Magnetic resonance imaging of spatially resolved acrylamide photopolymerizationLees, Tom J.; Balcom, Bruce J.
doi: 10.1002/mrc.1175pmid: N/A
Magnetic resonance imaging was employed to examine spatially and temporally resolved photopolymerization of acrylamide gels. Fast exchange between free and bound water results in single exponential T2 decay, where 1/T2 scales linearly with polymer concentration. Measured T2s are sensitive to the experimental conditions; however, the 1/T2 relationship to polymer concentration allows a straightforward interpretation of image contrast changes during photopolymerization. The polymer appears to form at a nearly constant rate until the monomer concentration is significantly depleted. Conventional spin‐echo images and quantitative CPMG‐weighted spin‐echo images were acquired. Photopolymerization of a partially masked sample produced a sharp transition (1 mm width) between polymer and monomer regions of the sample. The image intensity is uniform throughout the illuminated region of the sample, indicating uniform polymer formation. Interrupting the illumination quenches polymer formation. Copyright © 2003 John Wiley & Sons, Ltd.
Proton high‐field NMR study of tomato juiceSobolev, Anatoli P.; Segre, Annalaura; Lamanna, Raffaele
doi: 10.1002/mrc.1176pmid: N/A
A detailed analysis of the proton high‐field (600 MHz) NMR spectra of tomato juice and pulp is reported for the first time. A combination of J‐resolved, COSY, TOCSY, DOSY, 1H–13C HSQC and 1H–13C HMBC 2D sequences was used to assign each spin system and to separate the components of the complex patterns in the 1D overlapped proton spectra. To obtain resolved proton spectra of tomato pulps the high‐resolution magic angle spinning technique was used; a comparison with the liquid‐state NMR spectra of the corresponding juices was accomplished. On the basis of the assignments made, the chemical composition of tomato juices from two cultivars (Red Setter and Ciliegino) was determined. Copyright © 2003 John Wiley & Sons, Ltd.
Conformational studies of novel estrogen receptor ligands by 1D and 2D NMR spectroscopy and computational methodsSebag, Albert B.; Hanson, Robert N.; Forsyth, David A.; Lee, Choon Young
doi: 10.1002/mrc.1150pmid: N/A
The solution conformations of the novel estrogen receptor ligands (17α,20E)‐(p‐trifluoromethylphenyl)vinylestradiol (1) and (17α,20E)‐(o‐trifluoromethylphenyl)vinylestradiol (2) were investigated in 2D and 1D NOESY studies and by comparison of 13C NMR chemical shifts with theoretical shieldings. The 1H and 13C assignments of 1 and 2 were determined by DEPT, COSY and HMQC experiments. The conformations of the 17α‐phenylvinyl substituents of 1 and 2 are of interest because of their differing receptor binding affinities and effects in in vivo uterotrophic growth assays. A statistical method of evaluating contributing conformers of 1 and 2 from predicted 13C shifts of possible structures correlated fairly well with conformational conclusions derived from the NOE data. The 17α substituents of 1 and 2 apparently exist in similar conformational equilibria, suggesting that while 1 and 2 would occupy a similar receptor volume, interactions with the protein may shift the equilibrium and thereby influence the expression of the ligand. Copyright © 2003 John Wiley & Sons, Ltd.
1 H and 13 C NMR signal assignments of carboxyl‐linked glucosides of bile acidsIida, Takashi; Kakiyama, Genta; Shimada, Akari; Mushiake, Kumiko; Mano, Nariyasu; Goto, Junichi; Nambara, Toshio
doi: 10.1002/mrc.1173pmid: N/A
Complete 1H and 13C resonance assignments were carried out for a new type of carboxyl‐linked glucosides of chenodeoxycholic (3α,7α‐dihydroxy‐5β‐cholan‐24‐oic) and hyodeoxycholic (3α,6α‐dihydroxy‐5β‐cholan‐24‐oic) acids by using several homonuclear (1H–1H) and heteronuclear (1H–13C) 2D NMR techniques. Differences in the 1H and 13C resonances between the α‐ and β‐anomers of the ester glucosides of bile acids were clarified for the first time. A comparison of the 1H and 13C signal shifts induced by β‐D‐glucosidation at the 24‐carboxyl and 3α‐hydroxyl groups in the parent 5β‐cholanoic acid was also made. Copyright © 2003 John Wiley & Sons, Ltd.
Structure elucidation of a novel ring‐constrained biaryl pyrazole CB 1 cannabinoid receptor antagonistFrancisco, Ma. Elena Y.; Burgess, Jason P.; George, Clifford; Bailey, Gregory S.; Gilliam, Anne F.; Seltzman, Herbert H.; Thomas, Brian F.
doi: 10.1002/mrc.1174pmid: N/A
Upon irradiation with a 450 W high‐pressure mercury lamp, the CB1 cannabinoid antagonist N‐(piperidinyl)‐5‐(4‐chlorophenyl)‐1‐(2,4‐dichlorophenyl)‐4‐methyl‐1H‐pyrazole‐3‐carboxamide (SR14‐1716; 1) undergoes a photocyclization reaction to yield a single reaction product. This product, 2, the structure of which is based on a pyrazolo(1,5‐f)phenanthridine ring system, was established by two‐dimensional NMR techniques (COSY, HSQC, HMBC and ROESY), and was later confirmed by single‐crystal x‐ray diffraction analysis. The crystal structure shows two independent molecules of 3 and a half molecule of the 1,2‐dichloroethane solvate. Compound 2 has reasonably high affinity for the CB1 receptor (Ki = 48.0 ± 2.7 nM). Copyright © 2003 John Wiley & Sons, Ltd.
Substituent effects on 13 C chemical shifts of ketenimines: a GIAO/HF and DFT studyTahmassebi, Daryoush
doi: 10.1002/mrc.1171pmid: N/A
GIAO/HF and DFT methods were utilized to predict the 13C chemical shifts of substituted ketenimines. GIAO HF/6–311+G(2d,p) and B3LYP/6–311+G(2d,p) methods were applied on the optimized B3LYP/6–31G(d) geometries and 13C chemical shifts of Cα and Cβ of substituted ketenimines were correlated with group electronegativities. HF and DFT calculations indicated that increasing substituent group electronegativity leads to increasing chemical shift of Cβ of substituted ketenimines, whereas the Cα values decrease. Copyright © 2003 John Wiley & Sons, Ltd.