Succinic Acid Moiety Research Articles

Grafting PEG and alkyl comb polymers onto bleached wood pulp fibres

AbstractComb polymers were prepared by reacting a poly(ethylene‐alt‐maleic anhydride) with alkyl amines or poly(ethylene glycol) (PEG) amines. The resulting polymers were used to modify bleached softwood kraft pulp fibre surfaces by catalyst‐free grafting in a process suitable for pulp mill implementation. Pulp fibres were impregnated with a polymer solution and cured above 100°C. High grafting yields were obtained despite having up to 88% of the anhydride groups consumed by amine derivatization. Grafting yields were more than 90% when the polymer dosage was <13 g/kg (dry polymer/dry fibre) for alkyl derivatives and < 38 g/kg for PEG derivatives. We propose that the upper dosage limit for efficient grafting reflects the need for direct contact between cellulose and every polymer chain for ester linkage formation. For a given polymer dosage, the cured pulp sheets had a maximum wet tensile index, TImax, when either curing time or temperature was increased. Both the alkyl and PEG derivatives fit the power law for the wet TImax~βΓru0.54–0.62 where β values were the estimated conversion of succinic acid moieties to anhydrides when the pulp sheets were cured, and Γru is the dimensionless polymer content that is numerically equal to the amount of applied polymer in mmol repeat units/g dry fibre. However, high polymer dosages give experimental TImax values that fall below the power law, irrespective of curing intensity, because the pulp sheets contain unfixed polymer chains that lubricate fibre/fibre joints, lowering wet strength.

Alkaline cations dramatically control molecular hydrogelation by an amino acid-derived anionic amphiphile

Understanding the factors that control the formation of (supra)molecular hydrogels permits a rational tuning of their properties and represents a primary challenge for developing smart biocompatible soft materials. Hydrogel formation by molecular amphiphilic anions at millimolar concentrations is counterintuitive, considering the solubility of these species in water. Here we report hydrogel formation by a simple anionic molecular amphiphile and a rationale for the fibrillisation process observed. The studied molecule, DodValSuc, consists of a 12C alkyl chain, an l-valine unit and a terminal succinic acid moiety. Hydrogelation depends to a large degree on the nature and concentration of the alkaline cations present in the medium (Li+, Na+ or K+). As a result, gelation efficiency and properties like thermal stability or rheology are highly tunable using the alkaline cation present or its concentration as variables.A detailed study is reported, which includes the determination of minimum gelation concentration (MGC) by tabletop rheology, critical micelle concentration (CMC) using pyrene as a fluorescent probe, thermal stability (solubility) by 1H NMR, the morphology of the fibres by transmission electron microscopy (TEM), crystallinity by X-ray diffraction (XRD) and gel strength by oscillatory rheology. Additionally, dynamic light scattering (DLS) was used to evaluate the size of the micelles and permitted monitoring of the fibrillisation process.Altogether, the results are consistent with the formation of micelles that experience head crystallisation and subsequent aggregation into crystalline fibres. The alkaline cations play a crucial role in providing the cement that glues together the gelator molecules, making their concentration a critical parameter for gelation efficiency and properties. Furthermore, the gelation-promoting effects are inversely correlated with the size of the cations so that the highest thermal stability and rheological strength were found for the hydrogels formed in the presence of Li+.

Efficient and selective adsorption of U(VI) by succinic acid modified iron oxide adsorbent

Abstract The iron oxide surface was modified with succinic acid moiety and the adsorbent obtained, Fe-SUC, was evaluated for the adsorption of U(VI) (Uranium (VI)) from aqueous solution. The Fe-SUC was characterized by FT-IR (Fourier Transform Infrared Spectroscopy), Raman spectroscopy, thermogravimetry, X-ray diffraction, SEM-EDX (Scanning Electron Microscope - Energy-dispersive X-ray Spectroscopy), and particle size analysis. The adsorption behavior of U(VI) on Fe-SUC was studied as a function of pH, contact time, and concentration of U(VI) in the aqueous phase. The adsorption of U(VI) increased with increase in the pH of aqueous phase, and the adsorption saturation occurred at pH = 6. The kinetic data obtained for the adsorption of U(VI) on Fe-SUC were modeled with the pseudo-first-order and pseudo-second-order rate models. Similarly, the U(VI) adsorption isotherm was fitted with Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherm models. The Langmuir adsorption capacity of U(VI) on Fe-SUC was about ∼176 mg g−1. The selectivity of the adsorbent toward U(VI) was evaluated in the presence of several possible interfering ions. The adsorbed U(VI) was recovered by 0.5 M sodium carbonate solution and the spent adsorbent was tested for its reusability.

Synthesis and evaluation of dual-action kanglemycin-fluoroquinolone hybrid antibiotics

Bacterial resistance threatens the utility of currently available antibiotics. Rifampicin, a cornerstone in the treatment of persistent Gram-positive infections, is prone to the development of resistance resulting from single point mutations in the antibiotic’s target, RNA polymerase. One strategy to circumvent resistance is the use of ‘hybrid’ antibiotics consisting of two covalently linked antibiotic entities. These compounds generally have two distinct cellular targets, reducing the probability of resistance development and potentially providing simplified pharmacological properties compared to combination therapies using the individual antibiotics. Here we evaluate a series of semi-synthetic hybrid antibiotics formed by linking kanglemycin A (Kang A), a rifampicin analog, and a collection of fluoroquinolones. Kang A is a natural product antibiotic which contains a novel dimethyl succinic acid moiety that offers a new attachment point for the synthesis of hybrid antibiotics. We compare the activity of the Kang A hybrids generated via the acid attachment point to a series of hybrids linked at the compound’s naphthoquinone ring system. Several hybrids exhibit activity against bacteria resistant to Kang A via the action of the partnered antibiotic, suggesting that the Kang scaffold may provide new avenues for generating antibiotics effective against drug-resistant infections.

High-yield grafting of carboxylated polymers to wood pulp fibers

Poly(ethylene-alt-maleic acid), PEMAc, is a linear polymer that, along with its isomer polyacrylic acid, has the highest carboxylic acid content of any polymer. The goal of this work was to elucidate the mechanisms that control the amount of PEMAc that is permanently fixed on pulp fibers after the impregnation of dry pulp with a dilute PEMAc solution followed by drying/heating (curing). Two mechanisms by which PEMAc is fixed to cellulose fibers were discovered, chemical, and physical fixation. With room temperature drying only physical fixation is operative. Evidence supports the explanation that physical fixation is a consequence of the slow swelling and dissolution of thick dried PEMAc deposits on fiber surfaces. Chemical fixation includes grafting to cellulose plus enhanced cohesion within thick PEMAc layers, possibly due to interchain crosslinking. The pH of the PEMAc impregnation solution determines the fixation mechanism for curing temperatures above 100 °C. Physical fixation dominates when pH > 8 whereas chemical fixation dominates for impregnation pH values ≤ 7, suggesting the curing reactions require partial or complete protonation of the succinic acid moieties. The yield of impregnated polymer fixed to the fibers after washing depends upon the fixation mechanism. When chemical fixation dominates, the yields for low and high molecular weight PEMAc doses less than 0.1 meq/g (6.3 kg PEMA/tonne dry pulp) were close to or equaled 100%. By contrast, when the primary mechanism is physical fixation, yields are ~50% for high molecular weight PEMAc and 0–20% for low MW PEMAc. These results show that high PEMAc fixation yields can be achieved under curing conditions that could be implemented in pulp drying machines producing dry market pulp.

High Yield Poly(ethylene-alt-maleic acid) Grafting to Wood Pulp while Minimizing Fiber/Fiber Wet Adhesion.

Heating bleached kraft pulps treated with poly(ethylene-alt-maleic acid) (PEMAc) can lead to high yields of carboxylated polymer grafted to fibers. However, in many cases, the cured, dry pulp cannot be effectively repulped (redispersed in water) because the wet strength is too high. Impregnation with PEMAc solutions at pH 4 followed by high temperature (120-180 °C), catalyst-free curing for short times can give fixation yields >85% while maintaining repulpability. The combination of high fixation yields with low wet strength is possible because the extent of curing required for high grafting yields is less than the curing requirement for high wet strength. Two challenges in moving this technology to practicable applications are (1) identifying the optimum laboratory pulp curing conditions and (2) translating laboratory curing conditions to industrial processes. A modeling tool was developed to meet these challenges. The model is based on the observation that for curing conditions giving high fixation yields the wet tensile indices of grafted pulp sheets showed a power-law dependence on the βΓ product where β is the conversion of the succinic acid moieties in PEMAc to the corresponding succinic anhydride groups in the curing step and Γ is the amount of polymer applied to the pulp. For two PEMAc molecular weights and two pulp types, the power-law slopes were 0.6; however, the pre-exponential terms depended upon the specific polymer and pulp type combination. We propose that the relationships between the wet tensile index and βΓ, from polymer-treated, laboratory pulp handsheets, can be used to predict if proposed curing conditions for larger-scale processes will produce a repulpable product.

Amidic succinic acid moiety anchored silica gel for the extraction of UO22+ from aqueous medium and simulated sea water

A solid phase adsorbent containing amidic carboxylic acid functional group on the surface of the silica gel was prepared by organo-surface modification reactions and characterized the product, Si-SUC, by FT-IR, Raman, thermogravimetry, X-ray diffraction, SEM-EDX and pH titration techniques. The extraction behaviour of U(VI) from aqueous solution was studied as a function of various parameters such as the aqueous phase pH, duration of equilibration, presence of interfering ions and concentration of U(VI) in aqueous phase to evaluate the feasibility using Si-SUC for the recovery of U(VI) from sea water. The kinetic data on the extraction of U(VI) was fitted into second order rate equation, and the U(VI) extraction isotherm was fitted using Langmuir, Freundlich, Dubinin- Radushkevich and Temkin adsorption models. The performance of Si-SUC was evaluated under dynamic conditions by following a break-through behaviour of U(VI) in the column study. The effect of flow-rate and concentration of U(VI) in the feed solution, on the break-through behaviour of U(VI) was studied and fitted the breakthrough curve using Thomas model.

Tuning the Handedness: Role of Chiral Component in Peptide-Appended Bolaamphiphile-Based Coassembled Hydrogels.

Chirality is the intrinsic property of a molecule that can be tuned by the change in chirality of a molecule or by the addition of a chiral component as an external stimulus. An l-leucine-based dipeptide-appended succinic acid-based bolaamphiphile coassembled with d-tartaric acid to form supramolecular right-handed nanostructured hydrogel, whereas l-tartaric acid coassembled to form supramolecular left-handed nanostructured hydrogel. Scanning electron microscopy and transmission electron microscopy experiments revealed the right- and left-handed helical nanofibers that are responsible for the formation of supramolecular nanostructured hydrogels. The synergistic chiral effect of l-leucine in peptide bolaamphiphile and d/l-tartaric acid plays a significant role in bicomponent gelation with helical nanofibers. The first two amino acids attached to both sides of succinic acid moiety act as a tuning button for supramolecular chirality of amino acids/peptides attached with succinic acid-based bolaamphiphiles. The second amino acid plays the role of modulating supramolecular chirality if the first two amino acids act neutrally to the chirality of bolaamphiphiles, which was confirmed by circular dichroism spectroscopy.

Solubility, Emulsification and Surface Properties of Maleic Anhydride, Perfluorooctyl and Alkyl Meth-Acrylate Terpolymers.

The solubility of terpolymers containing alkyl, and perfluoroalkyl side chains as well as succinic acid moieties in the main chain, P[RFMA0.2-co-RHMA0.65-co-MAH0.15] (RH = C4H9- or C12H25-, RF- = C10H4F19-) with ca. 20 mol % fluorinated side chains and 10–22 mol % of succinic anhydride rings was tested in a number of solvents varying from water to non polar mineral oils. The polymers are well soluble in fluorinated solvents like Freon-113® and 1,3-bis(trifluoromethyl) benzene, in semi-polar solvents like chloroform, THF or lower esters and also in hydrocarbons with polymers containing dodecyl methacrylate. In self-emulsification experiments, a stable water emulsion of P[F8H2MA0.2-co-BMA0.65-co-MAH0.15] was obtained. The dispersability and emulsification of these polymers in mixtures of organic solvents and water yielded stable emulsions in the presence of additional surfactant. Thin films coated from organic solutions as well as from emulsions on glass resulted in water and oil-repelling surfaces with contact angles up to 140° against water and 71° against hexadecane. An enhancing effect of annealing was not observed.

QM-HiFSA-Aided Structure Determination of Succinilenes A-D, New Triene Polyols from a Marine-Derived Streptomyces sp.

Based on profiles of secondary metabolites produced by marine bacteria obtained using LC/MS, succinilenes A–D (1–4), new triene polyols, were discovered from a culture of a Streptomyces strain SAK1, which was collected in the southern area of Jeju Island, Republic of Korea. The gross structures of 1–4 were primarily determined through analysis of NMR spectra. The double bond geometries of the succinilenes, which could not be established from conventional 1H NMR spectra because of the highly overlapped olefinic signals, were successfully deciphered using the recently developed quantum-mechanics-driven 1H iterative full spin analysis (QM-HiFSA). Succinilenes A–C (1–3) displayed inhibitory effects against lipopolysaccharide (LPS)-induced nitric oxide (NO) production, indicating their anti-inflammatory significance. These three compounds (1–3) commonly bear a succinic acid moiety, although succinilene D (4), which did not inhibit NO production, does not have this moiety in its structure. The absolute configurations of succinilenes A–D (1–4) were established through J-based configuration analysis, the modified Mosher’s method following methanolysis, and CD spectral analysis.

Triterpenoids from Momordica balsamina: Reversal of ABCB1-mediated multidrug resistance

The ability as P-glycoprotein (P-gp, ABCB1) modulators of thirty (1–30) triterpenoids of the cucurbitane-type was evaluated on human L5178 mouse T-lymphoma cell line transfected with the human MDR1 gene, through the rhodamine-123 exclusion assay. Compounds (1–26, and 29, 30) were previously obtained from the African medicinal plant Momordica balsamina, through both isolation (1–15) and molecular derivatization (16–26 and 29, 30). Compounds 27–28 are two new karavilagenin C (34) derivatives having succinic acid moieties. Apart from 4, 6, 8, 10 and 11, most of the isolated compounds (1–15) displayed strong MDR reversing activity in a dose-dependent mode, exhibiting a many-fold activity when compared with verapamil, used as positive control. At the lowest concentration tested, compounds 2 and 7 were the most active. However, a decrease of activity was found for the acyl derivatives (16–30). In a chemosensitivity assay, the MDR reversing activity of some of the most active compounds (1–3, 5, 7, 12–15) was further assessed on the same cell model. All the tested compounds, excepting 15, corroborated the results of the transport assay, revealing to synergistically interact with doxorubicin. Structure–activity relationship studies, taking into account previous results, showed that different substitution patterns, at both the tetracyclic nucleus and the side chain, play important role in ABCB1 reversal activity. An optimal lipophilicity was also recognized.

Succinylation of Non‐ionic Surfactants: Physicochemical Characterization, Functional Properties, Biodegradability and Mathematical Modeling of the Polarity Tuning

AbstractAnionic surfactants comprising succinic acid end groups were synthesized by succinylation of non‐ionic surfactants using succinic anhydride as a potentially bio‐sourced building block. A solvent‐ and catalyst‐free synthesis was designed for succinic anhydride mono esterification with octyl‐, decyl and dodecylpolyxylosides, di‐ and tetraethylene glycol dodecylethers and glycerol monolaurate. The physicochemical and functional properties of anionic surfactants thus obtained were studied and compared with their non‐succinylated counterparts. A correlation between these properties and the polarity changes induced by the addition of the hydrophilic succinic acid moiety was established. The biodegradability of the succinylated surfactants has also been investigated. Finally, through a desirability function approach, mathematic predictions were correlated to the properties in order to find an optimum and to discriminate surfactants with respect to targeted physicochemical properties and resulting applications.

HCV polymerase inhibitors.

The invention provides a compound of formula (I) and methods for making and using the same, where R1 and R2 are independently hydrogen, C1-6 alkyl or C1-6 haloalkyl; R3 is hydrogen, halogen, C1-6 alkyl or C1-6 alkoxy; R4 is hydrogen or halogen; and R5 is a mono- or di-amino acid moiety, a succinic acid moiety, a urea moiety, or a derivative thereof. The invention also provides pharmaceutical compositions comprising a compound of formula (I), and methods for making and using the same.

Synthesis and SAR of a novel, potent and structurally simple LTD4 antagonist of the quinoline class.

The two geminal ethyl groups in the succinic acid moiety of CGP57698 (4-[3-(7-fluoro-2-quinolinyl-methoxy)phenyl-amino]-2,2-diethyl-4-oxo- butanoic acid) are responsible for the high in vitro and in vivo potency of this peptidoleukotriene antagonist of the quinoline type. The synthesis and structure activity relationships of CGP57698 and its analogs are described.

Investigations on the dissociation behavior of hydrolyzed alternating copolymers of maleic anhydride and alkenes:13C-NMR spectra and potentiometric titrations

The pKa values of the succinic acid moieties of hydrolyzed alternating ethene- and isobutene-maleic anhydride copolymers were determined in D2O. The pD-dependence on the 13C chemical shift of selected signals was analyzed for these copolymers. Four different pKas were determined for the copolymer with ethene due to the existence of both the erythro- and threo-configuration of the succinic acid moiety: pK01,erythro = 4.2, pK0.1,threo = 4.1, pK02,erythro = 6.1, pK02,threo = 6.8. The isobutene-maleic anhydride copolymer contains only threo-units. Therefore, only two dissociation steps with pK01 = 3.0 and pK02 = 8.7 were observed for the hydrolyzed form. © 1996 John Wiley & Sons, Inc.

Bacterial siderophores: structure elucidation, and 1H, 13C and 15N two-dimensional NMR assignments of azoverdin and related siderophores synthesized by Azomonas macrocytogenes ATCC 12334

Two major azoverdins were isolated from the cultures of Azomonas macrocytogenes ATCC 12334 grown in irondeficient medium. Their structures have been established using fast atom bombardment-mass spectroscopy, homonuclear and heteronuclear two-dimensional 15N, 13C and 1H NMR, and circular dichroism techniques. These siderophores are chromopeptides possessing at the N-terminal end of their peptide chain the chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline common to pyoverdins. The linear peptide chain (l)-Hse-(d)-AcOHOrn-(d)-Ser-(l)-AcOHOrn-(d)-Hse-(l)-CTHPMD has at its C-terminal end a new natural amino acid which is the result of the condensation of 1 mol of homoserine and 1 mol of 2,4-diaminobutyric acid forming a cyclic amidine belonging to the tetrahydropyrimidine family: 2-homoseryl-4-carboxyl-3,4,5,6-tetrahydropyrimidine. The azoverdins differ only by a substitutent bound to the nitrogen on C-3 of the chromophore: azoverdin, the most abundant one, possesses a succinamide moiety, whereas azoverdin A bears a succinic acid moiety. 15N-labelled azoverdin afforded readily, after the complete assignment of the 15N spectrum of the siderophore, a sequence determination of the peptidic part of the molecule and gave evidence for the presence of two tetrahydropyrimidine groups on the molecule: one on the chromophore and the second at the C-terminal end of the siderophore.

Application of high affinity binding concept to radiolabel avidin with Tc-99m labeled biotin and the effect of pI on biodistribution

In order to label avidin with Tc-99m, we took advantage of the high affinity binding of biotin to avidin; we radiolabeled a biotin derivative with Tc-99m and then bound this Tc-99m labeled biotin derivative to avidin. For our labeling approach, Nϵ-biotinyl- l-lysine (Biocytin) was reacted with the N-hydroxy-succinimide ester of benzoylmercaptoacetyltriglycine (Bz-MAG3). The resulting Bz-MAG3-Biocytin was labeled with Tc-99m using Tc-99m glucarate as a Tc-99m transchelating agent and mixed with avidin at a 1:1 molar ratio resulting in almost a quantitative labeling yield. Tc-99m-MAG3-Biocytin/Avidin was stable in serum at 37 °C with 97 and 95% of the total Tc-99m activity still bound to avidin at 2 and 24 h, respectively. The biodistribution of Tc-99m-MAG3-Biocytin/Avidin in normal Balb/c mice showed a high liver and kidney uptake with 56.6 and 28.9%, respectively at 10 min. We attempted to lower the liver and the kidney activities by reducing the isoelectric point (pI) of avidin by conjugating succinic acid moieties at lysine residues of avidin (pI 10). The kidney uptake decreased to 19.0, 3.1 and 1.7% when the pI of avidin was reduced to 7.0–9.3, 5.5–6.2 and 4.0–4.8, respectively. The lowering of the pI, however, did not change the liver activity appreciably.

Crystal Structure of 2′-O-Succinyladenosine 3′,5′-(Cyclic)phosphate Monohydrate: A Model Compound to Study Protein–Nucleic Acid Interactions

Abstract The crystal and molecular structure of 2′-O-succinyladenosine 3′,5′-(cyclic)phosphate monohydrate has been determined by X-ray diffraction techniques. The compound crystallizes in the orthorhombic space group P212121; Z=4 with a=5.633(1), b=15.853(2), c=20.607(3) Å. The final R value is 0.029. The adenine base is protonated at N(1). The base is in syn conformation (χ=−95.8°) with respect to the sugar, which has a C(3′)-endo-C(4′)-exo pucker (4T3). A six-membered ring formed by phosphate group and ribose shows chair conformation. The succinic acid moiety, which resembles side chains of certain amino acids, is found to have a bent skeleton. The cyclic AMP, which is known to play diverse roles in many metabolic processes, forms the nucleotide portion of the title compound. The succinic acid moiety that is covalently linked to this nucleotide in the present compound, shows direct and water mediated interactions with phosphate and base nitrogens of the nucleotide respectively. Such compounds can therefore serve as models to study the protein–nucleic acid interactions, which play a central role in many of the biological processes.

Transfer of phosphoethanolamine residues from phosphatidylethanolamine to the membrane-derived oligosaccharides of Escherichia coli.

The membrane-derived oligosaccharides (MDO) of Escherichia coli are periplasmic constituents composed of glucose residues linked by beta-1,2 and beta-1,6 glycosidic bonds. MDO are substituted with phosphoglycerol, phosphoethanolamine, and succinic acid moieties. The phosphoglycerol residues present on MDO are derived from phosphatidylglycerol (B. J. Jackson and E. P. Kennedy, J. Biol. Chem. 258:2394-2398, 1983), but evidence as to the source of the phosphoethanolamine residues has been lacking. We now report that phosphatidylethanolamine, exogenously added to intact cells of E. coli, provides a source of phosphoethanolamine residues that are transferred to MDO. The biosynthesis of phosphoethanolamine-labeled MDO is osmotically regulated, with maximum synthesis occurring during growth in medium of low osmolarity.

Convenient Ruthrnium-complex Catalysed Synthesis of Enterolactone from the Corresponding Dibenzylidene Succinic Acid Moiety

Convenient Ruthrnium-complex Catalysed Synthesis of Enterolactone from the Corresponding Dibenzylidene Succinic Acid Moiety