Could anyone help me align this multiline equation correctly? I am having very little luck. It is too long for one line, so I have spread it over 4 lines. I am trying to get all the +(#) terms after '\chemspec_\text{vit}' to be aligned to the left to remove the white space between the equations (so all the plus signs sit underneath each other).
\documentclass{article}
\usepackage[english]{babel}
\usepackage{amsmath}
\begin{document}
% commands
\newcommand{\dydx}[2]{\frac{\text{d}#1}{\text{d}#2}}
\newcommand{\pRPEc}[1]{p_\text{RPE}^{(#1)}}
\newcommand{\pILMc}[1]{p_\text{ILM}^{(#1)}}
\newcommand{\kelc}[1]{k_\text{el}^{(#1)}}
\newcommand{\Sret}{S_\text{ret}}
\newcommand{\Vvit}{V_\text{vit}}
\newcommand{\SVit}{\frac{\Sret}{\Vvit}}
\newcommand{\konv}{k_\text{on}^{(v)}}
\newcommand{\koffv}{k_\text{off}^{(v)}}
\newcommand{\KDv}{K_\text{D}^{(v)}}
\newcommand{\konn}{k_\text{on}^{(n)}}
\newcommand{\koffn}{k_\text{off}^{(n)}}
\newcommand{\chemspec}{\R}
\newcommand{\area}{\text{ret}}
\newcommand{\V}{v}
\newcommand{\R}{r}
\newcommand{\VR}{c}
\newcommand{\RVR}{h}
\newcommand{\N}{n}
\newcommand{\RN}{m}
\newcommand{\VRN}{f}
\newcommand{\RVRN}{\left(n_0-\left\{\N+\RN+\VRN\right\}\right)}
\newcommand{\Rone}[1] {\koffv \VR_#1 - 2\konv\V_#1\R_#1} % R1
\newcommand{\Rtwo}[1] {2\koffv \RVR_#1 - \konv\R_#1\VR_#1} % R2
\newcommand{\Rthree}[1]{\koffn \RN - \konn\R_#1\N} % R3
\newcommand{\Rfivec}[1]{\koffv \RVRN - \konv\R_#1\VRN} % R5c
\begin{alignat}{2}
% derivative
\dydx{\chemspec_\area}{t} &=
% transfer
\left(\SVit\right)\pILMc{\chemspec}\chemspec_\text{ret} % ret --> vit
-\left[\left(\SVit\right)\pILMc{\chemspec}+\kelc{\chemspec}\right]\chemspec_\text{vit} % vit --> ret
% reactions
&+\left(\Rone{\area}\right)\\ % R1
&&+\left(\Rtwo{\area}\right)\nonumber\\ % R2
&&+\left(\Rthree{\area}\right)\nonumber\\ % R3
&&+\left(\Rfivec{\area}\right)\nonumber % R5c
\end{alignat}
\end{document}
EDIT: I explained that poorly, this is what I'm trying to achieve:
\text
like this. Use for example_{\mathrm{...}}
or use textup or textnormal instead of mathrm. The\text
command does not do what you thing it does. This is a very common error. – daleif Jan 11 '18 at 10:19