The relative orientation of the lipid and carbohydrate moieties of lipochitooligosaccharides related to nodulation factors depends on lipid chain saturation

Lipochitooligosaccharides (LCOs) signal the symbiosis of rhizobia with legumes and the formation of nitrogen-fixing root nodules. LCOs 1 and 2 share identical tetrasaccharide scaffolds but different lipid moieties (1, LCO-IV(C16:1[9Z], SNa) and , LCO-IV(C16:2[2E,9Z], SNa)). The conformational behaviors of both LCOs were studied by molecular modeling and NMR. Modeling predicts that a small lipid modification would result in a different relative orientation of the lipid and tetrasaccharide moieties. Diffusion ordered spectroscopy reports that both LCOs form small aggregates above 1 mM. Nuclear Overhauser spectroscopy (NOESY) data, collected under monomeric conditions, reveals lipid-carbohydrate contacts only for 1, in agreement with the modeling data. The distinct molecular structures of 1 and 2 have the potential to contribute to their selective binding by legume proteins.     

Unprecedented metal template effect on the coupling of dithiafulvene moieties

Coordination of two dithiafulvenyldiphenylphosphines on a Mo(CO)(4) fragment allows a carbon-carbon bond formation upon oxidation, leading to a novel type of metallacycle substituted by a redox active vinylogous tetrathiafulvalene.     

Effect of pendent oxyethylene moieties on the properties of aromatic polyisophthalamides

Twelve novel polyisophthalamides containing short sequences of oxyethylene as pendent substituents were synthesized by the reaction of three aromatic diamine monomers and four novel diacid monomers containing pendent oxyethylene units. Two of the diacid monomers were derived from 5‐hydroxyisophthalic acid and the other two diacid monomers were derived from 5‐aminoisophthalic acid. The polymers were prepared in high yield and high molecular weight by the phosphorylation method of polycondensation. All of the polymers were soluble in organic aprotic solvents at room temperature and gave creasable films by casting from solution. The mechanical properties of the films were reasonably good, with tensile strengths in the range of 70–100 MPa and moduli around 2.5 GPa. However, the presence of the oxyethylene side sequences greatly diminished the thermal resistance and the glass transition temperatures of the present polymers compared with wholly aromatic polyisophthalamides. A study was also made on the effect of the chemical composition on water uptake. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45:4671–4683, 2007     

Dimeric liquid crystals with two troponoid mesogenic moieties: effect of the direction of the carbonyl group on the mesomorphic properties

Three twin types of troponoid liquid crystals, in which the directions of the tropone carbonyl groups are different from each other, were prepared to establish their thermal properties. Symmetrical type I dimers, in which the two tropone carbonyl groups are directed inwards, had monotropic smectic C phases, whereas two other symmetrical type IIa and IIb dimers, whose troponoid dipoles are directed outwards, were not mesomorphic except for one type IIa compound having two long terminal chains and a short alkylene spacer. Unsymmetrical type III dimers had smectic A phases. Among the dimers, unsymmetrical type III dimers had the highest clearing point when the number of atoms of the inner and outer spacers was fixed. X-ray diffraction studies of a type III dimer, in which the number of the atoms of the inner spacer was odd, showed that the molecules form an interdigitated layer structure. The binary system between type I and type IIb dimers showed an induced enantiotropic smectic A phase, in which the dipole moments of the tropone rings were cancelled.     

Dimeric liquid crystals with two troponoid mesogenic moieties: effect of the direction of the carbonyl group on the mesomorphic properties

Three twin types of troponoid liquid crystals, in which the directions of the tropone carbonyl groups are different from each other, were prepared to establish their thermal properties. Symmetrical type I dimers, in which the two tropone carbonyl groups are directed inwards, had monotropic smectic C phases, whereas two other symmetrical type IIa and IIb dimers, whose troponoid dipoles are directed outwards, were not mesomorphic except for one type IIa compound having two long terminal chains and a short alkylene spacer. Unsymmetrical type III dimers had smectic A phases. Among the dimers, unsymmetrical type III dimers had the highest clearing point when the number of atoms of the inner and outer spacers was fixed. X-ray diffraction studies of a type III dimer, in which the number of the atoms of the inner spacer was odd, showed that the molecules form an interdigitated layer structure. The binary system between type I and type IIb dimers showed an induced enantiotropic smectic A phase, in which the dipole moments of the tropone rings were cancelled.     

Transport properties of polyimides containing phenylquinoxaline moieties

The gas permeabilities of a number of new structurally related polyimides containing phenylquinoxaline moieties were studied for the first time. The test polymers had different dianhydride units, whereas their diamine components differed in the presence of flexible ether bonds-O-in the main chain, a structure that is reflected in the effective packing of chains and, as a result, in transport parameters. The permeability, diffusion, and solubility coefficients for the gases H₂, He, O₂, N₂, CO, CO₂, and CH₄, as well as the ideal separation factors for gas pairs, were determined. The transport characteristics of polymers were compared within the given polymer series and with published data for other polymer series.     

The effect of radical trap moieties on electron capture dissociation spectra of substance P

To further test the hypothesis that electron capture dissociation (ECD) involves long-lived radical intermediates and radical migration occurs within these intermediates before fragmentation, radical trap moieties were attached to peptides with the assumption that they would reduce fragmentation by decreasing the mobility of the radical. Coumarin labels were chosen for the radical traps, and unlabeled, singly-labeled, and doubly-labeled Substance P were analyzed by ECD. The results demonstrated a correlation between the number and position of tags on the peptide and the intensity of side-chain cleavages observed, as well as an inverse correlation between the number of tags on the peptide and the intensity of backbone cleavages. Addition of radical traps to the peptide inhibits backbone cleavages, suggesting that either radical mobility is required for these cleavages, or new noncovalent interactions prevent separation of backbone cleavage fragments. The enhancement of side-chain cleavages and the observation of new side-chain cleavages associated with aromatic groups suggest that the gas-phase conformation of this peptide is substantially distorted from untagged Substance P and involves previously unobserved interactions between the coumarin tags and the phenylalanine residues. Furthermore, the use of a double resonance (DR)-ECD experiment showed that these side-chain losses are all products of long-lived radical intermediate species, which suggests that steric hindrance prevents the coumarin-localized radical from interacting with the backbone while simultaneously increasing the radical rearrangements with the side chains.     

The photo-physicochemical properties of an octa-substituted zinc phthalocyanine containing 1,2,4-triazole moieties

4,5-Bis(2-(4-(4-methoxybenzylamino)-5-oxo-3-p-tolyl-4,5-dihydro-1H-1,2,4-triazol-1-yl)ethoxy)-substituted zinc(II) phthalocyanine (4) was synthesized from a phthalonitrile derivative (3). The compounds were characterized by several spectral methods such as electronic absorption, FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry, and elemental analyses. The photophysical and the photochemical properties of 4 were investigated in DMSO and DMF. The solvent effect on the photochemical and photophysical properties for 4 is also discussed.     

Structural investigation of the antibiotic ristomycin A: The 13C-NMR evidence on the carbohydrate moieties and their linkages to the aglycone

The ¹³C-NMR experiments, which define the last details of the structure of ristomycin A, are described.     

Complexing properties of cation-exchangers grafted with carboxyl moieties

The complexing properties of CM-52, Olvagel-COOH, MacroPrep 50 CM, and hypercrosslinked polystyrene MN (carboxyl-grafted sorbents) toward Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺, Mn²⁺, and Pb²⁺ have been studied. The optimal parameters for the sorption of these metal ions from solution have been determined. The pH effect on the ion uptake has been studied. The uptake is maximal at pHs higher than 5–6. When pH is lower than 2, the indicated ions are quantitatively desorbed. Olvagel-COOH is most selective toward these ions.     

Efficient synthesis of N- and O-linked glycopeptides using acid-labile Boc groups for the protection of carbohydrate moieties

Development of a synthetic method for the preparation of homogeneous glycopeptides and glycoproteins is important for the elucidation of their structures and functions. Here, we report on the concise and facile synthesis of glycopeptides using Boc groups for the protection of carbohydrate hydroxyl groups. This method enables us to remove the protecting groups from peptide and carbohydrate moieties in a single-step process without undesirable any side reaction.     

The effect of the ferrocene unit on mesomorphic properties

The synthesis of a number of 1,1'-disubstituted ferrocene-containing compounds is described; the structures of the compounds containing the ferrocene unit are related to those of mesogenic systems containing a 1,4-disubstituted benzene ring or a trans-1,4-cyclohexyl ring. Direct comparisons are made between the aryl-, cyclohexyl- and ferrocene-containing compounds in order to assess the effect on transition temperatures of replacing a benzene or cyclohexyl ring with a ferrocene unit. In comparison with conventional ring systems the ferrocene unit causes substantial reductions in clearing temperatures.     

The packing of azobenzene dye moieties and mesogens in polysiloxane copolymers and its impact on the opto-dielectric effect

Broadband dielectric spectroscopy (102-105Hz) is used to study the opto-dielectric effect in statistical polysiloxane copolymers with side groups containing chiral mesogenic units and others containing azobenzene moieties. Below 64 C, the unexposed copolymer is ferroelectric. UV-exposure induces a photoisomerization of the azobenzene to the cis -configuration, and the phase transition, ferroelectric/non-ferroelectric (SC*/SA), is shifted to lower temperatures. In the temperature interval between the phase transition temperatures ferroelectric/nonferroelectric of the exposed and unexposed samples, an opto-dielectric effect is observed. The efficiency of this opto-dielectric switching depends on the packing of the chromophore within the smectic layers.     

Synthesis and properties of polyurethanes bearing urethane moieties in the side chain

Polyurethanes bearing urethane groups in the side chains were prepared by the addition of isocyanates to the hydroxyl groups in poly(hydroxyurethane) prepared by the polyaddition of a bifunctional cyclic carbonate with 1,12‐diaminododecane. The urethanization proceeded quantitatively in the presence of a catalytic amount of di‐n‐butyltin dilaurate. The resulting polyurethane had a higher glass transition temperature than the original poly(hydroxyurethane), although its esterified product had a lower glass transition temperature. The urethanization with 3‐(triethoxysilyl)propyl isocyanate also proceeded effectively to afford both soluble and insoluble polymers, depending on the reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3408–3414, 2007     

Effects of decreasing carbohydrate content on properties of wood strands

Hot-water pretreatment was performed on wood strands to investigate effects of the extraction of hemicellulose under different temperature (140, 155, and 170 °C) and time durations (30 and 60 min) conditions. Hydrolysate was analyzed by means of high-performance liquid chromatography. Chemical changes in the surface of wood strands were studied by infrared spectroscopy. The effects of hemicellulose extraction on the wettability of wood strands were studied by measuring the contact angle and surface free energy. The mechanical properties of wood cell walls before and after treatment were studied by nanoindentation. Among the extracted monosaccharides, mannose was found in the highest concentration. The mechanical properties of cell walls showed little decrease after extraction. The chemical changes in the surface of the wood strands reduced wettability of wood surface by water and produced hydrophobic characteristics after extraction.     

1,4,7,10-Tetraazacyclododecane incorporating salicylic acid moieties synthesis and properties

The synthesis of salicylic acid derivatives of 1,4,7,10-tetraazacyclododecane has been described. The complexing properties of these compounds towards metal cations were investigated by absorption and emission spectroscopy, and ¹H NMR. The X-ray structure of L-2 nitrate is reported.     

Synthesis and properties of novel polymers having S-methyldibenzothiophenium salt moieties

A polymer having dibenzothiophenium salt moieties [poly(sulfonium salt), 2 ] was prepared by the reaction of poly(2-vinyldibenzothiophene) ( 1 ) with CH₃I and AgBF₄ in CH₂ClCH₂Cl at room temperature for 24 h. The obtained polymer 2 was found to contain 71% of the methyldibenzothiophenium tetrafluoroborate unit. A monomer carrying the sulfonium salt moiety, i.e., 5-methyl-2-vinyldibenzothiophenium tetrafluoroborate ( 4 ), was independently prepared and subjected to radical polymerization to give a polymer ( 5 ) in 88% yield (methyldibenzothiophenium tetrafluoroborate unit: 79%). The thermal decompositions of 2 and 5 took place in two steps; the first step involved the formation of polymer 1 by demethylation. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1779–1784, 1998     

Thickening properties and emulsification mechanisms of new derivatives of polysaccharide in aqueous solution 2. The effect of the substitution ratio of hydrophobic/hydrophilic moieties

The thickening properties and association behavior of aqueous solutions of HHM-HEC (hydrophobically-hydrophilically modified hydroxyethyl cellulose) with various hydrophobic and hydrophilic substitution degrees were investigated. The HHM-HEC was used as an oil-in-water emulsifier and stable compositional regions were investigated as a function of polymer concentration and substitution degree. The viscosity of aqueous solutions of HHM-HEC increased drastically at lower concentration for HHM-HEC with a higher hydrophobic/hydrophilic substitution ratio. The intensity ratio of the first and third vibrational bands of pyrene (I(1)/I(3)) decreased with the increase of HHM-HEC concentration and the I(1)/I(3) reached a lower plateau at a lower concentration for HHM-HEC with a higher hydrophobic/hydrophilic substitution ratio. The concentration ranges of HHM-HEC solutions which stabilize O/W emulsions differ by the hydrophobic/hydrophilic substitution ratio. However the viscosity ranges of these HHM-HEC solutions were almost the same regardless of the hydrophobic/hydrophilic substitution ratio. At the suitable concentration range for emulsification, HHM-HEC networks have two properties: (1) oil particle retention capacity and (2) laxation which can trap emulsified particles.     

Transport properties of poly(phenylquinoxalines) containing heterocyclic moieties

The transport behavior of a new class of membrane materials—a series of poly(phenylquinoxalines) containing heterocyclic fragments in the backbone—has been studied. These polymers contain moieties of a common chemical structure. Therefore, it is possible to follow how the transport parameters change upon introduction of various moieties into the backbone chain. The coefficients of permeability, diffusion, and solubility for H₂, He, O₂, N₂, CO, CO₂, and CH₄ along with the separation factors for the corresponding pairs of gases have been determined. The results are compared with the data for previously studied polymers of the poly(phenylquinoxaline) series.