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41.
Hegedus LS Geisler L Riches AG Salman SS Umbricht G 《The Journal of organic chemistry》2002,67(22):7649-7655
Butenolides 5a and 13 were used as optically active templates in the de novo synthesis of 4'-disubstituted nucleoside analogues. The butenolides were reduced and acylated in situ to give acetates 10 and 14. Vorbrüggen coupling gave the protected nucleoside analogues 11 and 15. Reduction of 11 gave 4'-ethoxy-2',3'-dideoxythymidine (6) and deprotection of 15 gave 4'-ethoxy-2',3'-dideoxydidehydrothymidine (7). The cis-dihydroxylation of a variety of butenolides occurred with the major product formed from oxidation of the beta-face. 相似文献
42.
In order to determine the effect of airborne emission of trace elements, e.g. Br, Rb Cs, Sc and Na on roadside ecosystem, concentrations were determined in different species of plants from an urban park at Lahore. For monitoring purpose attention was paid to the leaves ofSapindus mukorossis, Alstonia scholaris andDiospyros embryopteris. Different varieties of tissues were found to have different concentration of trace elements when compared among themselves. The concentration of trace element deposition was compared with the values reported in literature. Significant pollution was observed. 相似文献
43.
Khan KM Shujaat S Rahat S Hayat S Atta-ur-Rahman Choudhary MI 《Chemical & pharmaceutical bulletin》2002,50(11):1443-1446
Eight new beta-N-substituted acyl hydrazides along with their corresponding acyl derivatives were synthesized and screened for in vitro beta-glucuronidase inhibition and found to be active against the enzyme. All of these compounds were found to be noncompetitive inhibitors except for N'-(2-cyanoethyl)-4-hydroxy benzohydrazide (10), which was found to be an uncompetitive inhibitor. Structure-activity relationship studies indicated that the benzyloxy group present in compounds 12 and 13 is responsible for the beta-glucuronidase inhibition activity. 相似文献
44.
Lee BS Krishnanchettiar S Lateef SS Lateef NS Gupta S 《Rapid communications in mass spectrometry : RCM》2005,19(18):2629-2635
A method, which utilizes microwave-assisted partial acid hydrolysis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), to elucidate oligosaccharide composition of intact glycoproteins is presented here. Glycoproteins, such as ribonuclease B, avidin, alpha1-acid glycoprotein, and fetuin, are used as model systems to demonstrate this technique. Partial cleavage of oligosaccharides from whole intact glycoproteins with trifluoroacetic acid was observed after a short exposure to microwaves. Due to the high-resolution mass spectra obtained by MALDI-TOFMS from glycoproteins with molecular weights less than 20 kDa, the compositions of oligosaccharides are readily derived for ribonuclease B and avidin. The data agree with the proposed oligosaccharide structures of ribonuclease B (five glycoforms) and avidin (eight glycoforms). Larger glycoproteins such as alpha1-acid glycoprotein (many glycoforms) and fetuin (many glycoforms) exhibited only broad peaks with no glycoform resolution. Nevertheless, this method can be used successfully for analysis of glycoproteins with molecular weights greater than 20 kDa to determine the presence or absence of glycosylation. 相似文献
45.
Balest R Cho K Daoudi M Ford WT Johnson DR Lingel K Lohner M Rankin P Smith JG Alexander JP Bebek C Berkelman K Bloom K Browder TE Cassel DG Cho HA Coffman DM Drell PS Ehrlich R Gaiderev P Garcia-Sciveres M Geiser B Gittelman B Gray SW Hartill DL Heltsley BK Jones CD Jones SL Kandaswamy J Katayama N Kim PC Kreinick DL Ludwig GS Masui J Mevissen J Mistry NB Ng CR Nordberg E Patterson JR Peterson D Riley D Salman S Sapper M Würthwein F Avery P Freyberger A Rodriguez J Stephens R Yang S Yelton J 《Physical review letters》1994,72(15):2328-2331
46.
Acosta D Athanas M Masek G Paar H Bean A Gronberg J Kutschke R Menary S Morrison RJ Nakanishi S Nelson HN Nelson TK Richman JD Ryd A Tajima H Schmidt D Sperka D Witherell MS Procario M Yang S Balest R Cho K Daoudi M Ford WT Johnson DR Lingel K Lohner M Rankin P Smith JG Alexander JP Bebek C Berkelman K Besson D Browder TE Cassel DG Cho HA Coffman DM Drell PS Ehrlich R Galik RS Garcia-Sciveres M Geiser B Gittelman B Gray SW Hartill DL Heltsley BK Jones CD Jones SL Kandaswamy J Katayama N Kim PC 《Physical review D: Particles and fields》1994,49(11):5690-5700
47.
In solution, the [(tim)Co](2+) complex (tim = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) reacts only slowly with O(2), but upon adsorption on graphite electrodes, it becomes an active catalyst for the reduction of O(2) to H(2)O(2). The electroreduction of O(2) proceeds in a single voltammetric step at close to the diffusion-controlled rate at a relatively positive potential (0.25 V vs SCE). The remarkable enhancement in catalytic activity is attributed to a higher affinity for O(2) of the adsorbed complex as a result of its interactions with functional groups on the surface of roughened or oxidized graphite. A possible mechanism for the catalytic reduction of O(2) is proposed. It differs from the one employed by the analogous [(hmc)Co](2+) complex (hmc = C-meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) which operates at less positive potentials and exhibits two separated voltammetric steps in the reduction of O(2), via [(hmc)CoOOH](2+), to H(2)O(2). 相似文献
48.
I. Ihsanullah Y. Iqbal T. N. Khattak 《Journal of Radioanalytical and Nuclear Chemistry》2005,266(2):361-366
Summary Date samples were irradiated with different doses using a gamma-irradiator. Levels of moisture, protein, fibre and fats were
determined on monthly basis for 5 months. Generally, the moisture contents of control date samples packed in white polythene
decreased from 14.1±1.1 to 9.7±0.8% over a 5-month period while the irradiated samples were in the range of 10.4-11.2%, however,
no proper pattern of change was observed. After 5-month storage, the protein level of irradiated samples was reduced to 1.00-1.30%,
while the percent fibre levels were found to be in the range of 2.40-2.48. Similarly, the fat level decreases from 1.06±0.12
to 0.68±0.06 for control date sample while after 5-month the decrease in fat content was 0.45±0.04%, 0.44±0.04%, 0.44±0.05%,
0.42±0.05% and 0.40±0.04% for samples irradiated with 20, 50, 100, 200 and 300 krads, respectively. 相似文献
49.
John R. Beswick W. David Cotterill Muhammad Iqbal Robert Livingstone 《Journal of heterocyclic chemistry》1993,30(3):623-626
Reaction between some naphtho[2,1-b]pyrans and 1,1-diphenylethene affords 9,9-diphenyl-1,9,10,10a-tetrahydro-2H-phenaleno[1,9-bc]pyrans. 相似文献
50.
Bao‐Shiang Lee Sangeeth Krishnanchettiar Syed Salman Lateef Nabila Salman Lateef Shalini Gupta 《中国化学会会志》2006,53(3):745-750
Avidin functional affinity electrophoresis (AFAEP) is substituted for an avidin affinity column (AAC) to capture biotinylated peptides in the Isotope‐Coded Affinity Tagging (ICAT) technique which is a valuable tool in quantitative proteomics. In this new technique, the AFAEP‐captured ICAT‐labeled biotinylated peptides are extracted with the biotin tag intact from the polyacrylamide gel piece with aqueous 95% formamide (pH 8.2) at 65 °C for 20 min, and then detected by a matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometer. Bovine serum albumin (BSA) and the 12C‐ and 13C‐ICAT reagents are used to test this AFAEP‐ICAT technique. The results show that both AFAEP and AAC methods provide quantitative information of the relative amounts of 12C‐ and 13C‐ICAT‐labeled biotinylated tryptic peptides of BSA in a sample. Compared with AAC, the AFAEP is cheaper to perform, more stringent in capturing the biotinylated peptides, and capable of simultaneously processing multiple samples. 相似文献