Many studies are currently evaluating the potential role of thrombolytic therapy in patients with ischemic syndromes who have undergone previous coronary artery bypass grafting. Limited experience has been published regarding the use of local urokinase and streptokinase infusions and the use of systemic recombinant tissue-type plasminogen activator as thrombolytic agents in patients with previous coronary artery bypass surgery. To date, however, there has been no published experience regarding the use of recombinant tissue-type plasminogen activator (rt-PA) either systemically or locally in the post-bypass patient where angiographic demonstration of aortocoronary saphenous vein graft obstruction was available pre- and post-therapy. Similarly there has been no previous report of the use of rt-PA infused locally to recanalize an occluded aortocoronary saphenous vein graft. This report describes successful thrombolysis and subsequent balloon angioplasty of saphenous vein grafts with angiographically documented thrombus using systemic and local rt-PA infusion.
In
this work, we discuss the challenging time-resolved fluorescence
anisotropy of subtilisin Carlsberg (SC), which contains a single Trp
residue and is a model fluorescence system. Experimental decay rates
and quenching data suggest that the fluorophore should be exposed
to water, but the Trp is partially buried in a hydrophobic pocket
in the crystallographic structure. In order to study this inconsistency,
molecular dynamics simulations were performed to predict the anisotropy
decay rates and emission wavelengths of the Trp. We confirmed the
inconsistency of the crystallographic structure with the experimentally
observed fluorescence data and performed free energy calculations
to show that the buried Trp conformation is 2 orders of magnitude
(∼3 kcal/mol) more stable than the solvent-exposed one. However,
molecular dynamics simulations in which the Trp side chain was restricted
to solvent-exposed conformations displayed a maximum Trp emission
wavelength shifted toward lower energies and decay rates compatible
with the experimentally probed rates. Therefore, if the solvent-exposed
conformations are the most important emitters, the experimental anisotropy
can be compatibilized with the crystallographic structure. The most
likely explanation is that the fluorescence of the most probable conformation
in solution, observed in the crystal, is quenched, and this is consistent
with the low quantum yield of Trp113 of SC. Additionally, some experiments
might have probed denatured or lysed SC structures. SC anisotropy
provides an interesting target for the study of fluorescence anisotropy
using simulations, which can be used to test and exemplify how modeling
can aid the interpretation of experimental data in a system where
structure and solution experiments appear to be inconsistent.
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