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951.
Bradley SA Hu H Krishnamurthy K Hadden CE 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2005,174(1):110-115
We describe a unique band-selective method that utilizes a selective composite gradient to simultaneously achieve band selection and coherence pathway selection. This element is similar to the composite gradient known as the CLUB sandwich except the original broadband pulses have been replaced with selective pulses and the strengths of the antipolar gradients have been unbalanced. In this way, only the signals within the inversion band will continue to dephase throughout the duration of the element and satisfy the proper encoding-to-decoding gradient ratio necessary for coherence selection. Apart from the inverted polarity and asymmetry of the gradients, the band-selective CLUB sandwich is identical to the DPFGSE sequence and provides many of its desirable characteristics. We have successfully incorporated the band-selective CLUB into the DQF-COSY pulse sequence to create a band-selective experiment that offers the selectivity desired for resolution enhancement while maintaining excellent phase behavior. This is demonstrated on the congested aliphatic region of the ionophorous antibiotic Lasalocid A. 相似文献
952.
Díaz-Mochón JJ Bialy L Keinicke L Bradley M 《Chemical communications (Cambridge, England)》2005,(11):1384-1386
Enzymatic modifications of split and mix libraries were followed by "pulling down" onto a 2-dimensional DNA microarray, via PNA tagging; this allowed complete library interrogation of all members of the split and mix library. 相似文献
953.
Murphy AT Brown-Augsburger P Yu RZ Geary RS Thibodeaux S Ackermann BL 《European journal of mass spectrometry (Chichester, England)》2005,11(2):209-215
A quantitative method for the determination of a partially modified, 2'-ribose alkoxy 18-mer phosphorothioate oligonucleotide, in liver tissue has been developed. A liquid:liquid extraction, ion-pair reverse phase chromatographic separation, and tandem mass spectrometry were used to achieve a quantitation range of 125 to 10,000 ng g(-1) mouse liver tissue. A total cycle time of 5 min was obtained while maintaining separation of three potential impurities. Separations were performed using a Discovery RP-Amide C16, 100 x 2 mm column packed with 5 microm particles. The separation was facilitated by the use of triethylamine (TEA) and hexafluoroisopropanol (HFIP) as ion-pair agents. The method has subsequently been used for the determination of other phosphorothioate oligonucleotides in support of discovery research. 相似文献
954.
Richard C. Bradley 《Journal of Theoretical Probability》2001,14(3):717-727
A strictly stationary, countable-state Markov chain is constructed which is -mixing (with arbitrarily fast mixing rate) but fails to be *-mixing (interlaced-mixing). 相似文献
955.
[reaction: see text]. The Ugi reaction has been used to prepare divalent galactose derivatives. NMR analysis shows that a divalent neoglycoconjugate, where the glycopeptides are bridged by a terephthaloyl group, is an 83:17 mixture of two conformers; the amide groups of the major isomer have E-anti conformations. The spatial relationship and the relative orientation of the sugars are restricted, which may have consequences for the recognition of this and related structures in biological systems. 相似文献
956.
Structure/activity study of tris(2-aminoethyl)amine-derived translocases for phosphatidylcholine 总被引:1,自引:0,他引:1
Boon JM Lambert TN Smith BD Beatty AM Ugrinova V Brown SN 《The Journal of organic chemistry》2002,67(7):2168-2174
Sulfonamide and amide derivatives of tris(aminoethyl)amine (TREN) are known to facilitate phospholipid translocation across vesicle and erythrocyte membranes; that is, they act as synthetic translocases. In this report, a number of new TREN-based translocases are evaluated for their abilities to bind phosphatidylcholine and translocate a fluorescent phosphatidylcholine probe. Association constants were determined from (1)H NMR titration experiments, and translocation half-lives were determined via 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)/dithionite quenching assays. A rough correlation exists between translocase/phosphatidylcholine association constants and translocation half-lives. The tris-sulfonamide translocases are superior to the tris-amide versions because they associate more strongly with the phospholipid headgroup. The stronger association is due to the increased acidity of the sulfonamide NHs as well as a molecular geometry (as shown by X-ray crystallography) that is able to form tridentate complexes with one of the phosphate oxygens. Two fluorescent translocase analogues were synthesized and used to characterize membrane partitioning properties. The results indicate that the facilitated translocation of phospholipids by TREN-derived translocases is due to the formation of hydrogen-bonded complexes with the phospholipid headgroups. In the case of zwitterionic phosphatidylcholine, it is the neutral form of the translocases that rapidly associates with the phosphate portion of the phosphocholine headgroup. Complexation masks the headgroup polarity and promotes diffusion of the phospholipid-translocase complex across the lipophilic interior of the membrane. 相似文献
957.
Resin supported diazonium salts were synthesised. These were observed to be stable to storage and to provide a convenient means of compound handling and were employed in the solution synthesis of a 6 x 6 azo dye library. 相似文献
958.
959.
Arnold U Hinderaker MP Nilsson BL Huck BR Gellman SH Raines RT 《Journal of the American Chemical Society》2002,124(29):8522-8523
beta-Amino acids are incorporated into an enzyme by using the method of expressed protein ligation. In the resulting semisynthetic enzyme, an R-nipecotic acid-S-nipecotic acid module replaces Asn113 and Pro114 of ribonuclease A. The semisynthetic enzyme not only retains full catalytic activity but also gains conformational stability. Thus, structural elements can be replaced with foldameric equivalents to endow proteins with more desirable properties. 相似文献
960.
A `biocompatible' safety-catch linker based on an internal diketopiperazine release has been developed to allow the release of amine based compounds. The synthesis of the linker and its pre-loading with a representative set of amines is described. After immobilization onto an amino Tentagel resin, the linker was activated and the amines were released under biological conditions at pH 8. 相似文献