\begin{theindex}
\def\bigletter#1{{\Large\sffamily#1}\nopagebreak\vspace{1mm}}

  \bigletter M
  \item meta-stable, \hyperindexformat{\textbf}{35}

  \indexspace
  \bigletter S
  \item synapps, \hyperindexformat{\textbf}{35}

\end{theindex}
