Rotational and translational motions of human spermatozoa: angle dependence of dynamic laser light scattering.

We have studied how the dynamic components of laser light scattered from human spermatozoa depend on the scattering angle. This was done by investigating the halfwidth of the intensity autocorrelation function. A model of the spermatozoa as freely rotating and translating linear objects was adequate to describe the scattered light. Rotational motions determined the halfwidth of the intensity autocorrelation function at very small scattering angles and contribution from translational motions was dominant at scattering angles larger than 20 degrees. The contribution from translational motions increased with increasing scattering angle. We found a nearly linear relationship between the translation speed and the rotation frequency. However, the ratio between the two properties varied more than expected from the methodological error. Therefore we introduced a propelling efficacy as a concept to describe the swimming efficiency. This property might contain important information about the swim characteristics.