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51.
Lock JS May BL Clements P Lincoln SF Easton CJ 《Organic & biomolecular chemistry》2004,2(9):1381-1386
The preparation of 6(A)-deoxy-6(A)-(6-(2-(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)acetamido)hexylamino)-alpha-cyclodextrin, 3, 6(A)-deoxy-6(A)-(6-(2-(1,4,7,10,13-pentaoxa-16-azacyclooctadecan-16-yl)acetamido)hexylamino)-alpha-cyclodextrin, 4, and their beta-cyclodextrin analogues, 5 and 6, are described. (1)H (600 MHz) ROESY NMR spectra of the C(6) substituted beta-cyclodextrins, 5 and 6, are consistent with the intramolecular complexation of their azacyclopentadecanyl- and azacyclooctadecanyl(acetamido)hexylamino substituents in the beta-cyclodextrin annulus in D(2)O at pD = 8.5 whereas those of their alpha-cyclodextrin analogues, 3 and 4 are not complexed in the alpha-cyclodextrin annulus. This is attributed to the monoazacoronand components of the substituents being able to pass through the beta-cyclodextrin annulus whereas they are too large to pass through the alpha-cyclodextrin annulus. However, the substituents of 3 and 4 are intermolecularly complexed by beta-cyclodextrin to form pseudo [2]-rotaxanes. Metallocyclodextrins are formed by 5 through complexation by the monoazacoronand substituent component for which log (K/dm(3) mol(-1))= <2, 6.34 and 5.38 for Ca(2+), Zn(2+) and La(3+), respectively, in aqueous solution at 298.2 K and I= 0.10 mol dm(-3)(NEt(4)ClO(4)). 相似文献
52.
Abstract Dibutylstannylene acetals, particularly those derived from terminal diols, were found to be oxidized regiospeeifically to α-hydroxyketones in good to excellent yield by N-bromosuccinimide. One of the products, 3-deoxy-l,2-O-isopropylidene-α-D-erythro hexofuranos-5-ulose (8), exists to about 20% in solution as a mixture of dimers. One of the dimers can be obtained as a solid and its structure was determined tentatively by a combination of NMR experiments and MM3 molecular mechanics calculations. 相似文献
53.
54.
Devrishi Goswami Srikripa Devarakonda Michael J. Chalmers Bruce D. Pascal Bruce M. Spiegelman Patrick R. Griffin 《Journal of the American Society for Mass Spectrometry》2013,24(10):1584-1592
Application of typical HDX methods to examine intrinsically disordered proteins (IDP), proteins that are natively unstructured and highly dynamic at physiological pH, is limited because of the rapid exchange of unprotected amide hydrogens with solvent. The exchange rates of these fast exchanging amides are usually faster than the shortest time scale (10 s) employed in typical automated HDX-MS experiments. Considering the functional importance of IDPs and their association with many diseases, it is valuable to develop methods that allow the study of solution dynamics of these proteins as well as the ability to probe the interaction of IDPs with their wide range of binding partners. Here, we report the application of time window expansion to the millisecond range by altering the on-exchange pH of the HDX experiment to study a well-characterized IDP; the activation domain of the nuclear receptor coactivator, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α). This method enabled mapping the regions of PGC-1α that are stabilized upon binding the ligand binding domain (LBD) of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ). We further demonstrate the method’s applicability to other binding partners of the IDP PGC-1α and pave the way for characterizing many other biologically important ID proteins. Figure
? 相似文献
55.
Duc-Truc Pham Philip Clements Christopher J. Easton John Papageorgiou Bruce L. May 《Supramolecular chemistry》2013,25(6):510-519
This study shows that stereochemical factors largely determine the extent to which 6-(4′-t-butylphenylamino)-naphthalene-2-sulphonate, BNS? and its dimer, (BNS? )2, are complexed by β-cyclodextrin, βCD, and a range of linked βCD dimers. Fluorescence and 1H NMR studies, respectively, show that BNS? and (BNS? )2 form host–guest complexes with βCD of the stoichiometry βCD.BNS? (10? 4 K 1 = 4.67 dm3 mol? 1) and βCD.BNS2 2 ? (10? 2 K 2′ = 2.31 dm3 mol? 1), where the complexation constant K 1 = [βCD.BNS? ]/([βCD][BNS? ]) and K 2′ = [βCD. (BNS? )2]/([βCD.BNS? ][BNS? ]) in aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm3 at 298.2 K. (The dimerisation of BNS? is characterised by 10? 2 K d = 2.65 dm3 mol? 1.) For N,N-bis((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)succinamide, 33βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2su, N,N-bis(6A-deoxy-6A-β-cyclodextrin)succinamide, 66βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2ur, and N,N-bis(6A-deoxy-6A-β-cyclodextrin)urea, 66βCD2ur, the analogous 10? 4 K 1 = 11.0, 101, 330, 29.6 and 435 dm3 mol? 1 and 10? 2 K 2′ = 2.56, 2.31, 2.59, 1.82 and 1.72 dm3 mol? 1, respectively. A similar variation occurs in K 1 derived by UV–vis methods. The factors causing the variations in K 1 and K 2 are discussed in conjunction with 1H ROESY NMR and molecular modelling studies. 相似文献
56.
Treatment of trimethylsilyl isocyanate with 15N-hydroxylamine hydrochloride produces 15N-hydroxyurea, a valuable pharmacological tool, in an efficient, one-pot procedure in 74% yield. Recrystallization of the crude product yields analytically pure material in 47% overall yield. 相似文献
57.
In connection with another problem, we required authentic samples of 8-methylsiro[4.5]dec-7-en-6-one (1) and 6-methyl-spire[4.5]dec-6-en-8-one (2). The former compound is not reported in the literature. Although there are two reports of the latter material,1,2 the physical data ascribed to it do not agree. In this communication, we report the synthesis and characterization of the two isomers. 相似文献
58.
Jele Thabisile Brightwell Sithole Bruce Lekha Prabashni Andrew Jerome 《Cellulose (London, England)》2022,29(8):4629-4643
Cellulose - In this study, three different pulp and paper mill sludge (PPMS) samples collected from different South African mills were chemically and physically characterised to investigate their... 相似文献
59.
We report the first measurements and calculations of the intrinsic mobility of bridge-bonded oxygen (BBO) vacancies on a rutile TiO2(110). The sequences of isothermal (340-420 K) scanning tunneling microscope images show that BBO vacancies migrate along BBO rows. The hopping rate increases exponentially with increasing temperature with an experimental activation energy of 1.15 eV. Density functional theory calculations are in very good agreement giving an energy barrier for hopping of 1.03 eV. Both theory and experiment indicate repulsive interactions between vacancies on a given BBO row. 相似文献