Spontaneous strain

The choice of the strain of microorganism is one of the important variables in the process. The strains to be used in manufacture are mutants of the original producer, which are chosen as the result of a planned program of mutant selection. Sometimes a spontaneous mutation occurs usually, it is induced by mutagenic agents or irradiation of various sorts. The choice of the best strain depends on its abiUty to produce large amounts of the proper antibiotic in a reasonable time from ingredients that are economically feasible (73). 

Pyroelectrics. Pyroelectric ceramics are materials that possess a uoique polar axis and are spontaneously polarized ia the abseace of an electric field. Pyroelectrics are also a subset of piezoelectric materials. Ten of the 20 crystal classes of materials that display the piezoelectric effect also possess a unique polar axis, and thus exhibit pyroelectricity. In addition to the iaduced charge resultiag from the direct pyroelectric effect, a change ia temperature also iaduces a surface charge (polarizatioa) from the piezoelectric aature of the material, and the strain resultiag from thermal expansioa. 

The strained 60° bond angles in tetrahedral P4 make white phosphorus highly reactive. This form of the element must be kept out of contact with air, in which it spontaneously bums. 

Mammahan blood will clot spontaneously if allowed to stand however, on further standing, this clot may dissolve as a result of the action of a proteolytic enzyme called plasmin. Plasmin is normally present as its inactive precnrsor, plasminogen. Certain strains of streptococci were fonnd to produce a substance which was capable of activating plasminogen (Fig. 25.3), a phenomenon that suggested a potential use in liquefying clots. This snbstance was isolated, found to be an enzyme and called streptokinase. 

On the other hand, 3-phenylpropionitrile was synthesized from Z-3-phenyl-propionaldoxime (0.75 M) in a quantitative yield (98gP ) by the use of cells of E. coli JM 109/pOxD-9OF, a transformant harboring a gene for a new enzyme, phenylacetaldoxime dehydratase, from Bacillus sp. strain OxB-1. Other arylalkyl- and alkyl-nitriles were also synthesized in high yields from the corresponding aldoximes. Moreover, 3-phenylpropionitrile was successfully synthesized by the recombinant cells in 70 and 100% yields from 0.1 M unpurified P/Z-3-phenylpropionaldoxime, which is spontaneously formed from 3-phenylpropionaldehyde and hydroxylamine in a butyl acetate/water biphasic system and aqueous phase, respectively. 

The a-isomer of hexachlorocyclohexane exists in two enantiomeric forms, and both are degraded by Sphingomonas paucimobilis strain B90A by dehydrochlorination to 1,3,4, 6-tetrachlorocyclohexa-l,4-diene that is spontaneously degraded to 1,2,4-trichlorophenol. 

A bacterial strain BN6 oxidizes 5-aminonaphthalene-2-sulfonate by established pathways to 6-amino-2-hydroxybenzalpyruvate that undergoes spontaneous cyclization to 5-hydroxy-quinoline-2-carboxylate (Figure 2.2a) (Nortemann et al. 1993). 

The degradation of 1,2-dichloroethane by Pseudomonas sp. strain DCAl was initiated not by hydrolysis, but by monooxygenation with the direct formation of 1,2-dichloroethanol that spontaneously decomposed to chloroacetaldehyde (Hage and Hartmans 1999). 

Lee, T.D.G. and Wakelin, D. (1982) The use of host strain variation to assess the significance of mucosal mast cells in the spontaneous cure response of mice to the nematode Trichuris muris. International Archives of Allergy and Applied Immunity 67, 302—305. 

Maughan S.M., Kee H.H., Newson T.P., Simultaneous distributed fibre temperature and strain sensor using microwave coherent detection of spontaneous Brillouin backscatter, Meas. Sci. Technol. 2001 12 834-842. 

Scheme 33 illustrates the difference in reactivity between triazolines obtained from cyclohexanone and cyclo-pentanone enamines. Thus, the reactions of azidophosphonates 239 with cyclohexanone enamines produce unstable aminotriazolines 240 that cannot be isolated due to their spontaneous elimination of amines to provide triazoles 241. Contrary to that, triazolines 242, derived from cyclopentanone enamines, are isolated in good yield (76-88%) and cannot be converted to the corresponding triazoles even by thermolysis <1995H(40)543>. Probably, introduction of a double bond between two five-membered rings would involve too much molecular strain. 

In the real world the stress tensor never vanishes and so requires a nonvanishing curvature tensor under all circumstances. Alternatively, the concept of mass is strictly undefined in flat Minkowski space-time. Any mass point in Minkowski space disperses spontaneously, which means that it has a space-like rather than a time-like world line. In perfect analogy a mass point can be viewed as a local distortion of space-time. In euclidean space it can be smoothed away without leaving any trace, but not on a curved manifold. Mass generation therefore resembles distortion of a euclidean cover when spread across a non-euclidean surface. A given degree of curvature then corresponds to creation of a constant quantity of matter, or a constant measure of misfit between cover and surface, that cannot be smoothed away. Associated with the misfit (mass) a strain field appears in the curved surface. 

---