Effect of the amount and type of the crosslinker on the swelling behavior of temperature-sensitive poly(N-tert-butylacrylamide-co-acrylamide) hydrogels

Temperature-sensitive poly(N-tert-butylacrylamide-co-acrylamide) [P(NTBA-co-AAm)] hydrogels were synthesized by free-radical copolymerization in a water–methanol mixture using three types of crosslinkers: 1,2-ethyleneglycol dimethacrylate, N,N-methylenebisacrylamide, and 1,3-butandiol dimethacrylate. These thermosensitive hydrogels were swollen to equilibrium in water at 20°C and examined by gravimetric measurements. The influence of type and content of crosslinkers on the swelling ratio, the polymer–solvent interaction parameter (χ), the average molecular mass between crosslinks and the effective crosslinking density (ν _E) of the hydrogels were reported and discussed. The swelling process in water was found to be non-Fickian diffusion. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter for the hydrogels were determined by using the Flory–Rehner theory based on the phantom network model of swelling equilibrium. Negative values for ΔH and ΔS indicated that the hydrogels had a negative temperature-sensitive property in water; that is, swelling at a lower temperature and shrinking at a higher temperature. The temperature-reversibility and on–off switching properties of the P(NTBA-co-AAm) hydrogels may be considered as good candidates for designing novel drug-delivery systems.     

Iron speciation related to color of Jurassic sedimentary rocks in Turpan Basin, northwest China

Mesozoic-Cenozoic reddish and green beds are widely distributed in northwest China. Mössbauer spectroscopy revealed that the composition of iron species varies with color in the middle-upper Jurassic sedimentary rocks from the Turpan Basin. Three main kinds of iron species were identified: (1) ferric iron of hematite (hem-Fe³⁺), (2) paramagnetic ferric iron (para-Fe³⁺), and (3) paramagnetic ferrous iron (para-Fe²⁺). Pyrite iron (pyr-Fe²⁺) was revealed only in a few samples. In general, there is a direct correlation between rock color, iron species and total iron content, however, in detail, this relationship is more complicated. The reddish rocks contain higher contents of total iron and hem-Fe³⁺, whereas the gray rocks contain much more para-Fe²⁺. However, relatively low hematite content cannot give red color to rocks, probably due to suppression by other pigments such as organic matter in black or chlorite in green. The dark or green rocks normally contain either only paramagnetic Fe²⁺ and paramagnetic Fe³⁺ species or these two species associated with hematite Fe³⁺, but the relative content of hematite species is lower. The variations of different iron species control lithological properties such as color and also may reflect the sedimentary conditions. Moreover, iron speciation in these rocks is one of the main factors, which result the color features of rocks in remote sensing imagery.This revised version was published online in November 2005 with corrections to the Cover Date.     

An Efficient Method for the Synthesis of N-Acylsulfonamides: One-pot Sulfonylation and Acylation of Primary Arylamines under Solvent-Free Conditions

Summary. The preparation of N-acylsulfonamides is described using primary amines, arylsulfonyl chlorides and acyl chlorides. Reaction of primary aryl amines with arylsulfonyl chlorides in the presence of NaHCO₃ produced N-arylsulfonamides, which reacted in situ with benzoyl chloride furnishing the corresponding N-benzoyl-N-arylsulfonamides in 72–96% yields. Accordingly, 4-nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were used as acylating agents. All the reactions were carried out under solvent-free conditions at room temperature and the products were isolated after simple work-up in high yields and purity.     

Immobilization of the restriction endonucleasesPvuII andHindIII

The effects of several chemical reagents on the activity of the restriction endonucleasesPvuII andHindIII were investigated. Carbodiimide, which reacts preferentially with carboxyl groups, was found to inactivate these enzymes. This specific effect could be prevented by Mg²⁺ cation. pBR322 DNA, which containsPvuII andPvuII* sites andHindIII andHindIII* sites, did not protect the enzymes from the carbodiimide. On the other hand, glutaraldehyde, which reacts primarily with lysine residues, inactivatesPvuII andHindIII enzymes. This specific effect could not be prevented by pBR322 DNA. Preincubation with high concentrations ofN-ethylmaleimide, which reacts with sulfhydryl groups, caused slight inhibition ofPvuII activity, but had no effect on the activity ofHindIII enzyme. The effects of glutaraldehyde, carbodiimide, andN-ethylmaleimide on other restriction endonucleases were also investigated. Restriction endonucleasesPvuII andHindIII were immobilized by covalent coupling to various insoluble carriers. Both immobilized enzymes retained partial enzyme activities, when immobilized through phenolic groups and were stable for at least two months.     

Gangliosides from the starfishEvasterias echinosoma: identification of a disialoganglioside containing 8-O-methyl-N-acetylneuraminic acid andN-formylgalactosamine

Gangliosides were isolated from the starfishEvasterias echinosoma and their structures were elucidated by chemical and physicochemical methods. Two major gangliosides were found to be disialogangliosides, whose carbohydrate chain is based on the trisaccharide β-N-acylgalactosaminyl-(l→3)-β-galactosyl-(l→4)-β-glucose (acyl is formyl or acetyl), both residue at of 8-O-methyl-N-acetylneuraminic acid being attached to theN-acylgalactosamine residue at positions 3 and 6. The minor components are disialogangliosides with linear carbohydrate chains in which the terminal sialic acid residue is attached to the penultimateN-acetylneuraminic acid residue at positions 4, 8, or 9. The lipid part of the gangliosides consists of sphingenine and unsubstituted fatty acids (mainly, palmitic and stearic acids). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 156–161, January, 2000.     

The composition and antifungal bioassay of the essential oils of differentBetula species growing in Turkey

FiveBetula species,B. pendula, B. browicziana, B. medwediewii, B. litwinowii, andB. recurvata, were collected from different parts of Turkey. The leaves of these species were hydrodistilled to yield the consequent essential oils. The essential oil compositions were investigated by GC/MS. 14-Hydroxy--caryophyllene was the main constituent in the oil ofB. pendula. 14-Hydroxy-4,5-dihydro--caryophyllene, a new compound, was identified as the main constituent in the oils ofB. browicziana, B. litwinowii, and B. recurvata. In the oil ofB. medwediewii methyl salicylate was the main compound. Various phytopathogenic fungi were studied by the agar tube dilution technique to test the antifungal activities of the essential oils at 400 g/ml concentration. The essential oils showed strong antifungal activity againstCephalosporium aphidicola, Drechslera sorokinianse, Fusarium solani, andRhizoctonia cerealis.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 126–130, March–April, 2000.     

Reactions of 3,5-di(tert-butyl)-1,2-benzoquinone with terminal acetylenes in the presence of phosphorus trichloride. ipso-Substitution of the tert-butyl group

The reactions of 3,5-di(tert-butyl)-1,2-benzoquinone with aryl-and alkylacetylenes in the presence of phosphorus trichloride afford 4-aryl(alkyl)-8-tert-butyl-2,6-dichloro-2-oxo-2H-benzo[e][1,2]oxaphosphinines as the major ipso-substitution products of the tert-butyl group by the chlorine atom. 4-Aryl(alkyl)-6,8-di(tert-butyl)-2,5-dichloro-2-oxo-and 4-aryl(alkyl)-6-tert-butyl-2,8-dichloro-2-oxo-2H-benzo[e][1,2]oxaphosphinines were obtained as the minor products. The structures of the stable representatives of this series were confirmed by X-ray diffraction. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1836–1845, September, 2007.     

Essential Oils of Sideritis Species of Turkey Belonging to the Section Empedoclia

The paper summarizes the work done on the essential oil content and composition of fifty Sideritis species of Turkey belonging to the section Empedoclia. The water-distilled oils were analyzed by GC/MS. The oils were characterized as having mono- and sesquiterpenoids.     

Gangliosides from the starfishEvasterias echinosoma: identification of a disialoganglioside containing 8-O-methyl-N-acetylneuraminic acid andN-formylgalactosamine

Gangliosides were isolated from the starfishEvasterias echinosoma and their structures were elucidated by chemical and physicochemical methods. Two major gangliosides were found to be disialogangliosides, whose carbohydrate chain is based on the trisaccharide β-N-acylgalactosaminyl-(l→3)-β-galactosyl-(l→4)-β-glucose (acyl is formyl or acetyl), both residue at of 8-O-methyl-N-acetylneuraminic acid being attached to theN-acylgalactosamine residue at positions 3 and 6. The minor components are disialogangliosides with linear carbohydrate chains in which the terminal sialic acid residue is attached to the penultimateN-acetylneuraminic acid residue at positions 4, 8, or 9. The lipid part of the gangliosides consists of sphingenine and unsubstituted fatty acids (mainly, palmitic and stearic acids). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 156–161, January, 2000.     

Quantitative Determination of the Chemical Profile of the Plant Material “Qiang-huo” by LC-ESI-MS-MS

The rhizomes of Notopterygium incisum Ting. ex H. T. Chang and N. forbesii Boiss. are recorded in the pharmacopoeia of the People’s Republic of China under the same name “Qiang-huo”. Valid quality control of Qiang-huo is desirable due to the fact that the wild natural sources of Qiang-huo have almost been exhausted and large regulated cultivation is developing. In the present paper, HPLC fingerprinting was developed to identify and distinguish both species in detail. The unique properties of the HPLC fingerprint were validated by analyzing 15 batches of N. incisum and 11 batches of N. forbesii. A standardized procedure involving liquid chromatography–electrospray ionization–multiple stage mass spectrometry (HPLC-ESI-MSⁿ) was developed to identify the fingerprint components, and a total of eight characteristic peaks were unequivocally identified. An average chromatogram from 15 batches of N. incisum from different geographic sources, considered to be the original and genuine herbal medicine, was first established as the standard fingerprint. The chemical profiles of 11 batches of N. forbesii samples were found to be variable. The HPLC method can differentiate N. incisum from N. forbesii by either the marker compounds notoptol (4) and p-hydroxypenethylanisate (8) or the amounts of nodakenin (1), notopterol (5), and 6′-O-trans-feruloylnodakenin (7). The HPLC fingerprint analysis is specific and may serve for quality identification and comprehensive evaluation of Qiang-huo.     

Composition of the essential oil of Geocaryum cynapioides (Guss.) L. Engstrand

Volatile constituents from two fresh samples of the subendemic Geocaryum cynapioides (Guss.) L. Engstrand (Apiaceae) obtained by hydrodistillation were analyzed by GC and GC-MS. Forty four and one hundred-twenty three constituents identified in the oils accounted for 98.7 % and 98.4 % of the total oils, respectively. The major component of both oils was (E)-β-farnesene (73.3 % and 57.7 %) while the other major contributors were: (E,E)-α-farnesene (4.8 % and 14.6 %) and trans-sesquisabinene hydrate (12.2 % and 3.0 %). The constituents endo-fenchyl acetate, and three sesquiterpene lactones belonging to the selinane (callitrisin) and guaiane (grilactone and jalcaguaianolide) series, with a rather restricted natural occurrence, were present in only one of the samples (4.7 %, trace amount, 0.1 %, 0.5 %, respectively) and completely absent from the other distinguishing so the two samples. A chemotaxonomic discussion of the results is presented.     

Theoretical Investigations of the Effect of a Homologous Series of Anionic Surfactants on the Metabolism Bioactivity of Chromobacterium violaceum

Theoretical calculations were performed to obtain physicochemical properties associated with the effect of homologous anionic n-alkylsulfate surfactants on the metabolism of Chromobacterium violaceum. The quantitative experimental effects on the respiration process were those obtained from calorimetric data and were used to correlate the Structure–Activity–Relationship (SAR) of these compounds. Semiempirical AM1 and ab initio DFT levels, employing the set CEP-31G, were used for the theoretical calculations and were parameterized using the continuum-solvation model COSMO for solvent contributions. Chemometric analyses (HCA: hierarchical cluster analysis and PCA: principal component analysis) were used to correlate the physicochemical properties of these compounds and their biological activities. The results indicate that the biological activities of these compounds increase as the hydrocarbon chain length, volume, molar volume and exothermic enthalpy of formation (Δ_f H ^∘) increase; in contrast they decrease with decreases of the solvent effect (SE), ionization enthalpy (IE) and HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies.     

Study of mineral water resources from the Eastern Carpathians using stable isotopes

The Eastern Carpathians contain many mineral water springs that feed famous Romanian health resorts such as Borsec, Biborteni and Vatra Dornei. These waters have been used for their different therapeutic effects. In this work, mineral and spring waters from these Romanian regions were investigated by means of chemical and isotopic (δD and δ¹⁸O) analyses in order to understand the recharge mechanisms and also to determine their origins. Most of the investigated springs are of meteoric origin, having the average deuterium content of the local meteoric water. The higher ¹⁸O content with respect to the Meteoric Water Line (MWL) indicated an exchange reaction with crystalline igneous rocks at depth and with other rocks that the water encounters on its journey back to the surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Density functional studies of the dipole polarizabilities of the linear polyacenes benzene through nonacene

We report Ab Initio studies of the electric dipole polarizability of the linear polyacene series benzene through nonacene. A number of Ab Initio studies were done at different levels of theory for benzene, with all remaining Ab Initio calculations being at the B3LYP/6-311G(2d, 1p)//B3LYP/6-311+G(2d, 1p) level of theory. We find that the NN tensor component shows a constant increment of 20 atomic units per ring. AM1 and QSAR-quality empirical calculations show poor absolute agreement with the Ab Initio results but given excellent statistical correlation coefficients with the Ab Initio values. This implies that the results of such cheaper calculations can be suitably scaled for predictive purposes.     

Quinonimines and aminoquinones, the reaction products of 3,6-di(tert-butyl)-o-benzoquinone with primary and secondary amines

Reactions of 3,6-di(tert-butyl)-o-benzoquinone with primary amines occur by the nucleophilic 1,4-addition mechanism and lead to the corresponding 2-hydroxy-p-quinonimines, which exist in solutions in equilibrium with tautomeric 4-amino-o-quinones. The thermodynamic parameters of this prototropic isomerism were determined by NMR spectroscopy. In the case of a secondary amine (piperidine), a derivative of 4-amino-o-quinone was obtained; the corresponding o-semiquinone complexes were studied in solution by ESR spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1151–1155, July, 2006.     

Hydrodistillation–Headspace Solvent Microextraction: An Efficient Method for Analysis of the Essential Oil from the Seeds of Foeniculum vulgare Mill.

Hydrodistillation–headspace solvent microextraction (HD–HSME) has been used for isolation and preconcentration of the essential oil from the seeds of Foeniculum vulgare Mill. The effect on extraction efficiency of different conditions, for example sample mass, extraction time, microdrop volume, and choice of solvent, was studied and all were optimized. The results were compared with those from hydrodistillation, as reference method. Fourteen compounds were identified; the main components were trans-anethole (70.4%), fenchone (9.3%), and p-allylanisole (8.8%). The results were in good agreement with those obtained by hydrodistillation.     

Effect of the crosslinking density and the method of sample preparation on the observed microstructure of macroporous and conventional poly(N,N-dimethylacrylamide) hydrogels

SEM micrographs of macroporous and conventional poly(N,N-dimethylacrylamide) hydrogels were obtained for specimens synthesized in different conditions and prepared for microscopy by different methods (freeze drying of different solvents and critical point drying). The crosslinking density of both types of samples was determined through T _g measurements. Open structures (honeycomb-like, fibrillar networks) were more frequently observed in specimens prepared by freeze drying of benzene, which was attributed to its large pressure and temperature at the triple point. In spite of the different structure in the millimeter scale, there is no significant difference in the mesh size of fibrillar networks observed for macroporous and conventional samples, and in both cases it decreases with increasing crosslinking density. Other effects of the crosslinking density are that only incomplete honeycomb-like structures were formed in low-crosslinking samples and that collapsed structures were developed by phase separation throughout polymerization in highly crosslinked samples. Fibrillar networks of 1-μm mesh size were observed for the uncrosslinked polymer.     

A kinetic method for <Emphasis Type="Italic">para</Emphasis>-nitrophenol determination based on its inhibitory effect on the catalatic reaction of catalase

The inhibitory effect of para-nitrophenol on the catalytic reaction of catalase was investigated. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots obtained in the absence or in the presence of the inhibitor. The inhibitor pattern, revealed by the Lineweaver-Burk plots, suggested a fully mixed inhibition mechanism. Spectrophotometric monitoring of the indicator reaction: in conjunction with initial rate measurements was employed for the kinetic determination of the inhibitor. Calibration plots of initial rate vs. para-nitrophenol concentration were linear in the concentration range 0.9·10⁻⁵–2.5·10⁻⁵ mol/L and the detection limit was 3·10⁻⁶ mol/L (417 μg/L) para-nitrophenol. Interferences from other phenolic compounds like orto-cresole, meta-and orto-nitrophenol were observed.     

Classification of structurally related compounds fromAstragalus extract by correlation of the logk w andS

Summary The linear relationship between logk _w andS derived from molecular interactions and statistical thermodynamics was investigated by four series of different polar probe solutes. For each series of similar polar solutes, structurally related compounds with similar dipolarity/polarizability and hydrogen bonding energy, a linear relationship between logk _w andS was obtained. The more similar the solutes, the greater were the regression coefficients obtained. For two series of solutes with different strong polar groups resulting in different dipolarity/polarizability and hydrogen bonding energy, two parallel lines were observed in the logk _w-S plots. Each line represented one series of compounds and the distance between them indicated the difference in the dipolarity/polarizability and hydrogen bonding energy. Based on the parallel lines implying information on structurally related compounds in the logk _w-S plot, a method of classification of structurally related compounds was put forward and the linear logk _w-S correlation for unknown components in nonaqueous RP-HPLC analysis ofAstragalus extract with isopropanol-methanol mobile phase was studied. Two nearly parallel lines were obtained in the logk _w-S plot and two series of structurally related compounds were classified in this way.