Nanostructured morphology of a random P(DLLA-co-CL) copolymer

The random architecture of a commercial copolymer of poly(DL-lactic acid) and poly(ε-caprolactone), poly(DL-lactide-co-caprolactone), has been characterized by chemical structure analysis from hydrogen-1 nuclear magnetic resonance results. Moreover, spherical nanodomains have been detected in the thin films of this copolymer obtained after solvent evaporation. These nanodomains studied by atomic force microscopy and transmission elecron microscopy grow progressively under annealing until they collapse and form a homogenous disordered structure. This is the first time that the nanostructure of random poly(DL-lactic acid)/poly-(ε-caprolactone) copolymers is revealed, representing one of few experimental evidences on the possible nanostructuration of random copolymers.     

Synthesis of ε-caprolactone-b-l-lactide block copolymers by mean sequential polymerization,using diphenylzinc as initiator

Block copolymers of ε-caprolactone (CL) and l-lactide (l-LA) were synthesized by sequential polymerization using diphenylzinc as initiator. The composition of the copolymers was adjusted changing the comonomers in ratio. Copolymers were characterized by ¹H-NMR, ¹³C-NMR, DSC, and GPC. Results indicate that poly(ε-caprolactone)-b-poly(l-lactide) (PCL-b-PLA) block copolymers had a narrow molecular weight distribution and well-controlled sequences without random placement.     

Synthesis and solubility of polylactide-co-poly(amino acid) random copolymer

Random copolymers of polylactide-co-poly(amino acids) with a molecule weight range of 5,000–20,000 g/mol were obtained by ring-opening polymerization of l-lactic acid O-carboxyanhydride with amino acid-N-carboxyl anhydride in the presence of DMAP as an initiator. The structures of the copolymers were characterized with IR, ¹H-NMR, ¹³C-NMR, and GPC. The results show that the polymerization activity of amino acid-N-carboxyl anhydride is higher than that of l-lactic acid O-carboxyanhydride. Copolymers of polylactide-co-poly(amino acid) can improve the solubility of poly(amino acid) in organic solvents.     

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.     

An Interesting Complex: [Cd(l -trp) (d-trp)] n

A novel coordination polymer [Cd(l-trp) (d-trp)] _n (where l-trp and d-trp are l-tryptophan and d-tryptophan or (S)-2-amino-3-(3-indolyl)propionic acid and (R)-2-amino-3-(3-indolyl)propionic acid) was prepared by a solvent-thermal method and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The compound(monoclinic space group P2(1)/c with a = 19.759(2) Å, b = 5.2496(10) Å, c = 9.7594(16) Å, β = 97.2760(10)°, Z = 2) shows a two-dimensional plane structure. The crystallized coordination polymer has a centrosymmetric space group. Each Cd²⁺ ion coordinates with a pair of racemes, and the complex is a mesomer. Although l-trp was used, both l-trp and d-trp appear in the complex.     

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.     

Synthesis of 6-Substituted 1-oxoindanoyl Isoleucine Conjugates and Modeling Studies with the COI1-JAZ Co-Receptor Complex of Lima Bean

The conjugates of 6-substituted 1-oxoindanoyl carboxylic acids with L-isoleucine are mimics of the plant hormone (+)-7-iso-JA-L-Ile (3) that controls and regulates secondary metabolism and stress responses. In order to generate ligands that can be used as hormone-like compounds possessing different biological activities, an efficient and short synthesis of 6-bromo-1-oxoindane-4-carboxylic acid opens a general route to 6-Br-1-oxoindanoyl L-isoleucine conjugate (Br-In-L-Ile) (9a) as a key intermediate for several bioactive 6-halogen-In-L-Ile analogs (7a, 8a, 10a). The 6-ethynyl-In-L-Ile analog (11a) might be a valuable tool to localize macromolecular receptor molecules by click-chemistry. The activities of In-Ile derivatives were evaluated by assays inducing the release of volatile organic compounds (VOCs) in lima bean (Phaseolus lunatus). Each compound showed slightly different VOC induction patterns. To correlate such differences with structural features, modeling studies of In-Ile derivatives with COI-JAZa/b/c co-receptors of P. lunatus were performed. The modeling profits from the rigid backbone of the 1-oxoindanonoyl conjugates, which allows only well defined interactions with the receptor complex.     

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.     

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.     

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.     

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.     

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.     

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.     

Effect of l-Histidine Substitution on Sol–Gel of Transition Metal Coordinated Poly Ethyleneimine: Synthesis and Biochemical Characterization

The study was aimed to investigate the effect of chemical modification of branched poly ethyleneimine (PEI) on chelation of transition metal ions (Me²⁺) including Zn²⁺, Cu²⁺ or Ni²⁺ and sol–gel conversion thereof. To modulate chelation property of PEI, imidazole moieties were introduced into the polymer backbone by carbodiimide chemistry at different molar ratios of fmoc-protected l-histidine. The synthesis was characterized by ¹H-NMR spectroscopy and size exclusion chromatography. Potentiometric titration of PEI/Me²⁺ aqueous dispersions showed formation of stable complexes at pH above 5 depending on the degree of l-histidine substitution. FT-IR spectroscopy showed the imidazole ring of l-histidine was involved in the coordination interactions between PEI and Me²⁺. Addition of Zn²⁺ to PEI solution induced sol–gel conversion at a critical molar ratio decreasing by a higher degree of l-histidine modification. The gelation process led to formation of stable globular nanostructures as confirmed by atomic force microscopy with projected mean diameters less than 200 nm. Cellular experiment showed that l-histidine substitution enhanced cyto-compatibility of PEI, moreover cytotoxicity decreased significantly upon coordination of Zn²⁺ with the polymers. Conclusively, the coordination complexes of Zn²⁺ and l-histidine substituted PEI could serve as a nano system for biomedical applications.     

Optimization of temperature swing strategy for selective cooling crystallization of α-form l-glutamic acid crystals

l-glutamic acid can be crystallized as metastable α-form and stable β-form crystal. The α-form is desired because of its prismatic shape. Production of α-form of l-glutamic acid by cooling crystallization is not well-defined and α-form solid is commercially not available. In this study, an optimal cooling strategy to selectively produce large and narrowly distributed α-crystals is found by modeling and optimizing the crystallization and polymorphic transformation of l-glutamic acid. The optimal temperature profile is found to be cooling-heating-cooling concept where short nucleation period is followed by growth period in metastable zone. The obtained α-form of L-glutamic acid by optimal strategy had improved mean size, distribution, and purity compared to constant cooling.     

Synthesis of genistein-containing star-shaped homo- and copolyesters by the ring-opening polymerization

A novel initiator, naturally occurring in soy, has been developed for a direct synthesis of aliphatic star-shaped homo- and copolyesters. The synthesis is based on one of several known isoflavones, genistein, which has been employed as an initiator of homopolymerization of poly(l-Lactide) or co-initiator of copolymerization of ε-caprolactone and l-Lactide with Sn(Oct)₂ as a catalyst. The non-toxic chemicals used allow for an inexpensive and safe for human body facile synthesis of biocompatible functionalized polymers suitable for medical and pharmaceutical applications. The obtained polymers were characterized by ¹H, ¹³C NMR, FT-IR, SEC–MALLS and MALDI-TOF MS analysis.     

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.     

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.     

N-(18-Hydroxylinolenoyl)-l-Glutamine: A Newly Discovered Analog of Volicitin in Manduca sexta and its Elicitor Activity in Plants

Plants attacked by insect herbivores release a blend of volatile organic compounds (VOCs) that serve as chemical cues for host location by parasitic wasps, natural enemies of the herbivores. Volicitin, N-(17-hydroxylinolenoyl)-l-glutamine, is one of the most active VOC elicitors found in herbivore regurgitants. Our previous study revealed that hydroxylation on the 17th position of the linolenic acid moiety of N-linolenoyl-l-glutamine increases by more than three times the elicitor activity in corn plants. Here, we identified N-(18-hydroxylinolenoyl)-l-glutamine (18OH-volicitin) from larval gut contents of tobacco hornworm (THW), Manduca sexta. Eggplant and tobacco, two solanaceous host plants of THW larvae, and corn, a non-host plant, responded differently to this new elicitor. Eggplant and tobacco seedlings emitted twice the amount of VOCs when 18OH-volicitin was applied to damaged leaf surfaces compared to N-linolenoyl-l-glutamine, while both these fatty acid amino acid conjugates (FACs) elicited a similar response in corn seedlings. In both solanaceous plants, there was no significant difference in the elicitor activity of 17OH- and 18OH-volicitin. Interestingly, other lepidopteran species that have 17OH-type volicitin also attack solanaceous plants. These data suggest that plants have developed herbivory-detection systems customized to their herbivorous enemies.     

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 %.