Chemistry

Reporting a Break-Up

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Science  24 Sep 2010:
Vol. 329, Issue 5999, pp. 1577
DOI: 10.1126/science.329.5999.1577-b

Phospholipase enzymes play a role in a wide range of physiological processes—including digestion, inflammation response, membrane remodeling, and intercellular signaling—through the degradation of phospholipids. The A2 class of phospholipases (PLA2) acts on glycerophospholipids to produce free fatty acids and lysolipids. As dysregulation of PLA2 figures in many pathological conditions, measurement of its activity and concentration is important. PLA2 activity has been shown to be sensitive to environment though, so mounting colorimetric probes on a substrate does not provide accurate measures. Aili et al. skirted this problem through the use of a pair of complementary polypeptides, JR2EC and JR2KC. A cysteine residue in the central loop of JR2EC bound the peptide to a gold nanoparticle, whereas the cysteines in two JR2KC chains were covalently linked via a disulfide bridge to form a bifunctional dimer (JR2KC2). The JR2KC2 was then loaded into liposomes that were designed to be susceptible to PLA2 degradation. Once released, the JR2KC2 tended to hetero-associate with the gold-bonded JR2EC, causing aggregation of the gold nanoparticles and a corresponding red shift of the surface plasmon resonance visible to the naked eye. A lag in the detection time could be correlated with the concentration of PLA2 over a sensitivity range spanning 7 nM to 700 pM.

Nano Lett. 10, 10.1021/nl1024062 (2010).

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