The dynamics of folding and unfolding of secondary structural motifs found in proteins is crucial to understanding the protein folding problem. In this paper we study the short-time dynamics of loop unfolding and hydrogen bond formation and breaking in the alanine pentapeptide at room temperature, using several constant-energy molecular dynamics simulations of about 4 ns of duration. We analyze the results in terms of time histories of "core" alpha-carbon dihedral angles. We also perform a principal component analysis of the data. We find that the time scale for a considerable deformation of the dihedral angles formed by the alpha-carbons is on the order of 1 ns whereas hydrogen bonds seem to break and form on a shorter time scale.