Allen M J, Bradbury E M, Balhorn R
Digital Instruments, Inc., Santa Barbara, CA 93117, USA.
Scanning Microsc. 1996;10(4):989-94; discussion 994-6.
The fundamental structure formed when genomic DNA is packaged by protamine in the human sperm nucleus still remains essentially unresolved. It is known that the binding of protamine, a small arginine-rich protein, to DNA generates a large dense, hydrophobic complex making the sperm chromatin structure difficult to study microscopically. To visualize the internal nuclear structures, isolated human sperm nuclei were swollen extensively in saline buffer using only a reducing agent. The nuclei were swollen during deposition onto coverglass and then imaged in the atomic force microscope (AFM). The two main results obtained from imaging individual well-spread nuclei indicate that native human sperm chromatin is: (1) particulate, consisting primarily of large nodular structures averaging 98 nm in diameter, and (2) also composed of smaller, nucleosome-like particles observed to form linear chains near the nuclear periphery. These two types of chromatin particles imaged by AFM are remarkably similar to other AFM measurements made on native and reconstituted sperm and somatic chromatin.
当基因组DNA在人类精子细胞核中被鱼精蛋白包装时形成的基本结构仍然基本上没有得到解决。已知鱼精蛋白是一种富含精氨酸的小蛋白质，它与DNA的结合会产生一个大的致密疏水复合物，使得精子染色质结构难以通过显微镜进行研究。为了可视化细胞核内部结构，仅使用还原剂在盐缓冲液中对分离的人类精子细胞核进行广泛肿胀处理。细胞核在沉积到盖玻片上的过程中肿胀，然后在原子力显微镜（AFM）中成像。对单个充分展开的细胞核成像获得的两个主要结果表明，天然人类精子染色质是：（1）颗粒状的，主要由平均直径为98纳米的大结节状结构组成；（2）还由较小的、类似核小体的颗粒组成，这些颗粒在核周边附近形成线性链。通过AFM成像的这两种染色质颗粒与对天然和重构的精子及体细胞染色质进行的其他AFM测量结果非常相似。
