Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Label-free optical detection of single enzyme-reactant reactions and
  associated conformational changes   Monitoring the kinetics and conformational dynamics of single enzymes is
crucial in order to better understand their biological functions as these
motions and structural dynamics are usually unsynchronized among the molecules.
Detecting the enzyme-reactant interactions and associated conformational
changes of the enzyme on a single molecule basis, however, remain as a
challenge with established optical techniques due to the commonly required
labeling of the reactants or the enzyme itself. The labeling process is usually
non-trivial and the labels themselves might skew the physical properties of the
enzyme. Here we demonstrate an optical, label-free method capable of observing
enzymatic interactions and the associated conformational changes on the single
molecule level. We monitor polymerase/DNA interactions via the strong
near-field enhancement provided by plasmonic nanorods resonantly coupled to
whispering gallery modes in microcavities. Specifically, we employ two
different recognition schemes: one in which the kinetics of polymerase/DNA
interactions are probed in the vicinity of DNA-functionalized nanorods, and the
other in which these interactions are probed via the magnitude of
conformational changes in the polymerase molecules immobilized on nanorods. In
both approaches we find that low and high polymerase activities can be clearly
discerned via their characteristic signal amplitude and signal length
distributions. Furthermore, the thermodynamic study of the monitored
interactions suggests the occurrence of DNA polymerization. This work
constitutes a proof-of-concept study of enzymatic activities via plasmonically
enhanced microcavities and establishes an alternative and label-free method
capable of investigating structural changes in single molecules.

19
The categories of this paper are: eess
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph