  We present the first simulations of the tidal disruption of stars with
realistic structures and compositions by massive black holes (BHs). We build
stars in the stellar evolution code MESA and simulate their disruption in the
3D adaptive-mesh hydrodynamics code FLASH, using an extended Helmholtz equation
of state and tracking 49 elements. We study the disruption of a 1$M_\odot$ star
and 3$M_\odot$ star at zero-age main sequence (ZAMS), middle-age, and
terminal-age main sequence (TAMS). The maximum BH mass for tidal disruption
increases by a factor of $\sim$2 from stellar radius changes due to MS
evolution; this is equivalent to varying BH spin from 0 to 0.75. The shape of
the mass fallback rate curves is different from the results for polytropes of
Guillochon & Ramirez-Ruiz (2013). The peak timescale $t_{\rm peak}$ increases
with stellar age, while the peak fallback rate $\dot M_{\rm peak}$ decreases
with age, and these effects diminish with increasing impact parameter $\beta$.
For a $\beta=1$ disruption of a 1$M_\odot$ star by a $10^6 M_\odot$ BH, from
ZAMS to TAMS, $t_{\rm peak}$ increases from 30 to 54 days, while $\dot M_{\rm
peak}$ decreases from 0.66 to 0.14 $M_\odot$/yr. Compositional anomalies in
nitrogen, helium, and carbon can occur before the peak timescale for
disruptions of MS stars, which is in contrast to predictions from the
"frozen-in" model. More massive stars can show stronger anomalies at earlier
times, meaning that compositional constraints can be key in determining the
mass of the disrupted star. The abundance anomalies predicted by these
simulations provide a natural explanation for the spectral features and varying
line strengths observed in tidal disruption events.
