Types and species diversity of Cupressus communities in Southeast Tibet, China.

Cupressus communities are the important parts of natural forests in Southeast Tibet, with significance on plateau biodiversity conservation and ecological security. To clarify their types and plant species diversity, we analyzed species composition and diversity indices, diameter class pattern of constructive species in different communities in Milin County, Lang County and Bomi County, Southeast Tibet. The results showed that Cupressus communities could be classified into four types: C. torulosa-Lonicera lanceolate + Philadelphus tomentosus-Pteris cretica var. nervosa + Digitaria violascens community (Community1), C. gigantea-Desmodium elegans + Sophora moorcroftia-na-Tripogon filiformis + Cymbopogon distans + Orinus thoroldii community (Community2), C. gigantea-Leptodermis purdomii-Chenopodium hybridum + O. thoroldii community (Community 3), and C. gigantea-Ceratostigma minus-A. desertorum + O. thoroldii + Tribulus terrester community (Community 4). Across those four community types, Margalef index, Shannon index, Pielou index and interspecies encounter probability index all ranked with the decreasing order of Community1, Community2, Community 3 and Community 4. Diameter class pattern of the constructive species showed that many young and few middle/old individuals were within the four communities. High mortality rate occurred during the interim period from young to middle age classes. In general, populations of Cupressus plants showed a declining trend.

[Study on the interaction of DNA and norfloxacin by FT-Raman].

FT-Raman and surface enhanced Raman spectra (SERS) of norfloxacin and norfloxacin capsule on the silver colloidal substrate were recorded, and the vibrational and enhanced peaks were assigned; interactions of norfloxacin and DNA were researched. The experimental results proved that the characteristic vibrations of capsule's content and NFX standard, which is v(C-F), vs(O-C-O), v(C=C), did not change, while the changes in molecular skeleton's vibrations were substantial. Additives do not affect the Raman spectroscopy of norfloxacin substantively. An analytical method for detecting norfloxacin medcine can be established by FT-Raman. Without any ions, the interaction is mainly caused by the inserting-action mode between the ring of norfloxacin and the double helix structure of DNA, and norfloxacin could interact with DNA directly, providing reliable evidence for antibacterial mechanism of quinoxalone antibiotics.