病毒在它的等电离点以上时带负电荷.用英语怎么说？

病毒在它的等电离点以上时带负电荷.

A virus is nigatively charged above its isoelectric point.

virus

n. 病毒，病毒性疾病，毒素，毒害，[计算机科学]计算机病毒；

例句
The virus seems to have attacked his throat...
病毒看来已经侵蚀到他喉部了。

is

vt.& vi. 是（be的三单形式；n. 存在；

例句
Bollinger 'RD' is a rare, highly prized wine.
博林格RD香槟是一种名贵的备受推崇的葡萄酒。

charged

adj. 充满感情的，紧张的，可能引起激烈反应的；v. 填充；

例句
She was charged with abducting a six-month-old child.
她被控诱拐一个6个月大的孩子。

above

prep. 在…上面，超过，大于，不至于；adv. 在上面，超过，更大，上文；adj. 上述的；

例句
He lifted his hands above his head...
他将双手举过头顶。

its

pron. (it的所有格形式)它的，厥；

例句
The government is to accelerate its privatisation programme.
政府将加快其私有化计划的进程。

isoelectric

adj. 等电位的，零电位差的；

例句
The isoelectric points of ChA and ChB were obtained as 5.21 and 5.92 by isoelectrofocusing.
采用等电聚焦的方法测定得ChA和ChB的等电点分别为5.21和5.92.

point

n. 点，要点，得分，标点；vt. （意思上）指向，削尖，加标点于，指路；vi. 表明，指向；

例句
He was abrupt to the point of rudeness...
他的唐突已到了无礼的地步。