Search results for "Hydrolysis"
showing 10 items of 632 documents
Selective derivatisations of resorcarenes - 2. Multiple regioselective ring closure reactions
1997
Abstract The condensation of the C-pentyl resorcarene 1 with long chain aliphatic diamines 3a-d and excess formaldehyde leads under high dilution conditions to tetrabenzoxazine derivatives 4a-d in which pairs of adjacent oxazine rings are connected by an aliphatic chain. Six new rings are formed per resorcarene molecule during this reaction in a regioselective way. For one example (4a) the chiral cleft-like structure with C2 symmetry was proved by single crystal X-ray analysis. Hydrolysis of the oxazine rings gives the secondary amine derivatives 5a,b with C2v symmetry in high yield.
The Folding State of the Lumenal Loop Determines the Thermal Stability of Light-Harvesting Chlorophyll a/b Protein
2004
The major light-harvesting protein of photosystem II (LHCIIb) is the most abundant chlorophyll-binding protein in the thylakoid membrane. It contains three membrane-spanning alpha helices; the first and third one closely interact with each other to form a super helix, and all three helices bind most of the pigment cofactors. The protein loop domains connecting the alpha helices also play an important role in stabilizing the LHCIIb structure. Single amino acid exchanges in either loop were found to be sufficient to significantly destabilize the complex assembled in vitro [Heinemann, B., and Paulsen, H. (1999) Biochemistry 38, 14088-14093. Mick, V., Eggert, K., Heinemann, B., Geister, S., and…
Partial vinylphenol reductase purification and characterization from Brettanomyces bruxellensis
2008
International audience; Brettanomyces is the major microbial cause for wine spoilage worldwide and causes significant economic losses. The reasons are the production of ethylphenols that lead to an unpleasant taint described as 'phenolic odour'. Despite its economic importance, Brettanomyces has remained poorly studied at the metabolic level. The origin of the ethylphenol results from the conversion of vinylphenols in ethylphenol by Brettanomyces hydroxycinnamate decarboxylase. However, no information is available on the vinylphenol reductase responsible for the conversion of vinylphenols in ethylphenols. In this study, a vinylphenol reductase was partially purified from Brettanomyces bruxe…
Biologically Active Triterpene Saponins from Callus Tissue of Polygala amarella
1999
A new bioactive saponin (1), together with a known saponin (polygalasaponin XXVIII) has been isolated from the callus tissue culture of Polygala amarella. Based on spectroscopic data, especially direct and long-range heteronuclear 2D NMR analysis and on chemical transformations, the structure of 1 was elucidated as 3-O-beta-D-glucopyranosyl presenegenin-28-O-beta-D-galactopyranosyl-(1 --> 3)-beta-D-xylopyranosyl-(1 --> 4)-alpha-L-rhamnopyranosyl-(1 --> 2)-[beta-D-glucopyranosyl-(1 --> 3)]-beta-D-fucopyranoside. Both saponins showed significant immunological properties based on the enhancement of granulocyte phagocytosis in vitro.
Performance of a series of novel N-substituted acrylamides in capillary electrophoresis of DNA fragments
1996
DNA separations by capillary electrophoresis in viscous solutions of novel polymers, made with Ω-hydroxyl, N-substituted acrylamides (notably N-acryloyl amino propanol, AAP and N-acryloyl amino butanol, AAB) are evaluated. Whereas in standard poly(acrylamide), at 6% concentration, the theoretical plate number (N) does not exceed 500 000, in 6% poly(AAP) N reaches 922 000 and in 6% poly(AAB) N values as high as 1 200 000 are obtained. Also, copolymers of AAP and AAB give N values in excess of 1 million plates. The two novel monomers (AAP and AAB) remain extremely stable during alkaline hydrolysis and display very good hydrophilicity, while being devoid of the noxious habit of auto-polymeriza…
A clean analytical method for the spectrophotometric determination of formetanate incorporating an on-line microwave assisted hydrolysis step
1999
Abstract A fast and completely automated procedure is proposed for the spectrophotometric determination of formetanate in waters by means of its reaction with p-aminophenol (PAP). The method involves the on-line alkaline hydrolysis of formetanate to m-aminophenol (MAP) and its reaction, in the presence of KIO 4 as oxidant agent, with the quinoneimine form of PAP, to form a blue indophenol dye which absorbs at 576 nm. The on-line hydrolysis can be carried out in a 6 m reaction coil located inside the cavity of a domestic microwave oven operated at 650 W, or in a 4 m reaction coil located inside the cavity of a Microdigest 301 microwave system operated at 60 W and allows us, in both cases, a …
1-Naphthyl Acetate-Dependent Medium Acidification by Zea mays L. Coleoptile Segments
1991
Zea mays L. cv INRA 5a coleoptile segments ecidify the incubation medium on the addition of 1-naphthyl acetate (1-NA). The buffering capacity of the bathing solution increases during 1-NA stimulated medium acidification. The solution bathing the 1-NA treated coleoptile segment was analyzed by high performance liquid chromatography. A considerable amount of acetic acid was detected in the bathing solution used to measure 1-NA-dependent medium acidification. For the first time, the data demonstrate directly the release of acetic acid from 1-NA. The extent of medium acidification was proportional to 1-NA concentration. Simultaneous measurement of medium acidification and acetate content upon a…
Classification of vegetable oils according to their botanical origin using n-alkane profiles established by GC-MS.
2013
n-Alkane profiles established by gas chromatography-mass spectrometry (GC-MS) were used to classify vegetable oils according to their botanical origin. The n-alkanes present in corn, grapeseed, hazelnut, olive, peanut and sunflower oils were isolated by means of alkaline hydrolysis followed by silica gel column chromatography of the unsaponifiable fractions. The n-alkane fraction was constituted mainly of n-alkanes in the range C8-C35, although only those most abundant (15 n-alkanes, from 21 to 35 carbon No.) were used as original variables to construct linear discriminant analysis (LDA) models. Ratios of the peak areas selected by pairs were used as predictors. All the oils were correctly …
Screening of acetylcholinesterase inhibitors by CE after enzymatic reaction at capillary inlet.
2009
In this study the development of a procedure based on capillary electrophoresis after enzymatic reaction at capillary inlet methodology for the screening and in vitro evaluation of the biological activity of acetylcholinesterase (AChE) inhibitors is presented. The progress of the enzymatic reaction of the hydrolysis of acetylthiocholine at pH 8 in the presence of AChE and the inhibitor studied is determined by measuring at 230 nm the peak area of the reaction product thiocholine (TCh). In the method employed the capillary was first filled with 30 mM borate-phosphate buffer (pH 8.0) and subsequently, plugs of: (i) water, (ii) AChE solution, (iii) substrate solution with or without inhibitor,…
Stability of levan produced by Zymomonas mobilis
2005
Abstract The stability of levan produced by Zymomonas mobilis 113 “S” was investigated during storage of culture liquid at different pH and temperatures. Levan was not degraded if stored in a culture liquid for 120 h at 30 or 25 °C, but at 55 or 60 °C the degree of degradation was inversely proportional to pH. Cell biomass and levan sediment components did not cause the degradation of levan. The influence of organic acids (lactic-, acetic-, and gluconic) and HCl as levan hydrolyzing agents at pH 3.7, temperature 30 °C or 55 °C was investigated in a model solution. The hydrolytic effect was similar in the case of organic acids—ensuring more fructose formation, while HCl ensured higher amount…