吸附类蛋白质分子二级结构变化的研究

采用蒙特卡罗方法和基于三维格点的ODI模型,研究了类蛋白质分子二级结构变化与表面吸附能的关系.分别计算了链长为29,39,49时、不同吸附能下类蛋白质分子二级结构的个数.包括α螺旋、β折叠、紧密接触对.吸附能参数aε<2εh时,这三类二级结构个数均没有明显的变化,而在2εh<εa<4εh,二级结构的个数迅速减小,εa>4hε时,二级结构的个数基本维持不变.同时发现吸附能增强对螺旋结构变化的影响最大,对折叠结构的影响其次,对紧密接触对影响最小.这体现在螺旋结构的减小幅度为90%,折叠结构减小的幅度为45%,而紧密接触对减小的幅度为35%.通过统计吸附单体个数,得到当吸附单体占总单体数的40%时,二级结构开始变化,直至吸附单体为总单体数的90%时,二级结构基本不变.另外还计算了二级结构个数的涨落δNh、δNc以及吸附单体个数的涨落δNa.在εa>2εh时,涨落突然增大,在aε=2εh时,δNh和δNb具有涨落极大值,这是二级结构相变的临界点.在εa=3.75εh处,δNc和δNa具有极大值.

STUDIES ON SECONDARY STRUCTURE OF ADSORBED PROTEIN-LIKE CHAINS

The secondary structure of adsorbed protein-like chain was investigated by using Monte Carlo simulation method based on the modified orientation-dependent monomer-monomer interaction model(ODI).The number of secondary structure such as α-helics,β-sheets and contacts are all calculated for different adsorbed energy and different chain length.When adsorbed energy ε_a<2ε_h,the secondary structure of protein-like chains is nearly not changed.The chain is like a globe.While 2ε_h<ε_a<4ε_h,the number of α-helixs,β-sheets and contacts is reduced quickly.However,when ε_a>4ε_h,secondary stucture is almost keeping again.The chain is flat because most residues are adsorbed on the surface.The reduced number of α-helixs is 90% of that without adsorption.However,the reduced number of β-sheets is 45%,and that of contacts is 35%.That is to say the effect of adsorbed energy on α-helix is the most,while effect on contact is the least.On the other hand,the fluctuations of the number of α-helix,β-sheets and contacts δ_(Nh),δ_(Nb) are not changed at ε_a<2ε_h.A peak is shown at ε_a=3ε_h,which is the transition point of secondary structure.Phase behavior of secondary structure is found with adsorbed energy changing.The fluctuation of the number of contact δ_(Nc) and adsorbed residues δ_(Na) has the maximum at ε_a=3.75ε_h.