Chemically structured substrates

Planar but chemically inhomogeneous substrates are encountered in various practical application, in particular those related to open nanofluidics. One tries to understand the wetting and adsorption properties of such systems in terms of the wetting properties of separate, chemically homogeneous regions. A simple chemical step consists of two semi-infinite planes, each composed of a different material, say, (1) for x 0 and (2) for 

Each part of the substrate can be characterized by its own wetting transition temperature and respectively. The morphological properties of adsorbed wetting films can be anal3 ed conveniently either by or by the effective Hamiltonian 

The effective interface potential co C x)) corresponds to a planar and homogeneous substrate of type /, and 0(x) is the Heaviside function. Accordingly, the effective Hamaker constant o( (T) in Eqs. 3.4 and 3.5 depends on the corresponding wetting transition temperature and in the case of critical wetting o( (T) T — T In a refined description oj[ , x) does not vary step-like but smoothly across x = 0, which reflects the smooth variation of the total substrate potential in spite of a step-like variation of its chemical composition.  

The chemical inhomogeneity runs along the line x = 0, z = 0, where the two half-planes meet. The thickness l(x) of the wetting film varies along the x-axis. It approaches its asymptotic values l T,Sfi) and for x =foo, respectively. The rate 

) ln(S)u). One of the findings concerning the interface morphology across a chemical step is that its analysis based on local interface Hamiltonians provides results that are in both qualitative and satisfactory quantitative agreement with those based on a nonlocal interface Hamiltonian.  

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Jones, B. E. (1991a). Paradoxical sleep and its chemical/structural substrates in the brain. Neuroscience 40, 637-56. 

We now turn to a microscopic treatment of the. Toule-Thomson effect and begin with the limit of vanishing density. Th(j treatment below is very sinrilar to the one presented in Section 3.2.2 where we derived molecular expressions for the first few virial coefficients of the one-dimensional hard-rod fluid. Here it is important to realize that a mechanical expression for the grand potential exists for a fluid confined to a slit-pore with chemically structured substrate surfaces as we demonstrated in Section 1.6.1 [see Eq. (1.65)]. Combining this cxpres.sion with the tnolocular expression given in Eq. (2.81) we may write... 

Wetting and adsorption on chemically structured substrates can be analyzed macroscopically in terms of Cassie s and Wenzel s rules. " They introduce position-dependent contact angles 0 (R) and respectively. In the case of a chemically inhomogeneous... 

Besides various other t3qies of chemically structured substrates, one can also consider special choices of the thermod3mamic states of the system for which wetting is studied. In particular, in the case of critical adsorption on chemically structured substrates, one obtains universal scaling functions, which describe the behavior of the modulated excess adsorption near the bulk critical point Tc. 

W. Koch, S. Dietrich, and M. Napidrkowski, Morphology and line tension of liquid films adsorbed on chemically structured substrates, Phys. Rev. E, 51, 3300-3317 (1995). 

C. Bauer, S. Dietrich, and A. 0. Parry, Morphological phase transitions of thin fluid films on chemically structured substrates, EPL, 47,474-480... 

Figure 15-29. Chemical structures of the conjugated polymers used in the device and the device structure of the laminated solar cell. For the top half of the device, A1 or Ca was evaporated on glass substrates, and the acceptor material MEH-CN-PPV (and a small amount of POPT, usually 5%) was spin coaled. The half with the POPT (and a small amount of MEH-CN-PPV, usually 5%) was spin coaled on 1TO substrates and heated to 200"C under vacuum belore the device was laminated together by applying a light pressure.

Table 4 shows that the substrates usually involved in the reaction with polydichlorophosphazene belong to the categories of aliphatic or aromatic compounds containing in their own chemical structure free -OH and/or -NH2 functionalities, which can be easily found on the market in great abundance and at cheap prices. 

FIGURE 5.37 Chemical structure of a molecular probe with UV-Vis and fluorescence outputs for penicillin G amidase activity. The phenylacetamide group (red) is a substrate for PGA. The reporter units, 4-nitrophenol and 6-aminoquinoline, provide a visible signal and a fluorescence signal, respectively, upon release. (See the color version of this figure in Color Plates section.)... 

Figure 7.9 Chemical structures of ligands of the enzyme PNP. (A) The substrate inosine, (B) the inosine and phosphate transition state, and (C) the transition state mimic inhibitor Imucillin H.

Figure 3.6 Comparison of the chemical structures of rifamycin (Rifampicin ) and rifamycin CGP 4832 the latter is transported by FhuA. Note the entirely different chemical structures (Figure 3.2) and conformations (Figure 3.5) of the ferrichrome and albomycin FhuA transport substrates.

A comprehensive list of P-gp modulators or inhibitors, classified according to their chemical structures, has been published recently [87]. This shows that the structures of inhibitors are almost as heterogeneous as those of the substrates. A small but representative selection of inhibitors is shown in Fig. 20.12 and Table 20.1. In an attempt to clarify the different mechanisms of P-gp modulation or inhibition, the H-bonding concept discussed above is applied. To this end, the modulators or inhibitors in Table 20.1 were ordered according to their H-bond acceptor potential and divided in three groups comprising compounds with (i) a low EUh (<2 i.e., not transported) (ii) an intermediate EUh (— 3—6) and (iii) a high H-bond acceptor potential ( EUh > 10 i.e., transported slowly). 

The chemical structure of the CL precursor, not only the central portion containing the electronically excited group, but also the side chain The nature and concentration of other substrates affecting the CL pathway and favoring other nonradiative competition processes The selected catalyst... 

Fig. 1. Chemical structures of some common GABA mimitics of restricted comformation that bind to the substrate binding sites in the GABAa receptor complex and the GABA transporters, respectively.

Figure 16 Measuring system for detachment of LB films from a QCM substrate at the air-water interface, and chemical structures of LB film-forming amphiphiles.

Three kinds of PAV films was prepared using methoxy pendant precursors. The chemical structures and synthetic route of the PAV films used in this study are shown in Fig. 19. The details of synthesis of the methoxy pendant precursors have been described in refs. 29 and 30. The precursors were soluble in conventional organic solvents, for example, chloroform, dichloromethane, benzene and so on. The precursor polymer thin films were spin-coated on fused quartz substrates from the chloroform solutions. The precursor films were converted to PAV films by the heat-treatment at 250 0 under a nitrogen flow with a slight amount of HC1 as a catalyst. This method provided high performance PAV films with excellent optical quality. 

Bartlett has derived a method181 for proving that a putative transition state analog exerts its inhibitory power from successfully mimicking the transition state. If a series of structurally-related inhibitors (all containing the identical core chemical structure meant to simulate the transition state) bind to the target enzyme with log (fQ) values that linearly correlate (slope = 1) with the log (KMlkcai) values of the same series of structurally-related substrates, then... 

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