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981.
P. Forgacs J. Provost A. Touche D. Guenard C. Thal J. Guilhem 《Tetrahedron letters》1985,26(29):3457-3460
From the trunk bark of Odyendea gabonensis (Pierre) Engl. Simaroubaceae, two-new quassinoids have been isolated : Odyendane and Odyendene. Their structures were established from spectral data and X-Ray diffraction analysis. 相似文献
982.
Analysis of the globins from fast human haemoglobins by isoelectrofocusing on polyacrylamide gel rods 总被引:2,自引:0,他引:2
M Castagnola P Caradonna L Cassiano C Degen F Lorenzin D Rossetti M L Salvi 《Journal of chromatography. A》1984,307(1):91-102
The globins from all fast haemoglobin (Hb) components obtainable by Bio-Rex 70 cation-exchange chromatography were examined by isoelectrofocusing on polyacrylamide gel rods with 8.0 mol/l urea. From this analysis HbA1a1 and HbA1a2 seem to be very heterogeneous components. HbA1b is separable into two components, one of which is varied in both the beta chains. Between HbA1b2 and the well-known HbA1c components two chromatographic peaks are separated, one with a noticeable percentage of glucosylated beta chain and one that probably contains HbF. HbA1c has both beta chains glucosylated, while HbA1x seems to be a beta monoglucosylated Hb form. Finally, the early part of the HbAo peak has a large amount of glucosylation on both alpha and beta chains. 相似文献
983.
984.
Mitsunobu's method of acetoacetic ester alkylation by -nitrophenyl-ethanol avoid the SRN1 reaction and is well appropriate for the correlation of absolute configuration and of the O and C alkylation products. 相似文献
985.
A study has been made of the nuclear quadrupole double resonance (NQDR) spectrum of deuterium in a powdered sample of potassium dihydrogen phosphate, KH2PO4 or KDP for short, both as a function of temperature and of percentage deuteration. Double transitions have also been observed and these enable the orientation of the ferroelectric electric field gradient (EFG) tensor to be determined. 相似文献
986.
Amyloglucosidase was immobilized onto granular chicken bone (BIOBONE?) by noncovalent interactions. The amount of activity bound relative to an equal amount of free enzyme was 13.6 ?0.4%. The estimated specific activity for amyloglucosidase decreased from 75.3?0.8 to 43.5 ?9.6 U/mg protein upon immobilization. TheKm value of the bone-immobilized enzyme using glycogen as substrate increased from 3.04?0.38 mg/mL (free) to 9.04? 1.51 mg/mL (immobilized), butKm showed no change upon immobilization when starches were used as substrates. A decrease in Vmax values occurred upon enzyme immobilization for all substrates, but this largely reflected the percentage of enzyme initially bound to the bone. Immobilization also improved enzyme stability in the presence of various additives (e.g., detergent, KC1, and ethanol) or under low or high pH reaction conditions. Bound amyloglucosidase maintained high activity (>90%) following five cycles of continuous use at moderate (23 ?C) and high (55?C) temperatures. Data derived from Lineweaver-Burk and Arrhenius plots indicated that substrate and product diffusion limitation were minimal. 相似文献
987.
Allylsilanes show in certain cases a behaviour towards electrophiles which is opposite to that of its carbon homologues. Theoretical calculations using Dewar's MINDO/3 method performed on 3-methyl 3-butenyl trimethylsilane and 2-methyl 2-butene show that geometrical optimization leads to a silicon-allylic carbon bond nearly parallel to the double bond π cloud, and both net atomic charges and HOMO coefficients indicate an inversion between these two substrates. 相似文献
988.
The variation of the electroactivity range with composition of water+ sulphuric acid mixtures has been studied. It is shown that ferrocene provides a reference potential independent of solvent at low H2SO4 contents while polynuclear hydrocarbons fulfill the same function at high H2SO4 contents. Water+H2SO4 mixtures become more oxidizing (reduction limit) and less reducing (oxidation limit) when the H2SO4 concentration increases. 相似文献
989.
The number of products and the H2/CH4 ratio obtained from the flow pyrolyses of (CH3)3GeH and (CH3)3SiH were very different. The (CH3)3GeH decomposition is consistent with the following mechanism:
The pyrolysis of (CH3)3SiH was found to be much more complex, presumably due to the formation of silicon-carbon double bonded intermediates and the (CH3)2Si(H)CH2 radical. We also present data which supports the presence of a H atom chain sequence during this pyrolysis. 相似文献
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990.
3-methylenebicyclo[2,2,1]heptane-2,6-carbolactone (previously incorrectly claimed) has now been prepared and converted to the 3-oxo-lactone. Some 3-hydroxy-bicyclo-[2,2,1]heptane-2,6-carbolactones have been prepared and their rates of oxidation with chromic acid determined. The results do not support a theory about the mechanism of oxidation, involving a dipolar interaction from the lactone. 相似文献