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PubMed2001

Specific packaging of nodaviral RNA2 requires the N-terminus of the capsid protein.

Flock house virus (FHV), a member of the family Nodaviridae, is a nonenveloped, icosahedral insect virus whose capsids are assembled from 180 copies of a single type of coat protein. The viral genome is split between two segments of single-stranded positive-sense RNA, RNA1 and RNA2, which are packaged into a single virion. We previously demonstrated that synthesis of FHV coat protein in the baculovirus expression system results in assembly of virus-like particles whose capsids are indistinguishable from those of native virions, although the encapsidated RNA represents primarily cellular RNA. In contrast, expression of a deletion mutant lacking N-terminal residues 2-31 results in formation of multiple types of particles which differ in size, shape, and RNA contents. We postulated that the polymorphism was imposed by the type of RNA that the coat protein selected for packaging. In the current study we tested this hypothesis by analyzing the assembly of the mutant coat protein in Drosophila cells in the presence of replicating FHV RNAs. As anticipated, the resulting particles had the same shape and dimensions as wt virions. Surprisingly, however, they contained little RNA2 while packaging of RNA1 was not affected. Small amounts of defective interfering RNAs, which emerged rapidly in the presence of the mutant coat protein, were also detected. Taken together, these observations confirm our earlier hypothesis that selection of nonviral RNAs for packaging can significantly alter the assembly process. In addition, they demonstrate that the N-terminus of the FHV coat protein contains important determinants for recognition and packaging of RNA2. Our results provide the first evidence that encapsidation of the two genomic RNAs occurs independently and that the coat protein uses different regions for the recognition of RNA1 and RNA2.

Amino Acid Sequence↗

PubMed2003

Self-assembly mechanism of a bimetallic europium triple-stranded helicate.

We report the self-assembly process of a supramolecular edifice based on the coordination of europium(III) by a ditopic strand L bearing tridentate bis(benzimidazolyl)pyridine subunits. Varying the metal/ligand ratio and using a fruitful combination of electrospray mass spectrometry and absorption spectrophotometry, we characterized three major complexes (EuL(2), Eu(2)L(2), and Eu(2)L(3)) in acetonitrile. Kinetic investigations showed an alternative "braiding" and "keystone" mechanism leading to Eu(2)L(3). The formation mechanism of the dinuclear triple-stranded helicate, which is mainly governed by electrostatic interactions, goes via the "side-by-side" Eu(2)L(2) intermediate. Our thermodynamic and kinetic data allow the prediction of the apparent "magic" self-assembly of Eu(2)L(3) which is fast and efficient only under a strict set of conditions.

Journal Article↗

PubMed2003

Arresting and releasing Staphylococcal alpha-hemolysin at intermediate stages of pore formation by engineered disulfide bonds.

alpha-Hemolysin (alphaHL) is secreted by Staphylococcus aureus as a water-soluble monomer that assembles into a heptamer to form a transmembrane pore on a target membrane. The crystal structures of the LukF water-soluble monomer and the membrane-bound alpha-hemolysin heptamer show that large conformational changes occur during assembly. However, the mechanism of assembly and pore formation is still unclear, primarily because of the difficulty in obtaining structural information on assembly intermediates. Our goal is to use disulfide bonds to selectively arrest and release alphaHL from intermediate stages of the assembly process and to use these mutants to test mechanistic hypotheses. To accomplish this, we created four double cysteine mutants, D108C/K154C (alphaHL-A), M113C/K147C (alphaHL-B), H48C/ N121C (alphaHL-C), I5C/G130C (alphaHL-D), in which disulfide bonds may form between the pre-stem domain and the beta-sandwich domain to prevent pre-stem rearrangement and membrane insertion. Among the four mutants, alphaHL-A is remarkably stable, is produced at a level at least 10-fold greater than that of the wild-type protein, is monomeric in aqueous solution, and has hemolytic activity that can be regulated by the presence or absence of reducing agents. Cross-linking analysis showed that alphaHL-A assembles on a membrane into an oligomer, which is likely to be a heptamer, in the absence of a reducing agent, suggesting that oxidized alphaHL-A is halted at a heptameric prepore state. Therefore, conformational rearrangements at positions 108 and 154 are critical for the completion of alphaHL assembly but are not essential for membrane binding or for formation of an oligomeric prepore intermediate.

Amino Acid Substitution↗

PubMed2000

Self-assembly and supramolecular organization of EMILIN.

The primary structure of human Elastin microfibril interface-located protein (EMILIN), an elastic fiber-associated glycoprotein, consists of a globular C1q domain (gC1q) at the C terminus, a short collagenous stalk, a long region with a high potential for forming coiled-coil alpha helices, and a cysteine-rich N-terminal sequence. It is not known whether the EMILIN gC1q domain is involved in the assembly process and in the supramolecular organization as shown for the similar domain of collagen X. By employing the yeast two-hybrid system the EMILIN gC1q domains interacted with themselves, proving for the first time that this interaction occurs in vivo. The gC1q domain formed oligomers running as trimers in native gels that were less stable than the comparable trimers of the collagen X gC1q domain since they did not withstand heating. The collagenous domain was trypsin-resistant and migrated at a size corresponding to a triple helix under native conditions. In reducing agarose gels, EMILIN also migrated as a trimer, whereas under non-reducing conditions it formed polymers of many millions of daltons. A truncated fragment lacking gC1q and collagenous domains assembled to a much lesser extent, thus deducing that the C-terminal domain(s) are essential for the formation of trimers that finally assemble into large EMILIN multimers.

Cell Line↗

PubMed1998

Assembly of the herpes simplex virus capsid: preformed triplexes bind to the nascent capsid.

The herpes simplex virus type 1 (HSV-1) capsid is a T=16 icosahedral shell that forms in the nuclei of infected cells. Capsid assembly also occurs in vitro in reaction mixtures created from insect cell extracts containing recombinant baculovirus-expressed HSV-1 capsid proteins. During capsid formation, the major capsid protein, VP5, and the scaffolding protein, pre-VP22a, condense to form structures that are extended into procapsids by addition of the triplex proteins, VP19C and VP23. We investigated whether triplex proteins bind to the major capsid-scaffold protein complexes as separate polypeptides or as preformed triplexes. Assembly products from reactions lacking one triplex protein were immunoprecipitated and examined for the presence of the other. The results showed that neither triplex protein bound unless both were present, suggesting that interaction between VP19C and VP23 is required before either protein can participate in the assembly process. Sucrose density gradient analysis was employed to determine the sedimentation coefficients of VP19C, VP23, and VP19C-VP23 complexes. The results showed that the two proteins formed a complex with a sedimentation coefficient of 7.2S, a value that is consistent with formation of a VP19C-VP23(2) heterotrimer. Furthermore, VP23 was observed to have a sedimentation coefficient of 4.9S, suggesting that this protein exists as a dimer in solution. Deletion analysis of VP19C revealed two domains that may be required for attachment of the triplex to major capsid-scaffold protein complexes; none of the deletions disrupted interaction of VP19C with VP23. We propose that preformed triplexes (VP19C-VP23(2) heterotrimers) interact with major capsid-scaffold protein complexes during assembly of the HSV-1 capsid.

Animals↗

PubMed2005

[Development of novel solid-phase polymeric catalysts for organic syntheses].

Highly active and reusable polymeric catalysts were produced by a self-assembly process of non-cross-linked amphiphilic polymeric ligands with inorganic species. Thus a new insoluble tungsten polymeric catalyst PWAA 1 was prepared from H(3)PW(12)O(40) and poly[(N-isopropylacrylamide)-co-(acrylamide with ammonium salt)], which was suitable for the oxidation of alcohols, amines, and sulfides in aqueous hydrogen peroxide. A new insoluble palladium polymeric catalyst PdAS 2 was produced by self-organization of (NH(4))(2)PdCl(4) and poly[(N-isopropylacrylamide)(10)-co-diphenylphosphinostyrene], which is an excellent recyclable catalyst for the Suzuki-Miyaura reaction in water, water-organic solvents, and organic solvents. It is commercially available from Tokyo Kasei Kogyo (TCI). An improved insoluble palladium polymeric catalyst PdAS-V 3 was assembled from (NH(4))(2)PdCl(4) and poly[(N-isopropylacrylamide)(5)-co-diphenylphosphinostyrene], providing a reusable system for the Mizorogi-Heck reaction. A solid-phase titanium asymmetric polymeric catalyst TiSS 4 was made from Ti (O-i-Pr)(4) and poly(styryl-linked binaphtholate-co-styrene) which promotes an enantioselective carbonyl-ene reaction as a recyclable catalyst.

Catalysis↗

PubMed2002

Mechanistic studies of the process of amyloid fibrils formation by the use of peptide fragments and analogues: implications for the design of fibrillization inhibitors.

The process of amyloid fibrils formation is a common mechanism of a large number of unrelated infectious, genetic and spontaneous diseases. A partial list includes the bovine spongiform encephalopathy (BSE), Alzheimer's diseases, Type II diabetes, Creutzfeldt-Jakob disease, and various unrelated amyloidosis diseases. In spite of its significant clinical importance, the mechanism of fibrillization is not fully understood. This review discusses the recent advancements in the mechanistic studies of amyloid formation by the use peptide fragments and analogues of amyloid-forming proteins and polypeptides. The use of short peptide shed much light of the mechanism of amyloid fibrillization. Recent studies clearly prove that very short peptide fragments (as short as pentapeptides) can form well-ordered amyloidal structures. Therefore, the molecular recognition and self-assembly process that lead to the formation of order structures is being mediated by small structural elements. Analysis of short amyloid-related fragment by the use of an alanine-scan and sequence analysis of a variety of unrelated peptide and protein fragments suggest that aromatic interaction may play a central role in the process of amyloid formation. Inhibitors that are based on the short aromatic elements already demonstrated clear potency in arresting the process of amyloid fibrils formation. Taken together, the recent advancement in the mechanistic understanding of the process of amyloid fibrils formation has a major importance in the development of inhibitors of fibrillization that may serve as future therapeutic means to treat amyloid diseases.

Amyloid beta-Peptides↗

PubMed2005

Functional interaction of the adenovirus IVa2 protein with adenovirus type 5 packaging sequences.

Adenovirus type 5 (Ad5) DNA packaging is initiated in a polar fashion from the left end of the genome. The packaging process is dependent on the cis-acting packaging domain located between nucleotides 230 and 380. Seven AT-rich repeats that direct packaging have been identified within this domain. A1, A2, A5, and A6 are the most important repeats functionally and share a bipartite sequence motif. Several lines of evidence suggest that there is a limiting trans-acting factor(s) that plays a role in packaging. Both cellular and viral proteins that interact with adenovirus packaging elements in vitro have been identified. In this study, we characterized a group of recombinant viruses that carry site-specific point mutations within a minimal packaging domain. The mutants were analyzed for growth properties in vivo and for the ability to bind cellular and viral proteins in vitro. Our results are consistent with a requirement of the viral IVa2 protein for DNA packaging via a direct interaction with packaging sequences. Our results also indicate that higher-order IVa2-containing complexes that form on adjacent packaging repeats in vitro are the complexes required for the packaging activity of these sites in vivo. Chromatin immunoprecipitation was used to study proteins that bind directly to the packaging sequences. These results demonstrate site-specific interaction of the viral IVa2 and L1 52/55K proteins with the Ad5 packaging domain in vivo. These results confirm and extend those previously reported and provide a framework on which to model the adenovirus assembly process.

Adenoviruses, Human↗

PubMed1996

Assembly of the herpes simplex virus capsid: characterization of intermediates observed during cell-free capsid formation.

The herpes simplex virus-1 (HSV-1) capsid is an icosahedral shell approximately 15 nm thick and 125 nm in diameter. Three of its primary structural components are a major capsid protein (VP5; coded by the UL19 gene) and two minor proteins, VP19C (UL38 gene) and VP23 (UL18 gene). Assembly of the capsid involves the participation of two additional proteins, the scaffolding protein (UL26.5 gene) and the maturational protease (UL26 gene). With the goal of identifying morphological intermediates in the assembly process, we have examined capsid formation in a cell-free system containing the five HSV-1 proteins mentioned above. Capsids and capsid-related structures formed during progressively longer periods of incubation were examined by electron microscopy of thin-sectioned specimens. After one minute, 90 minutes and eight hours of incubation the structures observed, respectively, were partial capsids, closed spherical capsids and polyhedral capsids. Partial capsids were two-layered structures consisting of a segment of external shell partially surrounding a region of scaffold. They appeared as wedges or angular segments of closed spherical capsids, the angle ranging from less than 30 degrees to greater than 270 degrees. Partial capsids are suggested to be precursors of closed spherical capsids because, whereas partial capsids were the predominant assembly product observed after one minute of incubation, they were rare in reactions incubated for 45 minutes or longer. Closed spherical capsids were highly uniform in morphology, consisting of a closed external shell surrounding a thick scaffold similar in morphology to the same layers seen in partial capsids. In negatively stained specimens, closed spherical capsids appeared round in profile, suggesting that they are spherical rather than polyhedral in shape. A three-dimensional reconstruction computed from cryoelectron micrographs confirmed that closed spherical capsids are spherical with T = 16 icosahedral symmetry. The reconstruction showed further that, compared to mature HSV-1 capsids, closed spherical capsids are more open structures in which the capsid floor layer is less pronounced. In contrast to closed spherical capsids, polyhedral capsids exhibited distinct facets and vertices, indicating that they are icosahedral like the capsids in mature virions. Upon incubation in vitro, purified closed spherical capsids matured into polyhedral capsids, indicating that the latter arise by angularization of the former. Partial capsids, closed spherical capsids and polyhedral capsids were all found to contain VP5, VP19C, VP23, VP21 and the scaffolding protein; the scaffolding protein being predominantly in the immature, uncleaved form in all cases. Polyhedral capsids and closed spherical capsids were found to differ in their sensitivity to disruption at 2 degrees C. Closed spherical capsids were disassembled while polyhedral capsids were unaffected. Our results suggest that HSV-1 capsid assembly begins with the partial capsid and proceeds through a closed, spherical, unstable capsid intermediate to a closed, icosahedral form similar to that found in the mature virion. Structures resembling HSV-1 partial capsids have been described as capsid assembly intermediates in Salmonella typhimurium bacteriophage P22. HSV-1 capsid maturation from a fragile, spherical state to a robust polyhedral form resembles the prohead maturation events undergone by dsDNA bacteriophages including lambda, T4 and P22. Because of this similarity, we propose the name procapsid for the closed spherical capsid intermediate in HSV-1 capsid assembly.

Capsid↗

PubMed1996

The gene 59 protein of bacteriophage T4. Characterization of protein-protein interactions with gene 32 protein, the T4 single-stranded DNA binding protein.

The gene 59 protein (gp59) of bacteriophage T4 stimulates the activities of gene 41 protein (gp41), the T4 replicative DNA helicase, by promoting the assembly of gp41 onto single-stranded (ss)-DNA molecules that are covered with cooperatively bound gene 32 protein (gp32). This helicase-ssDNA assembly process, which is important for the reconstitution of the primosome component of the T4 DNA replication fork, appears to require both gp59-gp41 and gp59-gp32 protein-protein interactions. In this study we characterize the physical and functional interactions of gp59 with gp32, the T4 ssDNA-binding protein. Experimental results presented herein indicate: 1) that gp59 binds specifically to both free and ssDNA-bound gp32 molecules; and 2) that in both cases binding involves contacts between gp59 and the acidic C-terminal domain of gp32 (the so-called "A-domain"). We further show that single-stranded DNA molecules coated with (gp32-A), a truncated form of gp32 lacking the A-domain, are refractory to gp59-dependent helicase assembly. The data indicate that specific contacts between gp59 molecules and the A-domains of gp32 molecules are essential for gp59-dependent assembly of gp41 onto gp32-ssDNA complexes. Our results are consistent with a model in which gp59 binds to gp32 molecules within the gp32-ssDNA complex and therein forms a target site for helicase-ssDNA assembly.

Adenosine Triphosphatases↗

PubMed1998

alpha-tocopherol inhibits the respiratory burst in human monocytes. Attenuation of p47(phox) membrane translocation and phosphorylation.

Vitamin E (alpha-tocopherol), one of the most important natural antioxidants, is assumed to be beneficial in the prevention of cardiovascular diseases. alpha-Tocopherol exhibits acyl-peroxyl-radical scavenger properties and exerts cell-mediated actions in the hemovascular compartment, such as inhibition of superoxide anion (O-2) production by leukocytes. The aim of this study was to examine the mechanism underlying the inhibitory effect of alpha-tocopherol on O-2 production by human monocytes. In activated monocytes O-2 is produced by the NADPH-oxidase enzyme complex. The oxidase activation elicited by phorbol myristate acetate (PMA) requires membrane translocation of several cytosolic factors. We found that in human PMA-stimulated adherent monocytes, alpha-tocopherol (but not beta-tocopherol) inhibited O-2 production in intact cells but had no effect on a membrane preparation containing activated NADPH-oxidase, suggesting that alpha-tocopherol impairs the assembly process of the enzyme complex. We showed that translocation and phosphorylation of the cytosolic factor p47(phox) were reduced in monocytes preincubated with alpha-tocopherol. We verified that the tryptic phosphopeptide map of monocyte p47(phox) was similar to that of neutrophil p47(phox), indicating that several serine residues were phosphorylated. Peptides whose phosphorylation is dependent on protein kinase C (PKC) were phosphorylated to a lesser degree when p47(phox) was immunoprecipitated from alpha-tocopherol-treated monocytes. In vitro, the activity of PKC from monocytes was inhibited by alpha-tocopherol in a specific manner compared with that of beta-tocopherol or Trolox(R). Membrane translocation of PKC was not affected. These results show that alpha-tocopherol inhibits O-2 production by human adherent monocytes by impairing the assembly of the NADPH-oxidase and suggest that the inhibition of phosphorylation and translocation of the cytosolic factor p47(phox) results from a decrease in PKC activity.

Biological Transport↗

PubMed2000

The cell biology and physiologic relevance of ApoE recycling.

Apolipoprotein E (apoE) is unique among the different apoproteins because of its many functions in the assembly, processing, and removal of plasma lipoproteins. Some of these functions require the presence of apoE inside the cell or in close association with its outer membrane. For example, the presence of apoE increases triglyceride content in newly formed very low-density lipoprotein (VLDL), whereas the fast removal of chylomicrons requires the presence of a cellular pool of apoE ready to surface and bind to membrane proteoglycans and possibly to lipoprotein receptors such as the LDL receptor-related protein (LRP). Our recent discovery that VLDL-apoE internalized by hepatocytes is partially protected from lysosomal degradation and recycles through the Golgi apparatus suggests that the biologic cycle of apoE may not be concluded when the lipoprotein is taken up by the cell, and that recycling apoE may have a physiologic role in lipoprotein assembly, remnant removal, and cholesterol efflux.

Animals↗

PubMed2000

Versatility of the accessory C proteins of Sendai virus: contribution to virus assembly as an additional role.

The P/C mRNA of Sendai virus (SeV) encodes a nested set of accessory proteins, C', C, Y1, and Y2, referred to collectively as C proteins, using the +1 frame relative to the open reading frame of phospho (P) protein and initiation codons at different positions. The C proteins appear to be basically nonstructural proteins as they are found abundantly in infected cells but greatly underrepresented in the virions. We previously created a 4C(-) SeV, which expresses none of the four C proteins, and concluded that the C proteins are categorically nonessential gene products but greatly contribute to viral full replication and infectivity (A. Kurotani et al., Genes Cells 3:111-124, 1998). Here, we further characterized the 4C(-) virus multiplication in cultured cells. The viral protein and mRNA synthesis was enhanced with the mutant virus relative to the parental wild-type (WT) SeV. However, the viral yields were greatly reduced. In addition, the 4C(-) virions appeared to be highly anomalous in size, shape, and sedimentation profile in a sucrose gradient and exhibited the ratios of infectivity to hemagglutination units significantly lower than those of the WT. In the WT infected cells, C proteins appeared to colocalize almost perfectly with the matrix (M) proteins, pretty well with an external envelope glycoprotein (hemagglutinin-neuraminidase [HN]), and very poorly with the internal P protein. In the absence of C proteins, there was a significant delay of the incorporation of M protein and both of the envelope proteins, HN and fusion (F) proteins, into progeny virions. These results strongly suggest that the accessory and basically nonstructural C proteins are critically required in the SeV assembly process. This role of C proteins was further found to be independent of their recently discovered function to counteract the antiviral action of interferon-alpha/beta. SeV C proteins thus appear to be quite versatile.

Animals↗

PubMed1997

A minimal spliceosomal complex A recognizes the branch site and polypyrimidine tract.

The association of U2 snRNP with the pre-mRNA branch region is a critical step in the assembly of spliceosomal complexes. We describe an assembly process that reveals both minimal requirements for formation of a U2 snRNP-substrate RNA complex, here designated the Amin complex, and specific interactions with the branch site adenosine. The substrate is a minimal RNA oligonucleotide, containing only a branch sequence and polypyrimidine tract. Interactions at the branch site adenosine and requirements for polypyrimidine tract-binding proteins for the Amin complex are the same as those of authentic prespliceosome complex A. Surprisingly, Amin complex formation does not require U1 snRNP or ATP, suggesting that these factors are not necessary for stable binding of U2 snRNP per se, but rather are necessary for accessibility of components on longer RNA substrates. Furthermore, there is an ATP-dependent activity that releases or destabilizes U2 snRNP from branch sequences. The simplicity of the Amin complex will facilitate a detailed understanding of the assembly of prespliceosomes.

Adenosine Triphosphate↗

PubMed1996

Collagen fibril formation.

Collagen is most abundant in animal tissues as very long fibrils with a characteristic axial periodic structure. The fibrils provide the major biomechanical scaffold for cell attachment and anchorage of macromolecules, allowing the shape and form of tissues to be defined and maintained. How the fibrils are formed from their monomeric precursors is the primary concern of this review. Collagen fibril formation is basically a self-assembly process (i.e. one which is to a large extent determined by the intrinsic properties of the collagen molecules themselves) but it is also sensitive to cell-mediated regulation, particularly in young or healing tissues. Recent attention has been focused on "early fibrils' or "fibril segments' of approximately 10 microns in length which appear to be intermediates in the formation of mature fibrils that can grow to be hundreds of micrometers in length. Data from several laboratories indicate that these early fibrils can be unipolar (with all molecules pointing in the same direction) or bipolar (in which the orientation of collagen molecules reverses at a single location along the fibril). The occurrence of such early fibrils has major implications for tissue morphogenesis and repair. In this article we review the current understanding of the origin of unipolar and bipolar fibrils, and how mature fibrils are assembled from early fibrils. We include preliminary evidence from invertebrates which suggests that the principles for bipolar fibril assembly were established at least 500 million years ago.

Animals↗

PubMed2006

Prenylation of HDAg and antiviral drug development.

Hepatitis delta virus (HDV) is an important cause of acute and chronic liver disease. Current medical therapies are unable to effectively eradicate HDV infections. Research into the molecular virology of the HDV life cycle has revealed a fascinating collection of biology. These insights are now beginning to be translated into new potential treatment strategies. For example, an essential step in the virus assembly process involves the post-translational lipid modification of a specific HDV protein, namely prenylation of large delta antigen. Preventing prenylation abolishes virus particle formation. Drugs capable of specifically inhibiting prenylation have been developed for use in humans. These agents represent a new class of antiviral agents, with HDV as a first target. Here, a brief review of the HDV life cycle emphasizing the role of prenylation is presented along with implications for drug development and therapy.

Antiviral Agents↗

PubMed2006

Dendrimer pattern formation in evaporating drops.

The redistribution of organic solutes during drop evaporation is a nanoscale self-assembly process with relevance to technologies ranging from inkjet printing of organic displays to synthesis of biosmart interfaces for sensing and screening. We have used solutions of dendrimer molecules with incrementally varying terminal site chemistry to explore whether the condensed dendrimer patterns resulting from microdroplet evaporation sensitively depend on, and are characteristic of, the surface chemistry of the solute molecules. This hypothesis has been experimentally confirmed by comparing the behavior of microdroplets of G4, G4-25%C12, and G4-50%C12 dendrimers dissolved in pentanol and deposited on mica substrates. For the dilute concentration studied here, the presence of periodically 'scalloped' dendrimer rings is ubiquitous. The instability wavelength of the scalloped rings is found to be proportional to the width of the ring, similar to observations of the rim instability in dewetting holes. The effect of dendrimer surface chemistry is obvious in the detailed structure of the self-assembled rings. G4 rings are diffuse and disordered with no evidence for layered growth. G4-25%C12 exhibits highly ordered ring structures and the onset of monomolecular terracing. G4-50%C12 exhibits highly periodic scallops and very distinct monomolecular height terraced growth of the rings with flat terraces and sharply defined steps. On the basis of these results, it is likely that the morphology of condensed molecule-based ring patterns formed by evaporation of microdroplets on surfaces can be used as a 'fingerprint' to identify, for example, solute molecule surface chemistry and concentration and function as a sensor for a variety of biochemical events.

Journal Article↗

PubMed2001

Pentanuclear homoleptic M(5)L(6) (M = Mn(II), Co(II), Zn(II)) complexes formed by strict self-assembly.

A series of trigonal bipyramidal pentanuclear complexes involving the alkoxo-diazine ligands poap and p3oap, containing the M(5)[mu-O](6) core is described, which form by a strict self-assembly process. [Co(5)(poap-H)(6)](ClO(4))(4).3H(2)O (1), [Mn(5)(poap-H)(6)](ClO(4))(4).3.5CH(3)OH.H(2)O (2), [Mn(5)(p3oap-H)(6)](ClO(4))(4).CH(3)CH(2)OH.3H(2)O (3), and [Zn(5)(poap-H)(6)](ClO(4))(4).2.5H(2)O (4) are homoleptic pentanuclear complexes, where there is an exact match between the coordination requirements of the five metal ions in the cluster, and the available coordination pockets in the polytopic ligand. [Zn(4)(poap)(poap-H)(3)(H(2)O)(4)] (NO(3))(5).1.5H(2)O (5) is a square [2 x 2] grid with a Zn(4)[mu-O](4) core, and appears to result from the presence of NO(3), which is thought to be a competing ligand in the self-assembly. X-ray structures are reported for 1, 4, and 5. 1 crystallized in the monoclinic system, space group P2(1)/n with a = 13.385(1) A, b = 25.797(2) A, c = 28.513(3) A, beta = 98.704(2) degrees, and Z = 4. 4 crystallized in the triclinic system, space group P1 with a = 13.0897(9) A, b = 18.889(1) A, c = 20.506(2) A, alpha = 87.116(1) degrees, beta = 74.280(2) degrees, gamma = 75.809(2) degrees, and Z = 2. 5 crystallized in the monoclinic system, space group P2(1)/n with a = 14.8222(7) A, b = 21.408(1) A, c = 21.6197(9) A, beta = 90.698(1) degrees, and Z = 4. Compounds 1-3 exhibit intramolecular antiferromagnetic coupling.

Journal Article↗