if (leftParticipants.Length >= 0) // Check to see if LeftParticipants exists
{
   for (int c = 0; c < leftParticipants.Length; c++)
   {
       var l_entityIDs =
          from BioList in o_data.Descendants(bp + "physicalEntityParticipant")
          where BioList.Attribute(rdf + "ID").Value == leftParticipants[c].TrimStart('#')
          select new
          {
              o_entityIDs = BioList.Elements(bp + "PHYSICAL-ENTITY")
              .Select(entityID => entityID.Attribute(rdf + "resource").Value).ToArray()
          };

       foreach (var entity in l_entityIDs)
       {
           this.physEntityPhysicalLeftEntityIDs = entity.o_entityIDs;  // Set SmallMolecules from Left
       }
    }
}

int destIndex = 0;
foreach (var entity in l_entityIDs)
{
    this.physEntityPhysicalLeftEntityIDs[destIndex] = entity.o_entityIDs;  // Set SmallMolecules from Left
    ++destIndex;
}

this.physEntityPhysicalLeftEntityIds = new int[l_entityIDs.Count()];