Phase behaviour of oleanolic acid,pure and mixed with stearic acid: Interactions and crystallinity

The phase behaviour of pure oleanolic acid (OLA) and in mixtures with stearic acid (SA) was characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and nuclear magnetic resonance (NMR). The crystalline OLA as received (OLA_ar) becomes amorphous after being dissolved in chloroform and vacuum-dried at 50 °C (OLA₅₀). Upon heating, both forms transform to the needle shape crystalline form (OLA₂₂₀). Dimerization through H-bonding between COOH groups was detected both in OLA_ar and OLA₂₂₀. Dimers are stronger in OLA₂₂₀, where H-bonding also involves the alcohol groups and plays a role in the crystalline organization. A eutectic type phase diagram was established for mixtures, with the eutectic composition close to pure SA. Mixtures rich in SA are miscible in the liquid and in the amorphous solid states, where the presence of SA–OLA co-dimers, formed through H-bonding between carboxyl groups, was detected. Miscibility and SA crystallinity decrease drastically with the OLA content.     

Phase behaviour of stearic acid-stearonitrile mixtures: A thermodynamic study in bulk and at the air-water interface

The solid-liquid phase behaviour of stearic acid (SA) and stearonitrile (SN) in binary mixtures was investigated by differential scanning calorimetry (DSC), and the formation of SA-SN mixed monolayers at the air-water interface was followed by surface pressure-area (π-A) measurements and by Brewster angle microscope (BAM) observation. The solid-liquid phase diagram is a eutectic type phase diagram, with the eutectic composition 0.90 < X_SN < 0.95 and T^eut = 40.9 °C. The DSC results also suggest that the two components are immiscible in the solid phase but form a liquid mixture with positive deviations to the ideal behaviour. At the air-water interface, the two components form liquid condensed monolayers in the entire range of compositions, at low surface pressures, while solid mixed monolayers only form at high surface pressures for X_SN < 0.8. Thermodynamic analysis indicates that SA and SN are miscible in the liquid condensed phase, with negative deviations from the ideal behaviour. The variation of the collapse surface pressure of mixed monolayers also indicates miscibility at the air-water interface.     

The binary phase behavior of 1, 3-dipalmitoyl-2-stearoyl-sn-glycerol and 1, 2-dipalmitoyl-3-stearoyl-sn-glycerol

The binary phase behavior of purified 1, 3-dipalmitoyl-2-stearoyl-sn-glycerol (PSP) and 1, 2-dipalmitoyl-3-stearoyl-sn-glycerol (PPS) was investigated at a very slow (0.1 °C/min) and a relatively fast (3.0 °C/min) cooling rate. Mixtures with molar fractions of 0.1 increments were studied in terms of melting and crystallization, polymorphism, solid fat content (SFC), hardness and microstructure. Only the α-form of a double chain length (DCL) structure was detected for all mixtures in both experiments. The kinetic phase diagram, constructed using heating DSC thermograms, displayed two distinct behaviors separated by a singularity at the 0.5_PSP composition: a eutectic in the X_PSP ≤ 0.5 and a monotectic in the X_PSP ≤ 0.5 concentration region. The singularity was attributed to the formation of a 1:1 (mol:mol) molecular compound. Apart from the segment from 0.0_PSP to the eutectic point, X_E, the simulation of the liquidus line using a model based on the Hildebrand equation suggested that the molecular interactions are strong and tend to favor the formation of unlike pairs in the liquid state and that the miscibility is not significantly dependent on cooling rate. The kinetic effects are manifest in all measured properties, particularly dramatically in the X_PSP ≤ X_E concentration region. An analysis of induction time as measured by pulse nuclear magnetic resonance (pNMR) showed that PPS retards crystal growth, an effect which can explain the peculiarity of this concentration region. At both cooling rates, fit of the SFC (%) versus time curves to a modified form of the Avrami model revealed two common growth modes for all the mixtures. The polarized light microscope (PLM) of the PSP-PPS mixtures revealed networks made of spherulitic crystallites of size, growth direction and boundaries that are varied and sensitive to composition and cooling rate. The change in the microstructure and final SFC (%), particularly noticeable at compositions close to the eutectic, explain in part the differences seen in relative hardness.     

Sheep major histocompatibility complex OLA: Gene frequencies in two french breeds with scrapie

Gene frequencies of 13 sheep lymphocyte factors (11 factors controlled by the sheep OLA complex including three closely linked loci, and two factors by two minor loci) were compared in 189 sheep of two breeds: a. infected with scrapie, b. healthy in a contaminated environment, and c., normal. In a and c, OLA gene frequencies were similar. In healthy sheep in a contaminated environment (b), some OLA gene frequencies were higher in one breed and lower in the other. In each breed, three antigens had their frequencies significantly modified; two of them were the same in the two breeds, but they showed an inverse variation. Thus, the relative risk of clinical scrapie decreased in one breed and increased in the other for the same OLA gene. These data indicate first, that OLA antigens are not directly involved in causing scrapie, and second, that the OLA complex is linked to at least one scrapie resistance/susceptibility locus. In practice, it should be possible to select more resistent sheep, using some OLA antigens but an investigation of the OLA genes and the resistance to scrapie in a given breed is necessary before the selection.     

Rapid phase change of lipid microdomains in giant vesicles induced by conversion of sphingomyelin to ceramide

To understand the role of sphingomyelinase (SMase) in the function of biological membranes, we have investigated the effect of conversion of sphingomyelin (SM) to ceramide (Cer) on the assembly of domains in giant unilamellar vesicles (GUVs). The GUVs were prepared from mixture of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), N-palmitoly-d-erythro-sphingosine (C₁₆Cer), N-palmitoyl-d-erythro-sphingosylphosphorylcholine (C₁₆SM) and cholesterol. The amounts of DOPC, sum of C₁₆Cer and C₁₆SM, and cholesterol were kept constant (the ratio of these four lipids is shown as 1:X:1-X:1 (molar ratio), i.e., X is C₁₆Cer/(C₁₆Cer + C₁₆SM)). Shape and distribution of domains formed in the GUVs were monitored by a fluorescent lipid, Texas Red 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (0.1 mol%). In GUVs containing low C₁₆Cer (X = 0 and 0.25), round-shaped domains labeled by the fluorescent lipid were present, suggesting coexistence of liquid-ordered and disordered domains. In GUVs containing intermediate Cer concentration (X = 0.5), the fluorescent domain covered most of GUV surface, which was surrounded by gel-like domains. Differential scanning calorimetry of multilamellar vesicles prepared in the presence of higher Cer concentration (X ≥ 0.5) suggested existence of a Cer-enriched gel phase. Video microscopy showed that the enzymatic conversion of SM to Cer caused rapid change in the domain structure: several minutes after the SMase addition, the fluorescent region spread over the GUV surface, within which regions with darker contrast existed. Image-based measurement of generalized polarization (GP) of 6-dodecanoyl-2-dimethylaminonaphthalene (Laurdan), which is related to the acyl chain ordering of the lipids, was performed. Before the SMase treatment domains with high (0.65) and low (below 0.4) GP values coexisted, presumably reflecting the liquid-ordered and disordered domains; after the SMase treatment regions with intermediate GP values (0.5) and smaller regions with higher GP values (0.65) were present. Generation of Cer thus caused a phase transition from liquid-ordered and disordered phases to a gel and liquid phase.     

Dodonaea viscosa var. angustifolia leaf: New source of polysaccharide and its anti-oxidant activity

Ultrasonic technology was applied for polysaccharide extraction from the leaves of Dodonaea viscosa and response surface methodology (RSM) was used to optimize the effects of processing parameters on polysaccharide extraction yield. Three independent variables were extraction time (X₁), extraction temperature (X₂) and ultrasonic power (X₃), respectively. The statistical analysis indicated the independent variables (X₁, X₂, X₃), the quadratic terms (X₁₁ and X₃₃) and the interaction terms (X₁X₂, X₁X₃, X₂X₃) had significant effects on the yield of polysaccharides (P < 0.05). The optimal extraction conditions of D. viscosa leaf were determined as follows: extraction time 50.54 min, extraction temperature 85 °C and ultrasonic power 400 W. Under these conditions, the experimental yield of polysaccharides was 9.455 ± 0.24%, which was agreed closely with the predicted value (9.398%). The evaluation of anti-oxidant activity suggested that the polysaccharide exhibited significant protection against DPPH and hydroxyl radicals and could be explored as a nutraceutical agent.     

Preparation and characterization of molecular weight fractions of glycosaminoglycan from sea cucumber Thelenata ananas using free radical depolymerization

A glycosaminoglycan from sea cucumber Thelenata anana (THG) was isolated as a polymer of molecular weight of around 70 kDa. Its low molecular weight derivatives were first prepared by free radical depolymerization with hydrogen peroxide in the presence of copper(II) ion. The parameters of the process were investigated by a high-performance gel permeation chromatography. Analyses of chemical composition and molecular weight distribution indicated that the fragmentation of the main-chain of THG occurred randomly, obeyed pseudo first-order kinetics, and produced species with rather narrow and unimodal distribution of molar mass. The characterization of different molecular weight fractions was investigated by using viscometry and atomic force microscopy (AFM). Analysis of molecular weight and intrinsic viscosity in terms of the known theories for unperturbed wormlike cylinder yielded 1201 ± 110 nm⁻¹, 15.3 ± 1.5 nm, and 1.5 ± 0.3 nm for molar mass per unit contour length M_L, persistence length q, and diameter d, respectively. The M_L and d values were approximately consistent with those observed by AFM. The present data suggest that THG may dissolve in 0.1 M aqueous NaCl as single-stranded helical chains.     

High catalytic activities in the norbornene polymerization with neutral palladium complexes containing N4-type tetradentate chelating ligands

Norbornene polymerization catalyzed by new Pd(II) complexes bearing N4-type tetradentate ligands obtained from the reaction between a 6-methyl-2-picolinic acid or picolinic acid and appropriate diamines has been studied. A class of new palladium complexes, [Pd(X¹X²bpb)] and [Pd(X¹X²-6-Me₂bpb)] (X¹ = Me, X² = Me (1 and 4); X¹ = H, X² = H (2 and 5); X¹ = H, X² = NO₂ (3 and 6); bpb = N,N′-(o-phenylene)bis(pyridine-2-carboxamidate); 6-Me₂bpb = N,N′-(o-phenylene)bis(6-methylpyridine-2-carbox-amidate)) were synthesized and characterized. The molecular structure of Pd complex 5 was determined by X-ray crystallography, showing distorted square planar configurations. Using modified methylaluminoxanes (MMAO) as an activator, the palladium complexes exhibited high catalytic activities for the polymerization of norbornene. The catalytic activities up to 4.0 × 10⁶ g of PNBEs/mol_Pd·h and M_w up to 8.34 × 10⁵ g/mol with PDI < 2.53 were observed. Amorphous polynorbornenes (PNBEs) were obtained with good solubility in halogenated aromatic solvents. Interestingly, the structural modification with the methyl groups of pyridyl rings and the strong electron-withdrawing substituents induced improvement in solubility, thermal stability and catalytic activity. FT-IR, ¹H, and ¹³C NMR analyses of the polymers suggest that the catalytic polymerization occurs via vinyl addition mechanism.     

Synthesis and crystal structure of bis{di-μ-hydroxobis[fac-tribromoaquotin(IV)]} heptahydrate

A product isolated from a reaction mixture of Br₂ and Ph₃ Sn(CH₂)₁₃CH₃ (3:1 mole ratio) in CHCl₃ solution in air was bis{di-μ-hydroxobis[fac-tribromoaquotin(IV)]} heptahydrate, 2[Br₃ (H₂O)Sn(μ-OH)₂ Sn(O₂H)Br₃] · 7H₂O, 2[fac-(1: X = Br)] · 7H₂O. Previous reports had indicated that the tin complexes, [fac-(1: X = Cl or Br)], had been obtained in various solvated forms from hydrolysis or oxidation/hydrolysis of appropriate tin(IV) or tin(II) halides. The crystal structure determination, reported here, provides an improved refinement of the core, i.e., [fac-(1: X = Br)], of 2[fac-(1: X = Br)] · 7H₂O compared to previous attempts. The solid state structure consists of a central rhomboidal planar Sn₂O₂ ring. The tin centres have distorted octahedral geometries, with each Br ligand trans to an O atom. The Br ligands, trans to the aqua ligands, form longer bonds to tin at 2.5556(7) and 2.5544(6) Å, than those trans to the bridging OH ligands, between 2.5021(7) and 2.5127(7) Å. The Br, OH and H₂O ligands as well as the solvate water molecules are all involved in an extensive hydrogen bonding system in 2[fac-(1: X = Br)] · 7H₂O.     

Subpicosecond midinfrared spectroscopy of the Pfr reaction of phytochrome Agp1 from Agrobacterium tumefaciens

Phytochromes are light-sensing pigments found in plants and bacteria. For the first time, the P_fr photoreaction of a phytochrome has been subject to ultrafast infrared vibrational spectroscopy. Three time constants of 0.3 ps, 1.3 ps, and 4.0 ps were derived from the kinetics of structurally specific marker bands of the biliverdin chromophore of Agp1-BV from Agrobacterium tumefaciens after excitation at 765 nm. VIS-pump-VIS-probe experiments yield time constants of 0.44 ps and 3.3 ps for the underlying electronic-state dynamics. A reaction scheme is proposed including two kinetic steps on the S₁ excited-state surface and the cooling of a vibrationally hot P_fr ground state. It is concluded that the upper limit of the E-Z isomerization of the C₁₅ = C₁₆ methine bridge is given by the intermediate time constant of 1.3 ps. The reaction scheme is reminiscent of that of the corresponding P_r reaction of Agp1-BV as published earlier.     

Optical properties of Ag(tripod)X with tripod = 1,1,1-tris(diphenyl-phosphinomethyl)ethane and X = Cl and I: Intraligand and ligand-to-ligand charge transfer

The complexes Ag^I(tripod)X with tripod = 1,1,1-tris(diphenylphosphinomethyl)ethane and X⁻ = Cl⁻ and I⁻ are luminescent in solution at r.t. It is suggested that the emission is a phosphorescence which originates from a tripod intraligand state for X = Cl (λ_max = 464 nm) and a X⁻ → tripod ligand-to-ligand charge transfer state for X = I (λ_max = 482 nm).     

Synthesis of rhodium and iridium boryl complexes via oxidative addition of haloboranes

B-Chlorocatecholborane undergoes oxidative addition to M(PR₃)₃Cl (M = Rh, R = Me; M = Ir, R = Me, Et) yielding six-coordinate complexes of general formula mer,cis-(PR₃)₃Cl₂M(BO₂C₆H₄). The same M(PR₃)₃Cl complexes also react with B-bromocatecholborane to give a mixture of metal boryl homo- and heterodihalides (PR₃)₃X¹X²M(BO₂C₆H₄) (X¹, X² = Cl, Br), and the observed disproportionation is believed to involve the formation of a heteronuclear halide-bridged intermediate. The alkene 4-vinylanisole failed to react with the six-coordinate, 18-electron (PR₃)₃Cl₂M(BO₂C₆H₄) complexes at ambient temperatures.     

Evaluation of bioenergy recovery processes treating organic residues from ethanol fermentation process

This study evaluates a two-stage bioprocess for recovering bioenergy in the forms of hydrogen and methane while treating organic residues of ethanol fermentation from tapioca starch. A maximum hydrogen production rate of 0.77 mmol H₂/g VSS/h can be achieved at volumetric loading rate (VLR) of 56 kg COD/m³/day. Batch results indicate that controlling conditions at S₀/X₀ = 12 with X₀ = 4000 mg VSS/L and pH 5.5-6 are important for efficient hydrogen production from fermentation residues. Hydrogen-producing bacteria enriched in the hydrogen bioreactor are likely utilizing lactate and acetate for biohydrogen production from ethanol-fermentation residues. Organic residues remained in the effluent of hydrogen bioreactor can be effectively converted to methane with a rate of 0.37 mmol CH₄/g VSS/h at VLR of 8 kg COD/m³/day. Approximately 90% of COD in ethanol-fermentation residues can be removed and among that 2% and 85.1% of COD can be recovered in the forms of hydrogen and methane, respectively.     

Differential expression of BK channel isoforms and β-subunits in rat neuro-vascular tissues

We investigated the expression of splice variants and β-subunits of the BK channel (big conductance Ca²⁺-activated K⁺ channel, Slo1, MaxiK, K_Ca1.1) in rat cerebral blood vessels, meninges, trigeminal ganglion among other tissues. An α-subunit splice variant X1_+ 24 was found expressed (RT-PCR) in nervous tissue only where also the SS4_+ 81 variant was dominating with little expression of the short form SS4₀. SS4_+ 81 was present in some cerebral vessels too. The SS2_+ 174 variant (STREX) was found in both blood vessels and in nervous tissue. In situ hybridization data supported the finding of SS4_+ 81 and SS2_+ 174 in vascular smooth muscle and trigeminal ganglion. β-subunits β2 and β4 showed high expression in brain and trigeminal ganglion and some in cerebral vessels while β1 showed highest expression in blood vessels. β3 was found only in testis and possibly brain. A novel splice variant X2_+ 92 was found, which generates a stop codon in the intracellular C-terminal part of the protein. This variant appears non-functional as a homomer but may modulate the function of other splice-variants when expressed in Xenopus oocytes. In conclusion a great number of splice variant and β-subunit combinations likely exist, being differentially expressed among nervous and vascular tissues.     

pH-control modes in a 5-L stirred-tank bioreactor for cell biomass and exopolysaccharide production by Tremella fuciformis spore

The effect of pH-control modes on cell growth and exopolysaccharide production by Tremella fuciformis was evaluated in a 5-L bioreactor. The results show that the maximal dry cell weight (DCW) and exopolysaccharide production were 23.57 and 4.48 g L⁻¹ in pH-stat fermentation, where the maximal specific growth rate (μ_max) and specific production rate of exopolysaccharide (P_P/X) were 1.03 and 0.24 d⁻¹, respectively; under pH-shift cultivation, the maximal DCW and exopolysaccharide production were 30.57 and 3.90 g L⁻¹, where the μ_max and P_P/X were 1.21 and 0.06 d⁻¹. Unlike batch fermentation, maximal DCW and exopolysaccharide production merely reached 15.04 and 2.0 g L⁻¹, where the μ_max and P_P/X were 0.86 and 0.05 d⁻¹, respectively. These results suggest that a pH-stat strategy is a more efficient way of performing the fermentation process to increase exopolysaccharide production. Furthermore, this research has also proved that the three-stage pH-control mode is effective for cell growth.     

Duration tenacity: A method for assessing acclimatory capacity of the Antarctic limpet, Nacella concinna

The limpet, Nacella concinna, collected from the Antarctic Peninsula (67°S), was incubated at − 0.3 °C and 2.9 °C for 9 months to test if the previously reported absence of acclimation capacity in Antarctic marine ectotherms could be due to the extended time it takes for them to adjust their physiology to a new stable state. Acclimation was tested through acute measurements of upper lethal limit and a modified measure of tenacity, that tested muscle capacity by measuring the length of time that N. concinna were able to remain attached to the substratum at different temperatures. Both measures acclimated in response to incubation to the higher temperature. Lethal limits were elevated in N. concinna incubated at 2.9 °C (8.1 ± 0.3 °C) compared to those incubated at − 0.3 °C (6.9 ± 0.4 °C). 2.9 °C incubated N. concinna also had a maximum tenacity at 2.1 °C, a higher temperature than the maximum tenacity of those incubated at − 0.3 °C, which occurred at − 1.0 °C. This study is the first to show that the Antarctic limpet can acclimate its physiology, but that it requires a greater period of time for acclimation to occur than previous studies have allowed for.     

How does acyl chain length affect thermotropic phase behavior of saturated diacylphosphatidylcholine–cholesterol binary bilayers?

Thermotropic phase behavior of diacylphosphatidylcholine (CnPC)–cholesterol binary bilayers (n = 14–16) was examined by fluorescence spectroscopy using 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and differential scanning calorimetry. The former technique can detect structural changes of the bilayer in response to the changes in polarity around Prodan molecules partitioned in a relatively hydrophilic region of the bilayer, while the latter is sensitive to the conformational changes of the acyl chains. On the basis of the data from both techniques, we propose possible temperature T–cholesterol composition X_ch phase diagrams for these binary bilayers. A notable feature of our phase diagrams, including our previous results for diheptadecanoylphosphatidylcholine (C17PC) and distearoylphosphatidylcholine (C18PC), is that there is a peritectic-like point around X_ch = 0.15, which can be interpreted as indicating the formation of a 1:6-complex of cholesterol and CnPCs within the binary bilayer irrespective of the acyl chain length. We could give a reasonable explanation for such complex formation using the modified superlattice view. Our results also showed that the X_ch value of the abolition of the main transition is almost constant for n = 14–17 (ca. 0.33), while it increases to ca. 0.50 for n = 18. By contrast, a biphasic n-dependence of X_ch was observed for the abolition of the pretransition, suggesting that there are at least two antagonistic n-dependent factors. We speculate that this could be explained by the enhancement of the van der Waals interaction with increases in n and the weakening of the repulsion between the neighboring headgroups with decreases in n.     

Biocompatible elastomer of waterborne polyurethane based on castor oil and polyethylene glycol with cellulose nanocrystals

Biocompatible waterborne polyurethane (WPU) based on castor oil (CO)/polyethylene glycol (PEG) filled with low level loadings of Eucalyptus globulus cellulose nanocrystals (ECNs) was prepared. The ECNs obtained by sulfuric hydrolysis, consisted of ‘rod-like’ crystals with an average length and diameter of 518.0 ± 183.4 nm and 21.7 ± 13.0 nm, respectively. The nanocomposites with low level loadings of ECNs showed significant enhancement in tensile strength and Young's modulus from 5.43 to 12.22 MPa and from 1.16 to 4.83 MPa, respectively. SEM results showed well dispersion of ECNs in the WPU matrix. Furthermore, it was verified that the nanosized ECNs favored the hard-segments (HSs)/soft-segments (SSs) microphase separation of the WPU, causing shifts of the SS glass transition temperature (T_g,s) and the HS melting temperature (T_m,h) toward higher temperatures.     

Synthesis, X-ray crystal structure, DFT- and TDDFT-based spectroscopic property investigations on a mixed-ligand chromium(III) complex, bis[2-(2-hydroxyphenyl)benzimidazolato]-(1,10-phenanthroline)chromium(III) isophthalate

A mixed-ligand Cr(III) complex with 2-(2-hydroxyphenyl)benzimidazole, 1,10-phenanthroline and isophthalic acid, [Cr(pbm)₂(phen)]X_0.5 (1X_0.5) (Hpbm = 2-(2-hydroxyphenyl)benzimidazole; phen = 1,10-phenanthroline; H₂X = isophthalic acid) has been prepared by heating in aqueous solution and characterized, and the geometric structure and spectroscopic properties, investigated experimentally and theoretically by using the density functional theory level (DFT) and the time-dependent density functional theory level (TDDFT). The theoretical-experimental agreement is satisfactory. Further theoretical analyses of electronic structure and molecular orbitals have demonstrated that the low-lying absorption bands in UV-Vis spectrum are mainly π → π∗ ligand-to-ligand charge transfer transition (LLCT) and or π → (d_z²-d_x²-y²-d_yz) ligand-to-metal charge transfer transition (LMCT) in nature.     

Deposition and characterization of ZnO thin films from a novel hexanuclear zinc precursor

The high nuclearity zinc complex, Zn₆(OAc)₈(μ-OH)₂(dmae)₂(dmaeH)₂ (1) (OAc = acetate and dmaeH = N,N′-dimethylaminoethanol), having a low decomposition temperature and sufficiently high solubility in non-polar solvents, was synthesized by a simple chemical technique in high yield and analyzed by melting point, elemental analysis, FTIR, NMR, single crystal X-ray crystallography and thermal analysis. Aerosol-assisted chemical vapor deposition technique was used to deposit a high-quality thin film with good adhesion to the glass substrate at relatively low temperature (320 °C). Scanning electron microscopy of the film shows clearly distinct crystallites of uniform shape with 2.4-2.9 μm size. Powder X-ray diffraction measurements have indicated the deposition of a crystalline phase of hexagonal ZnO with space group P63mc.