Pimelic Acid Research Articles

Modification of graphene oxide to induce beta crystals in isotactic polypropylene

Graphene oxide (GO) was functionalized with pimelic acid (PA) on its surface to produce a β-crystal nucleating agent. The functionalization was characterized by Fourier transform infrared spectroscopy, showing the presence of new bands at 1570 and 1406 cm−1 indicating a bridging bidentate link of the PA on the GO surface through the Ca used during the functionalization. These observations were concomitant with the Raman spectroscopy results where the D–G intensity ratio increased, suggesting that the disorder in GO structure increased when the PA molecules are attached on the GO surface. The modified graphene oxide (GO-PA) showed high thermal stability, making it attractive for melt blending composites. These results were observed by thermal differential scanning calorimetry (DSC) and thermogravimetric analysis. The DSC and wide-angle X-ray diffraction (WAXD) results demonstrated that the modified GO is an excellent β-nucleating promoter even at low percentages (0.05 GO-PA % w/w) in contrast to the unmodified GO. The content of β-crystals under isothermal crystallization conditions reached a value as high as 92% by DSC while the extrudes prepared by compression and analyzed by WAXD showed a kβ = 0.78 by Turner-Jones method at the same percentage of modified filler. The storage modulus for the iPP composites (GO/iPP and GO-PA/iPP) was in all cases higher than that for the raw iPP sample because of the presence of GO in the polymer matrix. However, a decrease in the storage modulus can be observed for the GO-PA/iPP composites because of the presence of high percentages of β-crystal.

Curing Reaction and Dielectric Properties of Rigid and Elastic Liquid Crystal Epoxy Networks Modified with Nanofillers

The aim of the paper is to compare the progress of the curing reaction and the dielectric properties of liquid crystalline epoxy networks of different elasticity and to investigate how modification with nanofillers influences their properties. The study focuses on a liquid crystalline epoxy monomer with four aromatic rings in the mesogen, cross-linked with 4,4′-diaminodiphenylmethane (DDM) and pimelic acid (PA) to produce rigid and elastic polymer networks. The obtained results are compared to networks modified with nanofillers (diphenyl aluminum phosphate nanorods). The curing process is monitored in situ with broadband dielectric spectroscopy, which is a good tool to view the progress of the reaction. Two stages with different reaction dynamics are observed in the studied cases. Dielectric properties of the products cured with two chosen agents show significant differences in the obtained parameters (activation energy, glass transition, and fragility index) as well as in the dynamics of the α and β relaxations. Although the curing agent is the main factor determining the properties of the product, the nanofiller additive also modifies the values of specific parameters that characterize both the process of the reaction and the properties of the final composites. Particularly, adding the nanofiller raises the glass transition temperature in both the cases. The obtained results are in good agreement with the earlier calorimetric study.

Effect of Particle Morphology on Cloud Condensation Nuclei Activity

Cloud condensation nuclei (CCN) activation is sensitive to the size, composition, and morphology of aerosol particles of <200 nm. By controlling the particle morphology of internally mixed samples (i.e., homogeneous versus phase separated), we have probed the effect of morphology on CCN activity using model organic aerosol systems, where ammonium sulfate was mixed with either pimelic acid or succinic acid in a 50:50 mixture by weight. Surprisingly, for systems of the same composition but distinct morphology, we observe a noticeable impact on CCN activity. Specifically, a phase-separated morphology results in activation diameters close to that of ammonium sulfate, while a homogeneous morphology yields an activation diameter in between the pure inorganic and organic components. Our results suggest that morphology-resolved CCN data may be an important parameter to consider in cloud microphysics models to improve predictions of CCN activity of complex organic aerosols. For laboratory CCN studies, it is import...

“Improvement in the energy dissipation capacity of polypropylene composites through a surface modification of titanium dioxide particles with a dicarboxylic acid”

In this work, we modified commercial TiO2 nanoparticles using pimelic acid (PA) as an agent to improve interaction of titanium dioxide (TiO2) into an isotactic polypropylene (iPP) matrix. The chemical bond of PA at the TiO2 surface, allows a thermal and UV stabilization of PA molecules avoiding its decomposition in a process involving high temperature. As a consequence of an appropriate TiO2 integration into iPP, the results of the dynamical-mechanical analysis reveal that the iPP filled with modified particles (c-TiO2) dissipate around two times more energy than those with the non-modified particles (n-TiO2). A multi-frequency analysis of these composites also allowed us to estimate the apparent activation energy required to carry out the vitreous transition of these composites filled with c-TiO2, which shows that particles are effectively well integrated with the iPP. These results validate the surface modification as an appropriate strategy to improve both, coloring capacity of TiO2 and mechanical stress resistance of iPP measured as dissipated energy into the bulk of iPP with modified TiO2 particles.

Structural studies of crystalline forms of triamterene with carboxylic acid, GRAS and API molecules.

Pharmaceutical salt solvates (dimethyl sulfoxide, DMSO) of the drug triamterene with the coformers acetic, succinic, adipic, pimelic, azelaic and nicotinic acid and ibuprofen are prepared by liquid-assisted grinding and solvent-evaporative crystallization. The modified ΔpKa rule as proposed by Cruz-Cabeza [(2012 ▸). CrystEngComm, 14, 6362-6365] is in close agreement with the results of this study. All adducts were characterized by X-ray diffraction and thermal analytical techniques, including single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry and thermal gravimetric analysis. Hydrogen-bonded motifs combined to form a variety of extended tapes and sheets. Analysis of the crystal structures showed that all adducts existed as salt solvates and contained the amino-pyridinium-carboxyl-ate heterodimer, except for the solvate containing triamterene, ibuprofen and DMSO, as a result of the presence of a strong and stable hemitriamterenium duplex. A search of the Cambridge Structural Database (CSD 5.36, Version 1.18) to determine the frequency of occurrence of the putative supramolecular synthons found in this study showed good agreement with previous work.

Descriptors for the α,ω-dicarboxylic acids from oxalic acid to sebacic acid

We use literature data on solubilities in water and solvents, water-solvent partition coefficients and vapor pressures at 298 K to obtain Abraham (Absolv) descriptors for the neutral, unionized, forms of oxalic acid, malonic acid, glutaric acid, succinic acid, pimelic acid, suberic acid, azaleic acid and sebacic acid. With a knowledge of equations for partition coefficients for numerous water-wet solvents, water to dry solvents and water to ionic liquid systems, we can then predict partition coefficients of the various acids in a huge number of systems. We set out the solubility of the acids in water and these, together with estimated partition coefficients yield solubilities of the acids into the corresponding solvents. The descriptors themselves show that the acids are dipolar, are strong hydrogen bond acids and reasonably strong hydrogen bond bases, although their hydrogen bond acidity is less than expected for compounds containing two (independent) carboxylic acid groups.

Synthesis and structure identification of 2-amino-4, 6- dimethyl pyrimidine with gallic acid and pimelic acid

Reaction of 2-amino-4, 6- dimethyl pyrimidine with carboxylic acid such as gallic acid and pimelic acid, yielded a salt and co-crystal, respectively. The new crystal forms were obtained from slow evaporation technique. The crystal structure and hydrogen bond interaction of the two crystals were determined by single X-ray diffraction analysis. Inter molecular interactions of the compounds were investigated using the 3D Hirshfeld surfaces and the associated 2D fingerprint plots. The functional groups were identified by the FTIR, FT-Raman spectral studies. The presence of carbon and hydrogen in the two samples were identified by the 1H and 13C NMR analysis. The excited energy was observed using UV–Visible spectral analysis. The fluorescence spectra revealed the emission state of the two samples. The thermal behaviour and stability of the two compounds were evaluated by the TGA-DSC analysis.

Preparation and crystallization of isotactic polypropylene composites filled by titanium dioxide-supported montmorillonite with a β-nucleating surface

To obtain multi-functional β-iPP composites, β-iPP composites are always filled by multiple fillers with α-nucleating ability. To prepare β-iPP/TiO2/MMT composites, TiO2-supported MMT with a β-nucleating surface was prepared through hydrolysis reaction of Tetra-n-butyl titanate and chemical reaction between pimelic acid and calcium ion. X-ray diffraction and scanning electron micrograph confirmed the formation of TiO2 on the surface of MMT. The differential scanning calorimeter and X-ray diffraction illustrated that the β-iPP composites filled by TiO2 and MMT had lower relative β-phase contents than β-iPP. It is observed by polarized optical microscope that addition of TiO2-supported MMT with a β-nucleating surface into iPP can increase the spherulite nuclei density and decrease the spherulite size significantly and obtain the β-iPP/TiO2/MMT composites with high relative β-phase content.

Functionalised CuO nanostructures for the detection of organophosphorus pesticides: A non-enzymatic inhibition approach coupled with nano-scale electrode engineering to improve electrode sensitivity

This study explores the potential of a newly-developed indium tin oxide (ITO) based electrode for the development of an electro-catalytic inhibition sensor system for organophosphorus pesticides. The sensor relies on the redox signal inhibition of pralidoxime chloride (PAM) immobilised over the pimelic acid functionalised CuO nanostructures grown in-situ over an ITO substrate. The in-situ growth enabled on-pot modification and functionalisation of ITO electrodes with the formation of uniform nanostructures possessing high surface area and excellent interface contact. The versatility of the proposed electrode was evident from its excellent electrochemical characteristics evaluated in comparison to bare and slurry-driven glassy carbon electrodes (GCEs). The high structural uniformity and greater surface coverage achieved by in-situ growth provided a uniform surface environment for electrode-analyte interaction, leading to good inhibition signal sensitivity and repeatability. The developed sensor was successful in detecting chlorpyrifos, fenthion and methyl parathion within the concentration range of 0.01–0.16 μM with signal sensitivity reaching down to 1.6 × 10−9, 2.5 × 10−9 and 6.7 × 10−9 M respectively. Moreover, the proposed sensor demonstrated excellent applicability when tested for chlorpyrifos from vegetable extracts using a standard addition method.

Carboxylate-Selective Chemical Cross-Linkers for Mass Spectrometric Analysis of Protein Structures.

Chemical cross-linking coupled with mass spectrometry (CXMS) facilitates structural analysis of proteins. As current CXMS applications are almost exclusively limited to lysine residues, they can only retrieve a small portion of the structural information theoretically accessible to CXMS. Chemical cross-linkers targeting the acidic residues Asp/Glu could greatly enhance the power of CXMS. However, it has been difficult to develop chemistries that offer selectivity and efficiency under physiological conditions. Here, we report a class of carboxylate-selective diazo-containing cross-linkers (Diazoker) of which Diazoker 1, with a spacer arm consisting of two ethan-1,2-diol units, is the best example. Unlike previously developed carboxylate-selective cross-linkers like pimelic acid dihydrazide (PDH), Diazoker 1 does not require a coupling reagent. We tested Diazoker 1 on nine model proteins and found that Diazoker 1 generated an average of 73 cross-linked peptide pairs per protein. Although this is 32% fewer than the number generated by PDH, the Diazoker 1 cross-links have a higher rate of compatibility with protein crystal structures. From a more complex protein mixture, Diazoker 1 and PDH identified 75 and 76 cross-linked peptide pairs, respectively. The Asp/Glu residues cross-linked by Diazoker 1 are not the same as those cross-linked by PDH. Diazoker 1 favors acidic residues that are less exposed to solvent. In conclusion, Diazoker 1 is complementary to existing cross-linkers and expands the toolkit of CXMS for structural analysis of proteins.

Dicarboxylic acids analyzed by time-of-flight secondary ions mass spectrometry. Part V: Heptanedioic acid

Time-of-flight secondary ion mass spectrometry was carried out to analyze a commercially available heptanedioic acid (pimelic acid) powder. Positive and negative polarity ion spectra were obtained using a 25 keV Bi3+ ion beam rastered over areas of 50 × 50 μm2. The main observed fragments were the protonated molecule [M+H]+ at 105 u and the deprotonated molecule [M-H]− at 103 Da with their respective oligomers.

The preparation of calcium pimelate modified OMMT from natural Ca-montmorillonite and its application as β-nucleating agent for polypropylene

Ca-montmorillonite (Ca-MMT) was first modified with different amount of two different kinds of surfactants to obtain organo-montmorillonites (OMMTs) directly via ion exchange between Ca2+ and alkyl ammonium cations. Then remained Ca2+ in OMMTs was reacted with pimelic acid (HA) to obtain CaHA-OMMTs. PP/CaHA-OMMT composites were prepared. Results of FT-IR demonstrate the existence of long-chain alkyl in OMMTs, and CaHA in CaHA-OMMTs. The reaction between HA and OMMT could lead to an increase in d-spacing value of clay. CaHA-OMMTs with high CaHA contents and obviously increased d-spacing values were obtained. Results of WAXD and TEM show exfoliated clay platelets in PP/CaHA-OMMT composites. The obviously increased Tc, and the high β-phase content in PP/CaHA-OMMT composites demonstrate the high β-nucleation efficiency of CaHA-OMMTs. Composites with higher content of β-phase epitaxial crystallized on exfoliated clay platelets display largely improved impact strength.

The only examples of cationic lanthanide pimelate frameworks decorated by π-conjugated 1,10-phenanthrolines

Abstract A series of lanthanide pimelates [Sm(phen)(Hpim)(pim)] n ·1.5nH 2 O ( 1 , phen = 1,10-phenanthroline, H 2 pim = pimelic acid), and [ Ln (phen)(pim)] n ·nClO 4 ·nH 2 O [ Ln = Gd ( 2a ), Tb ( 2b ), Er ( 2c )] have been hydrothermally synthesized and characterized structurally by elemental analysis, IR spectroscopy, thermogravimetric analysis and PXRD. Compound 1 contains 1-D neutral [Sm(phen)(Hpim)(pim)] n chain that is constructed by the linkages of [Sm(phen)] ions and pim 2− /Hpim − ligands, while compounds 2a - c contain 1-D cationic [ Ln (phen)(pim) + ] n chain with ClO 4− ion as counterion. Although a lot of lanthanide coordination polymers were obtained with aliphatic dicarboxylic acids, they usually show neutral frameworks. Compounds 2a - c provide the only examples of cationic lanthanide pimelate frameworks decorated by phen chromophores. The photoluminescent properties of 1 and 2b - c , and magnetic properties of all compounds have been studied.

β‐Crystallization and mechanical properties of aluminum hydroxide‐filled polypropylene composites

In order to provide aluminum hydroxide with β‐nucleating surface (β‐ATH) for PP crystallization, the calcium pimelate supported on the surface of ATH was prepared through chemical reaction between calcified ATH and pimelic acid in our lab. The β‐ATH particles were characterized by Fourier transform infrared spectrometry, X‐ray photoelectron spectroscopy and scanning electron microscopy. Effect of ATH, calcified ATH, and β‐ATH on crystallization and crystalline modification of PP was investigated by differential scanning calorimetry. The results indicated that the prepared β‐ATH has higher heterogeneous nucleation than ATH and calcified ATH for PP crystallization. Addition of ATH and calcified ATH has no influence on the crystalline modification of PP. The β‐ATH can induce the formation of β‐crystal in the ATH‐filled PP composites with β‐crystal content of above 90%. The transformation of surface nucleation mechanism of ATH from α‐nucleation into β‐nucleation was investigated. The effects of β‐ATH content, mass ratio of calcified ATH/pimelic acid and concentration of calcium acetate solution in the preparation of calcified ATH on the heterogeneous nucleation and β‐crystal content of β‐ATH‐filled PP composites were discussed. The mechanical performance of the prepared β‐ATH‐filled PP composites were also characterized. POLYM. COMPOS., 40:E194–E201, 2019. © 2017 Society of Plastics Engineers

Exploring sources of biogenic secondary organic aerosol compounds using chemical analysis and the FLEXPART model

Abstract. Molecular tracers in secondary organic aerosols (SOAs) can provide information on origin of SOA, as well as regional scale processes involved in their formation. In this study 9 carboxylic acids, 11 organosulfates (OSs) and 2 nitrooxy organosulfates (NOSs) were determined in daily aerosol particle filter samples from Vavihill measurement station in southern Sweden during June and July 2012. Several of the observed compounds are photo-oxidation products from biogenic volatile organic compounds (BVOCs). Highest average mass concentrations were observed for carboxylic acids derived from fatty acids and monoterpenes (12. 3 ± 15. 6 and 13. 8 ± 11. 6 ng m−3, respectively). The FLEXPART model was used to link nine specific surface types to single measured compounds. It was found that the surface category sea and ocean was dominating the air mass exposure (56 %) but contributed to low mass concentration of observed chemical compounds. A principal component (PC) analysis identified four components, where the one with highest explanatory power (49 %) displayed clear impact of coniferous forest on measured mass concentration of a majority of the compounds. The three remaining PCs were more difficult to interpret, although azelaic, suberic, and pimelic acid were closely related to each other but not to any clear surface category. Hence, future studies should aim to deduce the biogenic sources and surface category of these compounds. This study bridges micro-level chemical speciation to air mass surface exposure at the macro level.

In Vivo Roles of Fatty Acid Biosynthesis Enzymes in Biosynthesis of Biotin and α-Lipoic Acid in Corynebacterium glutamicum.

For fatty acid biosynthesis, Corynebacterium glutamicum uses two type I fatty acid synthases (FAS-I), FasA and FasB, in addition to acetyl-coenzyme A (CoA) carboxylase (ACC) consisting of AccBC, AccD1, and AccE. The in vivo roles of the enzymes in supplying precursors for biotin and α-lipoic acid remain unclear. Here, we report genetic evidence demonstrating that the biosynthesis of these cofactors is linked to fatty acid biosynthesis through the FAS-I pathway. For this study, we used wild-type C. glutamicum and its derived biotin vitamer producer BFI-5, which was engineered to express Escherichia coli bioBF and Bacillus subtilis bioI Disruption of either fasA or fasB in strain BFI-5 led to decreased production of biotin vitamers, whereas its amplification contributed to increased production, with a larger impact of fasA in both cases. Double disruptions of fasA and fasB resulted in no biotin vitamer production. The acc genes showed a positive effect on production when amplified simultaneously. Augmented fatty acid biosynthesis was also reflected in pimelic acid production when carbon flow was blocked at the BioF reaction. These results indicate that carbon flow down the FAS-I pathway is destined for channeling into the biotin biosynthesis pathway, and that FasA in particular has a significant impact on precursor supply. In contrast, fasB disruption resulted in auxotrophy for lipoic acid or its precursor octanoic acid in both wild-type and BFI-5 strains. The phenotypes were fully complemented by plasmid-mediated expression of fasB but not fasA These results reveal that FasB plays a specific physiological role in lipoic acid biosynthesis in C. glutamicumIMPORTANCE For the de novo biosynthesis of fatty acids, C. glutamicum exceptionally uses a eukaryotic multifunctional type I fatty acid synthase (FAS-I) system comprising FasA and FasB, in contrast to most bacteria, such as E. coli and B. subtilis, which use an individual nonaggregating type II fatty acid synthase (FAS-II) system. In this study, we reported genetic evidence demonstrating that the FAS-I system is the source of the biotin precursor in vivo in the engineered biotin-prototrophic C. glutamicum strain. This study also uncovered the important physiological role of FasB in lipoic acid biosynthesis. Here, we present an FAS-I enzyme that functions in supplying the lipoic acid precursor, although its biosynthesis has been believed to exclusively depend on FAS-II in organisms. The findings obtained here provide new insights into the metabolic engineering of this industrially important microorganism to produce these compounds effectively.

Polyamide-Polyamine Cryptand as Dicarboxylate Receptor: Dianion Binding Studies in the Solid State, in Solution, and in the Gas Phase.

Polyamide-polyamine hybrid macrobicycle L is explored with respect to its ability to bind α,ω-dicarboxylate anions. Potentiometric studies of protonated L with the series of dianions from succinate (suc2-) through glutarate (glu2-), α-ketoglutarate (kglu2-), adipate (adi2-), pimelate (pim2-), suberate (sub2-), to azelate (aze2-) have shown adipate preference with association constant value of K = 4900 M-1 in a H2O/DMSO (50:50 v/v) binary solvent mixture. The binding constant increases from glu2- to adi2- and then continuously decreases with the length of the anion chain. Further, potentiometric studies suggest that hydrogen bonding between the guest anions and the amide/ammonium protons of the receptor also contributes to the stability of the associations along with electrostatic interactions. Negative-mode electrospray ionization of aqueous solutions of host-guest complexes shows clear evidence for the selective formation of 1:1 complexes. Single-crystal X-ray structures of complexes of the receptor with glutaric acid, α-ketoglutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid assist to understand the observed binding preferences. The solid-state structures reveal a size/shape complementarity between the host and the dicarboxylate anions, which is nicely reflected in the solution state binding studies.

Effect of carbon chain length of dicarboxylic acids as cross-linking agents on morphology, encapsulation, and release features of protein-loaded chitosan microparticles

Chitosan microparticles were obtained by emulsion cross-linking technique. Impact of the carbon chain length of dicarboxylic acids (malonic, succinic, glutaric, adipic, pimelic, suberic, and azelaic) as cross-linking agents on morphology, encapsulation, and release of bovine serum albumin (BSA) was studied. Role of the polyglycerol polyricinoleate as surfactant to stabilize the pre-emulsions and its influence on the structure of the particles obtained was considered. The increase in the carbon chain length of dicarboxylic acids gives rise of the mass-average diameter of the microparticles. The greatest encapsulation ability of the cross-linked samples is observed for pimelic and suberic acids. The BSA encapsulation for azelaic acid decreases with the increase in the carbon chain length. The ratios of the initial and total cumulative releases of BSA for 24 h increase with the increase of the number of carbon atoms in dicarboxylic acid from 3 to 7. Beginning with the sample of cross-linked suberic acid, the dramatic decrease in the percentage of the initial release of BSA is occurred. The same dependence is observed for the swelling ratio due to the increase in the hydrophobic interactions within chitosan matrix and the growth of the thickness of dicarboxylic acid-polyelectrolyte layers on the surface of the microparticles. The carbon chain length of the above dicarboxylic acids was concluded to be available mode to control the properties of chitosan microparticles as vehicles for drug delivery and drug release.

Dicarboxylic acids analysed by x-ray photoelectron spectroscopy, Part V - heptanedioic acid anhydrous

X-ray photoelectron spectroscopy(XPS) was carried out to analyse a commercially available heptanedioic acidpowder.XPSspectra were obtained using incident monochromatic Al Kα radiation at 1486.6 eV. Snapshots and scans of C 1s and O 1s core level spectra are presented. The presence of characteristiccarbon and oxygen photoelectrons allows the use these results as a reference for dicarboxylic acids.

Synergistic Toughening Effect of Olefin Block Copolymer and Highly Effective β-Nucleating Agent on the Low-Temperature Toughness of Polypropylene Random Copolymer

In the present work, the synergistic toughening effect of olefin block copolymer (OBC) and a highly effective β nucleating agent (NA)-Calcium salt of pimelic acid (CaPim) on polypropylene random copolymer (PPR) was studied. Mechanical tests showed that with the introduction of 0.1 wt % CaPim, there was almost no change in the low-temperature (below 0 °C) toughness of PPR. Although introduction of OBC could obviously improve the toughness at 23 °C, high content is needed to effectively toughen PPR at low temperature. By coadding OBC and CaPim, PPR/OBC/NA blends showed not only great enhancement of toughness over the temperature range tested but also lower OBC content of undergoing brittle-ductile transition compared with PPR/OBC blends. The crystalline structure, crystallization behavior and phase morphology were investigated to explore the possible synergistic toughening mechanism. The high β-crystal content formed in PPR matrix and the finer distribution of OBC phase might be responsible for the superior...