Synthesis and characterisation of carboxylic acid and diphenylphosphine derivatives in the 1,3-diyne series: Spectral properties of polydiacetylene carboxylates

Symmetrically substituted 1,3-diynes containing hydroxyalkyl ( 1a-d ), bromoalkyl ( 1e-h ) (diphenylphosphinyl) ( 1i-k ) and carboxyalkyl ( 2a-d ) substituents have been prepared and characterised; the phosphine derivative ( 1k ) has been converted with alkyl iodides ( RI ; R = Me, Et) into bis(phosphonium) salts ( 1l and m ). During preparation of the diynedioic acid. ( 2a ), the non-centrosymmetrical diyne, HO₂CCH₂C?C—C?C(CH₂)₂OH ( 3 ), was also isolated. ⁶⁰Co γ-Irradiation of diacetylene monomers ( 2a – d ) and 10,12-tricosadiyn-1-oic acid gave the corresponding polydiacetylene derivatives ( 4a – d and 5 ), respectively. Rubidium salts of ( 4c ) and ( 4d ), a barium salt of ( 4c ), and a potassium salt of ( 5 ) were prepared and isolated; soluble potassium salts of the carboxylic acid polymers ( 4 ) were generated in aqueous solution. The effects of changes in pH on the UV/visible absorption spectra of aqueous solutions of selected carboxylic acid polydiacetylenes have been recorded, and are discussed.     

Thermal and spectroscopic properties of the polydiacetylene derived from docosa-10,12-diyne-1,22-diylbis(phenylacetate)

Polydiacetylene ( 2 ) of varying molecular weight has been formed by UV- or ⁶⁰Co γ-irradiation of the diacetylene PhCH₂CO₂(CH₂)₉-C?C? C?C(CH₂)₉O₂CCH₂Ph ( 3 ), with conversion of 30?>95%. Samples of ( 2 ) with differing physical properties have been studied, in the bulk phase, by CPMAS ¹³C NMR and VIS/UV spectroscopy and by DSC; complementary spectroscopic data on solutions of ( 2 ), including fluorescence studies, are also reported. Spectroscopic studies support the presence of an extended planar conjugated backbone in ‘as polymerised’ blue–black samples of ( 2 ), from which various forms of red-coloured polymer, with shorter conjugation lengths, can be obtained. Studies of the thermal behaviour indicate the existence of several differing thermal transitions for these materials and the results are discussed.     

Morphologic changes of starch granules in the apple cv. Mutsu during ripening and storage

Unripe (A), semiripe (B), and ripe (C) apples (Malus domestica cv. Mutsu) stored (2–4 °C, 90–95% RH) for 1 week were studied. The decrease in the starch content was as a function of storage time and ripeness. The size (area, perimeter and circularity) of starch granules was determined by image analyzer (Semper6, Synoptics) interfaced with a standard light microscope (Olympus, BH²) using a bright field illumination. Area (Ar) (larger than 100 pixel), perimeter (Pe), and circularity (Ci) of the granules were measured. The distribution of Ar, Pe, and Ci was calculated by the Distribution Fitting Statistical program; normality of frequency distribution of data (Chi-square test), average ± standard deviation, t-values were presented. All data were analyzed by principal component analysis. Area and perimeter decreased, circularity increased with the storage time and ripeness. Critical differences were observed in the semiripe apple cortex (CoB0) and the ripe apple skin (SC0) compared with the other samples (unripe skin and cortex) at the harvest. In both samples, most starch granules swelled (19–24%), and the starch contents were significantly less than in others. The stage of ripeness could be more exactly followed by image analysis than by the starch iodine test, or the color of apple skin. The ultrastructure (SEM) of starch did show typical changes as a function of storage time. More smaller starch granules could be seen in the stored apples than in the fresh ones. Damaged (pits, cavities) starch granules were found in all samples. Carbon-13 NMR spectra of isolated apple cortex starch were obtained with cross polarization (CP), magic angle spinning (MAS), and high power proton irradiation (HD). There were shoulders on the C-1 resonance and on the C-2, 3, 4, 5 cluster. These shoulders indicate the presence of amorphous starch.     

Skewed oligomers and origins of replication

In pigs, induction of embryonic degeneration, by exogenous oestrogens given early in gestation, has been long recognised. However, the underlying mechanisms responsible for this degeneration remain unclear. The present study was conducted to determine whether oestrogen-induced early porcine embryonic mortality was associated with changes in the levels of tumour necrosis factor-alpha (TNF-alpha) messenger RNA in the uterine endometrium. Prepubertal gilts were induced into oestrus with PG600 and artificially inseminated at their second natural oestrus and again 24 h later. After insemination, gilts were randomly assigned to treatment and given 0.5 ml intramuscular injections of either oestradiol valerate (10 mg ml-1) or corn oil on day 9 and 10 of gestation. The gilts were slaughtered on day 12, 15 or 18 of gestation. The reproductive tract was removed from each gilt and the uterine horns were flushed to check for the presence and integrity of embryos. Samples of uterine endometrial tissues were collected, snap-frozen in liquid nitrogen and stored at -80 degrees C. Total cellular RNA was isolated from frozen tissues using a guanidine isothiocyanate-cesium chloride method. The abundance of TNF-alpha messenger RNA was determined by Northern blot hybridisation analysis. Treatment of pregnant gilts with oestrogen resulted in severe fragmentation of embryos on days 15 (2/3) and 18 (2/2), confirming the embryocidal effect of exogenous oestrogen. Uterine TNF-alpha messenger RNA level was elevated in oestrogen-treated gilts compared with controls (P < 0.05). This observation of an association between increased levels of TNF-alpha mRNA in the uterus and embryonic degeneration in oestrogen-treated gilts suggests that TNF-alpha may be involved in mediating oestrogen-induced early embryonic mortality in the pig.     

Surface charge heterogeneity of kaolinite in aqueous suspension in comparison with montmorillonite

An analogous study to 2:1 type montmorillonite [Tombácz, E., Szekeres, M., 2004. Colloidal behavior of aqueous montmorillonite suspensions: the specific role of pH in the presence of indifferent electrolytes. Appl. Clay Sci. 27, 75–94.] was performed on 1:1 type kaolinite obtained from Zettlitz kaolin. Clay minerals are built up from silica tetrahedral (T) and alumina octahedral (O) layers. These lamellar particles have patch-wise surface heterogeneity, since different sites are localized on definite parts of particle surface. pH-dependent charges develop on the surface hydroxyls mainly at edges besides the permanent negative charges on silica basal plane due to isomorphic substitutions. Electric double layers (edl) with either constant charge density on T faces (silica basal planes) or constant potential at constant pH on edges and O faces (hydroxyl-terminated planes) form on patches. The local electrostatic field is determined by the crystal structure of clay particles, and influenced by the pH and dissolved electrolytes. The acid–base titration of Na-kaolinite suspensions showed analogous feature to montmorillonite. The initial pH of suspensions and the net proton surface excess vs. pH functions shifted to the lower pH with increasing ionic strength indicating the presence of permanent charges in both cases, but these shifts were smaller for kaolinite in accordance with its much lower layer charge density. The pH-dependent charge formation was similar, positive charges in the protonation reaction of (Si–O)Al–OH sites formed only at pHs below  6–6.5, considered as point of zero net proton charge (PZNPC) of kaolinite particles. So, oppositely charged surface parts on both clay particles are only below this pH, therefore patch-wise charge heterogeneity exists under acidic conditions. Electrophoretic mobility measurements, however, showed negative values for both clays over the whole range of pH showing the dominance of permanent charges, and only certain decrease in absolute values, much larger for kaolinite was observed with decreasing pH below pH  6. The charge heterogeneity was supported by the pH-dependent properties of dilute and dense clay suspensions with different NaCl concentrations. Huge aggregates were able to form only below pH  7 in kaolinite suspensions. Coagulation kinetics measurements at different pHs provided undisputable proofs for heterocoagulation of kaolinite particles. Similarly to montmorillonite, heterocoagulation at pH  4 occurs only above a threshold electrolyte concentration, which was much smaller, only  1 mmol l^− 1 NaCl for kaolinite, than that for montmorillonite due to the substantial difference in particle geometry. The electrolyte tolerance of both clay suspensions increased with increasing pH, pH  6–6.5 range was sensitive, and even a sudden change occurred above pH  6 in kaolinite. There was practically no difference in the critical coagulation concentration of kaolinite and montmorillonite (c.c.c. 100 mmol l^− 1 NaCl) measured in alkaline region, where homocoagulation of negatively charged lamellae takes place. Rheological measurements showed shear thinning flow character and small thixotropy of suspensions at and above pH  6.7 proving the existence of repulsive interaction between uniformly charged particles in 0.01 M NaCl for both clays. The appearance of antithixotropy, the sudden increase in yield values, and also the formation of viscoelastic systems only at and below pH  6 verify the network formation due to attraction between oppositely charged parts of kaolinite particles. Under similar conditions the montmorillonite gels were thixotropic with significant elastic response.     

Comparison of sorption domains in molecular weight fractions of a soil humic acid using solid-state 19F NMR

Humic acid was fractionated into eight different molecular size components using ultrafiltration. Solid-state CPMAS 13C NMR demonstrated that fractions larger than 100,000 Daltons were primarily aliphatic in character, while fractions smaller than 30,000 Daltons were predominantly aromatic in character. Solid-state 19F NMR examination of the sorptive uptake of hexafluorobenzene (HFB) by HA and each of the fractions gave spectroscopic evidence for the existence of at least three sorption sites in the smaller molecular size fractions, while two predominant sorption sites could be established in the larger molecular size fractions. Sorbed HFB displayed higher mobility in the smaller, more aromatic fractions while HFB in the larger, more aliphatic fractions displayed lower mobility. The relative mobilities of HFB in each sorption domain suggest that the rigid domain may be composed of aliphatic carbon rather than aromatic carbon moieties. In larger size fractions, this domain may be the result of rigid, glassy regions composed of aliphatic molecules or side chains.     

The most important bioactive components of cold pressed oil from different pumpkin (Cucurbita pepo L.) seeds

The composition and content of certain bioactive components of the cold pressed oil obtained from six samples of pumpkin seeds (Cucurbita pepo L.) cultivated in Serbia were analyzed by GC and GC/MS. The composition and content of fatty acids, tocopherols and phytosterols, and the total content of squalene were determined. The results indicate oil's excellent quality, with high contents of monounsaturated fatty acids (37.1 ± 0.70–43.6 ± 0.69 g/100 g of total fatty acids), total tocopherols (38.03 ± 0.25–64.11 ± 0.07 mg/100 g of oil), sterols (718.1 ± 6.1–897.8 ± 6.8 mg/100 g of oil) and especially squalene (583.2 ± 23.6–747 ± 16 mg/100 g of oil). High content of squalene, phytosterols and monounsaturated fatty acids recommend the use of this type of the oil in the nutritional and medical purposes.