Conformation kinetics

Clarke RJ, Apell H-J, Kong BY (2007) Allosteric effect of ATP on Na+,K+-ATPase conformational kinetics. Biochemistry 46 7034-7044... 

The conformational kinetic control of the chiral centres present in a molecule may be exemplified by the rran -diaxial opening of an epoxide i rf a polycyclic system [7]. In this case, the less stable conformation is also "frozen" by forming an auxiliary lactone bridge, which reverses temporarily the conformations of the rings and the substituents. 

The Mutarotation of 2-Deoxy-/3-D-erythro-pentose ( 2-Deoxy-/f-D-ribosc ). Conformations Kinetics, and Equilibria, ... 

Time-resolved FTIR spectrometry for protein conformation kinetic study... 

M 35] [protocol see [119]] A protein conformation kinetic study of the small protein ubiquitin was performed both in the continuous and in a stopped-flow mode at low reactant consumption [119], The bifurcation mixer was used prior to an IR flow cell for data monitoring. The change of conformation from native to the A-state was followed when adding methanol under low pH conditions to the protein solution. In the continuous mode, long data acquisition could be made and the reaction time was determined by the flow rate and the volume interconnecting zone between the mixer and IR flow cell, which was small, but not negligible. In the stopped-flow mode, the reaction time resolved was dependent on the time resolution of the FTIR instrument. 

B. D. Ross and N. S. True, NMR spectroscopy of cyclohexane. Gas-phase conformational kinetics. 

D chemical exchange (2-D EXSY) NMR experiments it was established that the interconversion between these two conformers occurs primarily via a higher energy 1,3-alternate conformer, with the three conformers kinetically related as shown in Figure 4.16. The faster rates for 46c (w = 1) compared with 46c n = 0) are ascribed to the squeezing of the cavity by the shorter bridge in the latter. 

Rabddt JF, Hofer D, Miller RD, Fickes GN (1986) Studies of chain conformational kinetics in poly(di-n-alkylsilanes) by spectroscopic methods. Macromolecules, /9 611... 

R. Edberg, D. J. Evans, and G. P. Morriss,/. Chem. Phys., 87,5700 (1987). Conformational Kinetics in Liquid Butane by Nonequilibrium Molecular Dynamics. 

R. Cerf, Cooperative conformational kinetics of synthetic and biological chain molecules, Adv. Chem. Phys. 33, 73 (1975). 

The relaxation time 1 and the pol3mer contribution to the viscosity rjp depend strongly on the polymer molecular weight, concentration, and equihbrium conformation. Kinetic theory can be used to obtain scaling behavior for these quantities. At dilute concentrations, for example, the Zimm bead-spring model predicts the relaxation time as a function of the drag on polymer chain segments. 

Although the number of research papers reporting the use of NMR spectroscopy, especially by comparison to and is small the range of applications is extensive (and is described in more detail in the book by Evans et al.). For example, the measurement of specific activity, optical purity, stereochemistry, solution conformation, kinetic acidities, hydrogen isotope exchange, hydrogen bonding, fractionation factors, and radiolysis. 

Lemieux, R. U., L. Anderson, and A. H. Conner The Mutarotation of 2-Deoxy-p-D-erythro-Vtniost ( 2-Deoxy-p-D-Ribose). Conformations, Kinetics and Equilibria. Carbohydr. Res. 20, 59 (1971). 

Isotropic correlation times and spin lattice relaxation times measured by and H-NMR for polyoxyethylene (POE) solutions in a variety of solvents have been computed using the DRIS formalism for isolated polymer chains [8]. For this purpose, the conformational kinetics of POE has been analyzed and kinetic schemes of rotameric transitions have been estimated for the three distinct types of bond pairs (CO, OC), (OC, CC) and (CC, CO) on the backbone. The effective friction coefficient is deduced from the viscosity of the solvent, irrespective of the size of the kinetic unit, assuming environmental effects and chain connectivity constraints to be of secondary importance compared to torsional energy barriers. The reader is referred to [8] for explicit expressions of... 

Physical Properties.—Further Z-ray studies of methyl thio- and dithio-esters have confirmed previous findings (see Vol. 5, p. 180) that the ester group is almost planar, with a Z conformation, Kinetic studies of the gas-phase pyrolysis of dithioacetates have shown that the reaction is a concerted unimolecular process, consistent with the mechanism shown in Scheme 10. °... 

Dielectric relaxation phenomena were investigated in different nematic materials like PAA [159-162], MBBA [163-169], nitriles [170-173] and other mesogens [174-177]. A recent review of rotational dynamics and conformational kinetics in liquid crystals can be found in Ferrarini [178]. 

A. Ferrarini, A. Polimeno, P. L. Nordio, Rotational dynamics and conformational kinetics in [195] liquid crystals, Liq. Cryst. 1993,14, 169. 

Figure 4 Gas-phase NMR spectra of /7-propyl nitrite at 240.6 K. The spectral region shown corresponds to the methylene protons attached to the carbon bonded to the oxygen. Samples contained 2 torr of /7-propyl nitrite and various pressures of CO2. Spectral labels refer to the total sample pressure in torr. In each plot the top trace is the simulated spectrum, the middle trace is the experimental spectrum and the lower trace is the difference between the two. Reprinted with permission from Moreno PO, True NS and LeMaster CB (1990) Pressure-dependent gas-phase NMR studies of conformational kinetics in a homologous series of alkyl nitrites. Journal of Physical Chemistry 94 8780-8787. 1990 American Chemical Society.

For ketones with n,n lowest triplets, significant intrinsic solvent effects on fcjj values are not apparent, although solvation of other functionalities in the molecule can affect conformational kinetics. Also, when the n,n triplet is of lower or comparable energy, polar solvents reduce overall reactivity by lowering the excitation energy of the lt,K triplet and raising that of the n,n triplet, thus decreasing values. 

---