Definition: Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.
Input: Abstract: Cow snout epidermal cells digested by 0.25% trypsin were separated into three regions of keratinocytes by Percoll density gradient centrifugation. The membrane fluidity of keratinocytes in each region was measured by electron spin resonance using 5-doxyl stearic acid (5-DSA) as a labeling agent. The order parameter(s) showed higher values as the depth of the epidermis decreased: lower region of epidermis, 0.632; upper region, 0.645; and horny cells, 0.680. These data indicated that membrane fluidity of epidermal cells decreased as cells approached the surface.

Spin labeling study on membrane fluidity of epidermal cell (cow snout epidermis).