ABSTRACT
The reaction paths of methylenecyclopropane 1 on the potential energy surfaces (PESs) of the lowest triplet (T1 ) state and the lowest excited singlet (S1 ) state, as well as that of the ground state (S0 ), were explored by using the nudged elastic band method at the MRMP2//MCSCF/6-31++G(d,p) and DFT(B3LYP)/6-31++G(d,p) levels of theory. After vertical excitation of 1, three transition states on the PES of the lowest triplet state and one transition state on the S1 PES were found along the reaction path to produce a carbene, cyclobutylidene 2. All of these transition states are lower in energy than the S1 state produced by vertical excitation at the S0 energy minimum in 1. Fast transition is predicted to occur from the T1 state or from the S1 state to the S0 state due to strong spin-orbit coupling or nonadiabatic coupling in the geometrical vicinity of 2. On the MRMP2 S0 PES, the energy barriers of 5.0, 10.3 and 13.5 kcal mol-1 were obtained for C migration reaction (backward reaction), 1,2-H migration reaction to cyclobutene 3, and 1,3-H migration reaction to bicyclopropane 4, respectively, started at 2. The introduction of phenyl groups makes the energy barriers smaller due to the π conjugation between the carbene center and phenyl groups.
ABSTRACT
Rhodococcus equi causes suppurative pneumonia in foals aged 1-3 months; moreover, it has emerged as a pathogenic cause of zoonotic diseases. After the initial report of the ruminant-pathogenic factor VapN encoded by the novel virulence plasmid pVAPN, several reports have described ruminant infections caused by vapN-harboring R. equi. Herein, we conducted a serological epidemiological surveillance in goats at a breeding farm (Farm A) and characterized the vapN-harboring R. equi isolates from this farm. First, we established a simple screening enzyme-linked immunosorbent assay (ELISA) using recombinant glutathione S-transferase-tagged VapN as an immobilized antigen. This method revealed that the VapN antibody titers were elevated in 12 of 42 goats. Subsequently, we attempted to isolate R. equi from the goat feces and soil of Farm A. choE+/vapN+R. equi was isolated from the feces of Goat No. 27 and a soil sample near the shed. The pulsed-field gel electrophoresis (PFGE) patterns of five vapN-harboring R. equi strains isolated from Farm A in 2013 and 2019 were investigated and found to be the same except for the strain (OKI2019F1). However, no difference was observed in VapN expression and growth in macrophages among these vapN-harboring R. equi isolates. Our results revealed that some goats had histories of vapN-harboring R. equi infections, and two genomic types of vapN-harboring R. equi were found in isolates from Farm A. Ruminant-specific (pVAPN-carrying) R. equi might be an unrecognized pathogen in Japan and further studies are required to determine its prevalence and distribution.
