| 1. |
- Klionsky, Daniel J., et al.
(författare)
-
Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
-
Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
-
Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
|
|
| 2. |
- Chang, Tingru, et al.
(författare)
-
High-Resolution Microscopical Studies of Contact Killing Mechanisms on Copper-Based Surfaces
- 2021
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:41, s. 49402-49413
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanisms of bacterial contact killing induced by Cu surfaces were explored through high-resolution studies based on combinations of the focused ion beam (FIB), scanning transmission electron microscopy (STEM), high-resolution TEM, and nanoscale Fourier transform infrared spectroscopy (nano-FTIR) microscopy of individual bacterial cells of Gram-positive Bacillus subtilis in direct contact with Cu metal and Cu5Zn5Al1Sn surfaces after high-touch corrosion conditions. This approach permitted subcellular information to be extracted from the bioinorganic interface between a single bacterium and Cu/Cu5Zn5Al1Sn surfaces after complete contact killing. Early stages of interaction between individual bacteria and the metal/alloy surfaces include cell leakage of extracellular polymeric substances (EPSs) from the bacterium and changes in the metal/alloy surface composition upon adherence of bacteria. Three key observations responsible for Cu-induced contact killing include cell membrane damage, formation of nanosized copper-containing particles within the bacteria cell, and intracellular copper redox reactions. Direct evidence of cell membrane damage was observed upon contact with both Cu metal and Cu5Zn5Al1Sn surfaces. Cell membrane damage permits copper to enter into the cell interior through two possible routes, as small fragmentized Cu2O particles from the corrosion product layer and/or as released copper ions. This results in the presence of intracellular copper oxide nanoparticles inside the cell. The nanosized particles consist primarily of CuO with smaller amounts of Cu2O. The existence of two oxidation states of copper suggests that intracellular redox reactions play an important role. The nanoparticle formation can be regarded as a detoxification process of copper, which immobilizes copper ions via transformation processes within the bacteria into poorly soluble or even insoluble nanosized Cu structures. Similarly, the formation of primarily Cu(II) oxide nanoparticles could be a possible way for the bacteria to deactivate the toxic effects induced by copper ions via conversion of Cu(I) to Cu(II).
|
|
| 3. |
- Ho, Anna Y. Q., et al.
(författare)
-
iPTF Archival Search for Fast Optical Transients
- 2018
-
Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 854:1
-
Tidskriftsartikel (refereegranskat)abstract
- There has been speculation about a class of relativistic explosions with an initial Lorentz factor Gamma(init) smaller than that of classical gamma-ray bursts (GRBs). These dirty fireballs would lack prompt GRB emission but could be pursued via their optical afterglow, appearing as transients that fade overnight. Here we report a search for such transients (that fade by 5-sigma in magnitude overnight) in four years of archival photometric data from the intermediate Palomar Transient Factory (iPTF). Our search criteria yielded 50 candidates. Of these, two were afterglows to GRBs that had been found in dedicated follow-up observations to triggers from the Fermi GRB Monitor. Another (iPTF14yb) was a GRB afterglow discovered serendipitously. Eight were spurious artifacts of reference image subtraction, and one was an asteroid. The remaining 38 candidates have red stellar counterparts in external catalogs. The photometric and spectroscopic properties of the counterparts identify these transients as strong flares from M dwarfs of spectral type M3-M7 at distances of d approximate to 0.15-2.1 kpc; three counterparts were already spectroscopically classified as late-type M stars. With iPTF14yb as the only confirmed relativistic outflow discovered independently of a high-energy trigger, we constrain the all-sky rate of transients that peak at m = 18 and fade by Delta m = 2 mag in Delta t = 3 hr to be 680 yr(-1), with a 68% confidence interval of 119-2236 yr(-1). This implies that the rate of visible dirty fireballs is at most comparable to that of the known population of long-duration GRBs.
|
|
| 4. |
- Wu, Hongwei, et al.
(författare)
-
Crystal Multi-Conformational Control Through Deformable Carbon-Sulfur Bond for Singlet-Triplet Emissive Tuning
- 2019
-
Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 58:13, s. 4328-4333
-
Tidskriftsartikel (refereegranskat)abstract
- Crystal-state luminophores have been of great interest in optoelectronics for years, whereas the excited state regulation at the crystal level is still restricted by the lack of control ways. We report that the singlet-triplet emissive property can be profoundly regulated by crystal conformational distortions. Employing fluoro-substituted tetrakis(arylthio)benzene luminophores as prototype, we found that couples of molecular conformations formed during different crystallizations. The deformable carbon-sulphur bond essentially drove the distortion of the molecular conformation and varied the stacking mode, together with diverse non-covalent interactions, leading to the proportional adjustment of the fluorescence and phosphorescence bands. This intrinsic strategy was further applied for solid-state multicolor emissive conversion and mechanoluminescence, probably offering new insights for design of smart crystal luminescent materials.
|
|
| 5. |
- Zhao, Weijie, et al.
(författare)
-
Corrosion inhibition of copper with octadecylphosphonic acid (ODPA) in a simulated indoor atmospheric environment
- 2021
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 192:109777
-
Tidskriftsartikel (refereegranskat)abstract
- The corrosion inhibition of self-assembled octadecylphosphonic acid (ODPA) layers on non-oxidized and pre-oxidized copper and Langmuir-Blodgett deposited ODPA layers on pre-oxidized copper was investigated under a simulated indoor atmospheric corrosion environment containing 80% RH and 100 ppb formic acid. The corrosion process was monitored in-situ with infrared absorption/reflection spectroscopy, and the corrosion products were further characterised by grazing incidence X-ray diffraction. Nano-FTIR microscopy was used to reveal the nature, size, and distribution of the corrosion products on the nanoscale. The combination of pre-formed cuprite and ODPA layers, both with only some nanometres thickness, provided an excellent protection under this environment.
|
|
| 6. |
|
|
| 7. |
- Zhao, Weijie, et al.
(författare)
-
Initial atmospheric corrosion studies of copper from macroscale to nanoscale in a simulated indoor atmospheric environment
- 2022
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 195
-
Tidskriftsartikel (refereegranskat)abstract
- Corrosion effects on copper exposed in a humid atmosphere with formic acid (mimicking indoor corrosion) have been explored through successive increase in surface lateral resolution from macroscale (IRRAS, GIXRD) over microscale (LOM, SEM, IR microscopy) to nanoscale (Nano-FTIR, FIB/SEM/EDS). Initial more uniform growth of Cu2O is followed by more varying topography and thickness until local removal of Cu2O enables the aqueous adlayer to react with the copper substrate. Local formation of Cu(OH)(HCOO) and adjacent Cu2O provide microscopic and spectroscopic evidence of corrosion cells. Nano-FTIR shows that the density of Cu(OH)(HCOO) nuclei, but not their size, increases with exposure time.
|
|
| 8. |
- Zhao, Weijie, et al.
(författare)
-
Nano Infrared Microscopy : Obtaining Chemical Information on the Nanoscale in Corrosion Studies
- 2019
-
Ingår i: Journal of the Electrochemical Society. - : ELECTROCHEMICAL SOC INC. - 0013-4651 .- 1945-7111. ; 166:11, s. C3456-C3460
-
Tidskriftsartikel (refereegranskat)abstract
- In this perspective article, the novel technique "nano infrared microscopy" is introduced as a valuable tool in the field of corrosion science to obtain chemical information with a spatial resolution of around 10 nm. Accordingly, the resolution is well below the diffraction limit, in contrast to conventional vibrational microscopy techniques. Thus, studies of corrosion initiation, localized corrosion, and thin protective films can be performed in greater detail than before. There are a few different types of nano infrared microscopes, but they all have in common that they are based on a combination of infrared (IR) spectroscopy and atomic force microscopy (AFM). In this article the theory of the different techniques is discussed, and some results are highlighted to show the ability of the technique in the field of corrosion science. Future possibilities of the technique in studies of corrosion and degradation of materials are also discussed.
|
|
| 9. |
- Zhao, Weijie
(författare)
-
Nanoscale studies of the atmospheric corrosion of copper protected by ultrathin organic films
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Copper (Cu) has been utilised by humans for millenniums and has become an indispensable metal in modern industry and in our infrastructure. However, corrosion, as a natural process for metallic materials, takes place on copper surfaces in most environments. Thus, understanding corrosion and corrosion protection of copper is of utmost importance to maintain its performance and prolong the lifetime of the applications. Corrosion has been revealed to start from local weak areas of the copper surface. However, the corrosion initiation and propagation mechanism on copper on a molecular level are far from clear.In this thesis, the corrosion initiation of copper under a simulated indoor atmosphere where formic acid and humidity are present was studied. The corrosion process was monitored in-situ, and the formed corrosion products were characterised on the macro-, micro-, and nanoscale by various analytical techniques from both horizontal and vertical directions of the corroded surfaces. The localised dissolution and formation of the Cu2O layer on narrowly separated areas on the nanoscale were observed both microscopically and spectroscopically. A novel technique, nano infrared spectroscopy (nano-FTIR), was used to probe the formed corrosion products on the nanoscale. Due to the novelty of nano-FTIR, only a few studies in corrosion science using this technique were reported. Thus, this thesis also shows the capability of employing nano-FTIR in corrosion studies.The ability of ultrathin organic films to protect copper under indoor atmospheres was also studied in this thesis. The main focus was on octadecylphosphonic acid (ODPA), for which the self-assembly process was examined in detail. A multilayer formation of ODPA on copper was observed under the self-assembly deposition, and the thickness of ODPA films increased with the deposition time. The reason for forming multilayers was attributed to the Cu+ ion release during the deposition, resulting in the formation of a Cu+-ODPA complex. The protective ability of these self-assembled ODPA films as well as Langmuir-Blodgett (LB)-deposited films on non-oxidised and pre-oxidised copper was examined under the same exposure conditions as for the unprotected copper. A remarkable ability to protect the surface was observed for the self-assembled and LB-deposited ODPA films on pre-oxidised copper.
|
|
| 10. |
- Zhao, Weijie, et al.
(författare)
-
The nature of self-assembled octadecylphosphonic acid (ODPA) layers on copper substrates
- 2021
-
Ingår i: Journal of Colloid and Interface Science. - : Academic Press Inc.. - 0021-9797 .- 1095-7103. ; 581, s. 816-825
-
Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: The self-assembly of amphiphilic molecules onto solid substrates can result both in the formation of monolayers and multilayers. However, on oxidized and non-oxidized copper (Cu), only monolayer formation was reported for phosphonic acids possessing one phosphate head group. Here, the adsorption of octadecylphosphonic acid (ODPA) on Cu substrates through a self-assembly process was investigated with the initial hypothesis of monolayer formation. Experiments: The relative amount of ODPA adsorbed on a Cu substrate was determined by infrared reflection/absorption spectroscopy (IRRAS) and by atomic force microscopy (AFM) investigations before and after ODPA deposition. X-ray photoelectron spectroscopy (XPS) with sputtering was used to characterize the nature of the layers. Findings: The results show that the thickness of the ODPA layer increased with deposition time, and after 1 h a multilayer film with a thickness of some tens of nm was formed. The film was robust and required long-time sonication for removal. The origin of the film robustness was attributed to the release of Cu ions, resulting in the formation of Cu-ODPA complexes with Cu ions in the form of Cu(I). Preadsorbing a monolayer of octadecylthiol (ODT) onto the Cu resulted in no ODPA adsorption, since the release of Cu(I) ions was abolished.
|
|
