A Tetranuclear Manganese Cluster with a Star‐Shaped Mn4O6 Core Motif: Directed Synthesis using a Mononuclear Precursor Complex

The tetranuclear manganese(II) complex [Mn₄(ppi)₆](BPh₄)₂ ( 2 ) (Hppi = 2‐pyridylmethyl‐2‐hydroxy phenylimine) is prepared by using the precursor complex [Mn(ppi)₂]·H₂O ( 1 ). Based on UV/Vis‐ and IR‐spectroscopy data in combination with mass spectrometry it has been concluded that 1 is a mononuclear neutral Mn^II complex, in which two ppi ligands chelate the manganese atom. Compound 2 crystallizes in the triclinic space group P1¯ (no. 2), with a = 17.500(3), b = 17.955(4), c = 19.101(4) Å, α = 113.79(3)°, β = 111.33(3)°, γ = 93.91(3)°, V = 4950(2) ų and Z = 2. In the tetranuclear [Mn₄(ppi)₆]²⁺ complex cation Mn(1), Mn(2), and Mn(3) are equivalently coordinated by two deprotonated Hppi ligands leading to a N₄O₂ donor set. The environment of the central Mn(4) is formed by coordination of three [Mn(ppi)₂] fragments resulting in a phenoxo bridged star‐shaped Mn₄O₆ core motif. The average distance of directly adjacent manganese ions is 3.310 Å, whereas the average distance of Mn(1), Mn(2), and Mn(3) among each other is 5.732 Å.     

Impairment of mitochondrial calcium handling in a mtSOD1 cell culture model of motoneuron disease

Background  

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective loss of motor neurons (MN) in the brain stem and spinal cord. Intracellular disruptions of cytosolic and mitochondrial calcium have been associated with selective MN degeneration, but the underlying mechanisms are not well understood. The present evidence supports a hypothesis that mitochondria are a target of mutant SOD1-mediated toxicity in familial amyotrophic lateral sclerosis (fALS) and intracellular alterations of cytosolic and mitochondrial calcium might aggravate the course of this neurodegenerative disease. In this study, we used a fluorescence charged cool device (CCD) imaging system to separate and simultaneously monitor cytosolic and mitochondrial calcium concentrations in individual cells in an established cellular model of ALS.     

Proficiency testing in analytical chemistry, microbiology and laboratory medicine: working discussions on current practice and future directions

A summary of the working group (WG) discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Rome, 5–7 October 2008 is provided. The eight WG’s covered a range of issues concerned with current practice and future directions; how frequently should laboratories participate in PT/EQA? (WG1); developments in PT/EQA within the EU—what is required in future? (WG2); what issues do developing countries face with regards to PT/EQA? (WG3), what issues are specific to microbiology PT/EQA? (WG4); what new fields are emerging for PT/EQA? (WG5); what will be the impact of the new ISO/IEC 17043 standard? (WG6); do current PT/EQA schemes meet the needs of participants? (WG7); and what are the issues that affect the quality of proficiency test items? (WG8). Delegates with different backgrounds were on each WG in order to capture a range of views and experience from a number of different sectors. Working group representatives included PT/EQA providers, participants in PT/EQA schemes and end users of PT results such as accreditation bodies and regulatory authorities, from countries around the world.