Flip-flop interaction

Since the contributions of the three constiments of the van der Waals attraction are additive, one can consider each contribution separately. This indeed proves to be convenient not only because all the contributions exhibit distinct scaling with the parameters, but each contribution comes to dominate the expansivity at somewhat distinct temperatures. We consider first the ripplon-ripplon attraction. This contribution appears to dominate the most studied region around 1 K. The off-diagonal (flip-flop) interaction between the ripplons has the form... 

Neglecting the small inflection observed for the A coefficients (Fig. 10c), the relaxation is exponential and can be considered to fall into three regions. In the extreme narrowing limit the relaxation contributions of the c- H and c- c dipolar interactions are essentially additive. Below "10 ° s, the rapid flip-flop Interaction which reflects the first term in... 

For the dilute aH spins surrounded by a large number of the 2H spins, the heteronuclear aH-H dipolar interaction is dominant, lifting the spectral overlap between the 1H packets. H spin diffusion is driven by the flip-flop term of the 1H-1H dipolar interaction, which becomes secular in the presence of spectral overlap. Thus, spin diffusion would be accelerated if it had not been for the 1H-2H dipolar interaction. In order to confirm this prediction, they used another RF channel of the OPENCORE... 

Cyclic hexapeptides with alternating chirality (ldldld) prefer a C3 symmetric structure (three y-turns) 311 For symmetry reasons six y-turns (three above and three below the ring plane) can also be adopted, although this structure is difficult to prove and to distinguish because of the rapid flip-flop between two structures each with three y-turns 311 These types of structures lead to self-organization by strong intermolecular interactions into nanotubes (see Section 6.8.6.1). 

Unpaired electronic density can be delocalized onto the various nuclei of the complex via through-bond scalar hyperfine interactions involving occupied orbitals containing s-character (direct interaction or polarization according to the Fermi mechanism, Wertz and Bolton (1986)). Random electron relaxation thus produces a flip-flop mechanism which affects the nuclear spin and increases nuclear relaxation processes (Bertini and Luchinat, 1996). Since these interactions are isotropic, they do not depend on molecular tumbling and re is the only relevant correlation time for non-exchanging semi-rigid complexes. Moreover, only electronic spin can be delocalized via hyperfine interactions (no orbital contribution) and the contact re-... 

Platelet participation in normal hemostasis. The hemostatic plug is the specific response to external vessel lesion and depends on the extent of vessel wall damage, the specific interaction between endothelial cells and activated platelets, release of the contents of platelets intracellular granules in response to activation, the conjoint activity of activated factor Vll and platelet agonists, and the open conditions of blood flow. After activation, platelets also produce the external ization of membrane phosphatidylserine through the flip-flop mechanism that will support the function of the prothrombinase complex ending in thrombin generation and local clot formation. 

It is now widely accepted that atherosclerosis is a chronic inflammatory arterial disease associated with risk factors, platelet, and other blood cells activities and their interactions with subendothelial cells, Activated platelets release active components from citosol and induce the externalization of phosphatidylserine through the flip-flop mechanism (23) that supports the function of the prothrombinase complex ending in thrombin generation,... 

Flip-flop mechanism Release of citosol components Interacts with leukocytes Source of inflammatory modulator. )... 

Electron spin-electron spin interaction. The transition betwen a and P spin states takes place by the interaction between the A spins and the surrounding off-resonant spins (called B spins). The most important process in this type of the relaxation is cross relaxation. In the cross relaxation, the excess energy of the A spin system is resonantly transferred to the surrounding B spins through a flip-flop process. The relaxation rate depends on either the distance betwen the A and B spins or the number of the B spins surrounding an A spin. It is this relaxation mechanism which provides us with a means for studying the local spatial distribution of radical species. 

Switching on the 13C RF transmitter is represented by opening the valve between the reservoirs H and 13C. The relative powers of the proton and 13C RF transmitters are adjusted to maximize interactions between the two types of precessing nuclei. Polarization can then be transferred between neighboring nuclei through spin flip-flop processes. Optimization is achieved when the Hartmann-Hahn condition is met, i.e., the H and 13C RF field strengths are in a ratio set close to 1 4 (Pines et al. 1973). Magnetization is then transferred with a time constant TCH-... 

First-order approximation, 450 First-order decay, 18 First-order plot, 18, 35 First-order rate constant, 18, 31, 61 First-Older rate equation, 18, 31, 34 First-order reaaion. 18. 60 Flip-flop problem, 68 Flow methods, 177 Fluorescence quenching, 180 Flux, 134 chemical, 60 Force constant, 294 Force of interaction, intermolecular, 391... 

Membranes are structurally and functionally asymmetric, as exemplified by the restriction of sugar residues to the external surface of mammalian plasma membranes. Membranes are dynamic structures in which proteins and lipids diffuse rapidly in the plane of the membrane (lateral diffusion), unless restricted by special interactions. In contrast, the rotation of lipids from one face of a membrane to the other (transverse diffusion, or flip-flop) is usually very slow. Proteins do not rotate across bilayers hence, membrane asymmetry can be preserved. The degree of fluidity of a... 

Fig. 3.12B shows a more detailed molecular interpretation of the 6 cycle. A single ubiquinone species in a ubiquinone pocket of the Complex III monomer is shown to interact either with the quinol oxidase site (o), or with a semiquinone reductase site (i). Flip-flop of the headgroup (usually of SQ ) between the sites might take place, in principle as proposed for bulk phase ubiquinone (see Section 4.7.2). However, here it occurs within a specific proteinaceous pocket so that regulation by the enzyme is possible. 

Fig. 2.19 Diagram of the plasma membrane showing its integral proteins (fluid mosaic model) (adapted from S.J. Singer et af, 1972 and H. Knufermann, 1976). 1 external aqueous milieu, 2 internal aqueous milieu, 3 fracture plane of the apolar membrane layer, 4 externally orientated intrinsic protein (ectoprotein), 5 internally orientated intrinsic protein (endoprotein), 6 external extrinsic protein, 7 internal intrinsic protein, 8, 9 membrane-penetrating proteins with hydrophobic interactions in the inside of the membrane (P = polar region), 10 membrane pervaded by glycoprotein with sugar residues (, 11 lateral diffusion (A) and flip-flop (B), 12 hydrophilic region (A) and hydrophobic region (B) of the bilayer membrane...

Sobue, K., Morimoto, K., Inui, M., Kanda, K. and Kakiuchi, S. (1982). Control of actin-myosin interaction of gjzzard smooth muscle by calmodulin- and caldesmon-linked flip-flop mechanism. Biomed. Res. 3, 188-196. 

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