Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phosphate Vibrations Probe Electric Fields in Hydrated Biomolecules:
  Spectroscopy, Dynamics, and Interactions   Electric interactions have a strong impact on the structure and dynamics of
biomolecules in their native water environment. Given the variety of water
arrangements in hydration shells and the femto- to subnanosecond time range of
structural fluctuations, there is a strong quest for sensitive noninvasive
probes of local electric fields. The stretching vibrations of phosphate groups,
in particular the asymmetric (PO2)- stretching vibration {\nu}AS(PO2)-, allow
for a quantitative mapping of dynamic electric fields in aqueous environments
via a field-induced redshift of their transition frequencies and concomitant
changes of vibrational line shapes. We present a systematic study of
{\nu}AS(PO2)- excitations in molecular systems of increasing complexity,
including dimethyl phosphate (DMP), short DNA and RNA duplex structures, and
transfer RNA (tRNA) in water. A combination of linear infrared absorption,
two-dimensional infrared (2D-IR) spectroscopy, and molecular dynamics (MD)
simulations gives quantitative insight in electric-field tuning rates of
vibrational frequencies, electric field and fluctuation amplitudes, and
molecular interaction geometries. Beyond neat water environments, the formation
of contact ion pairs of phosphate groups with Mg2+ ions is demonstrated via
frequency upshifts of the {\nu}AS(PO2)- vibration, resulting in a distinct
vibrational band. The frequency positions of contact geometries are determined
by an interplay of attractive electric and repulsive exchange interactions.

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The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: math