可见光和银离子对p型和n型黄铜矿生物浸出的影响机理

研究可见光和银离子(Ag^(+))对嗜酸氧化亚铁硫杆菌浸出p型和n型黄铜矿(黄铜矿A和黄铜矿B)的不同影响及机理。通过霍尔效应试验、生物浸出试验、X射线衍射、扫描电子显微镜和X射线光电子能谱对黄铜矿的半导体性质、生物浸出行为、表面形貌、主要物相和表面物种进行分析。实验结果表明,黄铜矿A比黄铜矿B具有更高的载流子浓度和更大的载流子迁移率,因此其溶出速率更快。生物浸出24 d后,当光照和Ag^(+)同时存在时,黄铜矿A的铜浸出率为91.05%,比黄铜矿B的铜浸出率(73.19%)高17.86%。显然,可见光和Ag^(+)对黄铜矿A生物溶解过程的促进作用强于黄铜矿B,这主要归因于黄铜矿A具有更高的载流子迁移率。此外,在光照影响下,黄铜矿表面电荷转移加快,导致Ag2S积累增多(特别是黄铜矿A),从而导致钝化层致密结构被破坏,钝化效果降低,黄铜矿溶解加速。

斑铜矿在电化学溶解过程中表面钝化物的演变

在斑铜矿(生物)浸出过程中,中间产物的产生与氧化还原电位之间的关系尚不清楚。本文作者采用一系列电化学试验和表面分析方法研究天然斑铜矿的电化学溶解行为和表面硫物种的形成。电化学试验表明,在宽阳极电位下(300~800 mV(vs Ag/AgCl)),斑铜矿电极表面经历3种不同的变化,即“活化”(<400 mV(vs Ag/AgCl)),“钝化”(400~700 mV(vs Ag/AgCl))和“过钝化”(>700 mV(vs Ag/AgCl))。XPS结果表明,在斑铜矿电化学溶解过程中表面产生的含硫中间产物包括类铜蓝、S_(n)^(2−)/S_(0)和不溶性SO_(4)^(2-)。此外,原子力显微镜结果证实:当施加的电位分别为600和700 mV(vs Ag/AgCl)时,由于S_(n)^(2−)/S_(0)的积累,斑铜矿表面会受到严重钝化。斑铜矿(生物)浸出最有利的电位为400 mV(vs Ag/AgCl)。

利用光生空穴清除剂强化光催化黄铜矿生物浸出

通过嗜酸氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)研究光生空穴清除剂(抗坏血酸、草酸、腐质酸和柠檬酸)对光催化黄铜矿生物浸出的影响。设置4组生物浸出实验:(1)可见光+0 g/L光生空穴清除剂;(2)可见光+0.1 g/L不同光生空穴清除剂(抗坏血酸、草酸、腐植酸和柠檬酸);(3)黑暗+0.1 g/L不同光生空穴清除剂(抗坏血酸、草酸、腐植酸和柠檬酸);(4)黑暗+0 g/L光生空穴清除剂(对照组)。结果表明,光照条件下,抗坏血酸和草酸作为光生空穴清除剂时,能够显著促进黄铜矿生物浸出。可见光+0 g/L光生空穴清除剂组的铜离子溶出率比对照组高18.7%;可见光+0.1 g/L草酸组和可见光+0.1 g/L抗坏血酸组的黄铜矿溶出率分别比对照组高30.1%和32.5%。SEM,XRD和FT-IR分析表明,抗坏血酸和草酸作为光生空穴清除剂能够捕获光生空穴和抑制黄钾铁矾在黄铜矿表面形成,从而促进光催化黄铜矿的生物浸出。

可见光和Cd^2+对黄铜矿生物浸出的催化作用

利用扫描电镜(SEM)、同步辐射X射线衍射(SR-XRD)和X射线光电子能谱(XPS)研究在酸性氧化亚铁硫杆菌存在下,可见光和镉离子(Cd^2+)对黄铜矿生物浸出的影响。生物浸出28天后的结果表明,光照下铜的溶解提高4.96%;Cd^2+单独存在对黄铜矿的浸出有轻微的抑制作用;可见光和50 mg/L Cd^2+同时存在时,溶解铜的浓度提高14.70%。化学浸出结果表明,可见光能促进体系中铁元素的循环。SEM结果显示,Cd^2+在可见光下促进酸性氧化亚铁杆菌在黄铜矿表面的附着。综合SR-XRD和XPS结果可知,可见光和Cd^2+促进黄铜矿的浸出,但不会抑制钝化物的形成。提出可见光和Cd^2+对黄铜矿生物浸出协同催化作用机制的模型。

Characterization of neutral lipases revealed the tissue-specific triacylglyceroi hydrolytic activity in Nilaparvata lugens

The lipid metabolism plays an essential role in the development andreproduction of insects, and lipases are important enzymes in lipid metabolism. In Nilaparvatalugens, an important insect pest on rice, triacylglycerol hydrolytic activities weredifferent among tissues, with high activity in integument, ovary, and fat body, but low activityin intestine. To figure out the tissue-specific triacylglycerol hydrolytic activity, weidentified 43 lipases in N. lugens. Of these 43 lipases, 23 belonged to neutral lipases, sothis group was selected to perform further experiments on triacylglycerol hydrolysis. Thecomplete motifs of catalytic triads, β9 loop, and lid motif, are required for the triacylglycerolhydrolytic activity in neutral lipases, which were found in some neutral lipases withhigh gene expression levels in integument and ovary, but not in intestine. The recombinantproteins of 3 neutral lipases with or without 3 complete motifs were obtained, and the activitydetermination confirmed the importance of 3 motifs. Silencing XM_022331066.1,which is highly expressed in ovary and with 3 complete motifs, significantly decreasedthe egg production and hatchability of N. lugens, partially through decline of the lipidmetabolism. In summary, at least one-third of important motifs were incomplete in allneutral lipases with high gene expression in intestine, which could partially explain whythe lipase activity in intestine was much lower than that in other tissues. The low activityto hydrolyze triacylglycerol in N. lugens intestine might be associated with its food resourceand nutrient components, and the ovary-specific neutral lipases were important forN. lugens reproduction.

Biological and biochemical characterization of a red-eye mutant in Nilaparvata lugens （Hemiptera： Delphacidae）

A red-eye colony was established in our laboratory in brown planthopper （BPH）, Nilaparvata lugens （Stal）, a major rice pest in Asia. Except for the red-eye phenotype, no other differences were observed between the wild-type （brown eye） and the mutant-type （red eye） in external characters. Genetic analysis revealed that the red-eye phenotype was controlled by a single autosomal recessive allele. Biological studies found that egg produc- tion and egg viability in the red-eye mutant colony were not significantly different from those in the wild-type BPH. Biochemical analysis and electronic microscopy examination revealed that the red-eye mutants contained decreased levels of both xanthommatin （brown） and pteridine （red） and reduced number of pigment granules. Thus, the changes of amount and ratio of the two pigments is the biochemical basis of this red-eye mutation. Our results indicate that the red-eye mutant gene （red） might be involved in one common gene locus shared by the two pigments in pigment transportation, pigment granule formation or some other processes.

Effects of temperature on fitness costs in chlorpyrifos-resistant brown planthopper, Nilaparvata lugens （Hemiptera： Delphacidae）

Insecticide resistance is inevitable if an insecticide is widely used to control insect pests. Fortunately, the resistance-associated fitness costs often give chances to manage resistances. In most cases, the fitness cost in resistant insects is often evaluated under laboratory conditions for insect development, which limits its practical application in pest control in the field. In a laboratory population R9 with 253-fold resistance to chlorpyrifos after nine-generation selection with chlorpyrifos, the relative fitness was only 0.206 under laboratory conditions （25℃, humidity 70%-80% and 16 h light/8 h dark photoperiod）, when compared to S9, a susceptible counterpart （resistance ratio = 2.25- fold） from the same origin as R9 but without any selection with insecticides. Temperatures varied the resistance-associated fitness costs, with enhanced costs at high temperatures and reduced costs at low temperatures, such as 0.174 at 32℃ and 0.527 at 18℃. The copulation rate and fecundity were two key factors for the reduced costs at low temperatures. Another finding was that R9 individuals needed much more time to recover from heat shock than that of S9, but R9 and $9 individuals were similarly sensitive to cold shock. The low fitness cost at low temperatures would increase the overwintering population, which might further increase risks of rapid development and widespread distribution of chlorpyrifos resistance in Nilaparvata lugens.

karmoisin and cardinal ortholog genes participate in the ommochrome synthesis of Nilaparvata lugens (Hemiptera:Delphacidae)

Ommochrome is the major source for eye coloration of all insect species so far examined.Phenoxazinone synthetase (PHS)has always been regarded as the terminal step enzyme for ommochrome formation,which is encoded by cardinal or karmoisin genes. Our previous study indicated that the karmoisin ortholog gene (Nl-karmoisin)product in the brown planthopper (BPH)was a monocarboxylate transporter,while not a PHS. Here,based on full-length complementary DNA,the cardinal ortholog gene in BPH (Nl-cardinal)product was predicted to be a haem peroxidase rather than a PHS.We suggest for the first time that neither karmoisin nor cardinal encodes the PHS,but whether PHS participates in BPH eye pigmentation needs further research.Nymphal RNA interference (RNAi)experiments showed that knockdown Nl-cardinal transcript led the BPH ocelli and compound eye to color change from brown to red,while knockdown Nl-karmoisin only made the ocelli present the red phenotype.Notably,not only the Nl-cardinal transcript, dscd injection (Nl-cardinal targeting double-stranded DNA (dsRNA))also significantly reduced the Nl-karmoisin transcript by 33.7%,while dska (Nl-karmoisin targeting dsRNA) injection did not significantly change the Nl-cardinal transcript.Considering the above RNAi and quantitative real-time polymerase chain reaction results,we propose that Nl-cardinal plays a more important role in ommochrome synthesis than Nl-karmoisin,and it may be an upstream gene of Nl-karmoisin.The present study suggested that both karmoisin and cardinal ortholog genes play a role in ommochrome synthesis in a hemimetabolous insect.