The scaffold protein MUPP1 regulates odorant-mediated signaling in olfactory sensory neurons.

The olfactory signal transduction cascade transforms odor information into electrical signals by a cAMP-based amplification mechanism. The mechanisms underlying the very precise temporal and spatial organization of the relevant signaling components remains poorly understood. Here, we identify, using co-immunoprecipitation experiments, a macromolecular assembly of signal transduction components in mouse olfactory neurons, organized through MUPP1. Disruption of the PDZ signaling complex, through use of an inhibitory peptide, strongly impaired odor responses and changed the activation kinetics of olfactory sensory neurons. In addition, our experiments demonstrate that termination of the response is dependent on PDZ-based scaffolding. These findings provide new insights into the functional organization, and regulation, of olfactory signal transduction.

"Four-potential" ferrocene labeling of PNA oligomers via click chemistry.

The scope of the Cu(I)-catalyzed [2 + 3] azide/alkyne cycloaddition (CuAAC, click chemistry) as a key reaction for the conjugation of ferrocene derivatives to N-terminal functionalized PNA oligomers is explored herein (PNA: peptide nucleic acid). The facile solid-phase synthesis of N-terminal azide or alkyne-functionalized PNA oligomer precursors and their cycloaddition with azidoferrocene, ethynylferrocene, and N-(3-ethylpent-1-yn-3-yl)ferrocene-carboxamide (DEPA-ferrocene) on the solid phase are presented. While the click reaction with azidomethylferrocene worked equally well, the ferrocenylmethyl group is lost from the conjugate upon acid cleavage. However, the desired product was obtained via a post-SPPS conversion of the alkyne-PNA oligomer with azidomethylferrocene in solution. The synthesis of all ferrocene-PNA conjugates (trimer t(3)-PNA, 3, 4, 5, 6; 12mer PNA, 10 - t c t a c a a g a c t c, 11 - t c t a c c g t a c t c) succeeded with excellent yields and purities, as determined by mass spectrometry and HPLC. Electrochemical studies of the trimer Fc-PNA conjugates 3, 4, 5, and 6 with four different ferrocene moieties revealed quasi-reversible redox processes of the ferrocenyl redox couple Fc(0/+) and electrochemical half-wave potentials in a range of E(1/2) = -20 mV to +270 mV vs FcH(0/+) (Fc: ferrocenyl, C(10)H(9)Fe). The observed potential differences ΔE(1/2)(min) are always greater than 60 mV for any given pair of Fc-PNA conjugates, thus allowing a reliable differentiation with sensitive electrochemical methods like e.g. square wave voltammetry (SWV). This is the electrochemical equivalent of "four-color" detection and is hence denoted "four-potential" labeling. Preparation and electrochemical investigation of the set of four structurally different and electrochemically distinguishable ferrocenyl groups conjugated to PNA oligomers, as exemplified by the conjugates 3, 4, 5, and 6, demonstrates the scope of the azide/alkyne cycloaddition for the labeling of PNA with electrochemically active ferrocenyl groups. Furthermore, it provides a PNA-based system for the electrochemical detection of single-nucleotide polymorphism (SNP) in DNA/RNA.

Synthesis of organometallic PNA oligomers by click chemistry.

The facile side-specific insertion, on the solid phase, of one or two ferrocene moieties into peptide nucleic acid (PNA) oligomers by click chemistry is presented.