Strain discrimination

Sigurdson CJ, Nilsson KPR, Homemann S, Manco G, Polymenidou M, Schwarz P, Leclerc M, Hammarstrdm P, Wuthrich K, Aguzzi A (2007) Prion strain discrimination using luminescent conjugated polymers. Nat Methods 4 1023-1030... 

Variable-Number Tandem Repeats (VNTRs) are genomic regions with potentially extreme variation and has a great strain discrimination capacity [7], MLVA has been used for individual strain discrimination within several bacterial species with little genomic variation. 

Sigurdson, C. J. Nilsson, K. P. R. Hornemann, S. Manco, G. Polymenidou, M. Schwarz, R Leclerc, M. Hammarstrom, R Wuthrich, K. Aguzzi, A. Prion strain discrimination using luminescent conjugated polymers. Nat. Methods 2007, 4, 1023-1030. 

Okuda, T., M. Yanagishawa, F. Fujimori, Y. Nishizuka, Y. Takehana M. Sugiyama. 1995. New isolation methods and polymerase chain reaction strain discrimination techniques for natural products screening programs. Can. J. Bot. 73 (suppl. 1) S946-S954. 

These DNA markers have been successfully employed to track specific strain-associated loci in endo- and ectomycorrhizal populations from agricultural land, forest nurseries, plantations, and natural ecosystems. The simplest strategy (digesting PCR-amplified ITS with selected endonucleases) has identified their symbionts in various ecosystems (18,36-38). Species discrimination by ITS-RFLP matching can be improved by comparing data for the targeted DNA with those on sequence databases (37). 

These examples illustrate the issues that must be considered in analyzing the stereoselectivity of enolate alkylation. The major factors are the conformation of the enolate, the stereoelectronic requirement for an approximately perpendicular trajectory, the steric preference for the least hindered path of approach, and minimization of torsional strain. In cyclic systems the ring geometry and positioning of substituents are often the dominant factors. For acyclic enolates, the conformation and the degree of steric discrimination govern the stereoselectivity. 

Sexually differentiated responses to female-soiled bedding occur within the regions of the AOB only the rostral zone was -activated in males as opposed to that of females the caudal zone cells had no such differential activation VN-x removed the response (Dudley and Moss, 1999 Matsuoka et al., 1999). The number of Fos-ii cells was larger after exposure to females of ICR stain, than to BALB females. Male strain-differences gave equivalent amounts of rostral/caudal activity in females. It is probable that discrimination by females of between-strain chemosignals is related to the fine distinctions possible through the operation of cues related to influence of products from the MHC loci. 

Fig. 7.10(c)]. These ewes allowed both alien lambs and their own lambs to suckle (Booth et al., 2000). Since MOE-x still permitted own/ alien discrimination, it appears that lamb acceptance is dependent upon the ability of the AOS to distinguish familiarity. The discrepancies may derive from technique or strain differences. The combined, possibly central, effects of complete deafferentation are perhaps necessary to disrupt such important responses. Whether, for instance, multiparous rats could be at all resistant to such treatments has not been tested. 

Fig. 7.10 (Continued) (b) VN-x inhibits response to female urine by male guinea-pig X-2 sequential trials (duration, sec. x s.e.) (from Beauchamp et al., 1982). (c) Inter-strain (domestic vs. wild) discrimination by male domestic guinea pig of female urines [sequential testing sec/4 min, s.e., Ss above each bar intact/sham-VN-x. above]. WF= wild female, F = domestic female (from Beauchamp et al., 1982). (d) Effects of VN-x on maternal chemoinvestigation ewe responses to lambs, including tongue-manipulation of palate [c.f. Fig. 7.6(d)], procaine = MOE inhibition, a sign, versus control (from Booth and Katz, 2000).

Detector selectivity is much more important in LC than in GC since, in general, separations must be performed with a much smaller number of theoretical plates, and for complex mixtures both column separation and detector discrimination may be equally significant in obtaining an acceptable result. Sensitivity is important for trace analysis and for compatibility with the small sizes and miniaturised detector volumes associated with microcolumns in LC. The introduction of small bore packed columns in HPLC with reduced peak volume places an even greater strain on LC detector design. It is generally desirable to have a nondestructive detector this allows coupling several detectors in series (dual... 

Kansiz, M. Heraud, P. Wood, B. Burden, F. Beardall, J. McNaughton, D. Fourier transform infrared microspectroscopy and chemometrics as a tool for the discrimination of cyanobacterial strains. Phytochemistry 1999,52,407-417. 

Bernardo, K. Pakulat, N. Macht, M. Krut, O. Seifert, H. Fleer, S. Hunger, F. Kronke, M. Identification and discrimination of Staphylococcus aureus strains using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Proteomics 2002, 2, 747-753. 

Subsequently 36 strains of aerobic endospore-forming bacteria, consisting of six Bacillus species and one Brevibacillus species could be discriminated using cluster analysis of ESMS spectra acquired in the positive ion mode (m/z 200-2000).57 The analysis was carried out on harvested, washed bacterial cells suspended in aqueous acidic acetonitrile. The cell suspensions were infused directly into the ionization chamber of the mass spectrometer (LCT, Micromass) using a syringe pump. Replicates of the experiment were performed over a period of six months to randomize variations in the measurements due to possible confounding factors such as instrumental drift. Principal components analysis (PCA) was used to reduce the dimensionality of the data, fol-... 

Figure 11.3 Positive ion FIESMS spectra of crude cell extracts from Escherichia coli HB101 (A), Bacillus sphaericus DSM 28 (B), and Bacillus licheniformis NTCC 10341 (C). (D) A pseudo-3D plot of the first three discriminant functions (DF1-3) obtained from positive ion whole-cell DIESMS spectra of seven Bacillus subtilis strains (a-g) (E) the corresponding abridged dendrogram obtained from the same information as in D. (Adopted from Vaidyanathan et al.57)...

Another important advance has been the application of PyMS with ANNs to discriminate between methicillin-resistant and methicillin-sensitive Staphylococcus aureusIn this study DFA and HCA showed that the major source of variation between the pyrolysis mass spectra of 15 methicillin-resistant (MRSA) and 22 methicillin-sensitive Staphylococcus aureus (MSSA) strains resulted from the phage group of the bacteria, rather than from their resistance or sensitivity to methicillin. By contrast, ANNs could recognize those aspects of the pyrolysis mass spectra that differentiated MRSA and MSSA strains. These results gave the first demonstration that the combination of PyMS with ANNs could provide a rapid and accurate antibiotic-susceptibility testing technique. 

Bowles, J. and McManus, D.P. (1993a) Rapid discrimination of Echinococcus species and strains using a polymerase chain reaction-based RFLP method. Molecular and Biochemical Parasitology 57, 231-240. 

Preliminary research has shown that Brillouin fiber-optic sensing systems provide a possible method to detect leaks and third-party intrusion on a pipeline over distances of 25 km or more. Their intrinsic response to both temperature and mechanical strain allows for the separation of these parameters and the detection of anomalies in the scan profiles. In addition, the same sensor could be integrated into the pipeline system to detect possible ground movement relative to fixed reference points. Limited test results on surface loads associated with the intrusion of vehicles and people on a pipeline have demonstrated the sensitivity of the system and its ability to discriminate loads at different soil depths. 

Polar-substituted alkenes where the functionality is not attached to a strained ring are considerably more discriminating in their compatibility with metathesis catalysts and as a rule require relatively high catalyst charges. In the aliphatic series, unsaturated esters have received the most attention. Boelhouwer reported in 1972 the metathesis of the ester methyl oleate and its trans isomer, methyl elaidate, with a homogeneous catalyst based on a 1/1.4 molar combination of WCl6/(CH3)4Sn (23). At 70°C and an ester/W molar ratio of 33, near-thermodynamic equilibrium was attained, and 49 and 52% of the respective esters were converted to equal amounts of 9-octadecene and the dimethyl ester of 9-octadecene-1,18-dioic acid. 

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