Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-Photon Excited Fluorescence Dynamics in Enzyme-Bound NADH: the
  Heterogeneity of Fluorescence Decay Times and Anisotropic Relaxation   The dynamics of polarized fluorescence in reduced nicotinamide adenine
dinucleotide (NADH) at 436~nm under two-photon excitation at 720~nm by
femtosecond laser pulses in alcohol dehydrogenase (ADH)-containing buffer
solution has been studied experimentally and theoretically. A global fit
procedure was used for determination of the fluorescence parameters from
experimental data. The interpretation of the experimental results obtained was
supported by \emph{ab initio} calculations of NADH structure in solutions. A
theoretical model was developed for description of the polarized fluorescence
decay in enzyme-NADH binary complexes that considered several possible
interaction scenarios. We suggest that the origin of a significant enhancement
of the nanosecond decay time value in the ADH-bounded NADH compare with the
free NADH can be attributed to the significant decrease of non-radiative
relaxation probabilities due to decrease of charges separations in the
nicotinamide ring in the conditions of an apolar ADH-NADH binding site
environment. The existence of a single decay time in the ADH-NADH complex in
the nanosecond time-domain in comparison with two decay times observed in free
NADH can be attributed to a single NADH unfolded \emph{trans}-like conformation
bounded within the ADH site. Comparison of the experimental data obtained and
the theory developed suggested the existence of an anisotropic relaxation time
of about 1 ns related most likely with interactions between excited NADH and
the ADH binding site that resulted in the rearrangement of nuclear distribution
and rotation of fluorescence transition dipole moment.

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The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
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The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: cs
10
The categories of this paper are: q-bio
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con