Carrier Properties

Sugibayashi K, Morimoto Y, Nadai T, Kato Y (1977) Drug-carrier property of albumin microspheres in chemotherapy. I. Tissue distribution of microsphere-entrapped 5-fluorouracil in mice. Chem Pharm Bull 25 3433-3434. 

The storage of information in the ligand may allow control over the stability, selectivity, reactivity, and transport (carrier) properties of the complex. The following molecular and environmental features may serve for storing chemical information. 

Quite opposite is the case of ligand 19 whose conformation is very different in the free and complexed states (Figures 6). A study of the carrier properties of this ligand would be interesting since it may be an efficient carrier while retaining appreciable K+/Na+ selectivity.7)... 

The classical FEE retention equation (see Equation 12.11) does not apply to ThEEE since relevant physicochemical parameters—affecting both flow profile and analyte concentration distribution in the channel cross section—are temperature dependent and thus not constant in the channel cross-sectional area. Inside the channel, the flow of solvent carrier follows a distorted, parabolic flow profile because of the changing values of the carrier properties along the channel thickness (density, viscosity, and thermal conductivity). Under these conditions, the concentration profile differs from the exponential profile since the velocity profile is strongly distorted with respect to the parabolic profile. By taking into account these effects, the ThEEE retention equation (see Equation 12.11) becomes ... 

Table I consists of a compilation of r /4> ratios as a function of X. Our results and those presented for p-GaP and n-ZnO are in rough agreement with this simple model (8,9,30,31,32). Construction of a more refined model awaits incorporation of other data (nonexponential lifetimes, electroabsorption, carrier properties, intensity effects, quantitative evaluation of 4>nr by photothermal spectroscopy, e.g.) and examination of other systems.

Kinetic analyses allowed the experimental results to be related to the dependence of transport rates and selectivities on carrier properties [6.9, 6.17, 6.18]. Detailed studies of 8 and 9 in vesicles bore on the efficiency, the selectivity and the mechanism of the processes [6.19]. The rates of transport by proton ionizable macrocyclic carriers are pH dependent [6.12]. Diverse other ligands have been used as carriers, such as acyclic polyethers or calixarene derivatives [6.20, A.6]. 

Of greatest interest are those compounds that attempt to model hemoglobin directly. Simple iron(II) porphyrins are readily autoxidized first to superoxo species, then to //-peroxo dimers and finally to /x-oxo dimers, as represented in equation (60). Bridge formation must be prevented if carrier properties are to be observed. This has been achieved by the use of low temperature and sterically hindered or immobilized iron(II) porphyrins. Irreversible oxidation is also hindered by the use of hydrophobic environments. In addition, model porphyrins should be five-coordinate to allow the ready binding of 02 this requires that one side should be protected with a hydrophobic structure. Attempts have also been made to investigate the cooperative effect by studying models in which different degrees of strain have been introduced. 

Immobilized enzyme systems can be differentiated according to mode of immobilization, carrier properties, and rate-determining step. 

Carrier properties. Carriers can be shaped and configured as films, fibers, planar surfaces, or spheres. Surface morphology, i.e., surface texture and porosity, can exert a decisive influence as can carrier materials the most important are inorganic materials such as ceramics or glass, synthetic polymers such as nylon or polystyrene, and polysaccharide materials such as cellulose, agarose, or dextran. 

The carrier properties have been studied in numerous in vitro studies to understand the influence on powder performance, especially drug detachment. The particle size distribution of the carrier is of paramount importance for the delivery and dispersion of drug particles by a device at given flow-rate conditions (Steckel and Mueller 1997 French et al. 1996 Kassem et al. 1989). An increased proportion of fine particles results in more efficient dispersion (Podczeck 1999), which has led to the proposal to deliberately add microfine lactose as a ternary agent (Lukas et al. 1998). 

To enhance the drug carrier properties of inulin, it has been reacted with epichlorohydrin, the product of which is highly reactive and couples readily with substances containing amino groups (Schacht et al., 1984). The 3-chloro-2-hydroxypropyl derivative (9) of inulin is formed in reaction with epichlorohydrin. Likewise, an allyl bromide derivative (10) can be prepared using sodium hydroxide as a catalyst (Tomecko and Adams, 1923). 

Correlation of Carrier Properties with Malathion Stability... 

The stability of toxicant-carrier combinations used in pesticide wettable powder formulations cannot be easily predicted by evaluating various properties of the carrier. Several types of synthetic calcium silicates and their modifications were evaluated for malathion stability and other properties. The carriers were evaluated for pH (slurry), pK (surface acidity), moisture content, absorptive capacity, and/or ion exchange capacity. These properties were correlated with actual malathion stabilities as measured at 40° C. storage for 1, 2, 3, and 7 months. The carrier properties evaluated did not offer a simple means of predicting compatibility in the variety of carriers tested. 

Unfortunately, we found only a weak correlation of the properties we measured and the actual malathion stability results. Therefore, this paper shows that the carrier properties we measured do not offer a means of predicting carrier-malathion compatibility. We did not find a significant correlation with actual stability results and some of the properties suggested in the following references. 

As a result of the above comments, we believed that the following carrier properties should show a correlation with malathion stability and should serve as easy methods of screening new carriers as they were developed. Therefore, we measured ... 

Analysis. During our project, we evaluated 97 variations of carriers (Table I). We did not measure all carrier properties on all samples, and unfortunately, we measured only a few samples for ion exchange capacity. 

The best correlation resulted from regression of three variables that combined four of the measured carrier properties. The variables, moisture divided by pOH, water absorption, and reciprocal initial concentration, resulted in the following equation ... 

Apolipoproteins Methg and Methgo Loss of lipid-carrier properties (Mil)... 

The actinides plutonium, neptunium, protoactinium, and thorium (151,173) bind to transferrin. The larger Th4+ ion (radius, 0.94 A) still binds to both sites, although binding to the second site (probably the N-terminal site) is significantly weaker than that to the first and apparently involves only one Tyr ligand compared with two Tyr in the other (151). Although UV difference spectra for Pu4+ are equivocal (174), it seems likely that two Pu4+ are bound. The likely carrier properties of transferrin for Pu4+ makes the design of competitive chelators of some importance (151). 

This section briefly describes several methods addressed to the study of carrier properties at interfaces with semiconductors in UHV. We also examine the possibility of applying this approach in situ. 

Catalyst life might be extended by the development of low-ash lubricating oils and by modifying carrier properties such as surface chemistry, pore structure, and surface area, to create contamination-resistant catalysts. 

Gemeiner P, Polakovic M, Mislovicova D, and Stefuca V. Cellulose as a (bio)affinity carrier Properties, design and applications. J. Chromatogr. B 1998 715 245-271. 

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