Synthesis and surfactant properties of a new “extended” glucidoamphiphile made from D-glucose

We prepared a new nonionic surfactant, 8, in which the n-dodecyl chain is attached at the C-3 carbon of the D-glucose-based glucopyranose moiety by the linkage Z=?O-(α-PP-O) _n with ?O-(α-PP-O) _n being a commercial poly-(α-propyloxy) oligomeric mixture (with average ñ=6). This amphiphilic behavior study showed that, when compared to the reference compound 3-O-dodecyl-D-glucopyranose (Z=O), compound 8 exhibits (i) a water solubility that is 100-fold higher, (ii) a hydrophilic-lipophilic balance value increase from 8.5 to 12.6 units, and (iii) a slighly lower critical micelle concentration.     

The novel [(dME)2(HIM)P]2Ti(IV) complex: synthesize, characterization, and its utility in ROP of d,l-lactide

The novel {2,4-bis(1,1-dimethylethyl)-6-{[(2-hydroxyethyl)imino]methyl}phenoxy}₂ titanium(IV) complex {[(dME)₂(HIM)P]₂Ti(IV)} had been synthesized and characterized by EA, XRF, IR, and NMR methods. The [(dME)₂(HIM)P]₂Ti(IV) complex was reactive and promoted ring-opening polymerization (ROP) of d,l-lactide in the presence of benzyl alcohol (BnOH). And the results showed that ROP of d,l-lactide were produced upon addition of an excess (1–8?equiv.) of external BnOH. The complex showed a living and controlled fashion (M _w/M _n?=?1.15–1.32) for ROP of d,l-lactide and could produce the poly(d,l-lactide) with average molecular weight (M _n) up to 8.87?×?10⁴?g?mol^?1. The mechanism study by ¹H NMR spectrum of poly(d,l-lactide) with terminal benzyl ester group and [(dME)₂(HIM)P]₂Ti(IV) complex revealed that the polymerization proceeded through the traditional activated monomer mechanism and the acyl-oxygen bond cleavage mode of monomer. And the ¹³C NMR spectra and TG/DSC analysis showed that poly(d,l-lactide) was essential atactic and thermal stable polymer.     

l-Carnitine and Long-Chain Acylcarnitines are Positively Correlated with Ambulatory Blood Pressure in Humans: The SABPA Study

The prevalence of hypertension in sub-Saharan Africa is increasing rapidly, and treatment remains challenging. Although the use of l-carnitine in treatment has received much attention, studies reporting on physiological l-carnitine levels in hypertensives are limited. Our aim was to determine physiological levels of l-carnitine and acylcarnitines in African and Caucasian men, and to investigate associations between ambulatory blood pressure (BP) and carnitine levels. Participants included 101 African and 101 Caucasian teachers. Ambulatory BP measurements were conducted, and l-carnitine and acylcarnitine levels determined. African men showed significantly higher systolic BP (p < 0.001), diastolic BP (p < 0.001) and l-carnitine levels (p = 0.01). In both ethnic groups, partial regression analyses revealed a positive association between BP and l-carnitine, although in Caucasians it was with systolic (r = 0.20, p = 0.045), and in Africans with diastolic BP (r = 0.23, p = 0.023). After adjusting for confounders, an independent positive association between systolic (R ² = 0.37, β = 0.12, p = 0.041) and diastolic BP (R ² = 0.39, β = 0.14, p = 0.018) and l-carnitine and long-chain acylcarnitines (R ² = 0.38, β = 0.17, p = 0.005 and R ² = 0.39, β = 0.15, p = 0.011) were found, independent of ethnicity. Physiological l-carnitine levels were not only higher in Africans than in Caucasians but also above the expected reference range. Despite promising results on l-carnitine (and its short-chain derivatives) in hypertension treatment regimens, our findings paradoxically show that elevated BP is significantly associated with higher physiological l-carnitine and long-chain acylcarnitine levels.     

Another new family of “extended” glucidoamphiphiles. Synthesis and surfactant properties for different sugar head groups and spacer arm lengths

Following a new four-step route, we prepared a family of “extended” glucidoamphiphiles from D-glucose, D-galactose, and xylitol in which the n-dodecyl chain is attached to the glucidic moiety by the linkage Z=O-Et-O-Et-O-(α-PP-O-) _n′ where-O-(α-PP-O-) _n is a poly-(α-propyloxy) commercial oligomeric mixture (with average length n=6, 10, and 14). This amphiphilic behavior study showed that (i) the glucose derivative exhibits water solubility and hydrophilic-lipophilic balance values that are close to those found for the glucose compound with Z=-O-(α-PP-O-) _n (without the Et-O-Et group), (ii) all these compounds are more strongly hydrophilic than the corresponding glucidic derivatives with Z=O, (iii) the increase of the poly-(α-propyloxy) chain length from ñ=6 to ñ=14 tends to reduce the hydrophilicity slightly.     

Immobilized iron Schiff base histidine complexes on Al-MCM-41 and zeolite Y as catalyst for oxidation of cycloalkanes

Iron complexes of N-salicylidene-l-histidine with or without bipyridine ligand immobilized on Al-MCM-41 and zeolite Y designated as Fe(sal-l-his)(bipy)complex/Al-MCM-41 or Fe(sal-l-his)complex/Al-MCM-41 and Fe(sal-l-his)(bpy)complex/Y or Fe(sal-l-his)complex/Y respectively, were prepared and characterized by X-ray powder diffraction (XRD), FT-IR, N₂ adsorption/desorption and chemical analysis techniques. Fe(sal-l-his)/Al-MCM-41 and Fe(sal-l-his)(bipy)complex/Al-MCM-41 were found to successfully catalyze the oxidation of cyclohexane, methyl cyclohexane, cyclooctane and adamantane with H₂O₂. The oxidation results and promising catalytic behavior of Fe(sal-l-his)(bipy)complex/Al-MCM-41 for oxidation of cyclooctane with 90 % conversion and excellent selectivity toward the formation of cyclooctanone will be discussed in this presentation.     

Porous chitosan-based adhesive patch filled with poly(l-3,4-dihydroxyphenylalanine) as a transdermal drug-delivery system

Bioadhesives have been widely used on surgical areas for more than 50 years. Despite their numerous advantages, drawbacks such as cytotoxicity and low efficiency of transdermal drug delivery have limited their applications. Consequently, bioadhesives are mainly used during emergencies. To improve the physical properties of bioadhesive materials, poly(l-3,4-dihydroxyphenylalanine) or poly(l-DOPA) was synthesized and used to fill 2 kinds of porous chitosan patches (high and medium molecular weight). Bioaddisive and patch properties such as bond strength, drug-delivery efficiency, morphology, cytotoxicity, and histology were characterized. We ascertained that the optimal combination for high bond strength was 77.9 % polymethacrylic acid (PMA, molecular weight: 9,500 Da) and 22.1 % l-DOPA. Drug release was 1.5 times faster from the poly(l-DOPA)-filled chitosan patch of medium molecular weight than from the high molecular weight patch. Further, the medium molecular weight chitosan patch was more efficient at wound healing than commercial glue. These results indicate that chitosan-based materials filled with poly(l-DOPA) can be used as adhesive patches in various fields.     

l-Lysine-derived optically active poly(hydrazide-imide)s: synthesis, characterization and their application in removal of heavy metal ions

Six novel poly(hydrazide-imide)s (PHI _a–f ) were prepared from the reaction of a novel l-lysine-derived chiral diacid, ethyl l-lysine-N,N’-ditrimellitoyl diacide (1), with six synthetic dihydrazides by solution polycondensation. These polymers have inherent viscosities in the range of 0.22–0.45 dl g^?1, display optical activity, and are readily soluble in polar aprotic solvents. They start to decompose (T _10%) above 248 °C and display glass-transition temperatures at 164.37–210.20 °C. All the above polymers were fully characterized by UV, FT-IR, and ¹H NMR spectroscopy, TGA, DSC, inherent viscosity measurement and specific rotation.     

Separation of phenylalanine racemates using d-phenylalanine imprinted microbeads as HPLC stationary phase

A successful enantioseparation of d,l-phenylalanine (Phe) was achieved for the first time by using d-Phe imprinted P(MAA-co-EGDMA) microbeads as HPLC stationary phase. The d-Phe imprinted microbeads were prepared by a novel modified suspension polymerization method without derivatization of the water-soluble template molecule. This preparation method was employed in order to capture template molecules in organic phase droplets during polymerization. The prepared d-Phe imprinted P(MAA-co-EGDMA) microbeads were packed into an empty stainless steel column, which was used for the separation of the Phe enantiomers. The selection of a suitable mobile phase, mobile phase composition, pH and flow rate were investigated for determining the best resolution of the Phe enantiomers. Baseline separation was achieved using an organic–aqueous buffer (EtOH–acetate buffer) solution as a mobile phase. Separation factors of more than 2.56, with a resolution of 1.38, were obtained with a mobile phase containing 9–18% (v/v) EtOH in a 0.030 M acetate buffer solution. d-Phe imprinted microbeads were superior to the majority of the reported molecularly imprinted polymers with respect to chiral separation abilities. The column backpressure was less than 300 psi.     

l-Lactic acid biosensor based on multi-layered graphene

Pristine graphene platelets and graphene oxide were used as electrode modifiers, aiming the investigation of their electrochemical efficacy towards β-nicotinamide adenine dinucleotide (NADH). The electrochemical detection of NADH is one of the most studied areas of bioelectroanalysis because of the ubiquity of NAD(P)H-based enzymatic reactions in nature. Commercially available graphene and laboratory prepared graphene oxide were used to modify glassy carbon electrodes and the behaviour of such modified electrodes against potassium ferricyanide (III) and NADH was reported. Relying on the graphene-modified transducer, l-lactic dehydrogenase (l-LDH) was successfully immobilised in a 1 % Nafion^® membrane. The developed biosensor, working at +250 mV versus Ag/AgCl reference electrode, was used to assess l-lactic acid in four different types of yogurts, revealing an l-lactic acid concentration ranging between 0.3 and 0.6 %.     

Optimization of Lipase-Catalyzed Fractionation of Two Conjugated Linoleic Acid (CLA) Isomers

The separation of two isomers of conjugated linoleic acid is highly significant since each exhibits different biochemical properties. The aim of this study was to investigate and optimize several factors affecting the esterification of l-menthol with the c9,t11-CLA isomer in an organic solvent-free system using lipase from Candida rugosa (Lipase AY-30). D-optimal design with 5 factors and 3 levels were employed to evaluate the effects of synthesis parameters; reaction time (8–24 h), temperature (30–50 °C), enzyme content (2–20 U/ml), substrate molar ratio of conjugated linoleic acid oil to l-menthol (2:1–1:2) and pH (6–8) on esterification of c9,t11-CLA with l-menthol. Based on the analysis of the residual amount of c9,t11-CLA in the free fatty acid fraction after just one-step esterification, the optimum synthesis conditions were as follows: reaction time 23.12 h, temperature 32.65 °C, enzyme amount 135.40 U, molar ratio of CLA oil to l-menthol at 1:1.7 and pH at 7.7; the lowest purity of c9,t11-CLA in free fatty acid fraction based on the total content of c9,t11 and t10,c12-CLA isomers was 8.6 %.     

Non-isothermal cold crystallization behavior and kinetics of poly(l-lactide): effect of l-lactide dimer

The effects of l-lactide dimer as additives on the crystallization behavior of poly(l-lactide) (PLLA) films were studied. Hence, neat PLLA films and PLLA containing l-lactide (5 % w/w) (PLLA/La) were prepared in dichloromethane at room temperature via solution casting. The non-isothermal cold crystallization of PLLA films were studied using differential scanning calorimetry at various heating rates including 2.5, 5, 7.5, 10 and 15 °C/min. However, the X _C% was increased for PLLA/La films in comparison with neat PLLA films. The crystallization kinetics was then analyzed by the Avrami, Jeziorny, Ozawa and Mo kinetic models. It is found that all the kinetic models were established to describe the experimental data fairly well except the Ozawa model. The values of t _1/2, Z _C and F(T) indicated that the crystallization rate increased with increase in heating rates for PLLA and PLLA/La films. However, l-lactide dimer incorporated in PLLA films accelerates the crystallization process of PLLA at the high heating rate. The nucleation constant (K _g) and the surface free energy (σ _e) based on Lauritzen–Hoffman theory indicated that these parameters for PLLA/La films is lower than neat PLLA.     

Poly(ester amide)s based on l-lactic acid oligomers and glycine: the role of the central unit of the l-lactic acid oligomers and their molecular weight in the poly(ester amide)s properties

Novel biodegradable poly(ester amide)s (PEAs) based on l-lactic acid (l-LA) oligomers and glycine were successfully synthesized, through an easy and fast procedure, making use of inexpensive starting materials. The l-LA oligomers were prepared with different central units and different molecular weights in order to access the influence of such parameters in the final properties of the PEAs’. Both the central unit of the l-LA oligomer and its molecular weight have important influence in the PEAs’ final properties. The thermal stability is lower for the PEAs containing the l-LA with the shortest central unit and for the PEAs based on the l-LA oligomers of high molecular weight. The PEAs exhibit a semi-crystalline nature, except those derived from the l-LA oligomers with high molecular weight, which have an amorphous character. Both hydrolytic and enzymatic degradation are more pronounced in PEAs synthesized from the l-LA oligomers with low molecular weight. Different mechanisms of degradation were found for the PEAs: bulk erosion and surface erosion, for hydrolytic degradation and enzymatic degradation tests, respectively.     

Preparation of highly flexible chitin nanofiber-graft-poly(γ-l-glutamic acid) network film

In the previous study, we successfully prepared a chitin nanofiber film by regeneration from a chitin ion gel with an ionic liquid using methanol. In this study, we performed surface-initiated graft polymerization of γ-benzyl l-glutamate N-carboxyanhydride (BLG-NCA) from amino groups on a partially deacetylated chitin nanofiber (PDA-CNF) film. First, the chitin nanofiber film was immersed in 40 % NaOH aq. at 80 °C for 7 h for partial deacetylation. Then, the PDA-CNF film was immersed in a solution of BLG-NCA in ethyl acetate at 0 °C for 24 h for graft polymerization from amino groups on nanofibers to give a chitin nanofiber-graft-poly(γ-benzyl l-glutamate) (CNF-g-PBLG) film. The analytical results of the film indicated that graft polymerization of BLG-NCA occur on surface of nanofibers. Furthermore, the film was treated with 1.0 mol/L NaOH aq. to convert PBLG on nanofibers into poly(γ-l-glutamic acid sodium salt) (PLGA). Then, condensation of the resulting carboxylates with amino groups at the terminal ends of PLGAs or the remaining amino groups on nanofibers was performed using the condensing agent to produce a CNF-g-PLGA network film. The resulting film showed the good mechanical properties with high flexibility, which has potentials as promising materials for practical applications.     

Facile synthesis of branched chitin by glycosylation of fully trimethylsilylated chitin with a glucosamine-derived oxazoline

A simple and straightforward procedure for synthesizing branched chitin and chitosan has been developed on the basis of the glycosylation of trimethylsilylated chitin with an oxazoline derived from d-glucosamine. Chitin was first trimethylsilylated, and the derivative was treated with the oxazoline to introduce peracetylated d-glucosamine branches into the chitin backbone. The extent of branching was dependent on the amount of the oxazoline and reaction time, and under appropriate conditions, it reached around 0.65. Selective O-deacetylation or thorough N,O-deacetylation of the resulting glycosylated product gave chitin having N-acetyl-d-glucosamine branches or chitosan having d-glucosamine branches.     

The effect of thiourea, l(−) cysteine and glycine additives on the mechanisms and kinetics of copper electrodeposition

The influence of thiourea, l(?) cysteine and glycine on the mechanisms and kinetics of copper electrodeposition from aqueous solution at pH 1.00 ± 0.05 and 25 °C was investigated using several complementary techniques. Rotating disc electrode current density measurements and the kinetic parameters calculated from Koutecký–Levich analysis indicated that at 5 × 10^?3 M thiourea and l(?) cysteine addition the electro-reduction of Cu(II) was significantly inhibited. By contrast, upon similar addition of glycine, the reduction current density increased and the equilibrium potential moved towards more positive values. Microscopic imaging studies of the resulting Cu films showed that thiourea and l(?) cysteine led to fine-grained deposits, whilst glycine addition resulted in a coarser deposit. It is suggested the additives substantially altered the electron and mass transfer processes during electrodeposition. Both thiourea and l(?) cysteine appear to act by specific chemical interactions that lead to CuS co-crystallization. On the other hand, glycine is believed to act by mediating the Cu(II) to Cu(I) reduction process.     

Amprometric detection of Glycine, l-Serine, and l-Alanine using glassy carbon electrode modified by NiO nanoparticles

Glassy carbon electrode modified with nickel oxide nanoparticles has been used to investigate the electrochemical oxidation of Glycine, l-Serine, and l-Alanine in an alkaloid solution. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry in detail. The electrocatalytic behavior is further exploited as a sensitive detection scheme for the above amino acids by hydrodynamic amperometry. Under optimized conditions, the calibration curves are linear in the concentration ranges of 1–200?μM for Glycine, 1–400?μM for l-Serine, and 30–200?μM for l-Alanine, respectively. The respective detection limit (S/N?=?3) and sensitivity are 0.9?μM and 24.3 nA μM^?1 for Glycine, 0.85?μM and 12.4 nA μM^?1 for l-Serine, and 29.67?μM and 0.4 nA μM^?1 for l-Alanine. The prepared electrode exhibits a satisfactory stability and long life-time, while it is stored at ambient conditions.     

Poly(l-lactide) initiated by silver N-heterocyclic carbene complexes: synthesis, characterization and properties

Poly(l-lactide) (PLLA) was successfully synthesized by ring-opening polymerization (ROP) in bulk using silver N-heterocyclic carbene (Ag–NHC) complex. The effect of reaction time, temperature and monomer/initiator ratio on polymerization process were determined. The optimum conditions were found as 130 °C, 4 h and M/I molar ratio of about 100. The polymers were characterized by FTIR, ¹H-NMR, GPC and TG. High-molecular-weight PLLA (M _w = 3.78 × 10⁴, M _n = 1.91 × 10⁴, PDI = 1.97) was synthesized by the ROP of l-lactide (LLA) with bis-(N-methyl N′-dodecylimidazole) silver(I) di-bromo argentate (1a) in bulk. The effect of different N-substituted ligand groups on the polymerization was studied. The antimicrobial activity of the synthesized polymers were investigated by using minimum inhibitory concentration test against gram positive (Staphylococcus aureus) and gram negative (Escherichia coli and Pseudomonas aeruginosa). It was observed that the synthesized polymers displayed moderate antimicrobial activity.     

Chiral Homobimetallic Palladium(II) Complexes Composed of Chirality-Organized Quinonediimines Bearing Amino Acid Moieties

The chirality-organized quinonediimine derivatives bearing amino acid moieties were demonstrated to react with 2 molar equiv. of Pd(OAc)₂, resulting in the formation of the chiral homobimetallic palladium(II) complexes. The crystal structures of the chiral conjugated complexes revealed the coordination of the quinonediimine nitrogen to a palladium center and a chiral propeller twist conformation of the π-conjugated backbone. The mirror image relationship of the CD signals around the quinonediimine moieties in acetonitrile was observed between l- and d-derivatives, indicating the preservation of the chirality-organized structures even in a solution.     

Preparations and reactions of alkyl ethers of some aldohexoses

Aldohexose, such asd-glucose,d-galactose ord-mannose, reacted with acetone to give the following O-isopropylidene derivatives: 1,2;5,6-di-O-isopropylidene-d-glucofuranose (IA), 1,2;3,4-di-O-isopropylidene-d-galactopyranose (IB) or 2,3;5,6-di-O-isopropylidene-D-mannofuranose (IC). The O-isopropylidene derivative (IA～IC) reacted with alkyl/alkenyl halogenide to yield aldohexose ether compounds containing di-O-isopropylidene group, 3-O-alkyl-1,2;5,6-di-O-isopropylidene-d-glucofuranose (II), 6-O-alkyl-1,2;3,4-di-O-isopropylidene-d-galactopyranose (III) or 1-O-alkyl-2,3;5,6-di-O-isopropylidene-d-mannofuranoside (IV), in good yields. The Williamson ether synthesis was carried out using phase-transfer catalysis (PTC). The derived aldohexose alkyl ether containing di-O-isopropylidene group was hydrolyzed to give 3-O-alkyl-1,2-O-isopropylidene-d-glucofuranose (V) as a partial hydrolysis product; the complete hydrolysis of I～IV gave, as expected, 3-O-alkyl-glucopyranose (VI), 6-O-alkyl-galactopyranose (VII) or 1-O-alkyl-mannofuranoside (VIII). Further alkylation of (V) with Mel under PTC and subsequent acid hydrolysis gave 3-O-alkyl-5,6-di-O-methyl-d-glucofuranose (X). Methanolysis of III with catalytic amounts of H₂SO₄ gave 1-O-methyl-6-O-alkyl-d-galactofuranoside (XI). The elucidation of the galactofuranoside skeleton of (XI) was determined by means of its¹³C nuclear magnetic resonance spectra. The O-alkyl aldohexoses, e.g., X and XI, were evaluated and found to be emulsifiers.     

Random copolymerization of ε-caprolactone and l-lactide with molybdenum complexes

Dioxomolybdenum complexes were examined as catalysts for the copolymerization of ε-caprolactone (ε-CL) and l-lactide (l-LA). The bis-[(5-OMe)salicylaldehydato]dioxomolybdenum complex completed the copolymerization after 20 h at 110 °C with 0.05 mol% of the catalyst to produce a copolymer in high yield. The microstructure of the copolymer was analyzed using ¹H and ¹³C NMR spectroscopy and was determined to have a random structure. The r values calculated from the heterodiad analysis of the ¹H NMR data were r _LA = 0.91 and r _CL = 0.93, and the L values calculated from the triad analysis of the ¹³C NMR data were L _LA = 1.58 and L _CL = 1.81. Other dioxomolybdenum complexes, such as cis-α MoO₂[(3-MeO)DiMeSaltn], MoO₂(acac)₂ and (NH₄)₈[Mo₁₀O₃₄] exhibited comparable or slightly lower reactivity for the copolymerization. Consecutive polymerization of ε-CL followed by l-LA afforded a block copolymer without trans-esterification.