3链段序列数量/质量分布函数; (PM)=P(-P1)Wm),=x(-1) ·4.平均链段长度 ∑x(PM)2 N ∑(PM) [M2◼ 3.链段序列数量/质量分布函数; ( ) (1 ) 1 1 1 PM1 P1 1 P x x = − − 2 1 1 1 1 1 1 (W ) x P (1 P ) x M x = − − • 4. 平均链段长度 [ ] [ ] 1 ( ) ( ) 2 1 1 1 1 1 1 1 M M r PM x PM N x x x x M = = + = =