Mononitrosalted and phenylamido substituted chelate linkage isomers of quadridentate Schiff base copper(II) complexes

The nitrosation of monophenylamido substututed quadridentate Schiff base complexes of copper(II) are observed to adopt N-bonded isonitroso coordination whereas the phenylisocyanation of the corresponding mononitrosated quadridentate complexes are found to prefer O-bonded isonitroso coordination.

A note on synthesis of the general, two-degree-of-freedom linkage

A graphical method is presented for synthesis of the general, seven-link, two-degree-of-freedom plane linkage to generate functions of two variables. The method is based on point position reduction and permits synthesis of the linkage to satisfy upto six arbitrarily selected precision positions.

Bromination of Intermolecular Chelate Linkage Isomers of 3-Oximino-4,9-Dimethyl (or 4,7,9-Trimethyl)-5,8-Diazadodeca-4,8-Diene-2,11-Dionato Nickel(II)

The reaction of the title complexes (FIG. 1) with N-bromosuccinimide or bromine in chloroform yields isomeric bromo complexes on substitution of the γ-CH carbon proton by bromine. The brominated products have been characterised by ir, pmr, electronic absorption spectra, conductivity and magnetic susceptibility measurements. The linkage isomerisation of the brominated products in chloroform has been shown to depend on the diamine residue.

Linkage isomerism in nickel(II) I-isonitroso-imine ligand complexes

I-isonitroso-imine ligand complexes of nickel(II), namely, bis(isonitrosomethylacetoacetate-imino)Ni(II), Ni(IMI)(IMI); bis(isonitrosobenzoylacetoneimino)Ni(II), Ni(IBI)(IBI) and bis(isonitrosoacetoacetanilideimino)Ni(II), Ni(IANI)(IANI), have been prepared and characterized. On the basis of their spectroscopic and magnetic properties, these complexes are suggested to have a square-planar stereochemistry around the metal ion with both nitrogen (ligand denoted without prime) and oxygen (ligand denoted with prime) coordinated isonitroso groups. The i.r. and NMR spectra of these and other similar complexes are discussed.

Effect of the headgroup variation on the gene transfer properties of cholesterol based cationic lipids possessing ether linkage

Eight cholesterol based cationic lipids differing in the headgroup have been synthesized based on the ether linkage between the cationic headgroup and the cholesterol backbone. All the lipids formed stable suspensions in water. Transfection efficacies were examined in the absence and presence of serum using their optimized liposomal (lipid:DOPE) formulations. Our results showed that the transfection activities depend on the nature of the headgroup. Lipid bearing 4-N,N′-dimethylaminopyridine (DMAP) as headgroup showed the maximum transfection efficacy in the presence of serum. Importantly, the optimized formulation for this cationic lipid does not require DOPE, which is being used by most commercially available formulations. Cytotoxicity studies showed that the introduction of the positive charge decreases the cell viability of the cationic lipid formulations. Gel electrophoresis and Ethidium bromide exclusion assay revealed the different DNA binding abilities of formulations depending upon the headgroup of the cholesteryl lipid.

Confirmation of linkage and refinement of the RP28 locus for autosomal recessive retinitis pigmentosa on chromosome 2p14-p15 in an Indian family

PURPOSE: To report the linkage analysis of retinitis pigmentosa (RP) in an Indian family. METHODS: Individuals were examined for symptoms of retinitis pigmentosa and their blood samples were withdrawn for genetic analysis. The disorder was tested for linkage to known 14 adRP and 22 arRP loci using microsatellite markers. RESULTS: Seventeen individuals including seven affecteds participated in the study. All affected individuals had typical RP. The age of onset of the disease ranged from 8-18 years. The disorder in this family segregated either as an autosomal recessive trait with pseudodominance or an autosomal dominant trait. Linkage to an autosomal recessive locus RP28 on chromosome 2p14-p15 was positive with a maximum two-point lod score of 3.96 at theta=0 for D2S380. All affected individuals were homozygous for alleles at D2S2320, D2S2397, D2S380, and D2S136. Recombination events placed the minimum critical region (MCR) for the RP28 gene in a 1.06 cM region between D2S2225 and D2S296. CONCLUSIONS : The present data confirmed linkage of arRP to the RP28 locus in a second Indian family. The RP28 locus was previously mapped to a 16 cM region between D2S1337 and D2S286 in a single Indian family. Haplotype analysis in this family has further narrowed the MCR for the RP28 locus to a 1.06 cM region between D2S2225 and D2S296. Of 15 genes reported in the MCR, 14 genes (KIAA0903, OTX1, MDH1, UGP2, VPS54, PELI1, HSPC159, FLJ20080, TRIP-Br2, SLC1A4, KIAA0582, RAB1A, ACTR2, and SPRED2) are either expressed in the eye or retina. Further study needs to be done to test which of these genes is mutated in patients with RP linked to the RP28 locus.

Action of N-bromosuccinimide on human hemoglobin and its possible bearing on heme-globin linkage

A reaction of N-bromosuccinimide with the heme groups of hemoglobin has been studied spectrophotometrically. The reaction brings about the disappearance of characteristic absorption peaks of hemoglobin and is accompanied by the release of inorganic iron from the heme groups. Urea is obligatory for the reaction to take place at pH 4.0, while it can occur in the absence of urea at pH 7.0. The spectrum of hemoglobin which does not show any peak in the Soret region at pH 4.0 is “normalized” in the presence of urea or sucrose at the same pH. The effect of “normalization” in 8 M urea is apparent over the pH range 3.0–4.5. From the obligatory requirement of urea and sucrose for “normalization” of spectrum and the dependence of the release of inorganic iron on the concentration of urea, it is suggested that heme groups are “buried” within the globin at pH 4.0 and not dissociated from globin as supposed before.

Intermolecular Chelate Linkage Isomerism of the Hydroxyimino Group in the Nickel(II), Copper(II), and Palladium(II) Complexes of Quadridentate Schiff-base Ligands

The C-nitrosation of bivalent quadridentate β-imino ketone complexes of nickel(II), copper(II), and palladium(II), with nitrosating reagents has been investigated. The chemical analysis and spectroscopic results reveal that one of the α-CH groups of the coordinated lignad undergoes selective nitrosation forming mono(hydroxyimino) derivative. The hydroxyimino group introduced coordinates through either N- or O- atom to metal(II) by dislodging the carbonyl group already coordinated. This gives rise to two linkage isomers, one with N-bonded and the other with O-bonded hydroxyimino group in the case of nickel(II) (except for 1d) and palladium(II), and a single isomer with O-bonded hydroxyimino group in copper(II) complexes. The isomers obtained from 1b and 1i have been separated by column chromatography. In chloroform each of the isomers of nickel(II) isomerizes to give an equilibrium mixture of two isomers, but not those of copper(II) and palladium(II).

Tandemmassaspektrometrinen menetelmä neutraalien isomeeristen oligosakkaridien rakenteen määrittämisessä

Tutkimuksen tavoitteena oli ottaa käyttöön tandemmassaspektrometrinen (MS/MS) menetelmä, jolla voidaan analysoida polysakkarideista purkautuneiden oligosakkaridien rakenteita. Tavoitteena oli, että menetelmällä voidaan määrittää glykosidisten sidosten eri asemat monosakkaridirakenteiltaan samanlaisista neutraaleista lineaarisista oligosakkarideista. Kirjallisuustutkimuksessa tarkasteltiin oligosakkaridien rakenteiden määrittämiseen käytettyjä MS/MS-menetelmiä ja oligosakkaridien pilkkoutumisreaktioita MS/MS-analyysissa. Kirjallisuuden perusteella MS/MS-analyysissa oligosakkaridien pilkkoutuminen voi tapahtua joko glykosidisen sidoksen katkeamisella tai monosakkaridirenkaan halkeamisella. Monosakkaridirenkaan pilkkoutumisesta muodostuvia tuoteioneja voidaan käyttää glykosidisen sidoksen aseman määrittämiseen. Kokeellisessa tutkimuksessa selvitettiin aluksi monosakkaridirakenteiltaan isomeerisilla disakkaridimalliaineilla glykosidisen sidoksen sijainnin vaikutus disakkaridin pilkkoutumiseen MS/MS-analyysissa. Tämän jälkeen pyrittiin löytämään tunnetuista tri- ja tetrasakkaridimalliaineista näitä eri sidoksille tyypillisiä tuoteionien jakaumia. Tunnettujen tri- ja tetrasakkaridien pilkkoutuminen yhdenmukaisesti disakkaridien pilkkoutumisen kanssa antaisi mahdollisuuden pitkäketjuisempien oligosakkaridien glykosidisten sidosten tunnistamiseen sovelletulla MS/MS-menetelmällä. MS/MS-analyysit tehtiin ioniloukkumassadetektorilaitteistolla käyttäen sähkösumutusionisaatiota (ESI). Oligosakkaridit määritettiin positiivisella ionisaatiolla litium- ja natriumaddukti-ioneina ja negatiivisella ionisaatiolla kloridiaddukti-ioneina. Vertaamalla tri- ja tetrasakkarideista MS/MS-analyyseissa muodostuneita tuoteioneja disakkarideista muodostuneisiin tuoteioneihin, voitiin sekä positiivisella että negatiivisella ionisaatiolla määrittää oligosakkaridin pelkistävän pään sidoksen asema. Negatiivisella ionisaatiolla tri- ja tetrasakkarideista muodostuneista tuoteioneista voitiin määrittää myös muiden kuin pelkistävän pään sidosten asemia. Positiivisella ionisaatiolla muiden sidosten määrittäminen ei ollut mahdollista, koska rengasfragmentti-ioneja muodostui pääosin oligosakkaridin pelkistävästä päästä. Glykosidisen sidoksen katkeamisesta muodostuneet tuoteionit analysoitiin edelleen MS3-analyysilla. MS3-analyysissa muodostuneista tuoteioneista ei voitu tulkita sidosten asemia, koska lähtöionit koostuivat sekä terminaalisen että pelkistävän pään isomeerisista ioneista.

Constructions of 2D-Metallamacrocycles Using Half-Sandwich Ru-2(II) Precursors: Synthesis, Molecular Structures, and Self-Selection for a Single Linkage Isomer

Coordination-driven self-assembly of oxalato-bridged half-sandwich p-cymene ruthenium complex Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)(2)] (O3SCF3)(2) (1a) with several ditopic donors (L-a-L-d) in methanol affords a series of bi- and tetranuclear metallamacrocycles (2a and 3-5). Similarly, the combination of 2,5-dihydroxy-1,4-benzoquinonato (dhbq)-bridged binuclear complex Ru-2(mu-eta(4)-C6H2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](O3SCF3)(2) (1b) with a flexible bidentate amide linker (L-a) in 1:1 molar ratio gave the corresponding tetranuclear complex 2b. All the macrocycles were isolated as their triflate salts in high yields and were fully characterized by various spectroscopic techniques. Finally, the molecular structures of all the assemblies were determined unambiguously by single-crystal X-diffraction analysis. Interestingly, the combination of acceptor 1a or 1b with an unsymmetrical linear ditopic donor L-a results in a self-sorted linkage isomeric (head-to-tail) macrocycle (2a or 2b) despite the possibility of formation of two different isomeric macrocycles (head-to-head or head-to-tail) due to different connectivity of the donor. Molecular structures of the complexes 2a and 2b showed tetranuclear rectangular geometry with dimensions of 5.51 angstrom x 13.29 angstrom for 2a and 7.91 angstrom x 13.46 angstrom for 2b. In both cases, two binuclear Ru-2(II) building blocks are connected by a mu-N-(4-pyridyl)isonicotinamide donor in a head-to-tail fashion. Surprisingly, the macrocycle 2a loses one counteranion and cocrystallizes with monodeprotonated 1,3,5-trihydroxybenzene via strong intermolecular pi-pi stacking and hydrogen bonding. The tweezer complex 3 showed strong fluorescence in solution, and it showed fluorescence sensing toward nitroaromatic compounds. A fluorescence study demonstrated a marked quenching of the initial fluorescence intensity of the macrocycle 3 upon gradual addition of trinitrotoluene and exhibits significant fluorescence quenching response only for nitroaromatic compounds compared to various other aromatic compounds tested.

Coordination driven self-assembly of metallamacrocycles using ambidentate linkers and self-selection of single linkage isomer

Nicotinate-N-oxide and isonicotinate-N-oxide have been employed to synthesize four heterometallic metallamacrocycles (dppf)(2)Pd-2(nicotinate-N-oxide)(2)](OTf)(2) (1), (dppf)(2)Pt-2(nicotinate-N-oxide)(2)](OTf)(2) (2), (dppf) 2Pd2(isonicotinate-N-oxide)(2)](OTf)(2) (3) and (dppf)(2)Pt-2(isonicotinate-N-oxide)(2)](OTf)(2) (4). The complexes represent the first examples of metallamacrocycles driven by solely Pd(II)/Pt(II)-O coordination using carboxylate-N-oxide donor. All the complexes 1-4 are characterized by IR, UV-Vis, multinuclear NMR spectroscopic and ESI-MS studies. The molecular structures of the complexes 1 and 3 are unambiguously determined by single crystal X-ray diffraction analysis. Despite the possibility of formation of several linkage isomers due to ambidentate nature of the donors, exclusive formation of 2 + 2] self-assembled single isomeric metallamacrocycle in each case is interesting observation. (C) 2011 Elsevier B.V. All rights reserved.

Advantage of the ether linkage between the positive charge and the cholesteryl skeleton in cholesterol-based amphiphiles as vectors for gene delivery

Twelve novel cationic cholesterol derivatives with different linkage types between the cationic headgroup and the cholesteryl backbone have been developed. These have been tested for their efficacies as gene transfer agents as mixtures with dioleoyl phosphatidylethanolamine (DOPE). A pronounced improvement in transfection efficiency was observed when the cationic center was linked to the steroid backbone using an ether type bond. Among these, cholest-5-en-3b-oxyethane-N, N,N-trimethylammonium bromide (2a) and cholest-5-en-3b-oxyethane-N, N-dimethyl-N-2-hydroxyethylammonium bromide (3d) showed transfection efficiencies considerably greater than commercially available reagents such as Lipofectin or Lipofectamine. To achieve transfection, 3d did not require DOPE. Increasing hydration at the headgroup level for both ester- and ether-linked amphiphiles resulted in progressive loss of transfection efficiency. Transfection efficiency was also greatly reduced when a 'disorder'-inducing chain like an oleyl (cis-9-octadecenyl) segment was added to these cholesteryl amphiphiles. Importantly, the transfection ability of 2a with DOPE in the presence of serum was significantly greater than for a commercially available reagent, Lipofectamine. This suggests that these novel cholesterol-based amphiphiles might prove promising in applications involving liposome-mediated gene transfection. This investigation demonstrates the importance of structural features at the molecular level for the design of cholesterol-based gene delivery reagents that would aid the development of newer, more efficient formulations based on this class of molecules.