OPTICAL-ROTATORY DISPERSION AND CIRCULAR-DICHROISM OF SILVER(I)-POLYRIBONUCLEOTIDE COMPLEXES
OPTICAL-ROTATORY DISPERSION AND CIRCULAR-DICHROISM OF SILVER(I)-POLYRIBONUCLEOTIDE COMPLEXES
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DOI：
10.1002/bip.1975.360140907
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发表时间：
1975-01-01
期刊：
影响因子：
2.9
通讯作者：
YANG, JT
中科院分区：
文献类型：
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作者：
ARYA, SK;YANG, JT
单链和多链聚核糖核苷酸的旋光色散（ORD）和圆二色性（CD）光谱在与银离子结合时发生广泛的变化。这些变化与Ag（I）结合于杂环碱基而不结合于多核苷酸的磷酸基团的主张一致。当溶液中每两个核苷酸残基中有一个以上的Ag（I）时，poly（A）·poly（U）的银配合物与双螺旋水稻矮缩病毒RNA的ORD和CD表现出负的Cotton效应。这些观察结果表明，由于Ag（I）结合，双螺旋构象发生了显著扭曲。当溶液中每两个核苷酸残基有一个Ag（I）时，嘧啶多核苷酸的银（I）结合位点明显饱和，而嘌呤多核苷酸的每一个核苷酸残基有一个Ag（I）。这些数据与多核苷酸的嘧啶环上存在一些Ag（I）结合位点和咪唑环上存在额外位点的假设一致。当每个核苷酸残基存在一个Ag（I）时，poly（A）的沉降系数增加数倍。银（I）可在单链多核苷酸中引入链内和链间交联（通过双齿螯合物），导致结构具有高沉降系数。在所研究的多核苷酸中，poly（U）是一个例外。银（I）在中性pH下不影响聚（U）的光学性质（吸光度、ORD和CD）。
Optical rotatory dispersion (ORD) and circular dichroism (CD) spectra of single‐ and multistranded polyribonucleotides undergo extensive changes on binding of the silver ion. These changes are consistent with the proposition that Ag(I) binds to the heterocyclic bases and not to the phosphate groups of polynucleotides. ORD and CD of silver complexes of poly(A)·poly(U) and double‐helical rice dwarf viral RNA display negative Cotton effects when there is more than one Ag(I) per two nucleotide residues in solution. These observations suggest a significant distortion of the double‐helical conformation as a result of Ag(I) binding. Silver(I) binding sites of pyrimidine polynucleotides are apparently saturated when there is one Ag(I) per two nucleotide residues and those of purine polynucleotides at one Ag(I) per nucleotide in solution. These data are consistent with the supposition that some Ag(I) binding sites exist on the pyrimidine ring and additional sites on the imidazole ring of polynucleotides. The sedimentation coefficient of poly(A) increases by severalfold when one Ag(I) is present per nucleotide residue. Silver(I) may introduce intra‐ and interstrand cross‐links (through bidentate chelates) in single‐stranded polynucleotides, resulting in structures with high sedimentation coefficients. Among the polynucleotides studied, poly(U) was an exception. Silver(I) did not affect the optical properties (absorbance, ORD, and CD) of poly(U) at neutral pH.