Pulsed alkylation

MALDI Pulsed alkylation, study of protein folding Apuy et al. [383]... 

MALDI Ratiometric pulsed alkylation of a protein that interacts with toxic metals Apuy et al. [385]... 

Apuy, J.L., Park, Z.-Y, Swartz, P.D., Dangott, L.J., Russell, D.H., Baldwin, TO. (2001) Pulsed-alkylation Mass Spectrometry for the Study of Protein Folding and Dynamics Development and Application to the Study of a Folding/Unfolding Intermediate of Bacterial Luciferase. Biochemistry 40 15153-15163. 

Apuy, J.L., Busenlehner, L.S., Russell, D.H., Giedroc, D.R (2004) Ratiometric Pulsed Alkylation Mass Spectrometry as a Probe of Thiolate Reactivity in Different Metalloderivatives of Staphylococcus aureus pI258 CadC. Biochemistry 43 3824-3834. 

Studies have been carried out on the methylated complex [H3C-Niin(17)(H20)]2+, which is obtained from the reaction of methyl radicals (generated by pulse radiolysis) with [Ni(17)]2+. The volumes of activation are consistent with the coherent formation of Ni—C and Ni—OH2 bonds, as expected for the generation of a Ni111 complex from a square planar Ni11 precursor.152 The kinetics of reactions of [H3C-Niin(17)(H20)] + involving homolysis, 02 insertion and methyl transfer to Crn(aq) have been determined, and intermediates have been considered relevant as models for biological systems.153 Comparing different alkyl radicals, rate constants for the... 

Subczynski, W. K., J. S.Hyde, and A. Kusumi. 1991. Effect of alkyl chain unsaturation and cholesterol intercalation on oxygen transport in membranes A pulse ESR spin labeling study. Biochemistry 30 8578-8590. 

Yin, J.-J. and W. K. Subczynski. 1996. Effect of lutein and cholesterol on alkyl chain bending in lipid bilayers A pulse electron paramagnetic resonance spin labeling study. Biophys. J. 71 832-839. 

Triflic acid has also been supported on a porous silica carrier (220). The authors emphasized the importance of a strong interaction between the acid and the support to prevent leaching of the acid. In pulsed liquid-phase isobutane/ 1-butene alkylation experiments at 298 K, the catalysts produced a very high-quality alkylate, made up almost exclusively of isooctanes. With silanol groups on the silica surface or with added water, triflic acid was found to form a monohydrate that was firmly grafted to the silica surface. 

FDMR has also been used to detect the transient radical cations formed from secondary amines by pulse radiolysis. As mentioned earlier this technique has been used to study a variety of systems such as the radical cation of triethylamine. The radical cations of diethylamine, n-propyl amine and f-butylamine, have also been studied25. The results have shown that the FDMR signal is enhanced with increasing alkyl substitution of the amine as in the pyrrolidines (18) and the piperidines (19)25. 

Indoles can be also be converted into their radical cations by the use of C1C>2 as the oxidant produced by pulse radiolysis. From the reactivity of the resultant cation it was possible to establish the one-electron reduction potential of the indole in question. Typical results from this are illustrated in Table 234. As can be seen, the one-electron reduction potential is influenced by alkyl substitution. 

Dynamic motion of the alkyl stationary phases can also be obtained from NMR studies through an analysis of line shapes, comparisons between single-pulse (SP) and CP-MAS spectra, and various relaxation time constants. Zeigler and Maciel... 

For those systems where Ri = R2 = H or Ri = H, R2 = CH3, i.e. where the number of alkyl groups at C, is <1, and R3 = H to NO3, the alkoxynitroxyl radicals formed according to Eq. 7 under steady-state-ESR or pulse radiolysis conditions do not give rise to nitrobenzene radical anions. This means that the rate constants for heterolysis of the nitroxyls are < 10 s . This is not only true in weakly acidic (pH 4) or neutral but also in strongly alkaline solution (pH 13-14). The latter observation means that the nitroxyls are not susceptible to base catalyzed heterolysis. From this the rate constant for OH catalyzed decomposition can be estimated to be < 10 M s [19]. This low number for... 

The polymerization of ethylene was also qualitahvely inveshgated by pulse injec-hons of ethylene into helium flowing over thorium (67) and uranium (86) metallocene hydrocarbyl complexes supported on 7-AI2O3.950 at 25 °C, both revealing similar achvihes [171, 173]. Supported thorium half-sandwich complexes 65 exhibited higher achvity than surface species, resulhng from coordinatively more saturated tris(cyclopentadienyl) and metallocene U/Th-alkyl/hydride complexes, that is, 77, 79, 82, 90 and 91 [171]. C CP MAS NMR spectra revealed no clear evidence of ethylene insertion into [Th-CHs] or [AL5-CH3] moiehes of material... 

Oxidation of iodoalkanes involves removal of an electron from the halogen nonbonding orbital. The radical-cations of primary and secondary alkyl iodides can be identified in aqueous solution by their absorption spectra and have half-lives of microseconds [1]. They are formed during pulse radiolysis of the iodoalkane in aqueous solution in the presence of nitrous oxide. This system generates hydroxyl radicals, which remove an electron from the iodine atom lone pair. Iodoalkane radical-anions complex with the lone-pair on other heteroatoms to form a lollo three-electron bond. In aqueous solution, the radical-cation of iodomethane is involved in an equlibrium indicated by Equation 2.1. 

Figure 4.2. Dissociative electron transfer rates from aromatic anion-radicals to alkyl halides detetmined by cyclic votommeiry or by pulse-radiolysis (a) iodobutane (b) 1 -iodo-I -methylpropanc. Solvent N-methylpyrroHdone or dimethylformamidc. Data from refs, [3,5].

See, for example, reviews by Asmus, K.-D. von Sonntag, C. Schuchmann, H.-P. Houee-Levin, C. Sicard-Roselli, C. In Radiation Chemistry Present Status and Future Prospects, Jonah, C.D. Rao, B.S.M., Eds. Elsevier Amsterdam 2001 pp. 341, 513, and 553, respectively. See, for example, Brede, O. Res. Chem. Intermed. 2001,27, 709 and references therein for pulse radiolysis of phenols liquid halocarbons and alkyl halides and Lomoth, R. Brede, O. Chem. Phys. Lett. 1998, 288, 47 for pulse radiolysis of DNA bases in liquid acetone. 

Hermann, R. Brede, O. Mehnert, R. Energy Transfer from Alkane Singlets and Quenching of AlkaneFluorescences by Alkyl Chlorides. A. Pulse Radiolysis Study. Proceedings 5th Tihany Symposium on Radiation Chemistry Dobo, J. Hedvig, P. Schiller, R., Eds. Akademiai Kiado Budapest, 1983 503 pp. 

Absorption due to main intermediates such as polymer cation radicals and excited states, electrons, and alkyl radicals of saturated hydrocarbon polymers had not been observed for a long time by pulse radiolysis [39]. In 1989, absorption due to the main intermediates was observed clearly in pulse radiolysis of saturated hydrocarbon polymer model compounds except for electrons [39,48]. In 1989, the broad absorption bands due to polymer excited states in the visible region and the tail parts of radical cation and electrons were observed in pulse radiolysis of ethylene-propylene copolymers and the decay of the polymer radical cations were clearly observed [49]. Recently, absorption band due to electrons in saturated hydrocarbon polymer model compounds was observed clearly by pulse radiolysis [49] as shown in Fig. 2. In addition, very broad absorption bands in the infrared region were observed clearly in the pulse radiolysis of ethylene-propylene copolymers [50] as shown in Fig. 3. Radiation protection effects [51] and detailed geminate ion recombination processes [52] of model compounds were studied by nano-, pico-, and subpicosecond pulse radiolyses. 

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