英语翻译1.IntroductionAll organisms have evolved sophisticated m

英语翻译
1.Introduction
All organisms have evolved sophisticated mechanisms to sense
and respond to changes in their environment.Many environmental
perturbations are unpredictable,and cells employ signal transduction
mechanisms to sense these perturbations and mount appropriate
responses.In contrast,the cycles of light and temperature
arising from the rotation of the Earth about its axis – variations
that profoundly affect an enormous variety of organisms – are far
from random.Rather,the daily rising and setting of the sun is
the most universal,ancient,and predictable source of variation in
the environment.It comes as no surprise,then,that many organisms
from all kingdoms of life have acquired the ability not only
to sense,but also to predict,diurnal cycling of the environment.
From cyanobacteria to humans,endogenous biochemical oscillators
called circadian clocks keep track of the time of day,allowing
an organism to coordinate its physiology and behavior with the
day/night cycle [1].These clocks exert their influence over cellular
physiology in part by controlling gene expression.In the case of the
cyanobacterium Synechococcus elongatus PCC 7942,the model system
for the cyanobacterial clock,the circadian clock drives rhythmic
expression of over 30% of the genome [2].
A circadian clock forms an internal representation of external
time,but this timepiece continues to run even in the absence of
external cues.That is,circadian clocks oscillate with a period of
approximately 24 h (hence their name,meaning ‘‘about [circa] a
day [dies]”) under constant environmental conditions (constant
light and temperature),a phenomenon known as free-run and
one of their defining features.Furthermore,the period of oscillation
remains around 24 h across the physiological temperature
range despite the high sensitivity of typical biochemical reaction
rates to temperature.This temperature compensation is a second
defining feature of circadian clocks.Finally,a circadian clock would
be of little use to an organism if the clock’s phase bore no relationship
to the actual time of day.Hence,the phase can be altered by
environmental stimuli (e.g.,changes in light) in order to synchronize
the clock with the diurnal cycle of the environment; moreover,
in oscillating environments,the clock adapts to establish a
fixed relationship between its phase and that of the environment.
These related phenomena,which constitute the third defining feature
of a circadian clock,are known as phase resetting and entrainment,
respectively [1].
Generally,circadian clocks are highly robust biological oscillators.
For example,the S.elongatus clock is resistant to fluctuations
produced by metabolic repression [3,4],cell division [5,6],and
those arising from the inherent stochasticity of biochemical

序言
一切生物都有成熟的进化机制去感应和适应环境的变化.许多环境变动是不可预知的,细胞采取信号传导机制以感应这些变动,并作出正确反应.相反,光照和温度的周期则因地球围绕轴心转动而改变——这种变化对生物的多样性具有深远的意义——远高于随机性的.比较而言,日出日落则是环境中比较普遍而古老的可预知变化.它的出现并无任何惊奇,随之,各生物王国的物种感知并能预测到环境的昼夜循环.从蓝藻到人类,内置生化振荡即所谓生物钟保持与时间一致的步伐.从而保证生物体内的生理与日/夜循环相协调〔1〕.这些生物钟通过影响部分细胞生理,进而控制基因的表达.在PCC 7942的蓝藻吸虫案例中,该蓝藻的生物时钟模拟系统规律地表达了30％的基因组〔2〕.
生物钟是外部时间的内部表达.但这种时钟可以在即使没有外部线索的情况下运行.因此,生物钟是振荡周期大约为24小时（因此,它们的名字意思为“大约一天的消逝”）处于恒定环境条件下（常量光照和温度）按生物属性自行运转的一个现象.此外,除去对温度的高灵敏反应不说,振荡周期仍然能通过生理上的温度维持在24小时左右.这种温度补给是生物钟的第二个属性定义.最后,如果时钟的相位没有与一天中的实际时间有任何联系的话,生物钟会是一个没有多大用处的有机体.因此,该阶段会因环境刺激而改变（比如,改变光照）从而调整生物钟以适应环境的昼夜循环.而且,在变动的环境下,生物钟会建立一个稳定的关系以适应与环境之间的变动.这些相关的现象,构成生物钟的第三个定义,也就是所谓的时钟相对相位的调整和摆动.
一般来说,生物钟是非常强劲的生物振荡器.举例说明,S.elongatus的生物钟因代谢抑制而未波动〔3,4〕、细胞分裂〔5,6〕,那些均来源于生化遗传所固有的……………………
所在领域非生物类,所以翻译专有名词时应该会出现错误情况.请自行校对.