSynthesis of 8-NH2(CHA)2NH-cAMP-Sepharose. A threestep synthesis co...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.