Observation of a large coupling of a bound dihydrogen ligand to phosphorus ligands in trans-[(dppe)(2)Ru(eta(2)-H-2) (PF(OMe)(2))][BF4](2) complex

A new dicationic dihydrogen complex of the type trans-[(dppe)(2)Ru(eta (2)-H-2)(PF(OMe)(2))]BF4](2) has been prepared and characterized. A large coupling of about 50 Hz between the H-2 and trans-phosphorus ligand in this complex has been observed.

M.tuberculosis Pantothenate Kinase: Dual Substrate Specificity and Unusual Changes in Ligand Locations

Kinetic measurements of enzyme activity indicate that type I pantothenate kinase from Mycobacterium tuberculosis has dual substrate specificity for ATP and GTP, unlike the enzyme from Escherichia coli, which shows a higher specificity for ATP. A molecular explanation for the difference in the specificities of the two homologous enzymes is provided by the crystal structures of the complexes of the M. tuberculosis enzyme with (1) GMPPCP and pantothenate, (2) GDP and phosphopantothenate, (3) GDP, (4) GDP and pantothenate, (5) AMPPCP, and (6) GMPPCP, reported here, and the structures of the complexes of the two enzymes involving coenzyme A and different adenyl nucleotides reported earlier. The explanation is substantially based on two critical substitutions in the amino acid sequence and the local conformational change resulting from them. The structures also provide a rationale for the movement of ligands during the action of the mycobacterial enzyme. Dual specificity of the type exhibited by this enzyme is rare. The change in locations of ligands during action,observed in the case of the M. tuberculosis enzyme, is unusual, so is the striking difference between two homologous enzymes in the geometryof the binding site, locations of ligands, and specificity. Furthermore, the dual specificity of the mycobacterial enzyme appears to have been caused by a biological necessity. (C) 2010 Elsevier Ltd.All rights reserved.

Symmetrical Bisbenzimidazoles with Benzenediyl Spacer: The Role of the Shape of the Ligand on the Stabilization and Structural Alterations in Telomeric G-Quadruplex DNA and Telomerase Inhibition

The extremities of chromosomes end in a G-rich single-stranded overhang that has been implicated in the onset of the replicate senescence. The repeated sequence forming a G-overhang is able to adopt a four-stranded DNA structure called G-quadruplex, which is a poor substrate for the enzyme telomerase. Small molecule based ligands that selectively stabilize the telomeric G-quadruplex DNA, induce telomere shortening eventually leading to cell death. Herein, we have investigated the G-quadruplex DNA interaction with two isomeric bisbenzimidazole-based compounds that differ in terms of shape (V-shaped angular vs linear).While the linear isomer induced some stabilization of the intramolecular G-quadruplex structure generated in the presence of Na+ the other, having V-shaped central planar core, caused a dramatic structural alteration of the latter, above a threshold concentration. This transition was evident from the pronounced changes observed in the circular dichroism spectra and from the get mobility shift assa involving the G-quadruples DNA. Notably, this angular isomer could also induce the G-quadruplex formation in the absence of any added cation. The ligand-quadruples complexes were investigated by computational molecular modeling, providing further information on structure-activity relationships. Finally, TRAP (telomerase repeat amplification protocol) experiments demonstrated that the angular isomer is selective toward the inhibition of telomerase activity.

Metal-ion-ligand interactions in thermotropic liquid crystals

The interactions of lithium perchlorate with ligands such as dimethyl sulphoxide, acetonitrile, pyridine and the Schiff base liquid crystals are investigated. The experiments open a new field for the study of metal-ion-ligand interactions in thermotropic liquid crystals.

Competing magnetic interactions in a dinuclear Ni(II) complex: Antiferromagnetic O-H center dot center dot center dot O moiety and ferromagnetic N-3(-) ligand

Synthesis, structural characteristics, magnetic studies and DFT calculations in Ni(II) dinuclear complexes containing two bridging N-3(-) and an O-(HO)-O-... linkage reveal the existence of ferromagnetic interactions between Ni(II) centers via N-3(-) ligands and antiferromagnetic interactions through the H-bonded moiety. The overall magnetic behavior of the system depends on the delicate balance between these two competing interactions.

The Innocent Pleasure : A Study on Luther's theology of music

The aim of the study is to examine Luther s theology of music from the standpoint of pleasure. The theological assessment of musical pleasure is related to two further questions: the role of emotions in Christianity and the apprehension of beauty. The medieval discussion of these themes is portrayed in the background chapter. Significant traits were: the suspicion felt towards sensuous gratification in music, music as a mathematical discipline, the medieval theory of emotions informed by Stoic apatheia and Platonic-Aristotelian metriopatheia, the notion of beauty as an attribute of God, medieval aesthetics as the aesthetic of proportion and the aesthetic of light and the emergence of the Aristotelian view of science that is based on experience rather than speculation. The treatment of Luther s theology of music is initiated with the notion of gift. Luther says that music is the excellent (or even the best) gift of God. This has sometimes been understood as a mere music-lover s enthusiasm. Luther is, however, not likely to use the word gift loosely. His theology can be depicted as a theology of gift. The Triune God is categorically giving. The notion of gift also includes reciprocity. When we receive the gifts of God, it evokes praise in us. Praising God is predominantly a musical phenomenon. The particular benefit of music in Luther s thought is that it can move human emotions. This emphasis is connected to the overall affectivity of Luther s theology. In contrast to the medieval discussion, Luther ascribes to saints not just emotions but particularly warm and tender affections. The power of music is related to the auditory and vocal character of the Word. Faith comes through hearing the Word that is at once musical and affective perception. Faith is not a mere opinion but the affective trust of the heart. Music can touch the human heart and persuade with its sweetness, like the good news of the Gospel. Music allows us to perceive Luther s theology as a theology of joy and pleasure. Joy is for Luther a gift of the Holy Spirit that fills the heart and bursts out in voice and gestures. Pleasure appears to be a central aspect to Luther s theology. The problem of the Bondage of the Will is precisely the human inability to feel pleasure in God s will. To be pleased in the visible and tangible creation is not something a Christian should avoid. On the contrary, if one is not pleased with the world that God has created, it is a sign of unbelief and ingratitude. The pleasure of music is aesthetic perception. This in turn necessitates the investigation of Luther s aesthetics. Aesthetic evaluation is not just a part of Luther s thought. Eventually his theology as a whole could be portrayed in aesthetic terms. Luther s extremely positive appreciation of music illutrates his theology as an affective acknowledgement of the goodness of the Creation and faith as an aesthetic contentment.

Bonding isomerism in the chelate-exchange reactions of isonitroso-β-keto-imino isomeric nickel(ii) mixed ligand complexes

A novel chelate exchange reaction, leading to the formation of a series of N-alkyl substituent dependent mixed ligand isomeric complexes of the type Ni(R-AB)(AC') and Ni(R-AC)(AB') (Figure 1) are discussed. Here, AB and AC denote two different N-bonded isonitroso-β-keto-imino ligand moieties, while AB' and AC' are the corresponding O-bonded ligand moieties and R is an N-alkyl substituent. The isomeric complexes are suggested to be monomeric, neutral and diamagnetic with an asymmetric square planar geometry. The bonding isomerism of the isonitroso group in these complexes is discussed on the basis of the infrared and proton magnetic resonance spectral studies. A probable mechanism for the preparative route is also proposed.

Interaction of synthetic analogs of distamycin and netropsin with nucleic acids. Does curvature of ligand play a role in distamycin-DNA interactions?

Distamycin and netropsin, a class of minor groove binding nonintercalating agents, are characterized by their B-DNA and A-T basespecific interactions. To understand the CQI I ~OIT~ ~ I ~ ~aOnMd ~c hemical basis of the above specificities, the DNA-binding characteristics of a novel synthetic analogue of distamycin have been studied. The analogue, mPD derivative, has the requisite charged end groups and a number of potential hydrogen-bonding loci equal to those of distamycin. The difference in the backbone curvatures of the ligands, distamycin, the mPD derivative, and NSC 101327 (another structurally analogous compound),is a major difference between these ligands. UV and CD spectrosoopic studies reported here show the following salient features: The mPD derivative recognizes only B-DNA, to which it binds via the minor groove. On the other hand, unlike distamycin, it binds with comparable affinities to A-T and G-C base pairs in a natural DNA. These DNA-binding properties are compared with those reported earlier for distamycin and NSC 101327 [Zimmer, Ch., & Wahnert, U. (1986) Prog. Biophys. Mol. Biol. 47, 31-1121. The backbone structures of these three ligands were compared to show the progressive decrease in curvatures in the order distamycin, mPD derivative, and NSC 101327. The plausible significance of the backbone curvature vis-&vis the characteristic B-DNA and AT-specific binding of distamycin is discussed. To our knowledge, this is the first attempt (with a model synthetic analogue) to probe the possible influence of backbone curvature upon the specificity of interactions of the distamycin class of groove-binding ligands with DNA.

Mixed ligand cobalt(III) complexes of tetradentate N,N′-ethylenebis(acetylacetonimine) and flexidentate isonitroso-β-diketones and isonitrosomonoketones

A series of mixed ligand cobalt(III) complexes having the general formula Co(EA)X [where EA = dianion of N,N′-ethylenebis(acetylacetonimine) and X = anion of isonitroso-acetylacetone, IAA; isonitrosobenzoylacetone, IBA; isonitrosodibenzoylmethane, IDBM; isonitrosoethylacetoacetate, IEA; isonitrosoacetoacetanillide, IAN; isonitrosoethylmethylketone, IEMK; isonitrosobenzylmethylketone, IBMK and isonitrosopropiophenone, IPP] have been synthesised and characterised. A facial-cis-β structure (cis with respect to the coordinated two oxygen atoms of EA) with N,N,N,O,O,O ligational environment has been assigned for the complexes. The characterisation of the complexes has been based upon chemical analysis, electrical conductivity, magnetic moment, IR, PMR and electronic spectra.

Coated pits,endosome CURLing and intracellular receptor--ligand trafficking

In mediating endocytosis of extracellular macromolecules; the major mechanism in which cells ingest nutrients, degrade hormones and maintain the protein and lipid compositions of their organelle membrane, the cell surface receptors encounter 'coated pits', migrate continuously from one organelle to another, deliver the 'cargo' and often recycle back to the cell surface. This article is an attempt to give an account of the recent advances in our understanding of the molecular events involved in the 'round trip itinerary' of cell surface receptors.