Synthesis of novel MMT/acyl-protected nucleo alanine monomers for the preparation of DNA/alanyl-PNA chimeras

Alanyl-peptide nucleic acid (alanyl-PNA)/DNA chimeras are oligomers envisaged to be beneficial in efficient DNA diagnostics based on an improved molecular beacon concept. A synthesis of alanyl-PNA/DNA chimera can be based on the solid phase assembly of the oligomer with mixed oligonucleotide/peptide backbone under DNA synthesis conditions, in which the nucleotides are introduced as phosphoramidites, whereas the nucleo amino acids make use of the acid labile monomethoxytrityl (MMT) group for temporary protection of the α-amino groups and acyl protecting groups for the exocyclic amino functions of the nucleobases. In this work, we realized for the first time the synthesis of all four MMT/acyl-protected nucleo alanines, achieved by deprotection/reprotection of the newly synthesized Boc/acyl intermediates, useful monomers for the obtainment of (alanyl-PNA)/DNA chimeras by conditions fully compatible with the standard phosphoramidite DNA synthesis strategy

Nucleic acid-based fluorescent probes and their analytical potential

It is well known that nucleic acids play an essential role in living organisms because they store and transmit genetic information and use that information to direct the synthesis of proteins. However, less is known about the ability of nucleic acids to bind specific ligands and the application of oligonucleotides as molecular probes or biosensors. Oligonucleotide probes are single-stranded nucleic acid fragments that can be tailored to have high specificity and affinity for different targets including nucleic acids, proteins, small molecules, and ions. One can divide oligonucleotide-based probes into two main categories: hybridization probes that are based on the formation of complementary base-pairs, and aptamer probes that exploit selective recognition of nonnucleic acid analytes and may be compared with immunosensors. Design and construction of hybridization and aptamer probes are similar. Typically, oligonucleotide (DNA, RNA) with predefined base sequence and length is modified by covalent attachment of reporter groups (one or more fluorophores in fluorescence-based probes). The fluorescent labels act as transducers that transform biorecognition (hybridization, ligand binding) into a fluorescence signal. Fluorescent labels have several advantages, for example high sensitivity and multiple transduction approaches (fluorescence quenching or enhancement, fluorescence anisotropy, fluorescence lifetime, fluorescence resonance energy transfer (FRET), and excimer-monomer light switching). These multiple signaling options combined with the design flexibility of the recognition element (DNA, RNA, PNA, LNA) and various labeling strategies contribute to development of numerous selective and sensitive bioassays. This review covers fundamentals of the design and engineering of oligonucleotide probes, describes typical construction approaches, and discusses examples of probes used both in hybridization studies and in aptamer-based assays

Urban Leadership in German Local Politics: The Rise, Role and Performance of the Directly Elected (Chief Executive) Mayor

In the post-1945 rebuilding of local democracy and local government in West Germany the local government statutes enacted by each of the regions ("Länder") created a conspicuous variety of local governments that ranged from the council/directly elected (chief executive) mayor form (installed in the South German Länder of Baden-Württemberg and Bayern) to that of the (British local government-derived) council/council-elected mayor, and the city director form (introduced in the Land of Nordrhein-Westfalen). This made almost for a natural experiment with different local government models. Since the early 1990s, in a striking sequence of legislative moves, all Länder have adopted the ('South German') directly elected (chief executive) variant. The legislative motives behind this shift were twofold: first, to strengthen the direct democratic rights of citizens ('local democracy'); and, second, to improve the capacity of local leadership in running and managing the city ('governability'). The article argues that - as evidenced by the 50 year-long practice in the South German Länder - the directly elected (chief executive) mayor form seems capable of fulfilling the double goal of strengthening the administrative leadership in local government and of enhancing its political accountability to the citizens. Furthermore, experience indicates that the potentially 'over-powerful' position of the directly elected mayor (as political "and" administrative leader) has been counterbalanced and held in check by an active local council and by vigorous local political parties. Copyright Joint Editors and Blackwell Publishing Ltd 2004.