[Tex/LaTex] Hyphen within variable names (Proteins and Amino acids)

math-modespacing

I have to Amino acids as variable-names within LaTeX. So far I am using (and found out):

\documentclass{a4paper}{article}
\newcommand\dTRP{\mathit{d-TRP}}
\begin{document}
    $[\dTRP] = 3$ (Ignore the missing units :-) - MWE )
\end{document}

The hyphen between "d" and "TRP" is just too long and seems to contain small spaces between "d" and "TRP" which is not very appealing to me and I suppose that I didn't do it the genuine way.

Best Answer

You should use \textit instead of \mathit.

With \mathit, the tex engine interprets the groups of characters as "words" (compare, for example the output of $TRP$ and $\mathit{TRP}$), but non-letter characters are still denoting the mathematical symbol. In particular, here, the hyphen is a minus. The glyph is different, and the spacing is different.

On the other hand, \textit deals with elements of text, so words in the usual sense (so, possibly-containing hyphens).

To sum up:

  • $d-TRP$ should mean "variable d minus variable T times variable R times variable P"
  • $\mathit{d-DRP}$ should mean "variable d minus variable TRP" (and is poorly coded for that purpose)
  • $\textit{d-TRP}$ should mean "variable d-TRP"

Edit: To have \textit scaled normally in sub- and super-script, you should load the amsmath package. Thanks to David Carlisle for reminding me that, and for pointing my mistake about spacing around characters in \mathit.

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