Properties of carriers

The hexose-6-phosphate transporter UhpT protein also contains 12 transmembrane (TM) regions. Based on experimental data, Hall and Maloney [113] conclude that TM11 spans the membrane as an a-helix with approximately two-thirds of its surface lining a substrate translocation pathway. It is suggested that this feature is a general property of carrier proteins in the Major Facilitator Superfamily, and that, for this reason, residues in TM11 will serve to carry determinants of substrate selectivity [113]. 

Further demonstrations of this sort of counterflow phenomenon for many different substrates in virtually every type of cell have been used as functional hallmarks of carrier-mediated transport. Experimental demonstration of this effect precludes transport being mediated either by simple diffusion or by fixed pores in the membrane. In reviewing 20 years of experimental work related to the carrier hypothesis, LeFevre (1975) lists a number of key functional properties of carrier mediated transport, all of which have stood the test of the subsequent 20 years. These include saturation of transport with increased substrate concentration and associated phenomena such as competition between similar substrates, high rates of unidirectional transport, and countertransport. Also covered are flux coupling (including trans effects and cotransport), chemical specificity, inhibition by protein-specific reagents, hormonal regulation, and a steep dependence of the rate of transport on temperature (included only to bemoan its common inclusion in textbooks ). 

Apparently the properties of moisture divided by pOH, reciprocal initial concentration, and water absorption as given in Equation 1 are only part of the story. Measurement of other properties, better able to indicate interactions between the surfaces of the toxicant and the carrier, might give significant correlations. These properties should probably include some function of available alkalinity and some function of the absorption capacity of the carrier and its degree of saturation. It is hoped that eventually someone will develop test methods for more useful properties of carriers that will correlate significantly with stability results. 

The electronic properties of carriers near the interface are also influenced by bulk traps in the nitride or other dielectric material. Trapping at interface states and in the bulk dielectric are differentiated by their respective time constants. The distinction between fast interface states and slow bulk states is well known in crystalline silicon. Similarly, the injection of charge from the a-Si H layer into the nitride has a range of time constants which can extend for hours at room temperature. 

Passive targeting is defined as a method whereby the physical and chemical properties of carrier systems increase the target/non-target ratio of a quantity of a delivered drug. Biodistribution and the pharmacokinetic behaviors of polymeric micelles are determined by the micelles size and surface properties (e.g., charge, hydrophilicity, or hydrophobicity). 

Chen, A.B. et al., Comparison of ampholytes used for slab gel and capillary isoelectric focusing of recombinant tissue-type plasminogen activator glycoforms, J. Chromatogr. A, 744, 279, 1996. Sebastiano, R. et ah. Mass distribution and focusing properties of carrier ampholytes for isoelectric focusing I. Novel and unexpected results. Electrophoresis, 27, 3919, 2006. 

Simo, C. et al.. Mass distribution, polydispersity and focusing properties of carrier ampholytes for lEF II pH 4-6 intervals. Electrophoresis, 27, 4849, 2006. 

The colloidal properties of carrier-free radiotin are being investigated. The results will be published elsewhere. 

Properties of Carrier Gases for Gas Chromatography, 8-135 Properties of Cryogenic Fluids, 6-131 Properties of Fatty Acids and Their Methyl... 

Gene delivery is a multi-step process, in which an appropriate property of carriers would be needed to go through each step. Therefore, a major motivation for gene therapy research has been in need to rationally designed multifunctional polymeric vectors, which can overcome a series of extra- and intra-cellular barriers to develop novel treatments for diseases with no effective conventional treatment. 

Keywords hydrotreating catalyst, textural properties of carrier, catalyst active component localization... 

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