bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Characterization of New Biodegradable Polymers for Biomodeling and Biomedical Applications
Authors: Sung Yong Kiel , Song Dae Kyung
Published: May 2005

Biodegradable poly(1,2‐propanediol succinate) and poly(1,3‐propanediol succinate) were synthesized using 1,2‐propanediol and 1,3‐propanediol with succinic anhydride, respectively. The synthesized polymers were identified by NMR spectrometry and FT‐IR spectrophotometry. The weight average molecular weights were 8,900 in poly(1,2‐propanediol succinate) and 8,600 in poly(1,3‐propanediol succinate), respectively. The biodegradation behavior of polymers in microorganisms was studied by using a modified ASTM method. These polyesters were degraded to lower molecular weight compounds depending on hydrophobicity and hydrophilicity. The quantitative determination of carbon dioxide, generated during the treatment with the activated sludge, showed that poly(1,3‐propanediol succinate) was biodegraded faster than poly(1,2‐propanediol succinate). The biodegradation ability of the polymers by Aspergillus niger was monitored to check the molecular weights using GPC and to check the crystallinity change of the polymers using DSC. Based upon the visual observation of the biodegraded polymers, the crystalline structure of poly(1,2‐propanediol succinate) apparently retained its crystallinity longer than the similar structure in poly(1,3‐propanediol succinate).
Locust Bean Gum Hydrogels Formed by Freezing and Thawing
Authors: Hatakeyama Tatsuko , Naoi Sunao , IIjima M. , Hatakeyama Hyoe
Published: May 2005

Locust bean gum (LBG) hydrogels were prepared by freezing and thawing. It was found that the junction zone of LBG hydrogels is tightly formed by repeating freezing and thawing. During this process, LBG molecules not connected with the junction zone are excluded from the gel portion and the remaining molecules gradually form densely packed hydrogels. Molecular conformation in the sol state affects the rate of the junction formation. Obtained LBG hydrogels are thermally stable and no gel‐sol transition was observed in temperatures from 40 to 100 °C by the observation of differential scanning calorimetry (DSC). Non‐freezing water content calculated from the DSC melting peak of water in the gel indicates that the junction zone became dense with increasing freezing and thawing.
Influence of Heat Treatment on Biological Properties of Chitosan toward Vascular Cells in vitro
Authors: Lim Sae‐Hwan , Park Ki‐Sook , Park Hyun‐Sook , Gin Yong‐Jae , Noh In‐Sup , Park Chan‐Woong , Son Young‐Sook , Kim Chun‐Ho
Published: May 2005

The effects of heat treatment of chitosan film on the proliferation of vascular cells were examined in vitro. Chitosan film was heat treated at 110 °C in vacuo for 1∼3 days. Heat treatment slightly improved the hydrophilicity of chitosan, although the cross‐linking of chitosan took place after heat treatment. Chitosan films were cytocompatible toward smooth muscle cells (SMCs) and human dermal microvascular endothelial cells (HDMECs) before and after heat treatment of chitosan. In particular, the heat treated chitosan supported the proliferation of both vascular cell types for one day. The growth of HDMECs was greater than that of SMCs on heat treated chitosan film for one day. Heat treated chitosan has intrinsic biological activity which could contribute to a retardation of SMC growth relative to HDMECs.
Thermosensitive Chitosans as Novel Injectable Biomaterials
Authors: Chung Ho Jin , Bae Jin Woo , Park Hyung Dal , Lee Jin Woo , Park Ki Dong
Published: May 2005

Two kinds of water soluble thermosensitive chitosan copolymers were prepared by graft polymerization of N‐isopropylacrylamide (NIPAAm) onto chitosan using cerium ammonium nitrate (CAN) as an initiator (chitosan‐g‐NIPAAm) and by coupling monocarboxy Pluronic® with chitosan using 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide (EDC) and N‐hydroxysuccin‐imide (NHS) as coupling agents (chitosan‐Pluronic®). The physicochemical properties of the resulting copolymers were characterized and they formed thermally reversible hydrogel, which exhibits a lower critical solution temperature (LCST) at 34°C in aqueous solutions. The human mesenchymal stem cells (hMSCs) were cultured in the chiotsan‐g‐NIPAAm in vitro. Chondrogenic differentiation was induced in the chitosan‐g‐NIPAAm gel. Therefore, chondrogenic differentiated cells from MSCs with a thermo‐sensitive chitosan‐g‐NIPAAm could be used as an injectable cell‐polymer complex. In summary, chitosan‐g‐NIPAAm and chitosan‐Pluronic® attest to their usefulness as injectable materials because of their thermally reversible property and relatively good biocompatibility.
Novel Carbon Nanotube/Poly(L‐lactic acid) Nanocomposites; Their Modulus, Thermal Stability, and Electrical Conductivity
Authors: Moon Sung‐Il , Jin Fengzhe , Lee Cheol‐jin , Tsutsumi Sadami , Hyon Suong‐Hyu
Published: May 2005

The interest in poly(L‐lactic acid)(PLLA) has been increasing in recent years because this polymer is made from renewable resources and its properties are benign to the environment. Carbon nanotubes(CNTs) have shown exceptional stiffness and strength and remarkable thermal and electrical properties, which make them ideal candidates for the development of multifunctional material systems. In this study, mechanical and thermal properties as well as the electrical conductivity of CNTs/PLLA nanocomposites were investigated. Our study of the mechanical properties of these nanocomposites indicates that the tensile strength and ultimate elongation decreased, but Young's modulus slightly increased from 1 GPa to 2.5 GPa. Embedding the CNTs into the polymer matrix improves the thermal stability of the polymer. The thermogravimetric analysis (TGA) results of PLLA and the 3 wt% CNTs/PLLA nanocomposites in air show initial weight loss at the same temperature as PLLA, but the decomposition temperature for the nanocomposite is approximately 10°C higher than that of PLLA. Similar results were found for the other CNTs/PLLA composites (5, 10 wt%). In addition, electrical conductivity and electromagnetic wave shielding effect was also investigated.
Rheological, Thermal, and Morphological Characteristics of Plasticized Cellulose Acetate Composite with Natural Fibers
Authors: Choi Joon Soon , Lim Sung Taek , Choi Hyoung Jin , Hong Soon Man , Mohanty Amar K. , Drzal Lawrence T. , Misra Manjusri , Wibowo Arief C.
Published: May 2005

Plasticized cellulose acetates processed with biofibers like industrial hemp and henequen were investigated with respect to their thermal, morphological and rheological characteristics. Discernable fibril morphologies in the biocomposites were observed via a SEM investigation. Such morphological characteristics were further analyzed with the results of TGA and rheometry. Furthermore, the obtained rheological properties were also interpreted in conjunction with the formation and destruction of internal structure in biocomposites.
Biodegradable Composites of Poly(lactic acid) with Cellulose Fibers Polymerized by Aluminum Triflate
Authors: Funabashi Masahiro , Kunioka Masao
Published: May 2005

Biodegradable polymer composites consisting of poly(lactic acid) (PLA) and cellulose fibers (CF) were prepared by our newly developed method. L‐Lactic acid (LA) was reacted by ring‐opening polymerization with aluminum triflate as a catalyst, glycerol as an initiator and CF as a filler, in simple plastic tubes at 100 °C for 6 hours. By this method, CF could be mixed with the polymer matrix easily and homogeneously. The molecular weight and molecular weight distribution of the PLA matrix were determined by gel permeation chromatography (GPC). The Mn of the composite samples decreased from 6200 to 2800 with increasing CF content. The molecular weight distribution of composites was around 2.5 regardless of the CF content. Biodegradation of samples was determined by measuring the results from the Microbial Oxidative Degradation Analyzer (MODA) and the weight loss in compost. Biodegradation of composite samples of PLA with CF increases with increasing CF content as measured by the MODA. Apparent density of composite samples was calculated by using the weight and sizes of column shape specimens. The density of the composite samples was a bit lower than that of PLA pure samples without CF. Mechanical properties such as the elastic modulus and strength were investigated by compression tests using column shape specimens. For the sample with filter paper as CF, the strength of composite samples increases with increasing CF content.
Soil and Microbial Degradation Study of Poly(ϵ‐caprolactone) – Poly(vinyl butyral) Blends
Authors: Rohindra David , Sharma Praneel , Khurma Jagjit
Published: May 2005

Biodegradation of blends of poly(ϵ‐caprolactone) [PCL] with poly(vinyl butyral) [PVB] was studied in the soil and by bacterial strains of Bacillus subtilis and Escherichia Coli isolated from the soil. Miscibility of the blends was also analyzed using FT‐IR and optical microscopy at room temperature. Biodegradation of the blends was followed by weight loss, visual observations and scanning electron microscopy [SEM]. Blends with low polyester concentration, i.e., 30 wt% PCL and less, were clear and transparent and no spherulite formation was observed. Above 30 wt% PCL spherulites appeared, the size of which increased with increasing PCL concentration. Infra‐red studies of the blends with less than 30 wt% PCL showed that only the amorphous phase of PCL was present. Above 30 wt% PCL indicated the presence of both crystalline and blended PCL. The second derivative of the carbonyl peak of PCL also supported the presence of two phases in blends with more than 30 wt% PCL and only one peak for blends with 30 wt% or less PCL. Weight loss was observed in all the blends. PCL rich blends showed more degradation, which was faster in the natural environment than in the laboratory. Physical appearance and microscopic examination showed the films deteriorated in soil. Blends in the Bacillus subtilis strain showed more degradation as compared to the E. Coli. strain.
Synthesis of Starch‐g‐Poly(glycidyl methacrylate) and Its Blending with Poly(ϵ‐caprolactone) and Nylon 610
Authors: Kim Gwan Young , Park Eun Soo , Kim Kwangsok , Chin In‐Joo , Yoon Jin San
Published: May 2005

Different amounts of glycidyl methacrylate (GMA) were grafted onto corn starch dispersed in water or dimethyl sulfoxide (DMSO) to yield starch‐graft‐poly(glycidyl methacrylate) (ST‐g‐PGMA). ST‐g‐PGMAW, obtained by grafting PGMA onto corn starch that was dispersed in water, showed a higher PGMA grafting content and a lower content of the homopolymerized PGMA than ST‐g‐PGMAD, which was prepared in DMSO. The modified starches were blended with poly(ϵ‐caprolactone) (PCL) and nylon 610, respectively, and the tensile properties of the blends were measured by UTM. Mechanical properties of the biodegradable ST‐g‐PGMA/PCL blends were dependent on the PGMAD content grafted on starch. Without dramatic loss of the tensile properties of PCL, ST‐g‐PGMAW was melt blended with PCL. Meanwhile, an increase in the tensile modulus was observed in the ST‐g‐PGMAW/nylon 610 blend. When nylon 610 was reacted with ST‐g‐PGMAW in DMSO in the presence of triethylamine, the tensile modulus and strength were much higher than those of the pure nylon 610, and phase‐separated domains of starch were not observed microscopically.
Curing and Glass Transition of Epoxy Resins from Ester‐Carboxylic Acid Derivatives of Mono‐ and Disaccharides, and Alcoholysis Lignin
Authors: Hirose Shigeo , Hatakeyama Tatsuko , Hatakeyama Hyoe
Published: May 2005

Mono‐ and disaccharides (SAC) such as glucose (Glc), fructose (Frc) and sucrose (Suc), and also alcoholysis lignin (AL) were dissolved in ethylene glycol and each of the obtained mixtures was reacted with succinic anhydride to form a mixture of ester‐carboxylic acid derivatives such as SAC‐polyacid, SACPA, and AL‐polyacid, ALPA. Ethylene glycol‐polyacid (EGPA) was also prepared from ethylene glycol. Each of the obtained mixtures of ester carboxylic acid derivatives was reacted with ethylene glycol diglycidyl ether in the presence of a catalytic amount of dimethylbenzylamine to form ester‐epoxy resins. The molar ratios of epoxy groups to carboxylic acid groups ([EPOXY]/[ACID] ratios, mol mol−1) was maintained at 1.0. The contents of SACPA and ALPA in the mixtures of SACPA/EGPA, and ALPA/EGPA, respectively, were also varied from 0 to 100 %. The curing reaction of SucPA and ALPA was studied by differential scanning calorimetry (DSC). Activation energy of the curing reaction for the SucPA system was 80.5 kJ/mol. Thermal properties of epoxy resins were studied by DSC. Glass transition temperatures (Tg) decreased with increasing numbers of repeating units in ester chains between cross‐linking points, suggesting that ester chain lengths between cross‐linking points mainly affect the mobility of ester chains in epoxy resin networks.
Biodegradation of Plastics in Compost Prepared at Different Composting Conditions
Authors: Joo Sang Bum , Kim Mal Nam , Im Seung Soon , Yoon Jin San
Published: May 2005

Maximum temperature during the thermophilic phase and moisture content were controlled in the course of composting to examine the effects of these composting conditions on the quality of the compost used for the evaluation of the biodegradability of plastics. The moisture content during composting was controlled at 65%, while keeping the maximum temperature below 46°C, 58°C and 70°C, respectively. In turn, the maximum temperature was controlled to be below 58°C, while maintaining the moisture content at 45%, 55% and 65% respectively. The number of microbial cells was examined in the five compost samples thus prepared. Biodegradation of cellulose, polycaprolactone and poly(butylene succinate‐co‐butylene adipate) was conducted in the five compost samples, and the consistency and reproducibility of the test results were explored.
Accelerated Microbial Degradation of Poly(L‐lactide)
Authors: Tokiwa Yutaka , Jarerat Amnat
Published: May 2005

Acceleration of the biodegradation of poly(L‐lactide) (PLA) was studied. We found that the degradation rate of high molecular weight (1.3×105) PLA film was greatly increased by the addition of gelatin into the culture medium of the microorganisms. 100 mg of PLA film was almost completely degraded by the fungus, Tritirachium album (eukaryotic microorganisms), and by an actinomycete, Saccharothrix waywayandensis (prokaryotic microorganisms). In addition to gelatin, various insoluble proteins, peptides and amino acids also accelerate the biodegradation of PLA. Silk fibroin was the best inducer for the production of PLA‐degrading enzymes of an actinomycete, Amycolatopsis orientalis.
Rechnerische Behandlung der Verlagerung von Eigenspannungen in einem Stabmodell durch Überbelastung. Ein Beitrag zum mechanischen Schweißeigenspannungsbbau
Authors: Schimmöller H.
Published: May 2005

Der Mechanismus der Überbelastung, hervorgerufen durch die überlagerung von Last‐ und Eigenspannungen, wird für ein eindimensionales Zugstabmodell mit elastisch‐idealplastischem Stoff‐verhalten mathematisch formuliert. Die Rechnung ergibt ein Gleichungssystem, das in Abhängigkeit von dem vorhandenen Eigenspannungszustand, der Fließgrenze und der Belastung die elastisch‐plastische überlagerung von Last‐ und Eigenspannungen vollständig beschreibt. Die durch örtliches Fließen veränderten ursprünglichen Eigenspannungen ergeben sich durch elastische Entlasten. Das allgemein gültige Gleichungssystem wird für symmetrische Eigenspannungsverteilungen spezialisiert. Zur Ergänzung der theoretischen Darstellung wird ein einfaches Beispiel ausführlich durchgerechnet.
Das Explosivschweißen — eine wesentliche Ergänzung zu den bestehenden Fügeverfahren
Authors: Prümmer R.
Published: May 2005

Die Grundlagen des Explosivschweißens werden geschildert. Insbesondere wird auf die Bedeutung der Schweißparameter eingegangen. Eine einfache neue Methode zu deren Ermittlung wird beschrieben. Typische Schweißverbindungen mit und ohne Reaktionen in der Verbindungsschicht werden beispielhaft diskutiert. Ebenfalls werden typische Anwendungsfälle aufgezeigt.
C60 as a stationary phase for microcolumn liquid chromatographic separation of polycyclic aromatic hydrocarbons
Authors: Jinno Kiyokatsu , Yamamoto Kunihiko , Fetzer John C. , Biggs Wilton R.
Published: May 2005

Buckminsterfullerene C60 was evaluated as a stationary phase for the microcolumn liquid chromatographic separation of polycyclic aromatic hydrocarbons. Material prepared from a soot extract was packed into a fused‐silica capillary, 13‐mm times; 0.53‐mm i. d. The chromatographic characteristics were examined. The results indicate that C60 can work as a liquid chromatographic stationary phase, offering a unique shape selectivity for polycyclic aromatic hydrocarbons compared with octadecylsilica and dicoronylene stationary phase.
High‐resolution separation and detection of DNA adducts of benzo[a]pyrene
Authors: Harvey Scott D. , Bean Roger M. , Udseth Harold R.
Published: May 2005

Analysis of DNA adducts as indicators of human exposure to environmental levels of carcinogenic compounds represents an extreme challenge for trace analyses to chemists. At environmental exposure levels of benzo[a]pyrene, one can expect less than one adduct per 107 base pairs, or roughly 30 femtomoles of adduct per mg DNA. Microcolumn separation techniques are ideally suited for the trace analysis of DNA adducts due to the high separation efficiency, enhanced mass flow sensitivity, and ease of interfacing with highly specific and sensitive mass spectrometric detectors. This study describes the analysis of benzo[a]pyrene‐adducted deoxyguanosine‐5′‐monophosphate with micellar electrokinetic capillary chromatographic separation followed by fluorescence detection. Alternatively, adducts can be cleaved from the DNA by treatment with acid, resulting in the formation of highly fluorescent benzo[a]pyrene tetrahydrotetrols. Analysis of the tetrahydrotetrols by either capillary zone electrophoresis or microcolumn HPLC with fluorescence detection is described. Detection limits for the benzo[a]pyrene tetrahydrotetrols with either of the aforementioned separation techniques were approximately 3 femtomoles.
Carbon‐13 NMR spectra of isomeric 2‐arylimidazopyridines
Authors: Tretyakov A. V. , Rudaya L. I. , El'tsov A. V. , Larin M. F. , Lopyrev V. A.
Published: May 2005

The 13C NMR spectra of some 2‐arylimidazo‐[4,5‐c]‐ and ‐[4,5‐b]‐pyridines and their protonated forms have been studied. The nitrogen atom of the pyridine ring has been shown to be the most basic nitrogen in these compounds.
NMR studies of phosphonate carbanions: Influence of substituents on 1J(PC) and 1J(CH) and some INDO calculations
Authors: Webb G. A. , Simonnin M.‐P. , Seyden‐Penne J. , Bottin‐Strzalko T.
Published: May 2005

13C and 31P NMR data are reported for a series of phosphonate carbanions. In comparison with related uncharged molecules, the values of 1J(PC) are rather large. This is discussed with the help of some INDO‐SCPT spin‐spin coupling calculations, which reveal that while the positive contact term makes the dominant contribution to these couplings, the negative orbital term also plays an important role. The signs of 1J(PC) and 1J(CH) are predicted to be positive in all cases. Support for the proposal of a planar anionic carbon atom is forthcoming from the INDO‐SCPT calculations.
Carbon‐13 NMR of tertiary fluorosteroids as a stereochemical probe
Authors: Rozen Shlomo , Ben‐Shushan Giora
Published: May 2005

The 13C NMR spectra of tertiary fluorinated steroids possessing no functional groups in the vicinity of the fluorine have been measured. All α‐ and β‐carbons are deshielded by the fluorine atom. The γ‐carbons, however, are divided into two groups. The carbons gauche to the fluorine atom are all shielded by 1–8 ppm, whereas the γ‐carbons anti to the halogen are all deshielded by 2–5 ppm. Apart from the α‐Carbons, which have coupling constants of 170–180 Hz, all β‐Carbons are also coupled to the fluorine with a 2J(CF) value of approximately 20 Hz. The γ‐carbons gauche to the fluorine have a very small coupling constant (usually 0‐3 Hz), while the anti γ‐carbons are split by the fluorine by 6–8 Hz. Both chemical shifts and coupling constants can be used for the Stereochemical evaluation of fluorosteroids.
Investigation of the 31P NMR chemical shift dependence of phosphoryl compounds on the inductive and resonance effects of substituents
Authors: Rezvukhin A. I. , Dolenko G. N. , Krupoder S. A.
Published: May 2005

Linear dual‐parameter equations relating the 31P NMR chemical shifts in a series of phosphoryl compounds XYZP = O (X, Y, Z = various organic substituents or halogens) with the sums of inductive (σI) and resonance (σ) constants of the substituents have been obtained. The direction of the influence of the inductive and resonance components of the electron demand of substituents, and their relative contributions to the δ31P values, have been evaluated. The nature of the resonance contribution is discussed on the basis of the dependence between δ31P values and the charge characteristics of the phosphorus atom (x‐ray P Kα shifts).
17O NMR Spectra of 1‐adamantylphosphoryl derivatives
Authors: Duddeck Helmut , Hanna Atef G.
Published: May 2005

The 17O chemical shifts and one‐bond phosphorus‐oxygen coupling constants of a series of 1‐adamantylphosphoryl derivatives are reported and discussed. It was found that a significant 2p electron transfer towards the phosphoryl oxygen in the phosphonic esters is clearly reflected by the 17O NMR parameters.
Proton NMR study of methyl‐ and fluoro‐substituted 6‐ and 7‐ethoxy‐1‐methoxytricyclo[3.3.0.02,8]oct‐3‐enes
Authors: Jans A. W. H. , Van Arkel B. , Osselton E. M. , Cornelisse J.
Published: May 2005

1H NMR data (300 and 500 MHz) are reported for methyl‐ and fluoro‐substituted 6‐ and 7‐ethoxy‐1‐methoxytricyclo[3.3.0.02,8]oct‐3‐enes, products of the meta photocycloaddition of methyl‐ and fluoro‐anisoles to ethyl vinyl ether. COSY 45 (300 and 500 MHz) and COSY 90 (300 MHz) experiments were performed for the determination of the structures of these products.
Carbon‐13 NMR studies of primary amines and their corresponding 2,4,6‐trimethyl‐pyridinium salts
Authors: Balaban Alexandru T. , Dinculescu Antonie , Elguero José , Faure Robert
Published: May 2005

The 13C NMR chemical shifts of 37 N‐substituted 2,4,6‐trimethylpyridinium (TMP) salts with alkyl, aralkyl, aryl and heteroaryl N‐substituents are reported and discussed in comparison with those of the corresponding primary amines RNH2.
Halogeno‐substituted 2‐ and 3‐methylbenzo[b]thiophenes: Use of 1H NMR spectral analysis and 1H{1H} nuclear Overhauser effect for locating the halogen substituent
Authors: Cuberes Ma. Rosa , Moreno‐Mañas Marcial , Sánchez‐Ferrandom Francisco
Published: May 2005

Thirty‐seven halogeno‐substituted 2‐ and 3‐methyl‐(or halogenomethyl)‐benzo [b]thiophenes, including 17 new compounds, were prepared. The constitution of 14 of these was confirmed by full analysis (LAOCOON) of their 80 MHz1HNMR spectra and by 1H{1H} NOE measurements. In this way a by‐product from the preparation of 4‐ and 6‐bromo‐3‐bromomethylbenzo[b]thiophenes was shown conclusively to be 5‐bromo‐3‐bromomethylbenzo[b]thiophene. The 3‐substituted benzo[b]thiophenes showed greater NOE enhancement factors at H‐4 than at H‐2 when the 3‐methyl or halogenomethyl substituent was irradiated.
Secondary structure of peptides. 17—Cis/trans isomerism of solid proline‐containing oligopeptides as revealed by 13C NMR CP/MAS spectroscopy
Authors: Kricheldorf Hans R. , Haupt Erhard T. K. , Müller Detlef
Published: May 2005

The 75.4 MHz 13C NMR CP/MAS spectra of five classes of solid proline peptides were measured: cyclodipeptides, unprotected dipeptides, N‐tert‐butoxycarbonyl‐ (Boc) or N‐benzyloxycarbonyl‐ (Z)‐proline derivatives and N‐protected peptides with an aminoacyl—proline bond. In the case of solid N‐protected proline derivatives, the shift difference (Δδ) of the C‐β and C‐γ signals mainly reflects the cis/trans isomerism of the XPro bond, with Δδ = 3‐5 ppm being characteristic of trans and 7‐11 ppm of cis isomers. However, in the case of solid cyclodipeptides and unprotected dipeptides, the individual crystal lattices also affect the conformation of the side chain, so that the C‐β and C‐γ‐signals are not reliable indicators of the cis/trans isomerism.

When the N‐protected proline derivatives were crystallized slowly from various solvents, the N‐Boc‐ and N‐Z‐proline derivatives exclusively yielded the cis isomer, even when the cis/trans equilibrium in solution favoured the trans isomer. In the case of N‐aminoacylprolines, the trans isomer crystallized almost exclusively. Oligopeptides containing two proline units, such as ZProProOH or ZGlyProGly GlyProAlaOH, may possess a cis and a trans bond in the same molecule.
1H, 13C and 15N NMR observations on the protonation of 1‐ and 3‐deazapurine
Authors: Lindon J. C. , Williams J. M. , Barraclough P.
Published: May 2005

Using 1H, 13C and 15N NMR it has been concluded that 3‐deazarpurine protonates exclusively at N‐1 with a pK of about 5.6. The base exhibits rapid tautomerism with proportions of 70:30, with the N–7‐H tautomer in the majority. The salt exists predominantly as the N‐7‐H tautomer. 1‐Deazapurine protonates essentially in a 1:1 ratio at N‐3 and at the imidazole ring, with a pK of about 3.1. This base also exhibits rapid tautomerism with proportions of 30:70, this time with the N‐9‐H in the majority. The salt also exists in a tautomcric mixture with approximately equal proportions. One form has N‐3 and N‐9 bearing hydrogens and the other has N‐7 and N‐9 bearing hydrogens.
Structure determination of peracetylated glycosphingolipids by one‐ and two‐dimensional 1H NMR at 360 and 500 MHz
Authors: Dabrowski Janusz , Dabrowski Ursula , Hanfland Peter , Kordowicz Maria , Hull William E.
Published: May 2005

The analysis of two‐dimensional proton shift‐correlated 500 MHz NMR spectra of several peracetylated glycosphingolipids confirmed that peracetylated oligosaccharides are particularly well suited for the identification of the constituent sugar residues and the elucidation of the sites of glycosidic linkage. Although a number of partial sequences could be determined by inter‐residue nuclear Overhauser effect or long‐range scalar coupling across the glycosidic bonds, the full sequence determination of larger oligosaccharides has several limitations owing to experimental difficulties and possible ambiguities in assignments due to signal overlap. The following peracetylated glycosphingolipids were investigated by two‐dimensional methods at 500 MHz: Galα(1→4)Galβ(1→4)Glcβ(1→1)Cer (Cer = ceramide), GalNAcβ(1→3)Galα(1→4)Galβ(1→4)Glcβ(1→1) Cer (globoside) and Galα(1→3)Galβ(1→4)GlcNAcβ(1→3)Galα(1→3)Galβ(1→4)GlcNAcβ(1→6)Galβ(1→4)GlcNAcβ(1→3)Galβ(1→4)Glcβ(1→1)Cer. To compare the potential of one‐ and two‐dimensional methods, the spectra of peracetylated Galβ(1→4)Glcβ(1→1)Cer, Galβ(1→4)GlcNAcβ(1→3)Galβ(1→4)Glcβ(1→1)Cer. To compare the potential of one‐ and two‐dimentional methods, the spectra of peracetylted Galβ(1→4) Glcβ(1→1)Cer were assigned with the aid of spin‐decoupling difference spectroscopy at 360 MHz.
Geometry‐dependent complexation effects in 13C NMR spectra of (η6‐[n]paracyclophane)‐chromium and ‐iron complexes
Authors: Mori Nobuo , Takamori Michiko
Published: May 2005

Relationships between molecular geometry and complexation offects in 13C NMR spectra are reported for series of tricarbonyl (η6‐[n]paracyclophane)chromium complexes and (η6‐[n]paracyclophane) (η5‐cyclopentadienyl)iron(II) hexafluorophosphates, where n is 8, 9, 11, 12 and 15. In the Cr complex series in CDCl3, the complexation shift (Δδ) for the aryl tertiary carbon increases with a decrease in n, from 34.5 (n = 15) to 37.9 ppm (n = 8), whereas Δδ for the aryl quaternary carbon decreases from 27.9 to 22.0 ppm. Similar changes in Δδ with n are found in the Fe complex series, except that their Δδ values are larger. This dependence of Δδ on n is directly related to the interatomic distance between the metal and the ligand carbon. In addition, a significant geometry dependence of the complexation effects is observed for the benzylic‐ and the cyclopentadienyl‐carbon resonances, but not for the one bond aryl C–H spin–spin couplings.
Conformational analysis of DL‐, L‐ and D‐methionine by solid‐state 13C NMR spectroscopy
Authors: Díaz Luis E. , Morin Frederick , Mayne Charles L. , Grant David M. , Chang Ching‐jer
Published: May 2005

The conformational analysis of DL‐, L‐ and D‐methionine was studied by solid‐state 13C NMR with the help of cross‐polarization and magic‐angle spinning techniques. The spectrum of commercial crystalline DL‐methionine showed two chemical shifts (18.7 and 15.8 ppm) for the methyl carbon. Crystallization from water or water‐ethanol (95 : 5) allowed the separation of two crystalline forms (α and β), of which one had δ (CH3) 18.7 ppm and the other δ (CH3) 15.8 ppm. Therefore, each crystalline form of DL‐methionine consists of a single conformer, a result in agreement with x‐ray diffraction data. This conformational difference of the two crystalline forms was also reflected in the carbon resonances of C‐β and C‐γ. When L‐ and D‐methionine were crystallized from water‐ethanol (3 : 2), the solid‐state 13C NMR spectra showed that each isomer displayed two methyl carbon peaks at 18.1 and 16.2 ppm of equal intensities, while the α‐carbon resonances showed a broad peak due to two unresolved doublets. These results suggest that the L‐ or D‐methionine crystal contains two different conformers in one unit cell, a conclusion that is also supported by the x‐ray data.
Conformational study of chiral acyclic ketones by 1H and 13C NMR. I. (±)‐2,2,6,6‐tetramethyl‐5‐phenylheptan‐3‐one
Authors: Alvarez‐Ibarra C. , Arias‐Pérez M. S. , de Andrés A , Balcázar J. L.
Published: May 2005

The conformational analysis of a chiral acyclic ketone with one asymmetric carbon, (±)‐2,2,6,6‐tetramethyl‐5‐phenylheptan‐3‐one, has been achieved for the first time by means of an x‐ray diffraction study and the analysis of 1H1H and 13C1H geminal and vicinal coupling constants and 13C1H direct coupling constants. The application of the Durette‐Horton, Pachler and Altona empirical equations supports the hypothesis of a marked predominance in solution of the conformation observed in the solid state.
1H and 13C NMR studies on nitrosonaphthols, and their complexation with the dioxouranium(VI) ion
Authors: Vainiotalo Anto , Vepsäläinen Jouko
Published: May 2005

The 1H and 13C NMR spectra of 1‐nitroso‐2‐naphthol and its disodium 3,6‐disulphonate, 2‐nitroso‐1‐naphthol and its sodium 4‐sulphonate and the complexes of the sulphonated ligands with dioxouranium(VI) were recorded and analysed. The results show the nitrosonaphthols exist predominantly in the oxime form, and that the 1‐nitroso compounds have a preferred structure. The quinonoid oxygen does not take part in the complexation with dioxouranium(VI), which is effected by chelation through the oxime oxygen and nitrogen.
Non‐additive carbon‐13 NMR substituent chemical shifts. II—1,3‐disubstituted benzenes
Authors: Bromilow John , Brownlee Robert T. C. , Craik David J. , Sadek Maruse
Published: May 2005

Aromatic 13C chemical shifts are reported for an extensive set (15 common substituents) of 1,3‐disubstituted benzenes measured at low concentration in deuteriochloroform. The substituent chemical shift data show systematic non‐additivity. Data for the para‐ and two meta‐positions to the variable substituent were analysed using the recently developed non‐linear resonance (DSP‐NLR) and standard (DSP) dual substituent parameter equations. It is shown for these positions that mutual substituent interaction is responsible for the non‐additive shifts and that (a) this interaction has both an inductive (polar) and a resonance component, even for meta‐oriented substituents, and (b) the shift‐charge ratio term extends past the ipso‐position. These results are discussed in terms of local paramagnetic shielding contributions to 13C shifts.
Deuterium isotope effects on the 13C nuclear shielding of intramolecularly hydrogen‐bonded systems
Authors: Hansen Poul Erik
Published: May 2005

A large number of intramolecularly hydrogen‐bonded molecules were investigated by means of deuterium isotope effects on 13C nuclear shielding. The compounds illustrate three different types of molecules: compounds with a localized hydrogen bond (strongly asymmetric double minimum potential), and tautomeric molecules of symmetrical or unsymmetrical nature (symmetrical or almost symmetrical double minimum potential). In the localized case the strength of the hydrogen bond reflects itself in the magnitude of 2Δ COD. The presence of a hydrogen bond is, furthemore, demonstrated in an orientational dependence of 3Δ COD, and usually also in the presence of an 3Δ COD. The tautomeric systems can also be characterized by means of deuterium isotope effects. Investigations of β diketones showed the presence of an equilibrium isotope effect. Large long‐range isotope effects of naphthazarin are explained in a similar manner. Tautomerism was established in usnic acid and the type of tautomerism was determined. 2,6‐Dihydroacetophenone shows an interesting type of perturbation of the equilibrium on unsymmetric deuteriation.
Conformational analysis of a synthetic carboxylic ionophore in solution by 1H NMR spectroscopy
Authors: Kuboniwa Hitoshi , Yamaguchi Kazuo , Hirao Akira , Nakahama Seiichi , Yamazaki Noboru
Published: May 2005

The 1H NMR spectra of the potassium salt of a synthetic polyether carboxylic ionophore, HO[CH2CH2O(1,2‐C6H4)O]4CH2 (1,2‐C6H4)COOH (1), in CDCl3 were assigned by two‐dimensional NMR methods (2D chemical shift correlation and 2D NOE). The gauche conformer about the C—C bond of the 1,2‐dioxyethylene groups of the potassium salt of 1 were found to be predominant from the analysis of the proton‐proton vicinal coupling constants. Based on rotamer population analysis, together with nuclear Overhauser effect data, the preferred conformation of the potassium salt of 1 in the solution was estimated.
Studies on the substituent dependence of 1H chemical shifts. Unusual 1H shifts in trans‐9‐halogenodecalins
Authors: Schrumpf G. , Sanwald W. , Machinek R.
Published: May 2005

The 1H, 2H and 13C spectra of trans‐9‐chloro, ‐bromo‐ and ‐iodo‐decalins and their deuteriated analogues have been recorded in order to study the effect of chloro, bromo and iodo substituents on β antiperiplanar protons. All shifts were completely assigned. Unusually large upfield shifts were detected for β protons antiperiplanar to the halogen substituents. The electronegativity dependence of the β shifts is opposite to that hitherto reported.
13C NMR studies of the friedelane series of triterpenoids and the conformation of the D and E rings in friedelan‐7‐one
Authors: Prakash Om , Roy Raja , Garg H. S. , Bhakuni D. S.
Published: May 2005

The 13C chemical shifts in the spectra of friedelan‐7‐one (1), methyl 3‐oxofriedelan‐25‐oate (2), methyl friedelan‐25‐oate (3), 7‐oxofriedelan‐3‐α‐yl acetate (4), friedelan‐3‐one (5), 2‐hydroxy‐3, 4‐seco‐friedelan‐3‐oic acid (6), methyl 2‐oxo‐3,4‐seco‐friedelan‐3‐oate (7), methyl 2‐hydroxy‐3,4‐seco‐friedelan‐3‐oate (8) and 3,4‐seco‐friedelan‐2,3‐diol (9) have been fully assigned using two‐dimensional heteronuclear correlation NMR spectroscopy, BB proton decoupled, DEPT and selective heteronuclear spin decoupling methods. These assignments and the observation of substantial NOEs between 26‐methyl and 28‐methyl and between 28‐methyl and 30‐methyl support the boat to boat conformations for the D and E rings in 1. Corrections and correlations are made of some earlier literature assignments of friedelanones.
1H NMR parameters of chlorinated biphenyls
Authors: Yanagisawa Masaru , Hayamizu Kikuko , Yamamoto Osamu
Published: May 2005

Complete analyses of the 400 MHz 1H NMR spectra of 47 chlorinated biphenyls (PCBs) were carried out in order to obtain the 1H chemical shifts and coupling constants. The 1H chemical shifts and the coupling constants on the biphenyl ring are interpreted by additive contributions from the substituent effects of chlorine atoms.
Steric effects in the 17O NMR spectroscopy of aromatic methyl ethers
Authors: Wysocki M. A. , Jardon P. W. , Mains G. J. , Eisenbraun E. J. , Boykin D. W.
Published: May 2005

17O NMR spectroscopic data (natural abundance) were obtained for 19 methoxy‐aromatic compounds: a series of substituted anisoles with a single ortho substituent, a series of 2, 6‐disubstituted anisoles, a series of 3‐substituted‐1, 2‐dimethoxybenzenes and three multi‐substituted anisole derivatives. The chemical shifts of the highly hindered methoxy compounds are related to previously reported regiochemistry, spectroscopic results and from theoretical calculations for these compounds.
Stereostructural and NMR study of isomeric oxazines fused to the norbornane or norbornene skeleton
Authors: Sohár Pál , Pelczer István , Stájer Gáza , Bernáth Gábor
Published: May 2005

Norbornane‐ or norbornene‐fused 2‐aryldihydro‐1,3‐oxazines, ‐1,3‐oxazin‐2‐ones and – 1,3‐oxazine‐2‐thiones were synthesized and studied by 1H and 13C NMR spectroscopy to reveal the spectral effects of the saturation of the skeleton, diexo or diendo ring annellation and isomerism in compounds containing the oxygen and nitrogen hetero atoms in isomeric positions.
Use of J‐modulated spin echoes for approximate estimation of one‐bond CH coupling constants in 13C NMR
Authors: Molin Håkan
Published: May 2005

The J‐modulated spin‐echo pulse sequence can be used for the approximate estimation of one‐bond CH coupling constants in complicated spectral regions. The usefulness of this technique for spectral assignment purposes is demonstrated for a beta‐lactam compound.
Determination of the rα structures of ethylene and 1,1‐difluoroethylene by NMR of partially oriented molecules allowing for correlated deformation
Authors: Wasser R , Diehl P
Published: May 2005

The rα structures of ethylene and 1,1‐difluoroethylene have been determined by NMR of partially oriented molecules, considering the interaction between the solute molecule and the liquid crystal solvent which leads to a correlation between molecular vibration and rotation. The analysis of the data also provides the interaction parameters which characterize the torques acting on the individual molecular bonds, deforming and simultaneously orienting the solute. A linear relationship between the interaction parameters for the C  H bonds of the two solutes and methane in the same solvents has been found.
NMR spectra of the porphyrins 32—Conformational analysis of Pyrrolidine and 3‐Hydroxypyrrolidine using CoIII meso‐Tetraphenylporphyrin (CoTPP)
Authors: Abraham Raymond J. , Medforth Craig J.
Published: May 2005

The geometry of pyrrolidine and 3 hydroxypyrrolidine CoTPP complexes has been investigated by 1H NMR spectroscopy. The observed couplings and ring current shifts for pyrrolidine‐CoTPP are consistent with an envelope conformation with the nitrogen atom out of the ring plane and equatorial coordination of the cobalt atom. A complete analysis of the spectrum was not possible owing to close‐coupling of the β‐protons.

For 3‐hydroxypyrrolidine CoTPP two components in the ratio 85 : 15 were observed in the proton spectrum. The spectra of both compounds were completely analysed to give all the couplings in the five‐membered rings, and from these the ring conformations were deduced. The major (endo) component exists in an envelope conformation with C‐2 out of the plane of the other atoms, and the hydroxy group cis to the NH proton, both in pseudo‐axial orientations. The minor (exo) component is also in an envelope conformation, with C‐5 out of the plane of the other atoms and the hydroxyl group now trans to the NH proton.

The energy difference of ca 1 kcal mol−1 (4 kJ mol−1) in favour of the endo component was reproduced by theoretical (MNDO) calculations for protonated hydroxypyrrolidine, but not for the free base. This suggests that the stabilization of the endo component is due to the electrostatic attraction of the hydroxy group and positively charged nitrogen atom.
1,3‐dinitroso‐, 1‐nitroso‐3‐nitro‐, and 1,3‐dinitro‐1,3‐diazacycloalkanes. A multinuclear NMR study
Authors: Willer Rodney L. , Moore Donald W.
Published: May 2005

A series of five‐, six‐, and seven‐membered 1,3‐dinitroso‐, 1‐nitroso‐3‐nitro‐, and 1,3‐dinitro‐1,3‐diazacycloalkanes were investigated by 1H, 13C, and 15N NMR spectroscopy. Hindered rotation of the nitrosamine group leads to the existence of rotational isomers. The relative populations of rotamer forms are determined by steric and electrostatic interactions between nitroso groups and the remainder of the molecule, and by the size of the ring.
Long‐range CH correlation 2D NMR spectroscopy 3—long‐range J modulation of cross‐peak intensities
Authors: Krishnamurthy V. V. , Casida John E.
Published: May 2005

In long‐range heteronuclear chemical shift correlation experiments, modulation of the response intensities of cross‐peaks due to other long‐range couplings to the carbon, although slower than that by direct couplings, must be taken into consideration in optimizing the polarization transfer (Δ1) and refocusing (Δ2) delays. The long‐range modulation is experimentally confirmed using the standard CH correlation pulse sequence with a BIRD pulse midway through the refocusing delay. Analysis of aromatic correlations using hypothetical coupling constants shows that, in general, a choice of Δ2 = 0.667Δ1 is better than Δ2 = Δ1 for CCH correlations, particularly when other interfering long‐range couplings are involved. Guidelines for choosing optimal delays are given by response intensity and attenuation factor contours as a function of J and Δ1 values.
15N NMR spectra of wyosine (Y‐nucleoside) triacetate and its 7‐methyl congener. Chemical shifts and 15N,1H coupling constants
Authors: Glemarec C. , Remaud G. , Chattopadhyaya J.
Published: May 2005

The 15N chemical shifts and 15N,1H coupling constants of wyosine (Y‐nucleoside) triacetate were obtained through both fully proton‐coupled and selectively decoupled 15N NMR spectra at natural isotopic abundance, using modified INEPT pulse sequences. The spectra were analysed for 2J, 3J and 4J(NH) values. The results were compared with those for the parent compounds.
Two‐dimensional POMMIE J(CH)‐resolved 13C NMR spectrum editing. Application to peptide and carbohydrate derivatives
Authors: Coxon Bruce
Published: May 2005

A pulse sequence has been implemented for two‐dimensional POMMIE J(CH)‐resolved 13C NMR spectroscopy and has been used to explore three methods for the automated acquisition of data for two‐dimensional spectrum editing. In the first two methods, sets of three two‐dimensional data matrices are acquired in either sequential or interleaved modes, by use of three values, π = ϕ/6, π/2 and 5π/6, for the phase shift of the multiple quantum read pulse. Computation of linear combinations of these three data matrices by use of a Pascal program that had been written earlier for two‐dimensional DEPT spectrum editing yielded two‐dimensional POMMIE J(CH)‐resolved CH, CH2 and CH3 subspectra. In the third method, these subspectra are constructed directly during acquisition, by rotation of the phase shifts of the multiple quantum read pulse and the receiver. Selected small peptides and carbohydrate derivatives were used as model compounds for this study, and their 1H and 13C NMR assignments were confirmed by two‐dimensional COSY and heteronuclear CH chemical shift correlation techniques. The results show that if appropriate equipment is available, the two‐dimensional POMMIE method is easier to implement for J(CH)‐resolved spectral editing than the two‐dimensional DEPT technique. However, these methods are comparable in their ability to suppress residual signals.
Evaluation of pulse sequences combining 13C‐1H shift correlation and heteronuclear J spectroscopy with full 1H‐1H decoupling
Authors: Perpick‐Dumont Marion , Reynolds William F. , Enríquez Raúl G.
Published: May 2005

Three different two‐dimensional 13C‐1H shift‐correlation sequences which detect 1H chemical shifts and one bond 13C‐1H[J(CH)] couplings in f1 with full 1H‐1H decoupling are described and evaluated. They are particularly useful for detecting small differences in 1J(CH) for non‐equivalent methlene groups in natural products and other complex organic molecules. The best of the three allows determination of 1J(CH) and 1H chemical shifts to a precision better than 1 Hz, with sensitivity comparable to previous shift‐correlation and J‐resolved pulse sequences. 1J(CH) Values for a typical alkaloid suggest that these parameters are a useful probe of conformational, electronic and ring size effects in natural products.
Preparation and carbon‐13 NMR study of 3‐ and 20‐methylene analogues of steroid hormones
Authors: Gonzalez Mario D. , Burton Gerardo
Published: May 2005

20‐Methylpregna‐4,20‐dien‐3‐one and the corresponding 17α‐hydroxy, 20‐hydroxymethyl and 17α‐hydroxy‐20‐hydroxymethyl derivatives were prepared from the 20‐keto compounds by Wittig reaction or a modified Simmons‐Smith reaction. The 13C NMR spectra of these steroids and of 3‐methylene derivatives are analysed. Solvent effects produced by addition of methanol‐d4 in the spectra of the 20‐methylene steroids are correlated with intramolecular hydrogen bonding in the corresponding 20‐ketosteroids.
Further ESR studies of the cyclic sulphur nitride radical S3N2+ with a Q‐band spectrometer
Authors: Johnson K. M. , Preston K. F. , Sutcliffe L. H.
Published: May 2005

From measurements made with both Q‐band and X‐band ESR spectrometers on powder samples enriched in 33S, it has proved possible to establish with improved precision the 33S hyperfine interaction tensors of the cyclic inorganic free radical 1,2,4,3,5,‐trithiadiazolyl,
equation image
. The best set of spectral parameters consistent with all of the data presently available is g = (2.0013, 2.0060, 2.0252), a(215N) = (36.4, <0.5, <0.5) MHz, a(233S) = (108.0, −15, −17.0) MHz and a(133S) = (−37.0, 10, 2) MHz, where tensor components are in the order x, y, z and x is the direction perpendicular to the molecular plane. The anisotropic parts of the hyperfine tensors lead to estimates for the unparied spin population in the atomic px orbitals perpendicular to the atomic plane of 42% (2S), 15% (2N) and (−) 16% (1S). A quadrupolar tensor e2Qq = (±32, ∓28, ∓4) MHz determined for the two equivalent 33S nuclei is consistent with the proposed electronic structure of the free radical.
77Se NMR studies of bis(alkylthio)selenides of biological thiols
Authors: Rabenstein Dallas L. , Tan Khoon‐Sin
Published: May 2005

To determine the feasibility of using 77Se NMR spectroscopy to characterize bis(alkylthio)selenides formed by reaction of selenite with thiol groups of biological molecules, 77Se NMR spectra have been measured for bis(alkylthio)selenides formed by reaction of selenite with cysteine, homocysteine, penicillamine, N‐acetylpenicillamine, 2‐mercaptopropanoic acid, mercaptosuccinic acid, cysteamine and glutathione. The 77Se chemical shift is extremely sensitive to the nature of the alkylthiol group, covering a range greater than 150 ppm for this series of thiols. The chemical shift is also sensitive to the stereochemistry of the alkylthiol group, and resolved resonances are observed for meso and D,L‐stereoisomers, e.g. the meso and D,L‐stereoisomers of bis(cysteine)selenide. 77Se NMR spectra were also measured for mixed bis(alkylthio)selenides (RSSeSŔ) formed by reaction of selenite with two‐component mixtures of the various thiols. The effect of the two alkylthiol groups on the 77Se chemical shift is additive, with 77Se chemical shifts of the mixed bis(alkylthio)selenides located mid‐way between those of the two symmetric compounds. The 77Se chemical shift is also sensitive to the protonation state of carboxylic acid and ammonium groups of the alkylthiol, and pKA values were determined from 77Se chemical shift vs pH titration curves for selected symmetrical and mixed bis(alkylthio)selenides. The results demonstrate that 77Se NMR is a sensitive method for the characterization and study of bis(alkylthio)selenides.