NH Bending Research Articles

Controlled release of nerve growth factors incorporated in polyacrylamide/graphene oxide hydrogel and their effects on Schwann cells

This work is concerned with the study of the conformational structure and crystallinity of sericin from silk cocoon (Bombyx mori) and the role these play in the physical and chemical properties of the final materials. Silk sericin (SS) powders were prepared by degumming processes with different storage temperatures before drying into the final powders; defined as RT-SS (room, 25 °C), C-SS (10 °C) and F-SS (freezing, 0 °C), and then fabricated into films and scaffolds by reacting with poly(vinyl alcohol) (PVA) in the presence of a new cross-linker (dimethylolurea; DMU). RT-SS and C-SS structures favour random coil structuring as witnessed by Amide I (CO stretching), II (NH bending) and III (in phase combination of NH in plane-bending and CN stretching vibrations) being observed at 1661, 1538, and 1232 cm−1, respectively. Whereas, F-SS favours β-sheets structure proved by the amide bands shifting to a lower frequency. The NH stretching (3200–2400 cm−1) of F-SS is also observed at a lower frequency with a broader band than RT-SS and C-SS due to the hydrogen bonding in the β-sheets. The differences in the X-ray peaks between RT- and C-SS (d spacing = 1.9–5.2 Å) and F-SS (d spacing = 3.0 Å and 5.2–8.2 Å) were also measured. Films of PVA/RT-SS/DMU showed better properties than that of PVA/F-SS/DMU films in terms of the interactions (hydrogen bonding) between the components that formed the network. Therefore, RT-SS was chosen for the preparation of 3D porous scaffolds with different concentrations of DMU. All scaffolds showed good support for skin fibroblast cells, as well as promoted cell proliferation. However, a minimal amount of cross-linker, 10% DMU PVA/RT-SS scaffold with average pore diameter between 20 and 30 μm, was the best composition for cell viability and cell adhesion. In this work, therefore, a novel scaffold based on biomaterials was explored for tissue engineering scaffolds with the potential to be a new technology platform for skin tissue regeneration.

Properties of Aminosilane Modified Nanocrytalline Cellulose (NCC) from Oil Palm Empty Fruit Bunch (OPEFB) Fibers

Oil palm empty fruit bunch (OPEFB) is one of the lignocellulosic materials which very well known as an abundant waste at oil mills and need to be utilized. The nanocrystalline cellulose (NCC) was extracted from OPEFB fiber through several of chemical treatment and hydrolyzed with sulphuric acid (H2SO4). NCC acts as support to modify with aminosilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxy silane (AEAPDMS) which has possibility for carbon dioxide (CO2) capture. The objective of this study was to evaluate the effect of NCC properties after modified with AEAPDMS. The raw OPEFB fiber, cellulose, NCC and modified NCC were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), x-ray diffraction (XRD) but the morphology and the size of NCC was studied by transmission electron microscopy (TEM). The NCC treated with AEAPDMS was proved by FTIR with the emerging of several new peaks especially for NH2 bending and wagging around 1600 cm-1 and 798 cm-1, respectively. While, the XRD result showed the CrI of modified NCC decreased to 64 % from 76 % after the treatment due to the interaction of silanization occurred during the treatment since AEAPDMS has amorphous region. The NCC used in this study was classed as nanomaterial within nanosize and rod-like morphology observed by TEM analysis. Thus, these results give a good possibility for the AEAPDMS modified NCC to capture CO2 via covalent bonding.

QTAIM-Based Characteristic Group Infrared Intensities of Amino Acids and Their Transference to Peptides.

Dynamic atomic contributions (DACs) to the infrared intensities of 14 amino acids have been transferred to three peptide molecules, glycylglycine, trialanine, and the melanocyte-inhibiting factor MIF-1, to estimate the infrared intensities of the most strategic peptide bands. The DACs of the amino acids and infrared intensities of the peptides were determined at the DFT B3LYP/6-311+(d,p) level. The Quantum Theory of Atoms In Molecules (QTAIM) Charge-Charge Transfer-Dipolar Polarization (CCTDP) model at this Density Functional Theory (DFT) level was used to classify the O-H, NH2, N-H, and C═O stretching as well as the NH2 bending characteristic groups for use in the transference procedure. Contrary to the frequencies, the intensities within these groups can have very diverse values, although their electronic structure changes upon vibration have predictable QTAIM behaviors for each group. Compared to the DFT calculated values, the two transferred O-H stretching intensities of the peptides are estimated with a root-mean-square (rms) error of 19.1 km mol-1. Six NH2 symmetric and antisymmetric stretching intensities were determined with a 9.9 km mol-1 error. The eight estimated C═O stretching bands have a rms error of 78.0 km mol-1 or 23.6% of the average DFT peptide C═O intensity of 328.4 km mol-1. The proposed procedure is applicable to experimental infrared intensities if a calibration set of molecules with known atomic polar tensors and normal coordinate transformations is available.

Spectra-structure correlation based study of complex molecules of 1-isonicotinoyl-3-thiosemicarbazide with Ni2+, Mn2+ and Fe3+ using Raman, UV–visible and DFT techniques

In present work, we have analysed the structural property of newly synthesized ligand and its coordination complex molecules with Ni2+, Mn2+ and Fe3+. The spectroscopic techniques UV–visible, IR, Raman and DFT methods are used. The newly synthesized ligand 1-isonicotinoyl-3-thiosemicarbazide (Hintsc) has supramolecular architecture stabilized through various intermolecular interactions viz. NH⋯O, CH⋯O, CH⋯N, NH⋯S and CH⋯S type hydrogen bonds as observed in the single crystal of the ligand. The single crystals of the complexes could not be obtained with high degree of homogeneity from the solutions therefore plausible geometry of the complexes have been proposed on the basis of Raman spectroscopy, UV–visible and DFT methods and coordination properties of Ni2+, Mn2+ and Fe3+ with ligand (Hintsc). The ligand Hintsc contains the thiosemicarbazide (TSC) moiety through which Ni2+, Mn2+ and Fe3+ metals are coordinated. Raman spectroscopy is used to investigate the binding of Ni2+, Mn2+ and Fe3+ with ligand (Hintsc). In Raman spectra, the disappearance of NH bending/ NH stretching and lower wavenumber region Raman spectra clearly confirms that Ni2+ and Mn2+ metals are coordinated through N3 and O sites of thiosemicarbazide (TSC) and consequently formed the chelate ring {C6N2N3MO}, where M Ni2+ and Mn2+. In Fe complex, Fe3+ is coordinated through N2 and S sites of TSC and formed the chelate ring {C7N3N2FeS}. The structural and molecular property of 1-isonicotinoyl-3-thiosemicarbazide (Hintsc) and its complexes with transition metals Ni2+, Mn2+, Fe3+ have also been studied by DFT technique. By means of UV–visible, Raman spectroscopy and DFT technique, it is found that Ni2+, Mn2+ and Fe3+ exhibit the octahedral coordination property with 1-isonicotinoyl-3-thiosemicarbazide (Hintsc).

Investigation of silk sericin conformational structure for fabrication into porous scaffolds with poly(vinyl alcohol) for skin tissue reconstruction

This work is concerned with the study of the conformational structure and crystallinity of sericin from silk cocoon (Bombyx mori) and the role these play in the physical and chemical properties of the final materials. Silk sericin (SS) powders were prepared by degumming processes with different storage temperatures before drying into the final powders; defined as RT-SS (room, 25°C), C-SS (10°C) and F-SS (freezing, 0°C), and then fabricated into films and scaffolds by reacting with poly(vinyl alcohol) (PVA) in the presence of a new cross-linker (dimethylolurea; DMU). RT-SS and C-SS structures favour random coil structuring as witnessed by Amide I (CO stretching), II (NH bending) and III (in phase combination of NH in plane-bending and CN stretching vibrations) being observed at 1661, 1538, and 1232cm−1, respectively. Whereas, F-SS favours β-sheets structure proved by the amide bands shifting to a lower frequency. The NH stretching (3200–2400cm−1) of F-SS is also observed at a lower frequency with a broader band than RT-SS and C-SS due to the hydrogen bonding in the β-sheets. The differences in the X-ray peaks between RT- and C-SS (d spacing=1.9–5.2Å) and F-SS (d spacing=3.0Å and 5.2–8.2Å) were also measured. Films of PVA/RT-SS/DMU showed better properties than that of PVA/F-SS/DMU films in terms of the interactions (hydrogen bonding) between the components that formed the network. Therefore, RT-SS was chosen for the preparation of 3D porous scaffolds with different concentrations of DMU. All scaffolds showed good support for skin fibroblast cells, as well as promoted cell proliferation. However, a minimal amount of cross-linker, 10% DMU PVA/RT-SS scaffold with average pore diameter between 20 and 30μm, was the best composition for cell viability and cell adhesion. In this work, therefore, a novel scaffold based on biomaterials was explored for tissue engineering scaffolds with the potential to be a new technology platform for skin tissue regeneration.

The self-associating behavior of NH3 and ND3 in liquid xenon

In this study we report on the analysis of isothermal spectra of NH3 and ND3 solutions in liquid xenon at 203 K using newly developed and validated least-squares approaches to investigate the its self-associating behavior. For both species we observe clear dimer bands in the spectral area of the ν1+ν4, ν3+ν4 and ν1+ν2, ν3+ν2 combination bands. The analysis of the N−D stretching area, allows us to characterize clear contributions of dimers and trimers. The analysis of the NH stretching area is hampered by the occurrence of a time dependent band due to solid water traces during the experiments. For NH3 we also performed an investigation of the NH bending region, ν2, which demonstrated a small dimer absorption band. These obtained results compare well with literature data.

Structural and optical properties of neodymium doped lead chalcogenide (PbSe) nanoparticles

Wet chemical precipitation technique is successfully exploited to synthesize Neodymium undoped and doped lead selenide precipitated particles at pH 5.0. Structural analysis reveals the face centered cubic structure and particle size are found to be in the range of 25–40nm. The electron microscopic analysis clearly depicts the nanophase formation and EDAX confirmed the purity and stoichiometry ratio of the prepared samples. FT-IR analysis confirms the stretching vibration of PbSe and NH bending of hydrazine hydrate are observed at 707cm−1 and 1500cm−1, respectively. The strong blue shift in the UV–vis absorption region (560nm) confirms the nano dimensional state of Pb1−xNdxSe nano particles. The varying dopant concentration influences the particle size, surface morphology and energy gap of the nanostructured lead selenide.

Changes in soil mineralogy due to nitrogen fertilization in an agroecosystem

Additions of nitrogen (N) fertilizer to surface soil can trigger a wide array of complex effects, including changes in soil chemical, physical, and microbial properties which impact both the nitrogen and carbon cycles. While abundant literature exists regarding the influence of N amendments on processes and properties influencing the soil carbon cycle, there is little recognition given to potential changes in soil mineralogy. We collected surface soil (Maury silt loam, Typic Paleudalf) from a long-term agroecosystem under no-tillage management which has received annual inorganic N additions (0, 168, 336kgNha−1) for 34years and characterized the soil mineralogy and other relevant properties. With recent liming, N fertilizer addition was associated with only slight changes in soil pH and the suite of exchangeable cations. Silt mineralogy was not influenced by N, but x-ray diffraction found changes in the clay fraction. The clay mineral assemblage in the control (0kgNha−1) is complex, comprised of layers of pedogenic chlorite, vermiculite, hydroxy-interlayered vermiculite, mixed-layer chlorite–vermiculite, illite, kaolinite, and quartz. Fertilizer N additions resulted in a 3- and 3.3-fold decrease in the 1.4nm/1.0nm peak area ratios for Mg-clay slides in the 168 and 336kgNha−1 treatments. This decrease is likely due in part to fixation of NH4+ in vermiculite layers, corroborated by increases in the intensity of the infrared (IR) band at 1430cm−1 (assigned to the NH bending mode of NH4+) with added N. The role of biota emerged as shown by a negative relationship between water-soluble oxalate concentrations and the 1.4nm/1.0nm peak area ratios (r=0.56, P=0.06). Past acidification due to nitrification of added NH4+ which occurred prior to liming might have played a role in weathering of pH-sensitive minerals such as chlorite. Our findings raise questions about the capacity of reactive 2:1 mineral layers to fix NH4+ and how this is moderated by biota in no-till agroecosystems.

Water-adsorption properties of Xiazijie montmorillonite intercalated with polyamine

AbstractPolyamine is a novel inhibitor applied to water-based drilling fluids in order to reduce hydration of clays, especiallymontmorillonite (MT). In the present study, thewater-adsorption properties of montmorillonite intercalated with polyamine were characterized by X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and adsorption isotherm tests using water, benzene and heptane. According to the XRD, DRIFT and water-adsorption test results, polyamine (PA)- intercalated montmorillonite (PA-MT) adsorbs less water than either K+- or NH+4-intercalated montmorillonite (K-MT, NH4-MT). The surface energy of MT was analysed using the van Oss- Chaudhury-Good (VCG) approach based on thewater, benzene and heptane adsorption results. The surface energy between PA-MTand water was less than that of NH4-MT and K-MT. Compared with K-MT and NH4-MT, the surface energy of the Lewis acid portion of PA-MT underwent a more significant decrease, suggesting that the hydration of unexchanged Na+ did not make a discernible contribution. The experimental water-adsorption data were fitted using Langmuir, Brunauer-Emmett-Teller (BET), and Freundlich adsorption models. The Langmuir adsorption models can be used to fit the data for water adsorption on PA-MTacross the entire p/p0 range. After plotting the experimental data in the linear format of the Freundlichmodel, only one linear region for PA-MTwas observed, indicating a singlewater-adsorption mechanism for PA-MT. When compared with PA in the absence of clay, DRIFT spectroscopy showed that the NH2 bending mode for PA-MT shifted from 1571 cm–1 to 1619.7 cm–1. This suggested an increase in hydrogen bonding (H bonding) between the ammonium group and the interlayer water. Across the entire p/p0 range, water is suggested to have adsorbed onto PA-MT through H-bonding interactions between the ammonium group and the interlayer water.

Two-dimensional infrared spectroscopic study on the thermally induced structural changes of glutaraldehyde-crosslinked collagen

The thermal stability of collagen solution (5mg/mL) crosslinked by glutaraldehyde (GTA) [GTA/collagen (w/w)=0.5] was measured by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR), and the thermally induced structural changes were analyzed using two-dimensional (2D) correlation spectra. The denaturation temperature (Td) and enthalpy change (ΔH) of crosslinked collagen were respectively about 27°C and 88J/g higher than those of native collagen, illuminating the thermal stability increased. With the increase of temperature, the red-shift of absorption bands and the decreased AIII/A1455 value obtained from FTIR spectra indicated that hydrogen bonds were weakened and the unwinding of triple helix occurred for both native and crosslinked collagens; whereas the less changes in red-shifting and AIII/A1455 values for crosslinked collagen also confirmed the increase in thermal stability. Additionally, the 2D correlation analysis provided information about the thermally induced structural changes. In the 2D synchronous spectra, the intensities of auto-peaks at 1655 and 1555cm−1, respectively assigned to amide I band (CO stretching vibration) and amide II band (combination of NH bending and CN stretching vibrations) in helical conformation were weaker for crosslinked collagen than those for native collagen, indicating that the helical structure of crosslinked collagen was less sensitive to temperature. Moreover, the sequence of the band intensity variations showed that the band at 1555cm−1 moved backwards owing to the addition of GTA, demonstrating that the response of helical structure of crosslinked collagen to the increased temperature lagged. It was speculated that the stabilization of collagen by GTA was due to the reinforcement of triple helical structure.

Influence of surface functionalization on the hydrophilic character of mesoporous silica nanoparticles.

We report the synthesis and surface functionalization of MCM-41-like mesoporous silica nanoparticles (MSNs) with spheroidal shape and particle size of 141 ± 41 nm. The success of surface functionalization with aminopropyl and sodium ethylcarboxylate groups (giving amino-MSN and carboxy-MSN, respectively) was ascertained by infrared spectroscopy and ζ potential measurements. The former showed the decrease of surface silanol groups and the corresponding appearance of signals related to NH2 bending mode (δNH2) at 1595 cm(-1) and COO(-) stretching (νas and νsym) at 1562 and 1418 cm(-1). The latter showed a change in surface charge, in that the isoelectric point (IEP) changed from pH 3-4.5 to 8.5 when the MSN was functionalized with the amino groups, while carboxy-MSN showed a more negative charge in the whole pH range with respect to MSN. The hydrophilic character of the prepared materials was ascertained by quantitative microgravimetric measurements, allowing the calculation of the average isosteric adsorption heat (q[combining macron]st). This was found to be 51 ± 3 kJ mol(-1), 61 ± 4, and 65 ± 3 kJ mol(-1) for MSN, amino-MSN, and carboxy-MSN samples, respectively. The increase in q[combining macron]st after functionalization can be ascribed to the specific interaction of water molecules with the functionalizing agents, in agreement with a higher basicity with respect to silanol groups. Moreover, the possibility of multiple H-bonding interactions of water molecules with the carboxylate anion is put forward to account for the higher water uptake with respect to parent MSN.

Adsorption of Atenolol on Kaolinite

In this study the adsorption of atenolol (AT), aβ-blocker, on kaolinite, a clay mineral of low surface charge, was investigated under varying initial AT concentration, equilibrium time, solution pH, ionic strength, and temperature conditions. The results showed that the amounts of AT uptake by kaolinite were close to its cation exchange capacity value and the AT adsorption was almost instantaneous, suggesting a surface adsorption. The adsorption was exothermic and the free energy of adsorption was small negative, indicating physical adsorption. The increase in ionic strength of the solution drastically reduced AT uptake on kaolinite. A significant reduction in AT uptake was found at solution pH below 5 or above 10. The FTIR results showed band shifting and disappearance for NH bending vibration and benzene ring skeletal vibration at 3360 and 1515 cm−1and band splitting at 1412 and 1240 cm−1attributed to C–N valence vibration coupled with NH bending vibrations and alkyl aryl ether linkage, suggesting the participation of NH, –O–, and benzene ring for AT adsorption on kaolinite.

Modification of Montmorillonite with Diamine Surfactants

Sodium montmorillonite (Na-MMT) was modified with various type of diamine surfactants. The modification imparts hydrophobic characters of MMT, thus enhancing its compatibility and dispersibility in polymer matrix. In this research, pristine MMT was modified with three types of diamine surfactants, namely, 1,3 diaminopropane (DAP), 1,8 diamino octane (DAO) and 1,5 diamino-2-Methyl pentane (DAMP). These diamines have different molecular structures where DAP has a short linear structure, DAO has eight carbons while DAMP has a methyl branch on its backbone. The modification was carried via cationic exchange process. X-ray diffraction (XRD) analysis showed the enhancement of d-spacing of MMT galleries and the formation of intercalated structure with the incorporation of diamines. Overall, type of diamines did not give significant effect on the d-spacing values with DAMP-MMT exhibited a slightly higher d-spacing at 13. 36 Å. The presence of methyl branch on the DAMP backbone was thought provide more spacing for the diamine to intercalate through the MMT gallery. Meanwhile, the detection of –NH bending amine group at 1470 cm-1 on the Fourier infrared (FTIR) spectra, corresponding to the free surfactant tail, had confirmed the successfulness of cationic exchange reaction between the diamines and MMT surface.

Olive leaf extract as a crosslinking agent for the preparation of electrospun zein fibers

ABSTRACTIncorporating active agents, reinforcing structure by crosslinking, thus changing release properties, can be listed as possible modifications in preparation methods of biopolymer fibers. This study introduces oleuropein, major component of olive leaf extract (OLE), as a natural functional crosslinker for electrospun zein fibers, owing to its antioxidant and antimicrobial properties. Incorporation of OLE causes morphological and structural changes indicated by a decrease in fiber diameter up to 27%, an increase in intensity of NH bending region due to interaction with –OH groups and observation of characteristic oleuropein bands. Extract addition also enhances thermal stability. Zein fibers without OLE is fully degraded at 600°C, whereas 10% of OLE loaded zein fibers is left undegraded. Fifty percent of initial phenolic content loaded into fibers is released which indicate the effect of OLE incorporation as accumulation of oleuropein. OLE‐incorporated fibers immersed in PBS are less fused than pure zein fibers, due to the crosslinking effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41338.

Remediation of Eriochrome Black T-contaminated aqueous solutions utilizing H3PO4-modified berry leaves as a non-conventional adsorbent

The present investigation addresses the feasibility study of H3PO4-modified berry leaves (HMBL) towards the abatement of Eriochrome Black T (EBT) from aqueous solutions. The adsorbent is characterized by functional groups like hydroxyl, primary amine NH bending, aromatic phosphate (P–O–C stretch) and CH bending of alkyne group; BET surface area of 824.98 m2 g−1 and homogenous surface morphology. Retention of EBT in batch system was executed to optimize the influencing variables for better adsorptive performance. The dye uptake reached equilibrium at 1 h with an optimum adsorbent load of 2 g L−1 under optimum temperature of 303 K. Equilibrium adsorption isotherm data were in good agreement (R2 = 0.996) to Langmuir isotherm with monolayer adsorption capacity of 133.33 mg g−1 at 303 K. The adsorption process followed pseudo-second-order kinetics with higher R2 (0.9999) and lesser Δq% (0.439). Thermodynamic investigation revealed the adsorption process to be exothermic (ΔH = −37.149 kJmol−1) and spontaneous in nature (ΔG = −5.937 kJmol−1 at 303 K) with a decrease in the randomness (ΔS = −103.01 J K−1 mol−1) at the solid/liquid interface. The exhausted HMBL can be regenerated by 0.1 M NaOH and utilized for three adsorption–desorption cycles. The estimated cost of HMBL (USD 10.684/kg) is less as compared to commercial activated carbon (CAC) (USD 172.96/kg). The results implied the promising candidature of HMBL as a non-conventional low-cost alternative to CAC for dye removal.

Vibrational and quantum chemical investigation of cyclization of thiosemicarbazide group in 1-benzoyl-4-phenyl-3-thiosemicarbazide

1-Benzoyl-4-phenyl-3-thiosemicarbazide (H3bpt) was treated with acid - base in one sequence and base – acid in other sequence, both of which lead to ring formation of thiosemicarbazide group, giving N-phenyl-5-phenyl-1,3,4-thiadiazol-2-amine (Hppta) in the first case and 4,5-diphenyl-2,4-dihydro-1,2,4-triazole-3-thione (Hdptt) in the second case. The primary (H3bpt) as well as the resulting compounds (Hppta & Hdptt) has been characterized by elemental analyses, NMR, FTIR and Raman spectroscopic techniques. The quantum chemical calculations of the compounds are performed using DFT/B3LYP/6311G(d,p) method for geometry optimizations and also for prediction of the molecular properties. The cyclization is confirmed by disappearance of many bands belonging to the open chain subgroups of H3bpt such as; NH stretching, NH bending, CN stretching, NH puckering, CO stretching etc. The ring formation of 1-benzoyl-4-phenyl-3-thiosemicarbazide (H3bpt) has been further confirmed by the appearance of many bands belonging to the closed ring of thiosemicarbazide in the resulting compounds Hppta and Hdptt.

Naturally Occurring Alkaline Amino Acids Function as Efficient Catalysts on Knoevenagel Condensation at Physiological pH: A Mechanistic Elucidation

To maintain biological functions, thousands of different reactions take place in human body at physiological pH (7.0) and mild conditions, which is associated with health and disease. Therefore, to examine the catalytic function of the intrinsically occurring molecules, such as amino acids at neutral pH, is of fundamental interests. Natural basic α-amino acid of L-lysine, L-arginine, and L-histidine neutralized to physiological pH as salts were investigated for their ability to catalyze Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. Compared with their free base forms, although neutralized alkaline amino acid salts reduced the catalytic activity markedly, they were still capable to perform an efficient catalysis at physiological pH as porcine pancreatic lipase (PPL), one of the best enzymes that catalyze Knoevenagel condensation. In agreement with the fact that the three basic amino acids were well neutralized, stronger basic amino acid Arg and Lys showed more obvious variation in NH bend peak from the FTIR spectroscopy study. Study of ethanol/water system and quantitative kinetic analysis suggested that the microenvironment in the vicinity of amino acid salts and protonability/deprotonability of the amine moiety may determine their catalytic activity and mechanism. The kinetic study of best approximation suggested that the random binding might be the most probable catalytic mechanism for the neutralized alkaline amino acid salt-catalyzed Knoevenagel condensation.

Synthesis and Characterization of Solid Polymer Electrolyte from <i>N</i>-Succinyl Chitosan and Lithium Perchlorate

Batteries are being developed to solve the global energy crisis. Using portable electronic devices, especially mobile phones and notebook computers, has been increasing, and leading to a strong need of their power-sources. However, secondary batteries using a liquid electrolyte have weaknesses, such as prone to leakage and difficulty of packing. Solid polymer electrolyte is a solution to the existing problems. The objective of this research is to prepare an environmental-friendly and cheap material as the solid polymer electrolyte. In the present study, the effect of succinyl group on to polymer electrolyte membrane which synthesized from chitosan and lithium perchlorate salts was investigated. The N-succinyl chitosan was obtained by reacting chitosan with succinic anhydride. Solid polymer electrolyte membranes were derived from N-succinyl chitosan with different ratios of lithium perchlorate. The degree of deacetylation of chitosan was determined by FTIR analysis. Synthesis of N-succinyl chitosan has been successfully carried out, which is indicated by the characteristic peaks at wavenumbers of 1640 cm-1 and 1560 cm-1 correspond to -C=O stretching and -NH bending of succinyl groups on FTIR spectrum of N-succinyl chitosan. Modification of chitosan by the addition of succinyl group increases the membrane ionic conductivity values. A N-succinyl chitosan membrane contained 10% (w/w) lithium perchlorate showed conductivity of 8.01×10-3 S.cm-1. This solid polymer electrolyte membrane was suggested to have one potential used for polymer electrolyte in lithium battery applications.

Physical interaction induced self-assembly of glycopeptide and doxorubicin at physiological pH as promising hepatoma-targeted nanomedicine

coating of bilayers, bands at 2920 and 2850 cm−1 exhibit the CH stretching vibrations of alkyl groups (PAH and PSS) (Fig. 1C) b), and a stronger band at 1650 cm−1 results from the overlapping of SiOH vibrations and NH bending vibrations in PAH. Also, another NH bending vibration at 1525 cm−1 is observed in the spectrum of PAH/PSS-MSNs (Fig. 1C) b). The band at 1185 cm−1 can be attributed to the stretching of SO groups of PSS. Fig. 1D) shows that the release of DOX decreased with increasing pH value from 1.2 to 8.0. At pH 1.2, around 70% drug release was obtained in 50 h, whereas the drug release is less than 40% within 110 h in the release medium with pH 8.0. In conclusion, a pHresponsive DDS was successfully developed which allows controlled drug release of DOX from MSNs in the designed pH 1.2–8.0 solution.

Role of Ring-Constrained γ-Amino Acid Residues in α/γ-Peptide Folding: Single-Conformation UV and IR Spectroscopy

The capped α/γ-peptide foldamers Ac-γACHC-Ala-NH-benzyl (γα) and Ac-Ala-γACHC-NH-benzyl (αγ) were studied in the gas phase under jet-cooled conditions using single-conformation spectroscopy. These molecules serve as models for local segments of larger heterogeneous 1:1 α/γ-peptides that have recently been synthesized and shown to form a 12-helix composed of repeating C12 H-bonded rings both in crystalline form and in solution [Guo, L.; et al. J. Am. Chem. Soc. 2009, 131, 16018]. The γα and αγ peptide subunits are structurally constrained at the Cβ-Cγ bond of the γ-residue with a cis-cyclohexyl ring and by an ethyl group at the Cα position. These triamides are the minimum length necessary for the formation of the C12 H-bond. Resonant two-photon ionization (R2PI) provides ultraviolet spectra that have contributions from all conformational isomers, while IR-UV hole-burning (IR-UV HB) and resonant ion-dip infrared (RIDIR) spectroscopies are used to record single-conformation UV and IR spectra, respectively. Four and six conformers are identified in the R2PI spectra of the γα and αγ peptides, respectively. RIDIR spectra in the NH stretch, amide I (C═O stretch), and amide II (NH bend) regions are compared with the predictions of density functional theory (DFT) calculations at the M05-2X/6-31+G* level, leading to definite assignments for the H-bonding architectures of the conformers. While the C12 H-bond is present in both γα and αγ, C9 rings are more prevalent, with seven of ten conformers incorporating a C9 H-bond involving in the γ-residue. Nevertheless, comparison of the assigned structures of gas-phase γα and αγ with the crystal structures for γα and larger α/γ-peptides reveals that the constrained γ-peptide backbone formed by the C9 ring is structurally similar to that formed by the larger C12 ring present in the 12-helix. These results confirm that the ACHC/ethyl constrained γ-residue is structurally preorganized to play a significant role in promoting C12 H-bond formation in larger α/γ-peptides.