Friedrich Miescher FIG 1 Xray diffraction patterns of

核酸发现的创始人 Friedrich Miescher

FIG. 1. X-ray diffraction patterns of the Na salt of poly[d(I-C)] fibers. (a) D-form pattern of poly[d(I-C)] fiber at 75% r. h. recorded on a flat-plate camera. Specimen-to-film distance, 5 cm. (b) Precession photograph of the poly[d(I-C)] fiber at 75% r. h. Specimen -to-film distance, 6 cm. (c) B-form pattern of wet fiber poly[d(I-C)] (r. h. , 95%). The photograph was recorded on a flat-plate camera as in a.

Z DNA

Probe for Z-DNA Biophysical Journal Volume 90 May 2006 3203– 3207

N 3 of A and O 2 of T at the floor of the minor groove in AT Sequences form H-bond with minor groove binder.

What do the small molecules whisper to you? N 3 of A and O 2 of T at the floor of the minor groove in AT sequences.

• There are no general codes for sequencespecific recognition. • We cannot predict the atomic interactions between the protein side chains and the functional groups of the nucleotides given their sequences. • However, there are several general families of DNA-binding motifs ：α Helix is the most common structural element used for base recognition. β-sheets can be used as well.

三链DNA A triple-stranded DNA is a structure of DNA in which three oligonucleotides wind around each other and form a triple helix. In this structure, one strand binds to a B-form DNA double helix through Hoogesteen or reverse Hoogesteen hydrogen bonds.

PNA的应用 • Applications: target duplex DNA by strand invasion or triplex formation for sequencespecific detection, purification, or genetic manipulation。目前，PNA被广泛用于化学、 生物学、反义药物、分子识别、遗传诊断 等领域。

非天然核苷酸（Unnatural DNA base)

Summary