Paul C Frake | PubMed Health

PubMed2006

Pi-bonded quinonoid transition-metal complexes.

Coordination of the carbocyclic ring of hydroquinones to electrophilic transition-metal fragments such as Mn(CO)3+ and Rh(COD)+ produces stable pi-bonded eta6-complexes that are activated to facile reversible deprotonation of the -OH groups. The deprotonations are accompanied by electron transfer to the transition metal, which acts as an internal oxidizing agent or electron sink. With manganese as the metal, the resulting eta5-semiquinone and eta4-quinone complexes have been used to synthesize one- two- and three-dimensional polymeric metal-organometallic coordination networks. With rhodium as the metal, the pi-quinonoid complexes have been demonstrated to play a unique role in multifunctional C-C coupling catalysis and in the synthesis of new organolithium reagents. Both classes of pi-quinonoid complexes appear to have significant applications in nanochemistry by providing an excellent vehicle for templating the directed self-assembly of nanoparticles into functional materials.

Catalysis↗

PubMed2006

Prestorage leukoreduction prevents accumulation of matrix metalloproteinase 9 in stored blood.

OBJECTIVES: Transfusion of aged stored blood is associated with many neutrophil proinflammatory effects. The mechanism of these effects remains to be elucidated. The purpose of this study was to determine whether matrix metalloproteinases accumulate in packed red blood cells during storage and are responsible for some of the neutrophil proinflammatory events, and to determine whether prestorage leukoreduction prevents accumulation of matrix metalloproteinases and attenuates proinflammatory effects of stored packed red blood cells. DESIGN: Laboratory study. PARTICIPANTS: Healthy human volunteers. INTERVENTIONS: Units of blood were drawn from healthy volunteers. Half of each unit was filtered for leukoreduction, removing 99.9% of leukocytes. At biweekly intervals, aliquots were removed from packed red blood cell units, and the plasma fraction was isolated for assays. Plasma was assayed for specific molecules or incubated with isolated neutrophils, with or without a matrix metalloproteinase 9 inhibitor. MAIN OUTCOME MEASURES: Concentrations of matrix metalloproteinases 2 and 9 and tissue inhibitor of metalloproteinase 1; matrix metalloproteinase 9 activity; and neutrophil apoptosis. RESULTS: Concentrations of matrix metalloproteinase 9 and tissue inhibitor of metalloproteinase 1 but not matrix metalloproteinase 2 increased over time. This accumulation was abolished by leukoreduction. Matrix metalloproteinase 9 accumulated in an active form. Both leukoreduction and matrix metalloproteinase 9 inhibition reversed stored packed red blood cell-induced, delayed neutrophil apoptosis. CONCLUSIONS: Storage of packed red blood cells for 14 days or more is associated with increases in the concentrations of matrix metalloproteinase 9 and tissue inhibitor of metalloproteinase 1, with the enzyme in excess of its inhibitor. Prestorage leukoreduction prevents this accumulation. Delayed neutrophil apoptosis related to packed red blood cell plasma appears to be due, in part, to matrix metalloproteinase 9. Leukoreduction can help prevent the effects of matrix metalloproteinase 9 on neutrophil apoptosis.

Analysis of Variance↗