Kinetic study of the oxidation of catechol by aqueous copper(II).

The kinetics of the oxidation of catechol by aqueous copper(II) have been studied as a function of reactant concentrations at pH 6.4-7.2. To follow the reaction, a spectrophotometric method has been developed that circumvents the problem of precipitation of decomposition products of the initial o-quinone oxidation product. The rate law shows that the reactive species is the monocatecholate complex of Cu(II), and that this species undergoes rate-limiting intramolecular electron transfer with k = 1.9 x 10(-5) s(-1) (22 +/- 1 degrees C, mu = 0.125 M NaClO(4)). The results have allowed a reanalysis of previous work on the autoxidation in the aqueous Cu(II)-catechol-dioxygen system, and comparisons to mechanisms of copper(II) oxidases.

Complex formation constants for the aqueous copper(I)-acetonitrile system by a simple general method.

A simple spectrophotometric method for the evaluation of formation constants for aqueous copper(I) has been developed, based on the kinetics of reduction of Co(III)(NH(3))(5)X complexes. The method has been applied to the aqueous copper(I)-acetonitrile system to determine the successive formation constants beta(1), beta(2), and beta(3) as 4.3 x 10(2) M(-)(1), 1.0 x 10(4) M(-)(2), and 2.0 x 10(4) M(-)(3), respectively, in 0.14 M NaClO(4)/HClO(4) at 21 +/- 1 degrees C.

Surgical repair of coarctation of the aorta in infants less than six months of age: including the question of pulmonary artery banding.

High mortality rates (20% to 60%) have been reported in the repair of coarctation of the aorta in infancy. During a 4 year period, 34 infants less than 6 months of age had coarctation repair (two prior to 1976). Eleven were less than 2 weeks of age, nine were 2 weeks to 1 month, eight were 1 to 2 months, and six were 2 to 6 months. Associated lesions were patent ductus arteriosus (PDA) (82%), ventricular septal defect (VSD) (53%), and other intracardiac lesions (35%). Twenty-three patients (67%) had emergency operations; the other procedures were semielective. The indications for operation included congestive cardiac failure (91%), acidosis (32%), hypertension (29%), cardiogenic shock (26%), and cardiac arrest (18%). There was one operative death (2.9%) in a patient with severe pulmonary valve insufficiency and multiple VSDs. There was one late death a 4 months (Taussig-Bing complex). Primary repair was used in 15, patch-graft angioplasty in 19 (left subclavian artery in nine, left common carotid in one, and Dacron or pericardial patch in nine). Two (6%) required reoperation for recurrent coarctation (follow-up 3 to 36 months with a mean of 25.8). Of 15 patients with a large VSD, six had pulmonary artery banding with two deaths (one operative and one late), two had debanding plus VSD repair, and two are awaiting operation. The remaining nine patients did not have banding (no operative or late deaths), four patients required late VSD closure, two VSDs closed spontaneously, two VSDs became smaller, and one patient is awaiting VSD closure. The infrequent need for pulmonary artery banding may be partly due to "physiological banding" seen at Denver's high altitude. The VSD spontaneously closed or became smaller in 44% of nonbanded patients. The low operative mortality can be ascribed to (1) aggressive medical therapy, (2) emergency catheterization and repair, (3) avoidance of hypothermia, and (4) adequate relief of the coarctation.