Experimental Elimination of R Factors

2015 ◽  
pp. 196-226 ◽  
Author(s):  
Fred E. Hahn
Keyword(s):  
R Factors

scholarly journals Structure Solution of Nano-Crystalline Small Molecules Using MicroED and Solid-State NMR Dipolar-Based Experiments

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4652
Author(s):  
Nghia Tuan Duong ◽  
Yoshitaka Aoyama ◽  
Katsumi Kawamoto ◽  
Toshio Yamazaki ◽  
Yusuke Nishiyama
Keyword(s):  
Spin Dynamics ◽  
Double Resonance ◽  
Three Dimensional ◽  
Saturation Pulse ◽  
X Ray Crystallography ◽  
Nano Crystalline ◽  
Structure Solution ◽  
Validation Procedure ◽  
R Factors ◽  
Shift Calculation

Three-dimensional electron diffraction crystallography (microED) can solve structures of sub-micrometer crystals, which are too small for single crystal X-ray crystallography. However, R factors for the microED-based structures are generally high because of dynamic scattering. That means R factor may not be reliable provided that kinetic analysis is used. Consequently, there remains ambiguity to locate hydrogens and to assign nuclei with close atomic numbers, like carbon, nitrogen, and oxygen. Herein, we employed microED and ssNMR dipolar-based experiments together with spin dynamics numerical simulations. The NMR dipolar-based experiments were 1H-14N phase-modulated rotational-echo saturation-pulse double-resonance (PM-S-RESPDOR) and 1H-1H selective recoupling of proton (SERP) experiments. The former examined the dephasing effect of a specific 1H resonance under multiple 1H-14N dipolar couplings. The latter examined the selective polarization transfer between a 1H-1H pair. The structure was solved by microED and then validated by evaluating the agreement between experimental and calculated dipolar-based NMR results. As the measurements were performed on 1H and 14N, the method can be employed for natural abundance samples. Furthermore, the whole validation procedure was conducted at 293 K unlike widely used chemical shift calculation at 0 K using the GIPAW method. This combined method was demonstrated on monoclinic l-histidine.

scholarly journals Demonstration of R Factors From Pseudomonas aeruginosa

1974 ◽  
Vol 5 (6) ◽  
pp. 547-552 ◽  
Author(s):  
S. Iyobe ◽  
K. Hasuda ◽  
A. Fuse ◽  
S. Mitsuhashi
Keyword(s):  
Pseudomonas Aeruginosa ◽  
R Factors

scholarly journals Interactions between de-repressed F-like R factors and wild type Colicin B factors: superinfection immunity and represser susceptibility

1969 ◽  
Vol 14 (3) ◽  
pp. 315-322 ◽  
Author(s):  
Anna Frydman ◽  
Elinor Meynell
Keyword(s):  
Wild Type ◽  
Colicin B ◽  
R Factors

F-like R factors are related to ColB-K77, but not to ColB-K98 or ColB-K166, by the criterion of superinfection immunity. Tests of de-repressed mutant R factors for susceptibility to repression by ColB-K98, known to produce represser for F, showed that these could be either repressor-sensitive or insensitive. The former were independently shown not to produce repressor, which was thus, presumably the reason for their de-repressed state.

scholarly journals Chromosome transfer inPseudomonas aeruginosamediated by R factors

1971 ◽  
Vol 17 (2) ◽  
pp. 169-172 ◽  
Author(s):  
Vilma A. Stanisich ◽  
B. W. Holloway
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Specific Resistance ◽  
Host Chromosome ◽  
Chromosome Transfer ◽  
R Factors

SUMMARYR factors present inPseudomonas aeruginosastrains of clinical origin can be transferred to other strains ofP. aeruginosaand may act to promote host chromosome transfer. In general, their properties are similar to those R factors in Enterobacteria. The different R factors studied vary with respect to transferability, transfer of specific resistance properties, repressibility, and ability to promote chromosome transfer.

OBSERVATIONS ON THE IN VIVO TRANSFER OF R FACTORS

1971 ◽  
Vol 182 (1 The Problems) ◽  
pp. 80-90 ◽  
Author(s):  
H. Williams Smith
Keyword(s):  
R Factors
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