Efficiency of synthesis

The careful control of electronic properties is, of course, a key motivation of such structural changes the so-called band-gap tuning being a particularly important concern. Efficiency of synthesis and structural homogeneity of the products are essential ingredients of such an approach since failure to achieve e.g. quantitative transformation of precursor polymers or to couple benzene units exclusively in a para-fashion interrupts the extensive -conjugation and hampers a reliable structure-propcrty-relalion. 

Some peptide chemists believe that a shrink-swell step at this point will exercise the resin and help efficiency of synthesis, particularly when coupling is incomplete and recoupling will be used. To apply shrinking, wash the resin with MeOH (3 x 15 mL) to shrink the resin, then with CH2CI2 (3x) to swell the resin again before recoupling or the next coupling cycle. 

The main advantages associated with this method are the use of low temperatures, the possibility of obtaining phases and complex ceramics with high purity and the ability to obtain nanosized powders, while the main drawbacks are the high cost of some reactants, the formation of agglomerated powders and low efficiency of synthesis cycles. 

The outstanding electrical, thermal, mechanical and chemical properties of carbon nanotubes (CNTs), especially single-walled carbon nanotubes (SWNT), have interested researchers aU over the world. One of the major problems concerning the large scale nse of CNT was the high cost and low efficiency of synthesis and purification processes. Several different synthesis methods have been already developed in the last decade (Fig. 1.6). 

After genetic selection with HAT the culture contains hybridomas but only some of these will secrete antibodies. Although the efficiencies of synthesis vary considerably, about 10% of the population of hybridomas formed from... 

The synthesis of poly(dT) on the poly(dA) template is sharply optimal at pH 7.6 (50 mM Tris—Cl) in contrast to the broad pH optimum around pH 8.1—8.4 on poly(A). Varying the KCl concentrations from 0 to 60 mM has no significant effect on the rate of polymerization on poly(dA) in contrast to the reaction with poly(A) which is stimulated by 50-100 mM KCl. The efficiency of synthesis on poly(A) at the optimum MnCl2 concentration (0.7 mM) is —60% of that with MgCl2 (4 mM). In contrast, the synthesis on poly(dA) is maximal at 5 mM MnCl2 or 18 mM MgCl2 the preferred cation is Mn " " (100%) and not Mg " (30-40%). The RNA or DNA template-dependent differences are also manifested on the utilization of primers with different lengths (see below). Compared with the DNA DNA which adopts the B helix, the RNA DNA heteroduplex which adopts the A-form apparently allows more effective interactions with RTase. 

Another concept used to determine the efficiency of synthesis is step economy [3]. Synthesizing a complex molecule typically involves multiple steps, and the concept of step economy minimizes the number of steps needed for the synthesis. The use of protecting groups adds two steps, protection and deprotection, and thus lowers the step economy. This generates interest in minimizing the use of protecting groups in synthesis. 

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