Griffith O H, Habliston D L, Birrell G B, Skoczylas W P
Institute of Molecular Biology, University of Oregon, Eugene 97403.
Biophys J. 1990 May;57(5):935-41. doi: 10.1016/S0006-3495(90)82613-8.
Photoelectron imaging provides the possibility of a new method of mapping chromosomes. The basic concept is to cause DNA to emit electrons under the action of UV light. The criteria which must be met to map genomes by photoelectron imaging are set forth and discussed. Forming an image of the DNA by accelerating and focusing the electrons is a necessary but not sufficient condition for genome mapping. Equally important is to identify wavelengths of UV light which will cause selective emission from the base pairs, adenine-thymine and guanine-cytosine. The resulting image would then contain a modulation in the image brightness along the DNA duplex. By examining the photoelectron current from uniform films of homopolymers, a wavelength region is identified where marked differences in emission from base pairs is observed. At 160 nm, for example, the relative electron emission from a film of poly(dGdC) is approximately 5 times greater than for an equivalent film of poly(dAdT). Using the experimental data and known sequences, photoelectron gene maps are calculated for the bacteriophage lambda and for a short interspersed repetitive DNA sequence (an Alu repeat) of the human genome. The results suggest that a 5-nm physical map of chromosomes generated by photoelectron imaging would be informative and useful in mapping human and other large genomes.
光电子成像为染色体图谱绘制提供了一种新方法的可能性。其基本概念是使DNA在紫外光的作用下发射电子。阐述并讨论了通过光电子成像绘制基因组图谱必须满足的标准。通过加速和聚焦电子来形成DNA图像是基因组图谱绘制的必要条件，但并非充分条件。同样重要的是要确定能使碱基对（腺嘌呤 - 胸腺嘧啶和鸟嘌呤 - 胞嘧啶）产生选择性发射的紫外光波长。这样得到的图像将在DNA双链上沿图像亮度呈现一种调制。通过检查均聚物均匀薄膜的光电子电流，确定了一个波长区域，在该区域观察到碱基对发射存在显著差异。例如，在160纳米处，聚（dGdC）薄膜的相对电子发射大约是聚（dAdT）等效薄膜的5倍。利用实验数据和已知序列，计算了噬菌体λ和人类基因组的一个短散在重复DNA序列（一个Alu重复序列）的光电子基因图谱。结果表明，通过光电子成像生成的5纳米染色体物理图谱在绘制人类和其他大型基因组图谱方面将是信息丰富且有用的。
