Indicator strain

Replacement of Dha by Dhb and vice versa has been reported for several lantibiotics. Replacement of Ser at position 5 by Thr led to the production of Dhb instead of Dha in mature nisin The mutant exhibited increased resistance to chemical degradation, but this was accompanied by a 2- to 10-fold reduction in bioactivity toward various indicator strains. In contrast, replacement of Dha at position 2 in nisin Z with Dhb resulted in a mutant that was twice as active as native nisin Z. ° The gallidermin variant Dhbl4Dha did not exhibit any noticeable decrease in activity, ° and the DhblODha mutant of mutacin II also showed similar activity as wild type. " The promiscuity of the biosynthetic enzymes is also well illustrated by the production of a nisin mutant with a Dhb residue at position 18 in place of Gly after introduction of a Thr codon in nisA and the analogous introduction of a novel Dha in place of a Lys at position 18 in Pep... 

The strain energies of thiirane, thietane and thiolane are reported to be 81.1, 80.3 and 5.0 kJ mol-1 respectively (79MI51400). Molecular mechanics calculations indicate strain energies for thietane, 5-thiabicyclo[2.1.1]hexane, thiolane and thiane to be 82.4, 135.6, 17.2 and 2.5 kJ mol-1 respectively (75JA5167). 

For both EPDM-LDH and XNBR-LDH nanocomposites, the various tensile properties are summarized in Table 13 and their typical stress-strain plots are shown in Fig. 58 [104]. In Fig. 58a, the gum vulcanizates of both rubber systems showed typical NR-like stress-strain behavior with a sharp upturn in the stress-strain plot after an apparent plateau region, indicating strain-induced crystallization. With the addition of LDH-C10 in the XNBR matrix, the stress value at all strains increased significantly, indicating that the matrix undergoes further curing (Fig. 58b). 

Mohn, G.R., and J. Ellenberger. the use of Escherichia coli K12/343/113(X) as a multi-purpose indicator strain in various mutagenicity testing procedures,... 

Fig 2. Expression of chemokines with and without N-terminal tags. Murine RANTES and human herpesvirus 8 vMIP-lB were expressed either as mature proteins (native) or with the addition of the residues MKKKWPR- to the N-terminus (K3) using the T7 based expression vector pET24d in either BL21(DE3) or BL21(DE3)pLysS cells. Each lane of this Coomassie stained SDS-polyacrylamide gel contains 0.04 OD600 units of the indicated strain following a 3-h induction. 

An x-ray structural analysis of 3-keto-4,4-dimethyl-l-p-tolyl-l,2-thiazetidine 1-oxide shows a planar ring with a C-S-N angle of 75.7°, which indicates strain." " Its carbonyl stretching frequency is 1770cm and its mass spectrum indicates loss of sulfur monoxide or an isocyanate from the parent ion." "... 

DNT at an oral dose of 40 mg kg day for 2 years produced liver tumors in rats and at a dose of 97 mg kg day for 2 years produced renal tumors in male mice. 2,6-DNT at doses as low as 7 mg kg day produced hepatocellular carcinomas in male rats following a lyear oral exposure. The available data also indicate strain differences in the carcinogenic response for several of the DNT isomers. 

In a reversion assay, restoration of a mutated gene activity only occurs if the mutagen produces mutations of the same type, (base-substitution or frame-shift) as the revertible mutation carried by the indicator strain. In the Ames assay this problem is circumvented by using different indicator strains, some of which are reverted by base-substitution mutagens and others which are preferentially reverted by different types of frameshift mutagens. ... 

In the lactococcin M operon, two bacteriocins (LcnM and LcnN) and one immunity protein (LciM) were found, displaying a low antagonistic activity against L. lactis indicator strains [46,135]. In the lactococcin M operon, disruption of both IcnM and IcnN resulted in a non-producer phenotype. Therefore,... 

In a tensile-yield experiment carried out at 60 °C on a polymer the stresses shown in the table were required in order to produce yield at the indicated strain-rates. Use these data to calculate the best value of the activation volume per site, expressing your answer in nm. ... 

FIGURE 10.3 Fatigue lives N for test pieces having initial cuts of depth /, subjected to repeated extensions to the indicated strains. 

It is important to use high-quality solvents or to distill them because many commercial grade solvents contain plasticizers that are concentrated during the extraction procedure. These concentrated compounds can be toxic to the indicator strains or can interfere with the interpretation of results. 

The very last portion of the stress-strain curve indicates strain hardening, induced mainly by further chain orientation. In semi-crystalline polymers, one detects an increase in crystallinity and orientation—both leading to an increase of stress. In these cases, Sb > Sy. 

Fig. 17 Cyclic, thermomechanical tensile test for quantification of triple-shape effect - two step programming, (a) Strain and temperature as a function of time taken from the fifth cycle for MACL(45) multiphase network composed of crystallizable PCL segments and amorphous poly(cyclohexyl methacrylate) segments with 45 wt% PCL content (rtrans,A = Tm.PCL = 50°C and Ftrans.B = = Fg pcHMA = 140°C). The solid line indicates strain the dashed line indicates tem-...

The variation of trae stress with true strain is shown in Fig. 9.7 for nanosized silicon nitride ceramics it does not indicate strain hardening and very large strains may be achieved, as seen from the flow stress. 

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