Comparison of two methods for evaluation of the length of collagen molecules

Two microscopical methods for the evaluation of molecular length--the measurement of SLS aggregates and the rotary shadowing technique--are compared. Two types of collagen were used for the comparison: type I collagen, isolated by acid extraction from calf skin, and type IX, isolated from chicken cartilage. An average length of 303 nm was obtained for type I collagen (by measurement of SLS aggregates 247 nm). Type IX collagen forms three different types of SLS crystallites corresponding to molecular lengths of 61, 95 and 206 nm; with the rotary shadowing technique, lengths of 84, 116 and 197 nm were measured.