PubMed · 8753211
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Y Ohba. 1995. [Carboxyhemoglobin].. https://pubmed.ncbi.nlm.nih.gov/8753211/
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The relative contributions to changes in visible and near UV circular dichroism spectra of hemoglobin of heme ligation and tertiary and quaternary conformational transitions were separated by exploiting the slowing down of structural relaxations for proteins encapsulated in wet, nanoporous silica gels. Spectral signatures, previously assumed to be characteristic of T and R quaternary states, were demonstrated to be specific to different tertiary conformations. The results support the view that ligation and allosteric effectors can modulate the structural and functional properties of hemoglobin by regulating the equilibrium between the same tertiary species within both quaternary states.
Spectrally resolved infrared stimulated vibrational echo spectroscopy is used to measure the fast dynamics of heme-bound CO in carbonmonoxy-myoglobin (MbCO) and -hemoglobin (HbCO) embedded in silica sol-gel glasses. On the time scale of approximately 100 fs to several picoseconds, the vibrational dephasing of the heme-bound CO is measurably slower for both MbCO and HbCO relative to that of aqueous protein solutions. The fast structural dynamics of MbCO, as sensed by the heme-bound CO, are influenced more by the sol-gel environment than those of HbCO. Longer time scale structural dynamics (tens of picoseconds), as measured by the extent of spectral diffusion, are the same for both proteins encapsulated in sol-gel glasses compared to that in aqueous solutions. A comparison of the sol-gel experimental results to viscosity-dependent vibrational echo data taken on various mixtures of water and fructose shows that the sol-gel-encapsulated MbCO exhibits dynamics that are the equivalent of the protein in a solution that is nearly 20 times more viscous than bulk water. In contrast, the HbCO dephasing in the sol-gel reflects only a 2-fold increase in viscosity. Attempts to alter the encapsulating pore size by varying the molar ratio of silane precursor to water (R value) used to prepare the sol-gel glasses were found to have no effect on the fast or steady-state spectroscopic results. The vibrational echo data are discussed in the context of solvent confinement and protein-pore wall interactions to provide insights into the influence of a confined environment on the fast structural dynamics experienced by a biomolecule.
OBJECTIVE: To report four cases of carboxyhemoglobinemia associated with high doses of sodium nitroprusside after cardiac transplant in children. PATIENTS: Four children in the pediatric care unit of a university hospital aged 6 months-4 years. Carboxyhemoglonemia developed at levels of 5.5-7.7% in patients receiving high doses of sodium nitroprusside (7-16 microg/kg per minute and no other medication that could caused elevated carboxyhemoglobin). One patient died, and three recovered with no sequelae after discontinuation of sodium nitroprusside. CONCLUSIONS: High doses of sodium nitroprusside can induce carboxyhemoglobinemia in children after heart transplant, probably by inducing hemeoxygenase, with no other secondary effects.