Enhancement of tomogram interpretability using the locked self-rotation function

The interpretation of cryo-electron tomograms of macromolecular complexes can be difficult because of the large amount of noise and because of the missing wedge effect. Here it is shown how the presence of rotational symmetry in a sample can be utilized to enhance the quality of a tomographic analysis. The orientation of symmetry axes in a sub-tomogram can be determined using a locked self-rotation function. Given this knowledge, the sub-tomogram density can then be averaged to improve its interpretability. Sub-tomograms of the icosahedral bacteriophage phiX174 are used to demonstrate the procedure.     

The effect of end‐group substitution on surface self‐assembly of peptides

Biofouling, the undesirable accumulation of organisms onto surfaces, affects many areas including health, water, and energy. We previously designed a tripeptide that self‐assembles into a coating that prevents biofouling. The peptide comprises three amino acids: DOPA, which allows its adhesion to the surface, and two fluorinated phenylalanine residues that direct its self‐assembly into a coating and acquire it with antifouling properties. This short peptide has an ester group at its C‐terminus. To examine the importance of this end group for the self‐assembly and antifouling properties of the peptide, we synthesized and characterized tripeptides with different end groups (ester, amide, or carboxylic group). Our results indicate that different groups at the C‐terminus of the peptide can lead to a change in the peptide assembly on the surface and its adsorption process. However, this change only affects the antifouling properties of the coating toward Gram‐positive bacteria (Staphylococcus epidermidis), whereas Gram‐negative bacteria (Escherichia coli) are not affected.     

Acoustic stimuli from predators trigger behavioural responses in aggregate caterpillars

Prey detect their predators through predator signals and cues and, consequently, respond with anti‐predatory behaviours to inhibit the action of their aggressors. Lepidopterans can intercept signals emitted by predators and may defend themselves through chemical, morphological or behavioural responses. In this study, we investigated the effect of acoustic stimuli of different predators on defensive behaviour of gregarious caterpillars. Our results demonstrated that Hylesia nigricans (Lepidoptera, Saturniidae) caterpillars alter their behaviour (i.e. abruptly raising the head) in response to the acoustic stimulus of the predators (i.e. predation risk signals from birds and wasps). The magnitude of this response depended on predator identity and caterpillar body size. Larger caterpillars responded more strongly to predatory stimuli than smaller caterpillars. However, regardless of the size of the caterpillars, they responded more strongly to the stimuli of wasps. In addition, we identified that H. nigricans caterpillars emit ultrasonic noise after detecting the stimuli of the predators – this noise seems to function as an alert about the risk of predation during the early stages of development (second and fifth instars). The duration of ultrasonic emission (i.e. milliseconds) increases with the number of repetitions of the stimuli (i.e. wing‐beat sounds of the wasps and insectivorous birds). These results provide novel information about predation risk in interactions among caterpillars and their predators, and indicate possible communication among invertebrates mediated by the risk of predation.     

1-硝基-2-酰基蒽醌-缬氨酸通过抑制ERK1/2激活和ERCC1表达诱导结肠癌细胞死亡

化学方法合成是新药研发的一种重要途径。结合抗肿瘤药物的作用机制以及蒽醌类衍生物的构效关系,设计合成了一类新的蒽醌类衍生物1-硝基-2-酰基蒽醌-缬氨酸(简称C3),发现其具有很好的抗肿瘤活性。为了确定蒽醌类衍生物C3对结肠癌HCT116和HT29细胞的作用及其分子机制,首先通过MTT比色法检测C3对结肠癌HCT116和HT29细胞活性的影响。结果显示,C3对这两种结肠癌细胞具有明显的抑制作用,呈时间和剂量依赖性。60μg/mL的C3处理HCT116和HT29细胞48 h,细胞活性分别是50.67%和59.77%,达到了半抑制浓度;同时,其细胞形态和细胞核发生明显变化。进一步采用Western印迹和qRT-PCR技术,检测C3对DNA切除修复交叉互补1(excision repair cross-complementation group 1,ERCC1)转录水平和蛋白质水平表达及其稳定性的影响。结果表明,C3降低了ERCC1转录水平和蛋白质水平的表达,并且减弱了ERCC1转录水平和蛋白质水平的稳定性。最后,用U0126(MEK1/2抑制剂)和C3联合作用结肠癌HCT116和HT29细胞,通过Western印迹检测ERCC1蛋白质水平的表达。结果表明,C3通过降低p-ERK1/2的蛋白质水平的表达,从而抑制ERCC1的表达。上述结果证明,C3通过细胞外调节蛋白激酶(extracellular regulated protein kinases, ERK1/2)信号通路,降低了ERCC1转录水平和蛋白质水平的稳定性,使ERCC1转录水平和蛋白质水平表达发生下调,进而抑制结肠癌HCT116和HT29细胞的活性。     

Kin recognition and co‐operative foraging in Drosophila melanogaster larvae

A long‐standing goal for biologists and social scientists is to understand the factors that lead to the evolution and maintenance of co‐operative behaviour between conspecifics. To that end, the fruit fly, Drosophila melanogaster, is becoming an increasingly popular model species to study sociality; however, most of the research to date has focused on adult behaviours. In this study, we set out to examine group‐feeding behaviour by larvae and to determine whether the degree of relatedness between individuals mediates the expression co‐operation. In a series of assays, we manipulated the average degree of relatedness in groups of third‐instar larvae that were faced with resource scarcity, and measured the size, frequency and composition of feeding clusters, as well as the fitness benefits associated with co‐operation. Our results suggest that larval D. melanogaster are capable of kin recognition (something that has not been previously described in this species), as clusters were more numerous, larger and involved more larvae, when more closely related kin were present in the social environment. These findings are discussed in the context of the correlated fitness‐associated benefits of co‐operation, the potential mechanisms by which individuals may recognize kin, and how that kinship may play an important role in facilitating the manifestation of this co‐operative behaviour.     

Social and ecological factors alter stress physiology of Virunga mountain gorillas (Gorilla beringei beringei)

Living in a rapidly changing environment can alter stress physiology at the population level, with negative impacts on health, reproductive rates, and mortality that may ultimately result in species decline. Small, isolated animal populations where genetic diversity is low are at particular risks, such as endangered Virunga mountain gorillas (Gorilla beringei beringei). Along with climate change‐associated environmental shifts that are affecting the entire population, subpopulations of the Virunga gorillas have recently experienced extreme changes in their social environment. As the growing population moves closer to the forest's carrying capacity, the gorillas are coping with rising population density, increased frequencies of interactions between social units, and changing habitat use (e.g., more overlapping home ranges and routine ranging at higher elevations). Using noninvasive monitoring of fecal glucocorticoid metabolites (FGM) on 115 habituated Virunga gorillas, we investigated how social and ecological variation are related to baseline FGM levels, to better understand the adaptive capacity of mountain gorillas and monitor potential physiological indicators of population decline risks. Generalized linear mixed models revealed elevated mean monthly baseline FGM levels in months with higher rainfall and higher mean maximum and minimum temperature, suggesting that Virunga gorillas might be sensitive to predicted warming and rainfall trends involving longer, warmer dry seasons and more concentrated and extreme rainfall occurrences. Exclusive use of smaller home range areas was linked to elevated baseline FGM levels, which may reflect reduced feeding efficiency and increased travel efforts to actively avoid neighboring groups. The potential for additive effects of stress‐inducing factors could have short‐ and long‐term impacts on the reproduction, health, and ultimately survival of the Virunga gorilla population. The ongoing effects of environmental changes and population dynamics must be closely monitored and used to develop effective long‐term conservation strategies that can help address these risk factors.     

Serology and gene sequence analysis of rare subgroup A3 blood group

To investigate the serological phenotypic characteristics and possible mechanism of subgroup A₃, a blood donor's ABO phenotypes were detected by the conventional microcolumn gel method and classic tube method. N-acetylgalactosaminyl transferase activity was detected by the non-radioactive phosphate coupling method. ABO subtype genotyping was determined by PCR-SSP and exons 1-7 of ABO gene were analyzed by Sanger sequencing. The donor's blood type was subgroup A₃ as evaluated by serological test. There was no N-acetylgalactosaminyl transferase activity in the red blood cells and weak N-acetylgalactosaminyl transferase activity in the plasma. The ABO blood group genotyping result was ABO*AO1, and the gene sequencing result was confirmed as A221/O01. Sequencing results showed two mutations, 467C>T and 607G>A in exon 7 in ABO*A allele. In conclusion, it is suggested that the ABO blood group of the donor be subgroup A₃, which may be induced by mutations 467C>T and 607G>A, and led to a decrease in N-acetylgalactosaminyl transferase activity and resulted in weakened A antigen.     

Determination of community structure through deconvolution of PLFA-FAME signature of mixed population

Phospholipid fatty acids (PLFAs) as biomarkers are well established in the literature. A general method based on least square approximation (LSA) was developed for the estimation of community structure from the PLFA signature of a mixed population where biomarker PLFA signatures of the component species were known. Fatty acid methyl ester (FAME) standards were used as species analogs and mixture of the standards as representative of the mixed population. The PLFA/FAME signatures were analyzed by gas chromatographic separation, followed by detection in flame ionization detector (GC-FID). The PLFAs in the signature were quantified as relative weight percent of the total PLFA. The PLFA signatures were analyzed by the models to predict community structure of the mixture. The LSA model results were compared with the existing "functional group" approach. Both successfully predicted community structure of mixed population containing completely unrelated species with uncommon PLFAs. For slightest intersection in PLFA signatures of component species, the LSA model produced better results. This was mainly due to inability of the "functional group" approach to distinguish the relative amounts of the common PLFA coming from more than one species. The performance of the LSA model was influenced by errors in the chromatographic analyses. Suppression (or enhancement) of a component's PLFA signature in chromatographic analysis of the mixture, led to underestimation (or overestimation) of the component's proportion in the mixture by the model. In mixtures of closely related species with common PLFAs, the errors in the common components were adjusted across the species by the model.     

The role of phospholipid headgroups in mediating bilayer organization. Perturbations induced by the presence of a tethered chromophore

We report on the dynamics of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-lissamine rhodamine B sulfonyl ammonium salt (Rhodamine-PE), incorporated into unilamellar vesicles composed of 1,2-dimyristoyl-sn-phosphatidylcholine (DMPC). A key question in the investigation of any bilayer system using tethered fluorescent probes is the role that the chromophore itself plays in determining the organization of phospholipid bilayers. In this work, we investigate the role of headgroup-bound chromophores by measuring the steady state and time-resolved fluorescence response of the tethered rhodamine chromophore as a function of concentration in the bilayer. We find that both the steady state and dynamical properties of the chromophores change with concentration, in a manner consistent with the introduction of disorganization to the bilayers. Steady state fluorescence spectra show a clear perturbation of the rhodamine emission spectrum at a chromophore concentration of 0.25 mol%, which is not seen for lower concentrations, and fluorescence anisotropy data show that both the motional freedom and confining volume experienced by the chromophore increase with concentration. Taken collectively, our data point to the importance of using low concentrations of optical probes in the interrogation of bilayer structures.