V-shaped loop

Figure 2 Schematic and representative structures of different loops in G-quadruplexes (a) edgewise loop, (b) diagonal loop, (c) double-chain-reversal loop, and (d) V-shaped loop...

V-shaped loops connecting two corners of a G-tetrad core in which one supporting column is lacking [Figure 2(d)]. The types of loops depend strongly on the size and sequence of the linkers. Diagonal loops eontain three or more residues.Besides one example of a quadruplex with mixed tetrads,in... 

The d(G3AG2T3G3AT) forms a dimeric G-quadruplex (Figure 6) with several new structural elements.There is a V-shaped loop connecting two corners... 

Figure 6 Structure of a G-quadruplex with a V-shaped loop. (a) Ribbon and (b) schematic view of the structure, (c) Alignment of A -(GG-G-G) pentad...

The form of SThM most relevant to the subject of this discussion is carried out using near-field electrical resistance thermometry, and this method has been adopted in the work reported in this chapter. This is because miniaturized resistive probes have the considerable advantage that they can be used both in passive mode as a thermometer and as an active heat source. This enables local thermal analysis (L-TA see text below) as well as SThM to be carried out. At present the most common type of resistive probe available is the Wollaston or Wollaston Wire probe, developed by Dinwiddle et al. (1994) and first used by Balk et al. (1995) and Hammiche et al. (19%a) The construction details of this probe are illustrated in Fig. 7.3. A loop of 75-pm-diameter coaxial bimetallic Wollaston wire is bent into a sharp V-shaped loop. The wire consists of a central 5-pm-diameter platinum/10% rhodium alloy core surrounded by silver. The loop is stabilized with a small bead of epoxy resin deposited approximately 500 pm from its apex. The probe tip or sensor is made... 

The cystatins, which are a superfamily of proteins that inhibit papain-like cysteine proteases, are a classic example of these inhibitors. The cystatins (Fig. 3) insert a wedge-hke face of the inhibitor that consists of the protein N-terminus and two hairpin loops into the V-shaped active site of a cysteine protease. The N-terminal residues bind in the S3-S1 pockets in a substrate-like manner, but the peptide then turns away from the catalytic residues and out of the active site. The two hairpin loops bind to the prime side of the active site, which provides most of the binding energy for the interaction. Thus, both the prime and the nonprime sides of the active site are occupied, but no interactions are actually made with the catalytic machinery of the enzyme (23). 

The root locus method provides a very powerful tool for control system design. The objective is to shape the loci so that closed-loop poles can be placed in the. v-plane at positions that produce a transient response that meets a given performance specification. It should be noted that a root locus diagram does not provide information relating to steady-state response, so that steady-state errors may go undetected, unless checked by other means, i.e. time response. 

The shape of the hysteresis loop in the adsorption/desorption isotherms provides information about the nature of the pores. The loops have been classified according to shape as A, B and E (De Boer, 1958) or as HI - H4 by lUPAC (Sing et al, 1985). Ideally, the different loop shapes correspond to cylindrical, slit shaped and ink-bottle pores the loops in the isotherm IV and V of Figure 5.3 correspond to cylindrical pores. Wide loops indicate a broad pore size distribution (for an example see Fig. 14.9). The absence of such a loop may mean that the sample is either nonporous or microporous. These generalizations provide some initial assistance in assessing the porosity of a sample. In fact the adsorption/desorption isotherms are often more complicated than those shown in Figure 5.3 owing to a mixture of pore types and/or to a wide pore size distribution. 

The furnace is heated by low voltage (usually 10 V) and high current (up to 500 A) from a well stabilized step-down transformer. For optimum precision, the voltage should be well stabilized, often by a feedback loop which may be temperature feed-back based (see Section 3.6.1). A rapid rise-time of the temperature is also preferable, because of theoretical considerations of peak shapes. This has implications for power supply design and furnace design, as will be shown below. Currently, furnaces are available that reach temperatures of up to 3000°C, and temperatures of 2500°C should be reached in less than 2 s in a well designed furnace. 

The H20 adsorption-desorption isotherms of the above two carbons are plotted in Figure 3.22. Their isotherms are of type-V, and the shape is characterized by a sharp adsorption uptake accompanied by a clear hysteresis occurring over a medium relative pressure (P/P0) range. Such characteristics have often been observed in H20 isotherms of microporous carbons such as ACF [149,150], Mowla et al. found that the width of the hysteresis loop in H20 isotherms for microporous carbons depends on their pore size no hysteresis is observed for carbons with a pore size of less than 0.8 nm, but a wide loop exists for carbons having a larger pore size [151]. The latter is indeed the case for the present carbon samples. 

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