Antonino Ingargiola Replace section and paragraph with * version  about 8 years ago

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}  \hyphenation{smFRET}  \hyphenation{FRETBursts}  \renewcommand{\thesection}{\hspace*{-1.0em}}%  \renewcommand{\thesubsection}{\hspace*{-1.0em}}%  \newcommand{\beginsupplement}{%  \setcounter{table}{0}  \renewcommand{\thetable}{S\arabic{table}}%  \setcounter{figure}{0}  \renewcommand{\thefigure}{S\arabic{figure}}%  \renewcommand{\thesubsection}{S\arabic{subsection} Appendix}%  }  %% END MACROS SECTION 

\section{Introduction} \section*{Introduction}  \subsection{Open \subsection*{Open  Science and Reproducibility} Over the past 20 years, single molecule FRET (smFRET) has grown into one of the most  useful techniques in single-molecule spectroscopy~\cite{Weiss_1999,Hohlbein_2014}. 

Together with all the aforementioned tools, FRETBursts contributes to the growing  ecosystem of open tools for reproducible science in the single-molecule field.  \subsection{Paper \subsection*{Paper  Overview} This paper is written as an introduction to smFRET burst analysis and  its implementation in FRETBursts.  The aim is illustrating the specificities and 

(\href{https://github.com/tritemio/fretbursts_paper}{link}).  \section{FRETBursts \section*{FRETBursts  Overview} \label{sec:overview}  \subsection{Technical \subsection*{Technical  Features} FRETBursts can analyze smFRET measurements  from one or multiple excitation spots~\cite{Ingargiola_2013}. The supported 

kernel density distribution estimator (2CDE)~\cite{Tomov_2012}  are available as FRETBursts notebooks.  \subsection{Software \subsection*{Software  Availability} FRETBursts is hosted and openly developed on GitHub. FRETBursts homepage  (\href{http://tritemio.github.io/FRETBursts}{link})  contains links to the various resources. Installation instructions can be found in the 

without requiring any installation on the user's computer (\href{https://github.com/tritemio/FRETBursts_notebooks#run-online}{link}).  \section{Architecture \section*{Architecture  and Concepts} \label{sec:concepts}  In this section, we introduce some general burst analysis concepts  and notations used in FRETBursts.  \subsection{Photon \subsection*{Photon  Streams} \label{sec:ph_streams}  The raw data collected during a smFRET experiment consists in one or more arrays of 

\caption{\label{tab:ph_sel_alex}Photon selection syntax (ALEX)}  \end{table}  \subsection{Background \subsection*{Background  Definitions} \label{sec:bg_intro}  An estimation of the background rates is needed to both select a proper threshold for 

\end{figure}  \subsection{The \subsection*{The  \texttt{Data} Class} \label{sec:data_intro}  The \verb|Data| class 

\end{table}  \paragraph{Python \paragraph*{Python  details} Many \verb|Data| attributes are lists of arrays (or scalars) with the length of the lists  equal to the number of excitation spots. This means that in  single-spot measurements, an array of burst-data 

with an underscore, so that an equivalently syntax is  \verb|Data.nd_| instead of \verb|Data.nd[0]|.  \subsection{Introduction \subsection*{Introduction  to Burst Search} \label{sec:burstsearch_intro}  Identifying single-molecule fluorescence bursts in the stream of photons is 

the burst selection based on burst size  with another criterion such as burst duration or brightness (see section~\nameref{sec:burstsel}).  \subsection{Corrected \subsection*{Corrected  Burst Sizes and Weights} \label{sec:burstsizeweights}  The number of photons detected during a burst --the ``burst size''-- 

and using weights, is possible to build a FRET histogram with well-defined FRET sub-populations peaks  without the need of searching an optimal burst-size threshold (\nameref{sec:burstweights_theory}).  \paragraph{Python \paragraph*{Python  details} FRETBursts has the option to weight bursts using $\gamma$-corrected  burst sizes which optionally include acceptor excitation photons \verb|naa|.  A weight proportional to the burst size is applied by passing the argument 

However, using weights different from the size is not recommended  due to their less efficient use of burst information.  \section{smFRET \section*{smFRET  Burst Analysis} \label{sec:analysis}  \subsection{Loading \subsection*{Loading  the Data} \label{sec:dataload}  While FRETBursts can load several data files formats,  we encourage users to adopt the recently introduced Photon-HDF5 

can be found in the \verb|loader| module's documentation  (\href{http://fretbursts.readthedocs.org/en/latest/loader.html}{link}).  \subsection{Alternation \subsection*{Alternation  Parameters} \label{sec:alternation}  For μs-ALEX and ns-ALEX data, Photon-HDF5 normally stores parameters defining 

reloaded and the steps above repeated as described.  \subsection{Background \subsection*{Background  Estimation} \label{sec:bg_calc}  The first step of smFRET analysis involves estimating background rates. 

These impurities tend to bleach on timescales of minutes resulting in  background variations during the course of the measurement.  \paragraph{Python \paragraph*{Python  details} The estimated background rates are stored in the \verb|Data| attributes  \verb|bg_dd|, \verb|bg_ad| and \verb|bg_aa|, corresponding to photon 

\href{http://fretbursts.readthedocs.org/en/latest/background.html}{link}).  \subsection{Burst \subsection*{Burst  Search} \label{sec:burstsearch}  %\subsubsection{Burst %\subsubsection*{Burst  Search in FRETBursts} %\label{sec:burstsearch_code}  Following background estimation, burst search is the next step of 

different copies of \verb|Data| objects, the memory usage is minimized, even when  several copies are created.  \paragraph{Python \paragraph*{Python  details} Note that, while \verb|.burst_search()| is a method of \verb|Data|,  \verb|burst_search_and_gate| is a function in the \verb|bext| module  taking a \verb|Data| object as a first argument and returning a new 

collects ``plugin'' functions that provides additional algorithms  for processing \verb|Data| objects.  \subsection{Bursts \subsection*{Bursts  Corrections} \label{sec:corrcoeff}  In μs-ALEX, there are 3 important correction parameters: $\gamma$-factor, 

can be found online as an interactive notebook (\href{http://nbviewer.jupyter.org/github/tritemio/notebooks/blob/master/Derivation%20of%20FRET%20and%20S%20correction%20formulas.ipynb}{link}).  \subsection{Burst \subsection*{Burst  Selection} \label{sec:burstsel}  After burst search, it is common to select bursts according to different 

bursts in \verb|dsw|  will have sizes between 50 and 200 photons, and duration between 0.5 and 3~ms.  \paragraph{Burst \paragraph*{Burst  Size Selection} In the previous section, we selected bursts by size, using only  photons detected in both D and A channels during D excitation (i.e. Dex photons),  as in eq.~\ref{eq:burstsize_dex}. 

\verb|select_bursts.size| documentation  (\href{http://fretbursts.readthedocs.org/en/latest/burst_selection.html#fretbursts.select_bursts.size}{link}).  \paragraph{Python \paragraph*{Python  details} To compute $\gamma$-corrected burst sizes (with or without addition of \verb|naa|)  the method \verb|Data.burst_sizes|  (\href{http://fretbursts.readthedocs.org/en/latest/data_class.html#fretbursts.burstlib.Data.burst_sizes}{link})  is used.  \paragraph{Select \paragraph*{Select  the FRET Populations} In smFRET-ALEX experiments, in addition to one or more FRET populations, there are always  donor-only (D-only) and acceptor-only (A-only) populations. 

\end{center}  \end{figure}  \subsection{Population \subsection*{Population  Analysis} \label{sec:fretfit}  Typically, after bursts selection, E or S histograms are fitted to a model. 

as well as the documentation for \verb|bursts_fitter| function  (\href{http://fretbursts.readthedocs.org/en/latest/plugins.html#fretbursts.burstlib_ext.bursts_fitter}{link}).  \paragraph{Python \paragraph*{Python  details} Models returned by FRETBursts's factory functions (\verb|mfit.factory_*|)  are \verb|lmfit.Model| objects (\href{https://lmfit.github.io/lmfit-py/model.html}{link}). 

(\href{http://lmfit.github.io/lmfit-py/}{link}).  \section{Implementing \section*{Implementing  Burst Variance Analysis} \label{sec:bva}  In this section, we describe how to implement burst variance analysis (BVA) 

FRETBursts provides well-tested, general-purpose functions for timestamps and burst data  manipulation and therefore simplifies implementing custom burst analysis algorithms such as BVA.  \subsection{BVA \subsection*{BVA  Overview} Single-molecule FRET histograms show more information than just mean FRET efficiencies.  While in general the presence of several peaks clearly indicates the existence of  multiple subpopulations, a single peak cannot a priori be associated with 

\end{center}  \end{figure}  \subsection{BVA \subsection*{BVA  Implementation} The following paragraphs describe the low-level details involved in implementing the BVA using FRETBursts.  The main goal is to illustrate a real-world example of accessing and manipulating timestamps and burst data.  For a ready-to-use BVA implementation users can refer to the corresponding notebook included with FRETBursts  (\href{http://nbviewer.jupyter.org/github/tritemio/FRETBursts_notebooks/blob/master/notebooks/Example%20-%20Burst%20Variance%20Analysis.ipynb}{link}).  \paragraph{Python \paragraph*{Python  details} For BVA implementation, two photon streams are needed: all-photons during donor excitation (Dex)  and acceptor photons during donor excitation (DexAem).  These photon stream selections are obtained by computing boolean masks as follows 

\section{Conclusions} \section*{Conclusions}  \label{sec:conclusions}  FRETBursts is an open source and openly developed (see~\nameref{sec:dev}) implementation % SI_link 

Nesher Technologies and intellectual property used in the research  reported here. The work at UCLA was conducted in Dr. Weiss's Laboratory.  \beginsupplement  \section{Supporting \section*{Supporting  Information} \paragraph*{S1 Appendix.}