University of Erlangen-Nuremberg

About: University of Erlangen-Nuremberg is a education organization based out in Erlangen, Bayern, Germany. It is known for research contribution in the topics: Population & Immune system. The organization has 42405 authors who have published 85600 publications receiving 2663922 citations.

Structures of Organonitrogen—Lithium Compounds: Recent Patterns and Perspectives in Organolithium Chemistry

Abstract: Publisher Summary This chapter discusses the current patterns and perspectives in organolithium chemistry, including the structures of organonitrogenlithium (N-Li) compounds. The chapter explains the compounds with N-Li bonds. These are chiefly lithium imides [iminolithiums (RR’C=NLi) n ] and their complexes with added Lewis bases (L), and lithium amides [amidolithiums (RR’NLi) n ] and their complexes. For the lithium amide species, particularly, only those whose R,R’ groups that do not contain additional functionalities are described—that is, the R,R’ groups remain largely uninvolved with lithium centers. These species are termed “simple” lithium amides. N-Li compounds and, particularly, lithium amides (R 2 NLi) are widely used both in organic and in organometallic syntheses. For the former, these strong bases are employed as proton abstractors to generate new organolithiums. Although synthetic uses have dominated the interest in N-Li compounds, the chapter focuses on the structures. Most of the physical properties of organolithium compounds (the marked exception being conductance) arise, because of the overall size and shape of the units making up these materials and the nature of the peripheries of these units. The basic structural building block of any organolithium is an ion pair, R – L + . The identities and structures of complexed organolithiums are of particular importance.

Carbon catabolite repression in bacteria : choice of the carbon source and autoregulatory limitation of sugar utilization

Abstract: Carbon catabolite repression (CCR) in bacteria is generally regarded as a regulatory mechanism to ensure sequential utilization of carbohydrates. Selection of the carbon sources is mainly made at the level of carbohydrate-specific induction. Since virtually all carbohydrate catabolic genes or operons are regulated by specific control proteins and require inducers for high level expression, direct control of the activity of regulators or control of inducer formation is an efficient measure to keep them silent. By these mechanisms, bacteria are able to establish a hierarchy of sugar utilization. In addition to the control of induction processes by CCR, bacteria have developed global transcriptional regulation circuits, in which pleiotropic regulators are activated. These global control proteins, the catabolite gene activator protein (CAP), also known as cAMP receptor protein, in Escherichia coli or the catabolite control protein (CcpA) in Gram-positive bacteria with low GC content, act upon a large number of catabolic genes/operons. Since practically any carbon source is able to trigger global transcriptional control, expression of sugar utilization genes is restricted even in the sole presence of their cognate substrates. Consequently, CAP- or CcpA-dependent catabolite repression serves as an autoregulatory device to keep sugar utilization at a certain level rather than to establish preferential utilization of certain carbon sources. Together with other autoregulatory mechanisms that are not acting at the gene expression level, CCR helps bacteria to adjust sugar utilization to their metabolic capacities. Therefore, catabolic/metabolic balance would perhaps better describe the physiological role of this regulatory network than the term catabolite repression.

Fullerene for organic electronics

Abstract: This tutorial review surveys and highlights the integration of different molecular wires—in combination with chromophores that exhibit (i) significant absorption cross section throughout the visible part of the solar spectrum and (ii) good electron donating power—into novel electron donor–acceptor conjugates The focus is predominantly on charge transfer and charge transport features of the most promising systems