Transport vector

The series of molecular events responsible for the uptake process constitutes the endocytic pathway, which enables cells to internalize macromolecules from the cell exterior, forming an endosome. The endosome is an intermediate organelle that serves as an essential component for many receptor-mediated signaling pathways and as a transport vector for eventual delivery to a specialized organelle known as the lysosome. Once in the lysosomal lumen, digestive enzymes provide essential metabolites from these macromolecules (i.e. free amino acids and lipids) directly to the cytosol for their use. 

McGrath and Junge [36] reported a photoresponsive poly(aryl ether) dendrimer with azobenzene as the dendrimer core. These dendrimers exhibited reversible trans to cis photoisomerization by irradiation at 350 nm. The authors proposed the use of this type of dendrimer as novel photoswitchable transport vectors. This is based on the expected ability of dendrimers to encapsulate or eject small molecules reversibly upon light perturbation. 

The interest of glycosyl phosphoric acid triester moieties (9.43) as brain transport vectors is seemingly not limited to AZT and analogues. Indeed,... 

Carbon Dioxide as a Switchable Transport Vector for Simplified Separation... 

Comparison of the depositional fluxes shows that diatoms were the most important particle component transporting P to the sediment surface, accounting for 50-55% of the flux (Table II). Terrigenous material and calcite were also important transport vectors. Deposition varied markedly with season, as shown by the time series plot of the major particle components (Figure 13). The total P flux calculated by using the particle components model agreed with the flux measured by sediment traps (157-227 versus 185 mg/m2). The close agreement indicated that the major particle vectors were represented and associated P concentrations were accurately quantified. 

Uptake and Release by Diatoms. Diatoms represent a major sink and transport vector for P in Lake Michigan. The importance of diatom production is shown by the changes in dissolved reactive Si levels that resulted from incorporation into diatoms. During the mixed period (late March to mid-June) dissolved reactive Si decreased by 30.7 g/m2, representing 36% of the spring concentration. An additional 11.4 g/m2 was re-... 

Pardridge, W.M., et al. 1990. Evaluation of cationised albumin as a potential blood-brain barrier drug transport vector. Exp Neurol 255 893. 

W. M. Paidrige, D. THguao, J. L. Buciak, and J. Yhng. Evaluation of catinnized cat albumin as a potential Mood-brain drug transport vector. 1- Pharmacol Exp. Ther. 255 893-899 (1990). 

Exploitation of receptor-mediated transcytosis for drug delivery to the CNS. A transport vector, B non-transportable drug A-R receptor for transport vector B-R Receptor for peptide... 

Alternatively, monoclonal antibodies (Mabs) to the relevant receptors can be used as transport vectors. Anti-insulin (Mab83-7 and Mab83-14) and anti-transferrin (0X26) receptor antibodies have been proposed as efficient and selective BBB transport vectors. The antitransferrin receptor antibody binds to a site removed from the transferrin binding site and therefore does not compete with endogenous transferrin for transport across the BBB. Studies using radiolabeled peptides have shown that significant uptake of a... 

The nature of the slow transport vector and its mechanism has been the subject of intense debate for decades, but a consensus has recently been reached. Direct visualization of the movement of cytoskeletal elements within axons has demonstrated that these structures have an instantaneous transport rate that is equivalent to rapid transport and that is powered by the fast transport motors. Like mitochondria, the rapid movement of cytoskeletal elements is interrupted by long stationary periods, leading to a very slow net transport rate. Thus there is now a unified theory of all of anterograde axonal transport. 

Frequently the integral form of the conservation la v of the property is particularized as total and partial mass balance and also as energy or thermal balance [3.7]. For each particularization, a control volume must be selected in order to have a form capable of permitting the computation of each integral from the relation (3.5). As an initial condition, we have to declare the property, the transport vector and the property generation rate. Figure 3.2 presents the way to obtain the equations of the differential balance of total mass, mass species and energy (heat). The... 

The equation for the momentum transport in vectorial form, gives (by particularization) the famous Navier-Stokes equation. This equation is obtained considering the conservation law of the property of movement quantity in the differential form P = mw. At the same time, if we consider the expression of the transport vector Jt = f + w(pw) and that the molecular momentum generation rate is given with the help of one external force F, which is active in the balance point, the par-d(pw)... 

The equation of the ADF model flow can be obtained by making a particular species mass balance, as in the case of a plug flow model. In this case, for the beginning of species balance we must consider the axial dispersion perturbations superposed over the plug flow as shown in Fig. 3.31. In the description given below, the transport vector has been divided into its convective and dispersion components. 

Introduction. Colloidal suspensions are defined as suspensions of particles with a mean diameter less than 0.45 p.m, or a size range from 1 nm to 1 p,m. They represent potentially important transport vectors for highly insoluble or strongly sorbing radionuclides in the environment. Colloids are important in both experimental systems and natural settings. In the former, unrecognized presence of colloids may lead to overestimation of the solubility and underestimation of the sorption of radionuchdes if they are included in the estimation of the concentration of radionuclide solution species. In natural systems, they may provide an important transport mechanism for radionuclides not filtered out by the host rock. In fractured rock, local transport of radionuclides by colloids may be important. 

It is clear that macromolecule-drug conjugates or, more accurately, macromolecular prodrugs may well alter the pharmacological and immunological activity of the parent compound. The macromolecular transport vector may vary considerably in size, electrical charges, hydrophobicity and hydrophilicity, and its ability to act as a substrate for transmembrane transport mechanisms. 

TABLE 13.1 Examples of Nonclassical Transport Vectors and Their Applications... 

The Tat protein was one of the first nonclassical transport vectors to be recognized. A nuclear transcription activating protein of the HIV-1 retrovirus,90 Tat was initially... 

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