ABSTRACT
Loops are abundant in native RNA structures and proliferate close to the unfolding transition. By including a statistical weight approximately l(-c) for loops of length l in the recursion relation for the partition function, we show that the heat capacity depends sensitively on the presence and value of the exponent c, even for a short explicit tRNA sequence. For long homo-RNA, we analytically calculate the critical temperature and critical exponents which exhibit a nonuniversal dependence on c.
Subject(s)
Models, Chemical , RNA/chemistry , Nucleic Acid Conformation , RNA, Fungal/chemistry , RNA, Transfer, Phe/chemistry , Thermodynamics , Yeasts/chemistry , Yeasts/geneticsABSTRACT
This report describes a variant of transient regional left ventricular dysfunction in which isolated basal left ventricular akinesia with normal mid-ventricular (papillary-level) wall motion and apical hypercontractility were noted in young women (mean age 31 years). This finding was demonstrated in 3 consecutive patients; the first patient was experiencing emotional life-altering events, and the second presented with an acute flare of multiple sclerosis. The third patient presented < 24 hours after methamphetamine use. Coronary angiography demonstrated normal epicardial coronary arteries in all patients. Wall motion abnormalities resolved within 2 to 6 weeks. In conclusion, the entity described in this report is reminiscent of apical ballooning ("Tako-Tsubo"), mid-ventricular ballooning, and apical sparing syndromes; however, isolated basal left ventricular involvement has not been previously described and is a newer variant in the spectrum of transient cardiomyopathies. The pathophysiology of this entity has not been elucidated. A unifying feature between the transient cardiomyopathic syndromes most likely is in the concentration, distribution, and activity of cardiac adrenergic receptors.
