12 research outputs found
Long-Lived Nuclear Spin States in Methyl Groups and Quantum-Rotor-Induced Polarization
Substances containing rapidly rotating
methyl groups may exhibit
long-lived states (LLSs) in solution, with relaxation times substantially
longer than the conventional spin-lattice relaxation time <i>T</i><sub>1</sub>. The states become long-lived through rapid
internal rotation of the CH<sub>3</sub> group, which imposes an approximate
symmetry on the fluctuating nuclear spin interactions. In the case
of very low CH<sub>3</sub> rotational barriers, a hyperpolarized LLS
is populated by thermal equilibration at liquid helium temperature.
Following dissolution, cross-relaxation of the hyperpolarized LLS,
induced by heteronuclear dipolar couplings, generates strongly enhanced
antiphase NMR signals. This mechanism explains the NMR signal enhancements
observed for <sup>13</sup>C-γ-picoline (Icker, M.; Berger, S. <i>J. Magn. Reson.</i> <b>2012</b>, <i>219</i>,
1–3)
Synthesis of an Isotopically Labeled Naphthalene Derivative That Supports a Long-Lived Nuclear Singlet State
The synthesis of an octa-alkoxy substituted
isotopically labeled
naphthalene derivative, shown to have excellent properties in singlet
NMR experiments, is described. This highly substituted naphthalene
system, which incorporates an adjacent <sup>13</sup>C spin pair, is
readily accessed from a commercially available <sup>13</sup>C<sub>2</sub>-labeled building block via sequential thermal alkynyl- and
arylcyclobutenone rearrangements. The synthetic route incorporates
a simple desymmetrization approach leading to a small difference in
the chemical shifts of the <sup>13</sup>C spin pair, a design constraint
crucial for accessing nuclear singlet order
Differential expression of key pneumococcal virulence genes in vivo
© 2006 Society for General MicrobiologyFew studies have examined in vivo virulence gene expression in Streptococcus pneumoniae. In this study, expression of key pneumococcal virulence genes cbpA, pspA, ply, psaA, cps2A, piaA, nanA and spxB in the nasopharynx, lungs and bloodstream of mice was investigated, following intranasal challenge with the serotype 2 strain D39. Bacterial RNA was extracted, linearly amplified and assayed by real-time RT-PCR. At 72 h, cbpA mRNA was present at higher levels in the nasopharynx and lungs than in the blood. At this time-point, the mRNAs for PspA and PiaA were most abundant in the nasopharynx, whereas no significant difference in gene expression between niches was observed for ply, psaA and cps2A. Both nanA and spxB mRNAs were present in higher amounts in the nasopharynx than in the lungs or blood. These findings illustrate the dynamic nature of pneumococcal virulence gene expression in vivo.Kim S. LeMessurier, Abiodun David Ogunniyi, and James C. Pato
Production of Tense Morphology by Afrikaans-Speaking Children With and Without Specific Language Impairment
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