Carbon-donated hydrogen bonds (CDHBs) are weak forms of hydrogen bonding (0.5-1.0kcalmol-1) that are difficult to detect, and thus their roles in the structure and functionality of chemical systems often go unrecognized. Utilizing a computational approach, the existence of a structurally significant CDHB in the medically relevant protein Streptococcus pneumoniae hyaluronate lyase (SpnHL) is affirmed. The structure of a tetrapeptide fragment model containing the CDHB was optimized with second-order perturbation theory. From this, a CDHB with bond distance and angle consistent with previously discovered CDHBs and comparable to neighboring traditional HBs in the fragment model was found. The CDHB competes with another donor T253 OH, whereby the two alternate in strength between protein conformations, imbuing alphaHelix3 appreciable flexibility. The CDHB seems to exist in spite of torsional and steric strain on the donor methyl group. It is postulated that the CDHB could aid in either counteracting the macrodipole of alphaHelix3 or protecting the A249 CO from destabilizing interactions with the adjacent solvent. Employing the energy gradients from the optimization, the torque generated by the fragment model was computed, which accurately predicts the direction of rotation of alphaHelix3 observed from experiment. A strongly correlated motion between alphaHelix3 and alphaHelices2, 4, and 5 was noted, which the interactions of the fragment model help drive by generating a torque much larger than necessary to rotate just alphaHelix3. Considering these results, we conclude that CDHBs should be considered as possible beneficial components of chemical and biological phenomena. PUBLICATION ABSTRACT