The height of double-stranded DNA (dsDNA) is measured by lift mode AFM combined with conventional tapping mode AFM. While the tip scan height is raised step by step, the tip pressure on sample is decreased gradually. ...The height of double-stranded DNA (dsDNA) is measured by lift mode AFM combined with conventional tapping mode AFM. While the tip scan height is raised step by step, the tip pressure on sample is decreased gradually. As a result, the deformation of the DNA strands decreases, and the height of double-stranded DNA (dsDNA) molecule can be deduced by the tip lift height. The measured height of dsDNA is 1.5±0.2 nm in lift mode, but only 0.8±0.2 nm in conventional tapping mode. This demonstrates that the tip pressure is a key factor in soft sample height measurement resulting in artificating lower values via conventional tap- ping mode.展开更多
Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chro...Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chromosomes together until the metaphase I to anaphase I transition, is critical for proper chromosome segregation. Recent studies have suggested that the SPO 11 proteins have conserved functions in a number of organisms in generating sites of double-stranded DNA breaks （DSBs） that are thought to be the starting points of homologous recombination. Processing of these sites of DSBs requires the function of RecA homologs, such as RAD5 1, DMC 1, and others, as suggested by mutant studies; thus the failure to repair these meiotic DSBs results in abnormal chromosomal alternations, leading to disrupted meiosis. Recent discoveries on the functions of these RecA homologs have improved the understanding of the mechanisms underlying meiotic homologous recombination.展开更多
文摘The height of double-stranded DNA (dsDNA) is measured by lift mode AFM combined with conventional tapping mode AFM. While the tip scan height is raised step by step, the tip pressure on sample is decreased gradually. As a result, the deformation of the DNA strands decreases, and the height of double-stranded DNA (dsDNA) molecule can be deduced by the tip lift height. The measured height of dsDNA is 1.5±0.2 nm in lift mode, but only 0.8±0.2 nm in conventional tapping mode. This demonstrates that the tip pressure is a key factor in soft sample height measurement resulting in artificating lower values via conventional tap- ping mode.
基金The authors thank Alexandra Surcel and Carey L Hendrix Lord for helpful comments on this manuscript.The work in our laboratory is supported by grants from the National Science Foundation(IBN-0077832,MCB-9896340,MCB-0092075)the National Institutes of Health(R0 1 GM63871)+3 种基金the US Department of Agriculture(2001-35301-10570 and 2003-35301-13313)Wuxing L was partially supported by the Intercollege Graduate Degree Program in Plant PhysiologyHong M gratefully acknowledges the support of the John Simon Guggenheim Foundationthe National Institutes of Health(F33 GM72245-1).
文摘Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chromosomes together until the metaphase I to anaphase I transition, is critical for proper chromosome segregation. Recent studies have suggested that the SPO 11 proteins have conserved functions in a number of organisms in generating sites of double-stranded DNA breaks （DSBs） that are thought to be the starting points of homologous recombination. Processing of these sites of DSBs requires the function of RecA homologs, such as RAD5 1, DMC 1, and others, as suggested by mutant studies; thus the failure to repair these meiotic DSBs results in abnormal chromosomal alternations, leading to disrupted meiosis. Recent discoveries on the functions of these RecA homologs have improved the understanding of the mechanisms underlying meiotic homologous recombination.
