T/CTP

Ribonuc eoside [T CTP synthase 63.4.2 0 Nucleoside phosphate kinase2.Z.4.4... 

FAB has been used to analyse additives in (un) vulcanised elastomer systems [92,94] and FAB matrices have been developed which permit the direct analysis of mixtures of elastomer additives without chromatographic separation. The T-156 triblend vulcanised elastomer additives poly-TMDQ (AO), CTP (retarder), HPPD (antiozonant), and TMTD, OBTS, MBT and A,lV-diisopropyl-2-benzothiazylsulfenamide (accelerators) were studied in three matrix solutions (glycerol, oleic acid, and NPOE) [94]. The thiuram class of accelerators were least successful. Mixture analysis of complex rubber vulcanisates without chromatographic separation was demonstrated. The differentiation of matrix ions from sample ions was enhanced by use of high-resolution acquisition. 

Wieder, T., PerUtz, C., Wieprecht, M., Huang, R.T., Geilenm C.C. and Orfanosm, CR., 1995, Two new sphingomyelin analogs inhibit phosphatidylcholine biosynthesis by decreasing membrane-bound CTP phosphocholine cytidylyltransferase levels in HaCaT cells. Biochem. J. 311 873-879... 

So for each p-substituent we now have available two, alternative, substituent constants—electron-withdrawing substituents or cTp.x and o-p.x for electron-donating substituents— whose use depends on whether through-conjugation between p-substituent and reaction centre does, or does not, take place in a particular reaction. It would be nice to think that these dual substituent constant values would now take care of all eventualities, and an analysis was therefore made of no less than eighty different... 

The transition between the R and T states also involves large changes in the conformation of the r subunits. These changes include both the peripheral domain where CTP or ATP binds and the domain that interfaces with the c subunits (see figs. 9.17 and 9.18). However, it still is not clear how the binding of CTP to the peripheral domain tips the conformational equilibrium in favor of T, whereas ATP,... 

Stevens, R. C., J. E. Gouaux, and W. N. Lipscomb, Structural consequences of effector binding to the T state of aspartate carbamoyltransferase Crystal structures of the unligated and ATP- and CTP-complexed enzymes at 2.6 A resolution. Biochem. 29 7691, 1990. 

CMP-KDO synthetase (cytidine-5 -triphosphate cytidine-5 -mon-ophosphate-3-deoxy-D-manno-octulosonate cytidylyltransferase), the next enzyme in the pathway, catalyzes the formation of the nucleotide sugar, CMP-KDO from CTP and KDO. This enzyme was first studied by Ghalambor and Heath (IT). We have purified this enzyme to homogeneity (27). T i apparent K values for CTP nd KDO in the presence of 10 mM Mg were determined to be 2 x 10 M and 2.9 x 10 M, respectively. The enzy tic reaction was dependent upon the addition of CTP, KDO and Mg but did not require a reducing agent. The formation of CMP-KDO was not inhibited by the addition of CDP, CMP, KDO-8-phosphate or N-acetylneuraminic acid to the complete reaction mixture. In agreement with Ghalambor and Health (17), neither KDO-8-phosphate nor N-acetylneuraminic acid could substitute for KDO in the reaction mixture. Pyrophosphate, one of the end products, is a weak inhibitor of the reaction with an apparent Ijq value of 5.0 mM. The addition of CMP,CD or any of the other mono- or di-nucleotides did not inhibit the reaction. 

Fig. 15b shows the value of the integral and the amplitude 1 - Ctp as function of im, where the latter was determined from a suitable fit of the correlation functions. The good agreement indicates that the amount of correlation lost in the experimental time window provides a measure of the location of Gflg t). We emphasize that these results are not limited to NMR correlation functions, but they show that any time-domain experiment will not provide straightforward access to the mean time constant of a dynamical process that is governed by a distribution G lg t) broader than the experimental time window. 

Table XXII shows some of the parameters used to characterize the microstructure of the combustion wave. In general, the parameters can be divided into two groups. The first group characterizes the shape of the combustion front, and includes the local [F(y,f)] and average [F(r)] front profiles, as well as the front dispersion, CTp, which is a measure of roughness of the combustion front. The second group describes the combustion front propagation at the microscopic level. For this, the instantaneous, U(y,t) and average, U, velocities of the combustion wave, as well as the dispersion of the instantaneous velocities, ar calculated.

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