这个是PDB数据库原子坐标记录格式
HETATM 非标准基团原子坐标
e.g: 1 MG MG 168 4.669 34.118 19.123 1.00 3.16 MG2+
英文在PDB file 中的说明:The HETATM records present the atomic coordinate records for atoms within "non-standard" groups. These records are used for water molecules and atoms presented in HET groups.