many studies on the toxicity of nanoplastic particles (NPPs)
to aquatic invertebrates, the effects of ecological constituents such
as humic substances (HSs) are often neglected. In our study, Daphnia magna was used to evaluate the effects of
three HSs, natural organic matter (NOM), fulvic acid (FA), and humic
acid (HA), on NPP toxicity and corona formation. Acute toxicities
of NPPs were reduced by all HSs at environmentally relevant concentrations.
NPPs elicited the upregulation of all genes related to detoxification,
oxidative stress, and endocrine activity after 7 days of exposure.
The presence of NOM or HA resulted in the mitigation of gene expression,
whereas significantly higher upregulation of all of the genes was
observed with FA. The presence of FA led to increased protein adsorption
on NPPs in D. magna culture medium
(eco-corona, EC) and homogenates (protein corona, PC), while there
was less adsorption in the presence of HA. The highly abundant proteins
identified in EC are involved in immune defense, cell maintenance,
and antipredator response, while those in PC are responsible for lipid
transport, antioxidant effects, and estrogen mediation. Our findings
revealed the key influence of HSs on the toxicity of NPPs and provide
an analytical and conceptual foundation for future study.
An effective gold-catalyzed intermolecular nitrene transfer by the reaction of 2H-azirines and ynamides is reported, which provides highly substituted pyrroles in a straightforward manner. This transformation proceeds under mild conditions and gives the polysubstituted pyrroles in good-to-excellent yields. Preliminary results indicate that a nongold carbenoid pathway is preferred for current pyrrole synthesis.
To collect information about the genetic diversity of the plankton community and to study how plankton respond to environmental conditions, plankton samples were collected from five stations representing different trophic levels in a shallow, eutrophic lake (Lake Donghu), and investigated by PCR-DGGE fingerprinting. A total of 100 bands (61 of 16S rDNA bands and 39 of 18S rDNA bands) were detected. The DGGE bands unique to any single station accounted for 38% of the total bands, whereas common bands detected at all five stations accounted for only 11%. Using UPGMA clustering and MDS ordination of DGGE fingerprints, stations I and II were found to initially group together into one cluster, which was later joined by station V. Stations III and IV were isolated into two separate groups of one station each. Some differences in grouping relationships were found when analysis was completed on the basis of chemical characteristics and morphological composition, with zooplankton composition showing the greatest variability. However, the most similar stations (I and II) were always initially grouped into one cluster. Moreover, stations that exhibited the same or similar trophic level (stations III and IV), but different concentrations of heavy metals, were further differentiated by the DGGE method. Results of the present study indicated that PCR-DGGE fingerprinting was more sensitive than the traditional methods, as other studies suggested. Additionally, PCR-DGGE appears to be more appropriate for diversity characterization of the plankton community, as it is more canonical, systematic, and effective. Most importantly, fingerprinting results are more convenient for the comparative analyses between different studies. Therefore, the use of the described fingerprinting analysis may provide an operable and sensitive biomonitoring approach to identify critical, and potentially negative, stress within an aquatic ecosystem.
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