Hexacyanochromate ion, (Cr(CN)6)3-, was applied to ribonuclease T1 (RNase T1), which specifically cleaves RNA chains at guanylic acid residues. From kinetic studies, this anion was shown to bind to the active site of RNase T1 as a competitive inhibitor. Therefore, the line broadening effect of NMR resonances due to binding of (Cr(CN)6)3- was analyzed for the mapping of the active site of RNase T1. His-40 C2 proton resonance was significantly broadened, following His-92 C2 proton resonance upon binding of (Cr(CN)6)3-, while His-27 C2 proton resonance did not show any appreciable line broadening. Moreover, from the pH dependence of the line broadening effect, the binding of (Cr(CN)6)3- was shown to be controlled by the ionic state of Glu-58. Based on the present NMR results and x-ray crystal structure, the active site structure of RNase T1 is discussed.

Binding Sites↗

PubMedDate not supplied

Post-translational modifications of immunoglobulin G: a mouse IgG variant that lacks the entire CH1 domain.

In the present study, we characterized the post-translational modifications of a short-chain variant of mouse IgG2a that lacks the entire CH 1 domain. The short-chain IgG2a and its proteolytic fragments were subjected to electrospray ionization- and fast atom bombardment-mass spectrometric analyses. It has been demonstrated that approximately 14% of the heavy chain of the short-chain IgG2a is O-glycosylated with a disaccharide of Ga1-GalNAc- at Thr220A in the hinge region. while the Oglycosylation does not occur in its parent IgG2a molecule. Two additional modifications have been detected at the C-termini of both the heavy and light chains of the short-chain IgG2a. Biological significance of the post-translational modifications of the short-chain IgG2a variant is briefly discussed.

Alkylation↗

PubMedDate not supplied

Prolonged aortic cross-clamping in early infancy and method of myocardial preservation.

A cardioplegic solution containing blood with a low level of ionic calcium was prepared independent of pump-oxygenator perfusate blood, so as to contain a constant concentration of each component at any given time. Using this solution, Jatene's anatomic repair under prolonged periods of aortic cross-clamping ranging from 117 to 184 minutes (mean: 149 min) was performed on seven young infants with simple complete transposition. The ages of the patients ranged from 34 days to 3 months, with a median age of 2 months. Four patients, aged 39 days, 41 days, 2 months and 3 months, survived and showed uneventful postoperative hemodynamics. Two of the three non-survivors were considered retrospectively to have been unsuitable candidates for Jatene's anatomic repair due to their low left ventricular pressure (LV/RV pressure ratio less than 0.60 in both). The remaining infant who died had TGA with a large ventricular septal defect of the muscular type and developed a postoperative residual shunt. It was considered unreasonable to attribute the cause of death in this case to inadequate myocardial protection. Judging from our experience with these four survivors who underwent prolonged aortic clamping ranging from 117 to 160 minutes, our cardioplegic solution and the technique of its administration were considered to be effective and promising for heart surgery in young infants and neonates.

Blood↗

PubMedDate not supplied

The Blalock-Taussig shunt for simple complete transposition of the great arteries followed by later anatomic correction. Report of 2 cases with conflicting postoperative courses.

The Blalock-Taussig (BT) shunt was performed in two infants with simple transposition of the great arteries (TGA) after poor response to septostomy not only to improve hypoxia but also in expectation of preparing the left ventricle for later anatomic correction. One patient had adequate muscle mass and pressure of the left ventricle after the shunt and underwent successful anatomic correction. The other patient developed intractable heart failure following the shunt. Anatomic correction was performed with success in this patient after pulmonary artery banding and takedown of the BT shunt. Based on these experiences, if heart failure does not develop or is controllable after BT shunt, there may be a possibility of later anatomic correction. However, if uncontrollable failure occurs, the shunt should be taken down and arterial or venous switch correction should be performed as soon as possible.

Female↗