Mechanisms of internalization

This reaction bears a close similarity to the one discovered by J.F. Klebe who found that acid amides with dialkyldichlorosilanes yield disilaoxadiazines (2). The interesting intramolecular mobility of these compounds was studied by 11NMR spectroscopy and the mechanism of internal silyl migrations within their molecules arose some discussion in the literature (3,4). 

Therefore, evidence exists to support numerous possible mechanisms for the uptake promoted by TAT peptides. An alternative explanation is that TAT is a sticky opportunistic peptide that has the ability to bind to the cell surface and exploit multiple mechanisms in order to enter the cytoplasm (92). Clearly, the mechanism of internalization requires further study. Nevertheless, it has been observed that transfection with CPPs requires less lipid and therefore proves to be less cytotoxic to cells in vitro and in vivo, making it a promising vector system for future gene therapy (95,104). 

Simoes S, Slepushkin V, Duzgunes N, et al. On the mechanisms of internalization and intracellular delivery mediated by pH-sensitive liposomes. Biochim Biophys Acta 2001 1515 23-37. 

In addition to the well characterized roles of clathrin-caveolae-mediated endocytosis and macropinocytosis/phagocytosis, an ill-defined route of nonclathrin-noncaveolae mediated endocytosis still exists (31,32). It seems that all of the until now poorly understood mechanisms of internalization can be summarized in this topic. 

While GPCR phosphorylation at serine and threonine residues is involved in the internalization pathways of many receptors (134,176-178), it is likely that for some GPCRs internalization pathways may be distinct (134,176-178). These apparently nonarrestin mechanisms of internalization, however, may vary more between receptors than those identified for GRK-dependent processes (179,180). 

The biochemical mechanisms of internal and acquired resistances are identical and can be explained as the result of one of the following four reasons ... 

Almofti, M.R., Harashima, H., Shinohara, Y., Almofti, A., Baba, Y., Kiwada, H. (2003). Cationic liposome-mediated gene delivery Biophysical study and mechanism of internalization. Arch. Biochem. Biophys., 410(2), 246-253. 

Ross and co-workers have presented a mechanism of internal conversion for which Teller crossings 166 are not necessary. Following a line of reasoning similar to that of Robinson,5 they suggested that internal conversion can occur from any vibronic level, if from that level tunneling through the barrier can occur. 

With upwards of 100 international agreements, programs and initiatives, there is an obvious risk for overlaps and duplications. Therefore, many mechanisms of international coordination have emerged. They include eight initiatives that are briefly described in the following in approximate order of appearance that mirrors the trends described above. 

One case of apparent defiance of the trans requirement for oxetane formation has recently been reported in the solvolysis of the 3"tosylate (i6) of 3j5,5jS dihydroxycholestan"6"One [ 138]. Under strictly anhydrous conditions the major product was the 3 ff,5j5 oxetane (17), although aqueous solvents gave mainly the 3a,5jS-diol. The mechanism of internal cis substitution at C(3) is not known. Various possibilities include the formation of an internally "solvated ion-pair (18), as a consequence of the extra acidity imposed upon the 5i -hy-droxylic proton by the 6 oxo group this could be followed by oxetane formation with extrusion of a molecule of toluene- -sulphonic acid. 

In theory, each mechanism of mobility corresponds to the proper simplified solvable dynamic models of the polymer chain. They describe continuous viscoelastic or discrete rotameric mechanisms of internal mobfl-... 

C. Arcoumanis and J.H. Whitelaw, Fluid Mechanics of Internal Combustion Engines - A Review, Proc. Inst. Mech. Eng. 201 No. Cl (1987) 57. 

M. T. Marron, Energies, Energy Differences and Mechanisms of Internal Motions, in The Force Concept in Chemistry (B. M. Deb, ed.). Van Nostrand-Reinhold, New York, 1981. 

Anthrax toxin is composed of three proteins protective antigen (PA 83kDa), lethal factor (LF 90kDa), and edema factor (EF 89kDa). Individually, none of the three proteins are toxic but interact synergistically with at least one of the others. PA and LF (called LeTx) can cause lethal shock in experimental animals, and a mixture of PA and EF (edema toxin, EdTx) induces edema at the site of injection. Since two discrete units of the toxin are required for its action, the term binary toxin has been used to this and other bacterial toxins. Anthrax is unique from other binary toxins in that the binary moieties (EF and LF) interact only after being secreted from the bacteria. Further, EF and LF enter the cell via a single PA protein. Assembly of the three toxin proteins is initiated when PA binds to a proteinaceous cellular receptor and is activated by a member of the furin family of cellular proteases. The exact mechanisms of internalization of the toxin moieties are subject of scientific enquiry. Inside the cellular cytoplasm, EF (a calcium and calmodulin-dependent adenylate cyclase) causes a dramatic increase in intracellular cAMP concentrations and LF acts proteolytically to cleave certain MAPK kinases. 

Jevon M, Guo C, Ma B, et al Mechanisms of internalization of Staphylococcus aureus by cultured human osteoblasts. Infect Immun 1999 67 2677-2681. 

Figure 11.2 Energy diagram comparingfluorescenceandphosphorescence.Theshoitaxiowscoue-spond to mechanisms of internal conversion without emission ofphotons. The fluorescence results from transfers between states of the same multiplicity (same spin state) while the phosphorescence results from transfers between states of different multiplicity. The state Tj produces a delay in the return to the fundamental state, which can last several hours. The Stokes shift corresponds to the energy dissipated in the form of heat (vibrational relaxation) during the lifetime of the excited state, prior to photon emission. The real situation is more complex than this simplified Jablonski diagram suggests. To our scale, a compound can be both fluorescent and phosphorescent for, at the molecular scale individual species do not all exhibit the same behaviour.

Figures 24.5 and 24.8 show the drying rate per unit area R plotted against the free moisture content X - — X, or X. Figure 24.5 is the curve for a nonporous clay slab Fig. 24.8 is that for a porous ceramic plate. The difference in the shapes of these curves reflects the differences in the mechanism of internal moisture flow in the two materials.

A second mechanism of international influence embedded in these regimes was growing East-West scientific and technical collaboration, which in the 1980s and early 1990s armed environmental advocates and dissident groups with information on the problem and the extent of health and... 

While the mechanisms of international influence on the acid rain policies of CEE countries were broadly similar, these states responded with different compliance strategies depending on a range of domestic political and economic factors. In order to understand the sources of success and failure of acid rain policies in the region, we need to look also at the interplay between international and domestic policy incentives. 

Kashtalyan M, Soutis C. Mechanisms of internal damage and their effect on the behaviour and properties of cross-ply laminates. Int Appl Mech 2002 38 641-57. 

Seppanen, R., Tiberg, F. and Valignat, M. P., Mechanism of internal sizing by alkyl ketene dimers (AKD). The role of the spreading monolayer precursor, Nordic Pulp Paper Res. J., 15, 452-458 (2000). 

Yu, L. P. and Gamier, G., Mechanism of internal sizing with alkyl ketene dimers the role of vapour deposition, in The Fundamentals of Papermaking Materials, Vol. 2, Baker, C. F., (Ed.), Pira International, Leatherhead, UK, 1997, pp. 1021-1046. 

At higher gas pressures (and in solutions), the collisional broadening of / levels induces a shift from a strong-coupling case to the statistical limit, while the pressure effects on the molecules exhibiting the statistical behavior in collision-fi-ee conditions are less pronounced. One can hope that new information about the mechanisms of internal conversion may be deduced from systematic studies of pressure effects (Chihara and Baba, 1977). 

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