Part Four Additional Improvements

Equations 65 and 66 are unusual in that addition of a term in tt does not result in an improved correlation. Only four data points are involved. Most likely these equations are in part fortuitous, and a larger selection of substituents would reveal a role for tt and, possibly, E8. 

In the case of penicillin G, the outward rotation about the C3-C4 bond can occur vithout conflict with protein side chains. It relaxes the strained conformation along this bond previously enforced by the four-membered ring. Moreover, this rotation improves hydrophobic contact of the dimethyl and the sulfur part of the thiazolidine ring of penicillin with two leucine side chains, thus offering an additional driving force for the outward rotation. Experimental evidence is provided by the observed rotation of 35.2° in this direction about the C3-C4 bond that occurs in the acyl-enzyme complex formed between benzyl penicillin and a mutant class A beta-lactamase (RTEM-1) blocked in deacylation [9]. 

The process of generating electricity from steam comprises four parts a heating subsystem (fuel to produce the steam), a steam subsystan (boiler and steam delivery system), a steam turbine, and a condenser (for condensation of used steam). Heat for the system is usually provided by the combustion of coal, natural gas, or oil. The fuel is pumped into the boiler s furnace. The boilers generate steam in the pressurized vessel in small boilers or in the water-wall tube system in modem utility and industrial boilers. Additional elonents within or associated with the boiler, such as the superheater, reheater, economizer, and air heaters, improve the boiler s efficiency. 

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