( ( Arrow heads ) ( ( ( indicate ( DNA fragments ) ) ( with ( different mobilities ) ) ) . ) )
(ROOT (S (NP (NNP Arrow) (NNS heads)) (VP (VBP indicate) (NP (NN DNA) (NNS fragments)) (PP (IN with) (NP (JJ different) (NNS mobilities)))) (. .)))
Arrow heads indicate DNA fragments with different mobilities.
(ROOT (S (NP (JJ Reversible) (NNS reactions)) (VP (VBP are) (VP (VBN indicated) (PP (IN by) (NP (NP (JJ opposite-headed) (NNS kinds)) (PP (IN of) (NP (NNS arrows))))))) (. .)))
Reversible reactions are indicated by opposite-headed kinds of arrows.