Typesetting long equations in pnastwo document class

Question

Frequently, when using revtex4 or revtex4.1, in two column format, one wants to typeset a long equation. The standard way to do this is by using the widetext environment (see this question).

Similar to revtex4, there is a style class called pnastwo, which is a two-column style class. However, unlike revtex4, pnastwo has no support for the widetext environment.

How does one typeset a long equation in single-column mode when using the documentclass pnastwo?

Here is a minimal example that compiles.

\documentclass{pnastwo}

\usepackage[pdftex]{graphicx, color}
\DeclareGraphicsRule{.pdftex}{pdf}{.pdftex}{}
\usepackage{amsmath,amssymb,latexsym}

\usepackage[english]{babel}
\usepackage{lipsum}


\contributor{Submitted to Proceedings
of the National Academy of Sciences of the United States of America}
\url{www.pnas.org/cgi/doi/10.1073/pnas.0709640104}
\copyrightyear{2008}
\issuedate{Issue Date}
\volume{Volume}
\issuenumber{Issue Number}


\begin{document}
\title{Title Goes Here.}


\author{First{1}{University of Cambridge, Cambridge,
United Kingdom},
Second{2}{Universidad de Murcia, Bioquimica y Biologia
Molecular, Murcia, Spain}, \and Third\affil{2}{}}

\contributor{Submitted to Proceedings of the National Academy of Sciences
of the United States of America}


\maketitle


\begin{article}

\begin{abstract}
\lipsum[1]
\end{abstract}




\keywords{\LaTeX | problems}


\noindent{\bf Significance:} Why? 

\vspace{5mm}
\dropcap{T}his is some sample text that I want. \lipsum[3]
% this is the wide equation I want to type
\begin{equation}
Lots of math goes here. Lots of math goes here. Lots of math goes here. Lots of math goes here. Lots of math goes here. Lots of math goes here. 
\end{equation}
\lipsum[3]
\end{article}



\end{document}

Answer 1

You basically have a choice between breaking the equation so it does fit in one column, for example by including

\usepackage{amsmath}

then

\begin{align}
long math= this\\
         &= that\\
         &= the other
\end{align}

Or to make the formula a full width float at the top of some page

\begin{figure*}
\[ long expression here\]
\end{figure*}

so...

\documentclass{pnastwo}

\usepackage[pdftex]{graphicx, color}
\DeclareGraphicsRule{.pdftex}{pdf}{.pdftex}{}
\usepackage{amsmath,amssymb,latexsym}

\usepackage[english]{babel}
\usepackage{lipsum}


\contributor{Submitted to Proceedings
of the National Academy of Sciences of the United States of America}
\url{www.pnas.org/cgi/doi/10.1073/pnas.0709640104}
\copyrightyear{2008}
\issuedate{Issue Date}
\volume{Volume}
\issuenumber{Issue Number}


\begin{document}
\title{Title Goes Here.}


\author{First{1}{University of Cambridge, Cambridge,
United Kingdom},
Second{2}{Universidad de Murcia, Bioquimica y Biologia
Molecular, Murcia, Spain}, \and Third\affil{2}{}}

\contributor{Submitted to Proceedings of the National Academy of Sciences
of the United States of America}


\maketitle


\begin{article}

\begin{abstract}
\lipsum[1]
\end{abstract}




\keywords{\LaTeX | problems}


\noindent{\bfseries Significance:} Why? 

\vspace{5mm}
\dropcap{T}his is some sample text that I want. \lipsum[3]
% this is the wide equation I want to type
\begin{figure*}
\begin{equation}
Lots of math goes here. Lots of math goes here. Lots of math goes here. Lots of math goes here. Lots of math goes here. Lots of math goes here. 
\end{equation}
\end{figure*}
\begin{multline}
Lots of math goes here.\\
 Lots of math goes here.\\
 Lots of math goes here. Lots\\
 of math goes here. Lots of\\
 math goes here.\\
 Lots of math goes here. 
\end{multline}

\lipsum[3]
\end{article}



\end{document}

In this example the top float comes above the title, you can stop that elsewhere by not allowing top floats on the title page, also I got rid of \bf.