The methyl chloride metabolism of the homoacetogenic, methyl chloride-utilizing strain MC was investigated with cell extracts and cell suspensions of the organism. Cell extracts were found to contain all enzyme activities required for the conversion of methyl chloride or of H2 plus CO2 to acetate. They catalyzed the dechlorination of methyl chloride with tetrahydrofolate as the methyl acceptor at a rate of 20 nmol/min × mg of cell protein. Also, the O-demethylation of vanillate with tetrahydrofolate could be measured at a rate of 40 nmol/min × mg. Different enzyme systems appeared to be responsible for the dehalogenation of CH3Cl and for the O-demethylation of methoxylated aromatic compounds, since cells grown with methoxylated aromatic compounds exhibited a significantly lower activity of CH3Cl conversion than methyl chloride grown cells and vice versa. In addition, ammonium thiocyanate (5 mM) completely inhibited CH3Cl dechlorination, whereas the consumption of vanillate was not affected significantly. The data were taken to indicate, that the methyl chloride dehalogenation is catalyzed by a specific, inducible enzyme present in strain MC, and that tetrahydrofolate rather than the corrinoid-protein involved in acetate formation is the primary acceptor of the methyl group in the dechlorination reaction. 相似文献
A nonradioactive labelling and detection method for plant genomic DNA analysis is compared to the radioactive method. The radioisotopes are replaced by a nucleotide, digoxigenin-11-dUTP, and the signal detection is accomplished by the enzymatic reaction of alkaline phosphatase, conjugated to anti-digoxigenin antibodies, with the chemiluminescent substrate AMPPD (3-(2-spiroadamantane)-4-methoxy-4(3 phosphorytoxy) phenyl-1, 2-dioxetane). The sensitivity of the radioactive and nonradioactive methods are directly compared using identical Southern blots subjected to the radioactive and nonradioactive detection. The advantages of this nonradioactive method are discussed. 相似文献
Type B aortic dissection (TBAD) carries a high risk of complications, particularly with a partially thrombosed or patent false lumen (FL). Therefore, uncovering the risk factors leading to FL thrombosis is crucial to identify high-risk patients. Although studies have shown that morphological parameters of the dissected aorta are related to FL thrombosis, often conflicting results have been reported. We show that recent models of thrombus evolution in combination with sensitivity analysis methods can provide valuable insights into how combinations of morphological parameters affect the prospect of FL thrombosis. Based on clinical data, an idealized geometry of a TBAD is generated and parameterized. After implementing the thrombus model in computational fluid dynamics simulations, a global sensitivity analysis for selected morphological parameters is performed. We then introduce dimensionless morphological parameters to scale the results to individual patients. The sensitivity analysis demonstrates that the most sensitive parameters influencing FL thrombosis are the FL diameter and the size and location of intimal tears. A higher risk of partial thrombosis is observed when the FL diameter is larger than the true lumen diameter. Reducing the ratio of the distal to proximal tear size increases the risk of FL patency. In summary, these parameters play a dominant role in classifying morphologies into patent, partially thrombosed, and fully thrombosed FL. In this study, we point out the predictive role of morphological parameters for FL thrombosis in TBAD and show that the results are in good agreement with available clinical studies.
A complete series of terminally blocked, monodispersed homo-oligopeptides (to the pentamer level) from the sterically demanding, medium-ring alicyclic Cα,α-disubstituted glycine 1-aminocyclooctane-1-carb oxylic acid (Ac8c), and two Ala/Ac8c tripeptides, were synthesized by solution methods and fully characterized. The preferred conformation of all the oligopeptides was determined in deuterochloroform solution by IR absorption and 1H-NMR. The molecular structures of the amino acid derivative Z-Ac8c-OH, the dipeptide pBrBz- (Ac8c)2-OH and the tripeptide pBrBz-(Ac8c)3-OtBu were assessed in the crystal state by X-ray diffraction. Conformational energy computations were performed on the monopeptide Ac-Ac8c-NHMe. Taken together, the results obtained strongly support the view that the Ac8c residue is an effective β-turn and helix former. A comparison is also made with the conformational preferences of α-aminoisobutyric acid, the prototype of Cα, α-disubstituted glycines, and of the other members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n=3, 5–7) investigated so far. The implications for the use of the Ac8c residue in peptide conformational design are considered. 相似文献
The assembly of helical and -sheet peptide blocks containing reactive chain ends results inhighly branched chain architectures (locked-in folds) mimicking native tertiary structures.This molecular kit strategy allows to bypass the protein folding problem in protein de novodesign and gives access to protein mimetics of high thermodynamic stability. The validity ofthis concept is exemplified for the design and synthesis of locked-in folds mimicking the zincfinger and MHC folding motifs. 相似文献