Pediatric cardiopulmonary bypass circuits: a review of studies conducted at the Penn State Pediatric Cardiac Research Laboratories.

Cardiopulmonary bypass (CPB) circuits are frequently necessary in the repair of congenital heart defects in infants and children. Although advances in technology and operative technique have decreased the mortality associated with cardiac procedures requiring CPB, post-operative neuro-cognitive outcome and the role of the CPB circuit in post-operative morbidity remains a significant concern. There are several factors that have been suggested to play a significant role in general post-operative outcome, including intraoperative inflammatory responses caused by the interaction of blood with circuit component surfaces, selection of appropriate perfusion mode to optimize organ function during CPB, and the introduction of gaseous microemboli into the patient's systemic circulation through circuit manipulations and modifications.

Cdc6 stability is regulated by the Huwe1 ubiquitin ligase after DNA damage.

The Cdc6 protein is an essential component of pre-replication complexes (preRCs), which assemble at origins of DNA replication during the G1 phase of the cell cycle. Previous studies have demonstrated that, in response to ionizing radiation, Cdc6 is ubiquitinated by the anaphase promoting complex (APC(Cdh1)) in a p53-dependent manner. We find, however, that DNA damage caused by UV irradiation or DNA alkylation by methyl methane sulfonate (MMS) induces Cdc6 degradation independently of p53.

Insights into the serine protease mechanism from atomic resolution structures of trypsin reaction intermediates.

Atomic resolution structures of trypsin acyl-enzymes and a tetrahedral intermediate analog, along with previously solved structures representing the Michaelis complex, are used to reconstruct events in the catalytic cycle of this classic serine protease. Structural comparisons provide insight into active site adjustments involved in catalysis. Subtle motions of the catalytic serine and histidine residues coordinated with translation of the substrate reaction center are seen to favor the forward progress of the acylation reaction.

Role of the intramolecular hydrogen bond network in the inhibitory power of chymotrypsin inhibitor 2.

A series of mutants of chymotrypsin inhibitor 2 (CI2), at residues involved in intramolecular interactions that shape and constrain the binding loop, were studied to determine their relative importance for inhibition of the serine protease subtilisin BPN', and for resistance of the inhibitor to proteolysis. These functional properties were investigated in tandem with the crystal structures of the mutant inhibitor-enzyme complexes. A dense hydrogen bonding network that supports the binding loop in the vicinity of the scissile bond was found to be important both for enzyme affinity and for stability to proteolysis.

Binding, proteolytic, and crystallographic analyses of mutations at the protease-inhibitor interface of the subtilisin BPN'/chymotrypsin inhibitor 2 complex.

A series of mutants of chymotrypsin inhibitor 2 (CI2), at residues that interact with the inhibited enzyme subtilisin BPN', were studied to determine the relative importance of intermolecular contacts on either side of the scissile bond. Mutants were tested for inhibition of subtilisin, rates of hydrolysis by subtilisin, and ability to acylate subtilisin. Additionally, crystal structures of the mutant CI2 complexes with subtilisin were obtained.