Unusual luminescent properties of odd- and even-substituted naphthyl-derivatized dioxetanes

With the advent of enzymatically induced chemiluminescence and improved instrumentation for luminometry, ultrasensitive detection of a wide variety of analytes is now possible using standard immunoassay and DNA probe formats. Model molecular orbital calculations and literature precedent suggest that the singlet efficiencies observed upon decomposition of dioxetanes appended with donor substituted aromatic moieties are dependent on substitution pattern. We have recently discovered, in a series of 3-(2′-spiroadamantane)-4-methoxy-4-acetoxynaphth-2′-yl-1,2-dioxetanes, that enzymatic generation of a nonconjugated, charge transfer excited state results in luminescence of markedly different properties than that observed from an isomeric, conjugated excited state. An example of the former type, 3-(2′-spiroadamantane)-4-methoxy-4-(7″-acetoxy)naphth-2′-yl-1,2-dioxetane (1) emitting at 550 nm, not only provides an increase in Φ_CL but exhibits a dramatic bathochromic shift of 80–110 nm from the 460 nm emission of the conjugated isomer 3-(2′-spiroadamantane)-4-methoxy-4-(6″-acetoxy)naphth-2′-yl-1,2-dioxetane (2). These developments, along with the attendant glow-type luminescence kinetics displayed during the enzymatic decomposition of the new ‘odd-pattern’ dioxetane, allow the design of simple protocols capable of simultaneous or ‘multichannel’ detection of several analytes.     

Phospholipase A2 activity on mixed lipid monolayers: Inhibition and activation of phospholipases A2 from porcine pancreas and Crotalus adamanteus by anionic and neutral amphiphiles

The effects of anionic and neutral amphiphiles on porcine pancreatic and Crotalus adamanteus phospholipases A2 were studied in a monolayer system as a function of surface pressure. The insoluble amphiphile, dicetyl phosphate (DCP), inhibited the hydrolysis of didecanoylphosphatidylcholine (DDPC) by both enzymes below their normal cutoff pressures with pure DDPC. DCP, however, enhanced enzyme penetration and thus activated the pancreatic enzyme above its normal cutoff pressure. The soluble surfactants, 3,5-dibromo- and 3,5-diiodosalicyclate, acetyl salicylate, and salicylic acid, had similar effects. 1,2-Didecanoin inhibited the hydrolysis of DDPC below the normal cutoff pressures and increased the cutoff pressures for both enzymes. Zwitterionic detergents, N-dodecyl- and N-tetradecyl-N,N-dimethyl-3-aminopropanesulfonate, were found to be potent inhibitors of the pancreatic enzyme on DDPC monolayers. Relative substrate specificities for both enzymes were determined as a function of surface pressure with phosphatidylcholine, phosphatidylglycerol, and phosphatidic acid. Pancreatic phospholipase A2 was more active and penetrated to higher pressures with the anionic phospholipids, while the venom enzyme was more active with phosphatidylcholine.     

Parkin is an E3 ligase for the ubiquitin-like modifier FAT10, which inhibits Parkin activation and mitophagy

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